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Synthesis and structural characterization of a fully conjugated macrocyclic tetraaza(14)-membered Schiff base and its bivalent metal complexes

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Abstract

A novel 14-membered macrocyclic Schiff base derived from 3-cinnamalideneacetoacetanilide and o-phenylenediamine acts as a tetradentate and strongly conjugated ligand to form a cationic solid complex with CuCl2/NiCl2/CoCl2/ZnCl2. The ligand and the complexes were characterized by the usual spectral and analytical techniques. The main i.r. band of the macrocyclic Schiff base was compared to that of its metal complexes. The C=N bands are shifted to the lower wave number. The cyclic voltammogram of the copper complex shows that the macrocyclic ligand is able to stabilize the copper(III) oxidation state. The e.s.r. spectra of the copper complex in DMSO solution at room temperature and liquid N2 temperature were recorded and their salient features thoroughly discussed. The antimicrobial screening tests were also recorded and gave good results in the presence of metal ions in the ligand system.

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... Assignments of diffuse reflectance spectra of the metal complexes of SBL are given in Table 3 (Malik et al., 2015;Raman and Thangaraja, 2005;Lewis and Walton, 1966;Warad et al., 2000;Suja Pon Mini et al., 2014;Parekh and Patel, 2006;Mohamed et al., 2006;Montazerozohori et al., 2014). The position and shape of bands in diffuse reflectance spectra of complex of Cu(II) indicates that Cu(II) ion is having a teragonally distorted octahedral environment (Aswar and Bhave, 1994;Holm et al., 1971). ...
... 28 The appearance of bands 361-381 cm -1 and 432-448 cm -1 , corresponding to metal-chloride vibrations. 29 Table-2 provides a summary of the characteristic frequencies of the synthesized Sn(II) complexes. 31 Based on the spectral evidence (Fig.-1), the proposed structure for the Tin(II) complexes can be suggested. ...
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The novel complexes Sn(II), were synthesized of macrocyclic ligands derived from various diamine and dicarboxylic acids in the ratio of 2:2 and characterized by elemental analysis, molar conductance measurements, mass, NMR, FT-IR, and electronic spectra. The interactions of macrocyclic ligands (MLn) with SnCl2 in a 1:1 molar ratio in methanol produced the ensuing physiologically active [Sn(MLn)Cl2] type complexes, where n = 1 or 2. The complexes were initially identified using conductivity tests, molecular weight calculations, and elemental investigations. The bonding mode was determined using spectral data from the IR, 1 H NMR, and 119 Sn NMR. The complexes exhibit hexacoordinated octahedral geometry. The positive findings of Brine shrimp lethality of the ligands and their complexes have been discussed. The antimicrobial effects of each complex on several types of harmful fungus and bacteria have been assessed. The research focused on investigating and analyzing various aspects related to male fertility. It specifically investigated cauda epididymal spermatozoa density, sperm motility, testicular sperm density, fertility, and biological constraints of propagative tissues. The findings and discussions about these factors were presented in the study.
... 12,[15][16][17] Vitamin B12 also contains a macrocyclic corrin with cobalt at its centre. 13,14,18 Macrocycles are also useful as molecular switches and linear motors for constructing artificial nanoscale machinery, in mimicry of cellular receptors, as chemical sensors and as organic light emitting diodes. ...
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A novel macrocyclic Schiff base ligand 1,4,8,11-tetraaza-2,3,9,10-tetramethyl cyclotetradeca-1,3,8,10-tetraene was synthesized by condensation between butane-2,3-dione and propane-1,3-diamine in an alcoholic medium. The complexes of Co(II), Ni(II), Cu(II) and Zn(II) with Schiff base have been prepared from metal salts in an alcoholic medium. The synthesized Schiff base and its metal complexes are characterized by elemental analysis, molar conductance measurements, magnetic susceptibility, FTIR and electronic absorption spectral data. The higher molar conductance values of these metal complexes show their electrolytic nature. The Schiff base behaves as tetradentate ligand. The general molecular formula of the metal complexes has been found to be [M(L)(X)2] where M= Co(II), Ni(II), Cu(II) and Zn(II) , L=Schiff base and X= water, chlorine and ethanol . Thus, on the basis of elemental analysis and spectral studies octahedral geometry was assigned to metal complexes. The synthesized metal complexes showed more antimicrobial activity than free Schiff base ligand.
... [108]. B. H. M. Mruthyunjayaswamy and co-workers (March 2005) reported a group of di-and tetra-nuclear complexes synthesized from novel MSB ligand, L 22(Fig. ...
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The World is facing an epidemic of various diseases caused by viruses, bacteria, and fungi. Apart from it, cancer, malaria, and diabetes are some major health problems. So, a need arises to discover novel molecules that can be used as therapeutic drugs for several diseases, including cancer and diabetes. Macrocyclic Schiff base (MSB) transition metal complexes are popularly studied organometallic compounds due to their vast biological applications in treating infectious diseases and various health problems. This attracts the researchers to the Chemistry of Schiff base metal complexes in pharmaceutical applications and areas like biochemical, bio-inorganic, environmental, industrial, photochemical, photophysical, photoelectronic etc. So, the Novel synthesis of Schiff base metal complexes will design and develop more effective therapeutic drugs. Even though the topic is quite old and exploited, many researchers are still globally working to find new MSB complexes and their applications. Based on the above considerations, we have reviewed the pharmaceutical properties of MSB transition metal complexes synthesized in the last two decades.
... The Fe(III) complex, owing to transitions in it being spin-forbidden and the Zn(II), Cd(II) and Hg(II) complexes due to filled configurations do not show d-d bands .Based on the other data obtained, Fe(III) complex has been assigned octahedral (high spin) geometry and the other three complexes, tetrahedral geometry [16,17]. ...
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The Fe(tetrahedral in geometry. Further, the ligand and the metal complexes have been screened for their antimicrobial activities against two gram positive bacterial strains Basillus subtillus, Staphylococcus aurus and two gram negative bacterial strains Escherichia coli, Salmonella typhi, and two fungal strains Aspergillus niger and Penicillium rubrum by agar plate technique and the results are presented. Both the antibacterial and antifungal activities of the synthesized metal complexes were found to be more as compared to that of the ligand. Graphical Abstract N N NH 2 O H O OH OH N O N N Pyrazine-2-carbaxamide 2-hydroxy benzaldehyde HBPCA
... The band due to aldehydic -C=O band at 1680 cm -1 disappeared and band for imine stretching appear as sharp band in the region 1610-1621 cm -1 (1-3) [17,18], no peaks attributed to NH 2 groups implied that the effective Schiff's base condensation reaction has been completed. A strong absorption band around 1275, 513, and 2924 cm -1 corresponding to C-O, C-Br, and O-CH 3 stretching vibrations. ...
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The heterocyclic Schiff bases (N1Z,N4Z)-N1,N4-bis(3,4-methoxyphenyl)methylidene) benzene-1,4-diamine (1), (N1Z,N4Z)-N1,N4-bis(4-bromobenzylidene)benzene-1,4-diamine (2) and (N1Z,N4Z)-N1,N4-bis(furan-2-ylmethyliden)benzene-1,4-diamine (1) were synthesized by the reported procedure. The molecular structure of the compounds (1‒3) was characterized by FT‒IR and 1H NMR. The bond length, bond angle and HOMO‒LUMO energy gap were calculated out by DFT calculations. The synthesized heterocyclic compounds (1‒3) were screened for their antibacterial activity against Staphylococcus aureus and Escherichia coli. The compound 3 displays superior antibacterial activity compared to standard drug Streptomycin. All the compounds significantly interact with antibacterial protein beta-ketoacyl-acp synthase III and anticancer protein c-Kit tyrosine kinase via p–p, σ–p, hydrogen bonding, electrostatic and van der Waals interactions.
... N-benzylideneanilines are used as pigments, dyes, catalysts, intermediates in organic synthesis, polymer stabilizers, and they also exhibit a wide range of biological activities such as antifungal, antibacterial, antimalarial, antiproliferative, anti-inflammatory, antiviral and antipyretic properties. [18][19][20][21] It is observed that organic compounds such as stilbenes, azobenzenes, Nbenzylideneanilines and its derivatives exhibit conformational changes due to the rotation along longest molecular axis and consequently the molecules result in dynamic disorder displayed in their crystal structures. [22][23][24] The conformational interchange is recognized based on variable temperature single crystal X-ray diffraction and in the case of stilbenes and azobenzenes the dynamic disorder is explained as a "pedal motion" in literature. ...
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Search for multifunctional organic compounds which display technologically important properties has been pursued in recent years. Here we report the synthesis and structure of a series of single component N-benzylideneaniline analogues 4-(4-(4-nitrobenzylideneamino)benzyl)oxazolidin-2-one(NBOA), 4-(4-(4-chlorobenzylideneamino)benzyl)oxa-zolidin-2-one(CBOA) and 4-(4-(4-hydroxybenzy-lideneamino)benzyl)oxazolidin-2-one (HBOA). The dynamic disorder observed in the structure of NBOA is investigated using variable temperature single crystal X-ray diffraction. All three compounds display second harmonic generation, well defined PE loops with hysteresis at room temperature typical of ferroelectric materials and significant dielectric behavior with tolerance towards high electric fields.
... The ligand shows absorption between 250-310 nm which is intra-ligand charge transfer π-π* transitions of the ligand [19].The absorption bands in the region 370-420 nm is attributed to the metal -ligand charge transfer. The [Co(L)]Cl2complexhas a low intensity band at 640 nm is indicative of square planar geometry [20] and is assigned to the 4 A2g → 4 T1g transition of Co(II).The absorption spectrum of the [Ni(L)]Cl2complex display a low intensity band at 602 nm is due to the square planar environment around Ni(II) [21], and is assigned to the 1 A1g → 1 B1g transition. The absorption spectrum of the [Cu(L)]Cl2complex exhibit a weak band at 678 nm is indicative of square planar geometry [22] and is assigned to the 2 B1g → 2 Eg transition. ...
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A new series of Co(II), Ni(II), Cu(II) and Zn(II) complexes of the type [M(L)]X2 of a novel acyclic ligand derived from acenaphthene quinone and 1,8-diaminonaphthalene have been synthesized and characterized by spectroscopic studies. The synthesized compounds were characterized by molar conductance measurements, EI mass, 13 C NMR, FT-IR and electronic spectral studies. The electronic absorption spectral data of the complexes suggest square planar geometry around the central metal ions. All the complexes are soluble in DMF and DMSO and are 1:2 electrolytes. The interaction of the complexes with calf thymus (CT) DNA has been studied using absorption spectra, emission spectra, circular dichroic spectra and viscosity measurement. Spectrophotometric titrimetry revealed that the maximum absorption peak of the complex in the UV region, and showed an obvious hypochromic and bathochromic effects in the presence of increasing amount of DNA, suggesting thatthe complexes could intercalate into the base pairs of DNA. This result was further affirmed by the CD spectra, fluorescent ethidium bromide (EB) displacement experiments and viscosity measurements.
... The absorption band in the region 350-430 nm is attributed to the metal -ligand charge transfer. The Co(II) complex shows a low intensity band at 575 nm corresponding to 4 A2g → 4 T1g transition, which reveals that Co(II) complex exists in square-planar geometry [20]. The Ni(II) complex shows a low intensity band at 608 nm, which is assigned to 1 A1g → 1 B1g transition, arising from the square planar environment around the Ni(II) ion [21]. ...
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The DNA binding capability of the four novel transition metal complexes containing macroacyclic Schiff base ligand of the type N 1 ,N 8-bis(9-(benzylimino)phenanthren-10-ylidene)naphthalene-1,8-diamine were synthesized and structurally characterized by elemental analysis, IR and 13 C NMR and mass spectral studies. Spectroscopic data suggested the square planar geometry for all the complexes. Binding studies of these complexes with double-stranded (ds) DNA were analysed by absorption spectra, emission spectra, CD spectra and viscosity studies. The results revealed that the metal complex intercalates into the DNA base stack as intercalator. The intrinsic binding constant Kb and the apparent binding constant Kapp has been estimated at room temperature. These binding constant values for all the complexes obtained from absorption spectra and fluorescence spectra indicate that the complexes intercalate between the base pairs of the CT-DNA tightly.
... The absorption bands in the region350-380 nm are attributed to the metal -ligand charge transfer bands. The [Co(L)]Cl 2 complexhas a low intensity band at 560 nm is indicative of square planar geometry and is assigned 4 A 2g → 4 T 1g transition [34]. The absorption spectrum of the [Ni(L)]Cl 2 complex displays a low intensity band at 615 nm, which is due to the 1 A 1g → 1 B 1g transition, and assigned square planar geometry [35]. ...
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N) band in IR spectra and the signal observed in 13 C-NMR spectra. The stoichiometry and the nature of the complexes have been deduced from the results of elemental analyses and conductance data. The structural distortion in Cu(II) complex has been deduced on EPR data. The electrochemical behaviour of the Cu(II) complex has been studied by cyclic voltammetry. Absorption, Fluorescence, circular dichroism and viscosity measurement studies on the complexes proved a significant binding to calf thymus DNA.
... B.M. corresponding to one unpaired electron on a Cu(II) ion in an ideal square planar and/or octahedral environment ( Table 1). The electronic spectrum of complex (1) showed two bands at 2 B 1g ? 2 A 1g (17,825 cm -1 ) and 2 B 1g ? 2 E (22,270 cm -1 ), transitions, for square planar geometry [47,48]. The observed magnetic moment of 1.72 B.M. further supported the electronic results. ...
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Metal(II) complexes of 4-(((2-hydroxynaphthalen-1-yl)methylene)amino)-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one (HL) were prepared, and their compositions and physicochemical properties were characterized on the basis of elemental analysis, with1HNMR, UV–Vis, IR, mass spectroscopy and thermogravimetric analysis. All results confirm that the novel complexes have a 1:1 (M:HL) stoichiometric formulae [M(HL)Cl2] (M = Cu(II)(1), Cd(II)(5)), [Cu(L)(O2NO)(OH2)2](2), [Cu(HL)(OSO3)(OH2)3]2H2O(3), [Co(HL)Cl2(OH2)2]3H2O(4), and the ligand behaves as a neutral/monobasic bidentate/tridentate forming a five/six-membered chelating ring towards the metal ions, bonding through azomethine nitrogen, exocyclic carbonyl oxygen, and/or deprotonated phenolic oxygen atoms. The XRD studies show that both the ligand and Cu(II) complex (1) show polycrystalline with monoclinic crystal structure. The molar conductivities show that all the complexes are non-electrolytes. On the basis of electronic spectral data and magnetic susceptibility measurements, a suitable geometry has been proposed. The trend in g values (gll > g⊥ > 2.0023) suggest that the unpaired electron on copper has a dx2−y2dx2−y2 character, and the complex (1) has a square planar, while complexes (2)and (3) have a tetragonal distorted octahedral geometry. The molecular and electronic structures of the ligand (HL) and its complexes (1–5) have been discussed. Molecular docking was used to predict the binding between HL ligand and the receptors of the crystal structure of Escherichia coli (E. coli) (3t88) and the crystal structure of Staphylococcus aureus (S. aureus) (3q8u). The activation thermodynamic parameters, such as activation energy (Ea), enthalpy (ΔH), entropy (ΔS), and Gibbs free energy change of the decomposition (ΔG) are calculated using Coats–Redfern and Horowitz–Metzger methods. The ligand and its metal complexes (1–5) showed antimicrobial activity against bacterial species such as Gram positive bacteria (Bacillus cereus and S. aureus), Gram negative bacteria (E. coli and Klebsiella pneumoniae) and fungi (Aspergillus niger and Alternaria alternata); the complexes exhibited higher activity than the ligand.
... ppm correspond to aromatic ring protons of isatin and 3,4-diaminobenzophenone moiety. 49 The macrocyclic Schiff base complex fabrication has been validated by the absence of resonance signal expected at 6.24 ppm corresponding to primary amine (NH 2 ) of 3,4diaminobenzophenone. 50 The 13 C-NMR spectrum of Zn(II) complex revealed strong resonance signal at 195.52 ppm assigned to pendant carbonyl carbons (>C=O) of 3,4-diaminobenzophenone moiety ( Figure S2 (b) in Supplementary Information). 51 The absence of a signal at 184 and 159 ppm inferred complete condensation of isatin with 3,4-diaminobenzophenone while the resonance signals observed at 143.07 and 137.44 ppm belonged to characteristic imine functions (>C=N). ...
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The 12-membered Schiff base macrocyclic complexes, [Dichloro [5,6;11,12-dibenzophenone-1,4,7,10-tetraazacyclododeca-1,3,7,9-tetraene-2,3,8,9-diindole] metal(II) [M = Co(II), 1; Ni(II), 2; Cu(II), 3 and Zn(II), 4] were synthesized via template condensation of isatin and 3,4-diaminobenzophenone. These four complexes were characterized employing the analytical, spectral viz., FTIR, NMR, Mass, UV-Vis, EPR, TGA/DTA and SEM. The formation of metal complexes has been confirmed on account of the characteristic band positions in FTIR spectra and resonance signals in NMR spectra while the absorption bands in UV-Vis spectra and magnetic moment analysis signify the geometry of the complexes. However, the EPR study inferred distorted octahedral geometry in Cu(II) complex. The binding profile of the metal complexes (1–4) with CT-DNA was monitored by fluorescence and circular dichroism (CD) spectroscopy coupled with molecular docking studies. The binding constants were found to be highest for complex 3. Further, the hypothesis of preferential binding in the minor groove of double-stranded DNA is supported by CD and docking results. The antioxidative properties showed substantial radical scavenging potency of the complex 3. The comparative in vitro antibacterial study of the metal complexes against different pathogenic microbes (S. aureus, E. coli and C. albicans) revealed enhanced activity for complex 3 which is further certified by its efficacy to resist biofilm formation as investigated by XTT reduction assay.
... The spectrum showed a singlet peak at around 2.09-2.15 ppm assigned to methyl proton (CH3, 6H) of the dimethyltin moiety (Raman and Thangaraja, 2005). The 1 H NMR spectra of all the zinc complexes gave a multiplet in the region δ 3.48-3.65 ...
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Complexes of Co(II), Ni(II), Cu(II), and Zn(II) containing N2S2 ligand have been synthesized from the template condensation reaction between 1,2-ethanedithiol, o-bromoaniline and dimethyl tin dichloride in 1:2:1 molar ratio. It resulted in the formation of new series of 11-membered N2S2-Tin macrocyclic complexes [MLX2Sn(CH3)2] (M=Co(II) or Zn(II); X=Cl or NO3); and [MLSn(CH3)2]X2 (M=Ni(II) or Cu(II); X=Cl or NO3). The complexes were characterized using techniques including elemental analyses, IR, 1H NMR, 119Sn NMR, EPR, electronic spectral studies, conductivity, and magnetic susceptibility measurements. The reducing power of the Co(II) and Cu(II) complexes have been checked and compared. The complexes derived from nickel and copper have been found to show square-planar geometry, while octahedral geometry is projected for the cobalt and zinc complexes.
... A series of 4-substited-emoni-methyltetrazole [1.5-a] quinoline with appropriate amine by refluxing in dioxane (Scheme 46). They have been evaluated for their antiinflammatory and antimicrobial activities [66]. Raman plexes of Cu (II) from salicylidine-4-aminoantipyrine and PhNH2/substituted anilines. ...
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Schiff bases are the most widely used organic compounds. They have been shown to exhibit a broad range of biological activities, including antifungal, antibacterial, antimalarial, antiproliferative, anti-inflammatory, antiviral, and antipyretic properties. This review summarizes the synthesis and biological activities of Schiff bases and their complexes.
... [25] However, a singlet at 8.04 ppm may be attributed to the pendant secondary amino protons (C-NH-C; 2H). [26] The proton resonance peaks expected for various aromatic moieties on the macrocyclic framework were observed as multiplets in the region 6.61-7.09 ppm. ...
Article
A 16-membered tetraazamacrocyclic ligand has been synthesized by condensation reaction of 2-methyl acetoacetanilide with 1,8-diaminonaphthalene, and the metal complexes of the type [MLCl2] [M = Co(II), Ni(II), Cu(II), Zn(II)] were prepared by interaction of the ligand with metal salts. The ligand and its complexes were characterized by various spectroscopic studies. The mode of bonding and the overall geometry of these complexes have been deduced by elemental analysis, molar conductance values, Fourier-transform infrared (FT-IR), 1H-nuclear magnetic resonance (NMR), fast-atom bombardment (FAB) mass, electron paramagnetic resonance (EPR), and ultraviolet–visible (UV-VIS) spectroscopy along with magnetic measurement studies. An octahedral geometry has been envisaged for all these complexes, while a distorted octahedral geometry has been noticed for the Cu(II) complex. The cyclic voltammograme of the Cu(II) complex exhibits a quasi-reversible one-electron transfer wave for the Cu(II)/Cu(I) couple. The low conductivity data of all the complexes suggest their nonionic nature. These complexes have also been screened against pathogenic bacteria and fungi in vitro as growth-inhibiting agents.
... Raman et al47 have reported the synthesis of a novel 14-membered macrocyclic Schiff base derived from 3-cinnamalideneacetanalide and o-phenylenediamine which acts as a tetradentate and strongly conjugated ligand to form a cationic solid complex with Cu(II)/Ni(II)/Co(II) and /Zn(II). The ligand and the complexes were characterized by the usual spectral and analytical techniques. ...
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A new dialdehyde 1,5-bis(2-formylphenyl)pentane was synthesized from 1,5-dibromopentane with salicylaldehyde and K2CO3; macrocyclic ligand was synthesized by reaction of 2,6-diaminopyridine and 1,5-bis(2-formylphenyl)pentane. Cu(II), Ni(II), Pb(II), Zn(II), Cd(II) and La(III) complexes were synthesized by reaction of the ligand and Cu(ClO4)2 · 6H2O, Ni(ClO4)2 · 6H2O, Pb(ClO4)2 · 6H2O, Zn(ClO4)2 · 6H2O, Cd(ClO4)2 · 6H2O and La(ClO4)3 · 6H2O, respectively. The ligand and its metal complexes have been characterized by elemental analysis, IR, 1H and 13C NMR, UV-Vis spectra, magnetic susceptibility, conductivity measurements and mass spectra. All complexes are diamagnetic and Cu(II) complex is binuclear.
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Discrete event systems is a class of dynamic systems, which evolution s are characterized by asynchronous occurrences of discrete events. The complexity of these systems is important. This complexity can make fault appearance very often. For this reason, the diagnosis task is needed as it is one of the key technologies guaranteeing the system safety and reliability. In this context, t his paper deals with discrete event systems diagnosis. We propose a general app roach based on the use of Petri Nets in order to on-line diagnose multiple event and state faults. Petri Nets are particularly useful as they are intuitive graphical modelling language and advanced formal analysis method. Nowadays, they are considered as one of the main formalisms for modelling , analysis and control of discrete event systems (DES). Petri Nets are used, in our work, for modelling and diagnosis purposes. The proposed approach consists in defining a diagnosis Coverability tree and using invar iants to check the system place and state faults. To test the effectiveness of the proposed approach a diagnosis benchmark is used: the three- tank hydraulic system. A comparison between the results given by using the proposed Petri Nets approach and those given by automata tool is finally made.
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Knoevenagel condensate-based Schiff base ligands (L) containing N and S donor sites have been designed and synthesized [L = 3-cinnamalideneacetylacetonethiosemicarbazone (CAT)/3-cinnamalideneacetylacetoneethylthiosemicarbazone (CAET)/3-cinnamalideneacetylacetonephenylthiosemicarbazone (CAPT)]. They afford complexes of the type [ML] [M = Cu(II) and Zn(II)]. Both the ligands and their complexes were characterized by analytical and spectral data. Intercalative binding of these complexes with DNA has been investigated by electronic absorption spectroscopy, viscosity measurements, cyclic voltammetry, and differential pulse voltammetry. Electrophoretic study of the complexes indicates that they efficiently cleave supercoiled pUC19 DNA in the presence of hydrogen peroxide.
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A macrocyclic Schiff-base (H2L) ligand is prepared via condensation of 2,6-pyridine dicarboxaldehyde with triethylene tetramine. The ligand is characterized using elemental analysis, by mass spectrometry, infrared (IR) spectroscopy, and proton nuclear magnetic resonance spectroscopy. The corresponding 1:1 metal complexes with Cr(III), Fe(III), Co(II), Ni(II), Cu(II), Cd(II), UO2(II), and Th(IV) are additionally characterized by determining their magnetic moment, molar conductance, thermal analysis (thermogravimetry and differential thermoanalysis), and solid reflectance measurements. The complexes have the general formulae [M(H2L)(H2O)](X) n · yH2O (X = Cl or AcO, n = 2,3, y = 2–5) except for the Th(IV) complex having the formula [Th(H2L)(Cl)]Cl3. The molar conductance data reveal that all the metal chelates are electrolytes. IR spectra show that H2L is coordinated to the metal ions in a neutral pentadentate manner with 5N donor sites of the two azomethine–N, pyridine–N, and two amino–NH groups. The magnetic and solid reflectance spectra reveal that the complexes are octahedral. Thermal analysis shows that the complexes decompose in four to five steps. The activation thermodynamic parameters are calculated using the Coats–Redfern method. The parent Schiff base and its eight metal complexes were assayed against four bacterial species, two Gram negative, and two Gram positive. The Schiff base and five of its metal complexes showed antibacterial activity at different rates. The complexes Cr(III) and Cu(II) inhibited Gram-positive bacteria, while Co(II) complex inhibited all tested bacteria greater than the parent Schiff base. Three metal complexes (Ni, Cd, and Th) completely missed antibacterial activity.
Article
Two Schiff bases, L1 (5,6;11,12-dibenzophenone-2,3,8,9-tetramethyl-1,4,7,10-tetraazacyclododeca-1,3,7,9-tetraene) and L2 (6,7;13,14-dibenzophenone-2,4,9,11-tetramethyl-1,5,8,12-tetraazacyclotetradeca-1,4,8,11-tetraene), bearing functionalized pendant arms have been synthesized by cyclocondensation of 3,4-diaminobenzophenone with 2,3-butanedione and 2,4-pentanedione, respectively. Mononuclear macrocyclic complexes [FeL1Cl2]Cl, [FeL2Cl2]Cl, [ML1Cl2], and [ML2Cl2] (where M = Co(II) and Cu(II)) have been prepared by reacting iron(III), cobalt(II), and copper(II) with the preformed Schiff base. The ligands and their corresponding metal complexes were characterized by elemental analyses, ESI-mass spectra, conductivity, magnetic moments, UV-Vis, EPR, IR, 1H-, and 13C-NMR spectral studies, and TGA-DTA/DSC data. The TGA profiles exhibit a two-step pyrolysis, although the iron complexes decompose in three steps, leaving behind metal oxides as the final product. The ligands and complexes were screened in vitro against Gram-positive bacteria, Gram-negative bacteria, and fungi.
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Knoevenagel condensate Schiff base ligands [L = 3- cinnamalideneacetylacetone-thiosemicarbazone (CAT)/3-cinnama- lideneacetylacetoneethylthiosemicarbazone (CAET)/3- cinnamalideneacetylacetonephenylthiosemicarbazone (CAPT)] and their copper/zinc complexes were synthesized. They were characterized by analytical and spectral techniques. From these data it was found that the ligands adopt square-planar geometry on metalation with Cu2+ and Zn2+. To evaluate the antitumor and cytotoxic activity of the synthesized complexes in mice and human cancer cell lines, the antitumor activity of the complexes was evaluated against an Ehrlich ascites carcinoma (EAC) tumor model. The activity was assessed using survival time and short-term in vitro cytotoxic activity. Oral administration of complexes (100 mg/kg) increased the survival time. The cytotoxic activity of complexes was evaluated using human breast cancer (MDA-MB-231), colon cancer (HCT-116) and nonsmall lung cancer (NCI-H-23) cell lines. Both the complexes possessed significant antitumor and cytotoxic activity on EAC and human cancer cell lines. The in vitro antimicrobial screening effect of the investigated compounds was also tested against the various organisms by well diffusion method.
Article
A new series of 14-membered pendant arm hexaazamacrocyclic complexes of the type [MLX2]·[M=Co(II), Ni(II), Cu(II) or Zn(II) for X=Cl; Co(II), Ni(II), Cu(II) or Zn(II) for X=NO3] has been synthesized by metal template condensation of 1,2-phenylenediamine and 1,4-phenylenediamine with formaldehyde in methanol. The mode of bonding and overall geometry of these complexes have been deduced by elemental analyses, molar conductance values, FT-IR, 1H-NMR, 13C-NMR, EPR, ESI-mass and UV–VIS along with magnetic measurement studies. The fluorescence and UV–VIS studies revealed a significant binding ability to DNA.
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The Schiff base ligand, N,N'-bis-(2-furancarboxaldimine)-3,3'-diaminobenzidene (L) obtained by condensation of 2-furaldehyde and 3,3'-diaminobenzidene, was used to synthesize the mononuclear complexes of the type, [M(L)](NO3)2 [M=Co(II), Ni(II), Cu(II) and Zn(II)]. The newly synthesized ligand, (L) and its complexes have been characterized on the basis of the results of the elemental analysis, molar conductance, magnetic susceptibility measurements and spectroscopic studies viz, FT-IR, 1H and 13C NMR, mass, UV-vis and EPR. EPR, UV-vis and magnetic moment data revealed a square planar geometry for the complexes with distortion in Cu(II) complex and conductivity data show a 1:2 electrolytic nature of the complexes. Absorption and fluorescence spectroscopic studies support that Schiff base ligand, L and its Cu(II) and Zn(II) complex exhibit significant binding to calf thymus DNA. The highest binding affinity in case of L may be due to the more open structure as compared to the metal coordinated complexes.
Article
14 and 16 membered Schiff base macrocyclic ligands, 7,14-dimethyl-5,12-di(N-amino)-2-methylphenyl-1,4,8,11-tetraaza-cyclotetradecane-4,7,11,14-tetraene (L(1)) and 8,16-dimethyl-6,14-di(N-amino)-2-methylphenyl-1,5,9,13-tetraaza-cyclohexadecane-5,8,13,16-tetraene (L(2)) were synthesized by condensation reaction between 2'-methyleacetoacetanilide and aliphatic diamines. The metal complexes of the types, [ML(1)](NO(3))(2) and [ML(2)(NO(3))(2)] [M = Co(II), Ni(II), Cu(II) and Zn(II)] were prepared by interaction of ligands, L(1) or L(2) with hydrated metal(II) nitrates. The ligands and their complexes were characterized by elemental analysis, IR, (1)H and (13)C NMR, EPR, UV-Vis spectroscopy, magnetic susceptibility, conductivity measurements and ESI-mass spectral studies. The results of elemental analyses, ESI-mass and conductivity measurements confirmed the stoichiometry of ligands and their complexes while the characteristic absorption bands and resonance peaks in IR and NMR spectra confirmed the formation of ligand frameworks around the metal ions. The square planar geometry for complexes derived from ligand L(1) and octahedral environment for complexes derived from ligand L(2) with distortion in Cu(II) complex have been confirmed on the basis of results of electronic and electron spin resonance spectral studies and magnetic moment measurements. Absorption and fluorescence spectral studies revealed different binding mode for complex, [CuL(1)](NO(3))(2) as compared with [CuL(2)(NO(3))(2)] on interaction with calf thymus DNA.
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The present paper is a report on the synthesis and characterisation of some tin(II) and tin(IV) macrocyclic Schiff base complexes. These complexes have been prepared by the reaction of tin dichloride, tin tetrachloride and dimethyltin dichloride with 1,3-diaminopropane and benzil or m-phenylenediamine and acetylacetone in oxygen-free nitrogen atmosphere using THF as the reaction medium. On the basis of elemental analyses, conductance measurements, molecular weight determinations, and 119Sn Mössbauer, electronic, infrared, 1H NMR and 119Sn NMK spectral studies, structures have been proposed for these new complexes.
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A series of symmetrical tetradentate Schiff bases derived from substituted salicylaldehyde and ethylenediamine were prepared and characterized by elemental analysis, IR, UV-Visible and H NMR spectroscopy. The interaction of these bases with MnCl2 4H2O and CuCI2 2H2O have been studied, leading to the preparation of manganese(II) and copper(II) complexes. Microanalysis, molar conductance, IR, UV-Visible spectroscopy, magnetic measurements and ESR spectra have been used to elucidate the stucture of the resultant complexes The experimental data show that all the Schiff base Iigands N, N′-bis(2-hydroxybenzyl)ethylenediimine (H2L.), N, N′-bis(2-hydroxyacetophenyl)ethylenediimine (H2L) and N, N′-bis(2-hydroxypropiophenyi)ethylenediimine (H2L) yield 1:1 compounds except for the ligand H2L which gave a 2:1 compound with manganese(II) The spectral studies support the binding of the Iigands with two N. and two O donor sites to the metal(II) ion, giving an arrangement of N2O2 donor groups Magnetic and ESR data indicate that the manganese(II) adopts a high spin configuration in the complexes studied and the covalent character of the metal-ligand bonding in the copper(II) complexes increases with the increasing electron donating effect of the ligand substituents R. The electrochemical behaviour of the manganese(II) and the copper(II) complexes was determined by cyclic voltammetry which shows that the chelate structure and electron donating effects of the ligand substituents are among the factors influencing the redox potentials of the complexes
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Two macrocyclic copper(II) complexes, [CuL1](ClO4)2 (L1 = 2,6,9,13-tetraparacyclophane, a Schiff base) and [CuL2]Cl2 [L2 = 3,10-bis(2-benzyl)-1,3,5,8,10,13-hexaazacyclotetradecane] have been prepared and characterized by elemental analysis, u.v.–vis., i.r. and mass spectra. Absorption, fluorescence, circular dichroic spectra and viscosity experiments have been carried out on the interaction of the two complexes with calf thymus CT DNA. The results suggest that both complexes can bind to CT DNA by intercalation via the aromatic moiety ring in the macrocycle into the base pairs of DNA. [CuL1](ClO4)2 binds to CT DNA more strongly than [CuL2]Cl2. The position of the aromatic ring in the macrocycle plays an important role in deciding the extent of binding of the complexes to DNA. Significantly, the complexes have been found to be single-strand DNA cleavers in the presence of H2O2 or/and 2-mercaptoethanol.
Article
Palladium(II) and platinum(IV) chloride react with 2-substituted benzimidazole to give complexes of the formula MLCI where M = Pd(II) and Pt(IV), L = 1,2-bis(2-benzimidazolyl) ethanol (BBIE) and 1,2-bis(2-benzimidazolyl) ethane thiol (BBIET). These complexes have been characterized on the basis of elemental analysis, conductance measurement. IR and NMR studies. The square-plahar geometry has been suggested for these complexes. These complexes have been evaluated for their fungicidal activity against Alternaria alternata and Aspergillus niger by spore germination inhibition method.
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The theory of stationary electrode polarography for both single scan and cyclic triangular wave experiments has been extended to systems in which preceding, following, or catalytic (cyclic) chemical reactions are coupled with reversible or irreversible charge transfers. A numerical method was developed for solving the integral equations obtained from the boundary value problems, and extensive data were calculated which permit construction of stationary electrode polarograms from theory. Correlations of kinetic and experimental parameters made it possible to develop diagnostic criteria so that unknown systems can be characterized by studying the variation of peak current, half-peak potential, or ratio of anodic to cathodic peak currents as a function of rate of voltage scan.
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The oxidation of various [CuL] (where L are the dianions of quadridentate Schiff bases derived from salicylaldehyde, and 1,2-diaminoethane, namely 2,2′-[1,2-ethanediylbis(nitrilomethylidene)diphenatol], salen, its 1,3-propane homologue, saltn, or from glyoxal and ortho-aminphenol, namely 2,2′-[(ethanediimine)diphenato], glyaph, as well as some of their analogues) has been studied by cyclic voltammetry. Anodic sweeps show one, or two, usually irreversible, oxidation peaks originated by the presence of CuII, since neither LH2 nor [ZnL] are oxidized under the same conditions. The oxidations of the 5-NO2-substituted derivatives are reversible at high scan rate (1 V s−1). The oxidation potentials of the complexes with substituents at the aromatic rings suggest that the electronic influence of such substituents are transmitted to the metal centre via the phenato, rather than the azomethine groups. The glyaph and saltn derivatives are oxidized at potentials higher than the corresponding salen complexes. Electronic and ESR spectroscopy studies on [CuL] samples, oxidized with a H2O2/H5IO6 mixture, suggest that the initially formed [CuIIIL]+ rapidly decomposes to CuII species, presumably through [Cu(II)0L ·]+ intermediates. Some poorly stable complexes of the formula [CuL]HSO4·2H2O have been isolated.
Article
New copper(II) complexes [Cu(H2L)(H2O)n]Cl2·xH2O (n = 0 or 2) with linear and tripodal tetradentate ligands have been synthesized and characterized using elemental analysis, molar conductance, IR spectra, magnetic measurements, electronic and ESR spectra. The spectral studies support the binding of linear ligands with two N and two O donor sites to copper(II) ion, providing a square planar geometry and show also that tripodal ligands were coordinated to the metal ion by oly one nitrogen atom, giving an arrangement of NO3 donor groups, the other axial sites being occupied by the solvent. The ESR data indicate that the covalent character of the metal-ligand bonding in the copper(II) complexes increases with increasing electron donating effect of the ligand substituents R. From the results of cyclic voltammetry, it is shown that chelate structure and ligand geometry, steric bulk and electron donating effects of the ligand substituents are among the factors influencing the redox potentials of the complexes.
Article
Two new hexadentate ligands having thioether and thiolate groups in pairs along with two amide nitrogens have been synthesized. The thiols are protected as their tertiary butyl derivatives. On refluxing the ligands with a copper(II) or a nickel(II) salt in isopropanol, the S-tertiary butyl group was cleaved to form the corresponding hexa-coordinated neutral complex with the chromophore MIIN2S*2S2, where the four sulphurs are equatorial and the amide nitrogens are axial. Both the copper(II) complexes show pseudo-reversible responses (ΔEp = 100 mV) in cyclic voltammograms with E = 0.5 V vs S.C.E. at room temperature in acetonitrile, attributable to a CuIII/CuII couple. The corresponding nickel(II) complex shows an irreversible response in the region −1.0 to +1.0 V. In their electronic spectra the copper(II) complexes show a strong band near 600 nm, attributable to a σ(thiolate) → CuII LMCT transition. Each of the copper(II) complexes show ligand field bands typical of a tetragonally distorted octahedral complex. The nickel(II) complexes show three ligand field bands typical of octahedral geometry.
Article
The ‘half-unit’ (AEH) obtained by reacting equimolar quantities of pentane-2,4-dione and diaminoethane may be used to produce non-symmetrical tetradentate Schiff base. The species under examination results from the condensation of an (AEH) unit with 3-(ethoxymethylene)-2,4-pentanedione. This ligand and its copper(II) and nickel(II) complexes display two carbonyl groups which, according to various physical probes, are very different; one is strongly affected by a COCH3 substituent while the other (which is far remote from this substituent) is almost unaffected. However, both groups are amenable to condensation with ethylenediamine to yield a new type of macrocyclic complex. The properties of the related 13-acetyl-5,7-14-trimethyl-1,4,8,11-tetraazacyclotetradeca-4,6,12,14-tetraenato-(2−) copper(II) and nickel(II) are reported.
Article
Four cobalt(II) tetraaza macrocyclic complexes of the ‘lacunar cyclidene’ type have been prepared, including two new, unbridged, examples. The reactions of these complexes with oxygen have been investigated, either in solution, in a mixture of acetonitrile–pyridine (4 : 1 v/v), or when dispersed in the matrix of a copolymer containing 4-vinylpyridine (vpy), dissolved in dichloromethane. Three different copolymers have been used as supporting matrices (vpy content in parentheses); vpy–styrene (6.2), –methyl methacrylate (5.2) and –butyl methacrylate (15.2%). The oxygenation reactions have been studied both by ESR spectroscopy of frozen solutions and by electronic spectroscopy at or near room temperature. The presence of the polymeric supports has a marked influence on both the formation of Co–O2 adducts and their stability with respect to autoxidation. The polymer-supported ‘copoly complex’ oxygen adducts have much greater lifetimes than those of the O2 dioxygen adducts of the same complexes ‘free’ in solution. The results are discussed in terms of the complex structure, polymer type and the temperature of the reaction.
Article
Two cationic mixed-ligand complexes, [Co(L)cyc]NO3 C2H5OH (A) and [Co2(L)tpmc](CJO4)2 CH3CN (B), were prepared, where eye = 1, 4, 8, 11-tetraaza-cyclotetradecane, tpmc = N, N′, N″, N′″-tetrakis(2-pyridylmethyl)-1, 4, 8, 11-tetraaza-cyclotetradecane and L = bicyclo[2. 2. 1]-hept-5-en-endo-2, 3-cis-dicarboxylate dianion. The complexes were characterized by elemental analyses, ion-exchange chromatography, magnetic moments, conductance measurements, IR, C NMR and UV/VIS spectroscopy and cyclic voltammetry. It is suggested that the complexes A and B have octahedral structures with endobidentate or exo-(bis)-bidentate coordination of L.
Article
Three ligands have been formed by the 1:2 molar condensation of ℴ-phenylenediamine with salicylaldehyde, 2-hydroxy-l-naphthaldehyde or ℴ-hydroxyacetophenone. The potentially tetradentate ligands are N,N-bis-(salicylaldehyde)-ℴ-phenylenediamine (SalophH2), N,N-bis(2-hydroxy-1-naphthalde-hyde)-ℴ-phenyIenediamine (NophH2) and N,N-bis(ℴ-hydroxyacetophenone)-ℴ-phenylenediamine (AophH2), respectively. These ligands form 1:1 complexes with nickel, copper and zinc ions. The complexes have been characterized by IR, H NMR, MS, UV/Vis spectra in addition to elemental analyses. The spectral data of the ligands and their complexes are discussed in connection with the structural changes which occur due to complexation.
Article
The readily available complex [Ti(NBu(t))Cl-2(Bu(t)py)(2)](Bu(t)py = 4-tert-butylpyridine) is a useful precursor to a range of sandwich- and half-sandwich titanium imido derivatives including [Ti(eta-C(9)H(4)Me(3)) (NBu(t))Cl(Bu(t)py)] (C(9)H(4)Me(3) = trimethylindenyl), [Ti(eta-C5H5)(2)(NBu(t))(Bu(t)py)], [Ti(dmbpz)(NBu(t))Cl(Bu(t)py)] [dmbpz = tris(3,5-dimethylpyrazolyl) borate] and [Ti(eta(4)-Me(n)taa)(NBu(t))] {n = 4 or 8; Me((4 or 8))taa = (tetra- or octa-)methyl-dibenzotetraaza[14]annulene respectively}.
Article
The tetraaza macrocycle-supported titanium and zirconium imido complexes [Ti(NR)(Mentaa)] [R = But, Ph, Tol or 4-C6H4NO2; n = 4 or 8 where H2Mentaa = tetra- or octa-methyldibenzotetraaza[14]annulene, respectively] and [Zr(NC6H3Pri2-2,6)(py)(Me4taa)] react with isocyanates or carbon dioxide to form cycloaddition products generally of the type [M{N(R)C(O)E}(Mentaa)] (M = Ti or Zr, R = aryl or tert-butyl, E = O, NBut or N–aryl). The complex [Zr{N(C6H3Pri2-2,6)C(O)N(But)}(Me4taa)] is also formed by reaction of the bis(arylimide) [Zr(NHC6H3Pri-2,6)2(Me4taa)] with ButNCO. The crystal structures of [Ti{N(Tol)C(O)O}(Me4taa)] (Tol = p-tolyl) and [Zr{N(C6H3Pri2-2,6)C(O)N(But)}(Me4taa)] are described. The tert-butyl imido complexes [Ti(NBut)(Mentaa)] (n = 4 or 8) react with Ph2NNH2 to give the corresponding terminal N,N-diphenylhydrazido derivatives [Ti(NNPh2)(Mentaa)] and these yield the cycloaddition products [Ti{N(NPh2)C(O)O}(Mentaa)] or [Ti{N(NPh2)C(O)N(Tol)}(Me4taa)] with CO2 or TolNCO, respectively. The related titanium oxo complexes [Ti(O)(Mentaa)] (n = 4 or 8) react with p-tolyl isocyanate to form the N,O-carbamate products [Ti{N(Tol)C(O)O}(Mentaa)], and with ditolylcarbodiimide to form the N,N-ureate derivative [Ti{N(Ph)C(O)N(Ph)}(Mentaa)] in which complete rupture of the TiO linkage has occurred. Reaction of the N-phenyl-N-tolyl (asymmetric) ureate [Ti{N(Ph)C(O)N(Tol)}(Me4taa)] with an excess of PhNCO gave quantitative conversion to the N,N-symmetric product [Ti{N(Ph)C(O)N(Ph)}(Me4taa)] and TolNCO. Crossover NMR tube experiments suggest that this reaction occurs via an associative mechanism.
Article
Tetraaza macrocycle-supported tert-butyl titanium imido complexes [Ti(NBut)(Mentaa)] (n = 4 2 or 8 3; H2Mentaa = 6,8,15,17-tetra- or 2,3,6,8,11,12,17,18-octa-methyl-5,14-dihydrodibenzo[b,i][1,4,8,11]tetraazacyclotetradecine, respectively), [Ti(NBut)(Me4taen)] (5, H2Me4taen = 5,7,12,14-tetramethyl-1,4,8,11-tetraazacyclotetradeca-4,6,11,13-tetraene) and [Ti(NBut)(TTP)] (6, H2TTP = 5,10,15,20-tetratolylporphyrin) together with the N2O2-donor Schiff base analogue [Ti(NBut)(acen)] (7, H2acen = 4,9-dimethyl-5,8-diazadodeca-3,9-diene-2,11-dione) were prepared in good yield from the readily available [Ti(NBut)Cl2(py)3] and the dilithium or disodium salts of the tetradentate ligands. The TiNBut groups in 2 and 3 underwent imido group exchange reactions with anilines to form [Ti(NR)(Mentaa)] (n = 4, R = C6H3Me2-2,6 4, Ph, C6H4(NO2)-4, C6H4(NMe2)-4; n = 4 or 8, R = C6H4Me-4), and with H2E (E = O or S) to give the oxo and sulfido analogues [Ti(E)(Me4taa)]. Compound 4 was also prepared in good yield from [Ti(NC6H3Me2-2,6)Cl2(py)3] and Li2[Me4taa]. Reaction of 2 with 2 or 1 equivalents of ROH (R = Me or C6H3Me2-2,6) or pinacol afforded [Ti(OR)2(Me4taa)] and [Ti{OC(Me)2C(Me)2O}(Me4taa)] respectively. The crystal structures of 3 and 4 have been described.
Article
[VO(acac)2] serves as a good precursor and undergoes ligand exchange reaction where one or both acetylacetonato groups can easily be exchanged with organic ligands having coordinating atoms of different potentialities. Usually oxovanadium(IV) complexes form when [VO(acac)2] reacts with ligands under anhydrous conditions. Under aerobic conditions most vanadium complexes stabilize in their highest oxidation state (i.e. V). Factors such as nature of ligands, solvents, pH of the reaction and reaction medium etc. have, however, great influence on the stoichiometry and nature of the resulting complexes. The synthesis and structural characterization of these oxovanadium(V) and dioxovanadium(V) species and their reactivities are considered in this review. Complexes containing phosphorus, and macrocyclic, ligands have also been incorporated. The abstraction of oxygen from [VO(acac)2] under typical reaction conditions and design of non-oxovanadium complexes have also been demonstrated. Relevant coordination chemistry of oxovanadium(IV) is considered where ever necessary.
Article
We have been interested in the coordination behaviour of biologically active ligands containing N and O donor atoms towards metal ions and boron. Structural and spectroscopic studies have been carried out. Also, the stability, chemical structure and behaviour of some of the coordination compounds in solution have been studied and their effect on photosynthetic activities investigated.
Article
Single condensation of acetylacetone (AcacH) with 1,2-diaminoethane (En) yields the terdentate “half-unit” 7-amino-4-methyl-5-aza-3-hepten-2-one (abbreviated as AEH). In the presence of a metal ion, this ligand leads to the macrocycle 5,7,12,14-tetramethyl-1,4,8,11-tetraazacyclo tetradeca-4,6,11,13-tetraene, which can be considered as resulting from the condensation of two molecules of (AcacH) with two molecules of (En). This “half-unit” can also be used to obtain acyclic ligands and complexes made with one (AcacH) molecule and two (En) molecules (1:2) or conversely two (AcacH) molecules and one (En) molecule (2:1). Using reagents other than (AcacH) and (En), this “half-unit” may yield homo and heterodinuclear complexes, macrocyclic compounds and non-symmetrical tetradentate Schiff bases.
Article
ESR spectra of copper complexes have been interpreted by means of molecular orbital theory, and the ``covalent'' character of both σ and π bonds have been discussed for a variety of compounds. Overlap integrals have been considered in a consistent manner in treating σ bonds. Particular attention has been given to Cu phthalocyanine and several of its derivatives. The in‐plane π bonding may be as important in determining the properties of a Cu complex as is the in‐plane σ bonding.
Article
The new Schiff base 14-membered macrocycles, 1,5,8,12-tetraazacyclotetradeca-6,7,13,14-tetraaminoacetic acid-5,7,12,14-tetraene (L-1), 1,5,8,12-tetraazacyclotetradeca-6,7,13,14-tetraaminophenyl-5,7,12,14-tetraene (L-2) and 1,5,8,12-tetraazacyclotetradeca-6,7,13,14-tetraaminopyridyl-5,7,12,14-tetraene (L-3), have been synthesized by the reaction of N,N-dicarboxymethyloxamide, N,N-diphenyloxamide or N,N-dipyridyloxamide with 1,3-diaminopropane. Their complexes with Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) ions have been prepared and characterized by elemental analyses, IR, H-1 NMR and electronic spectra, magnetic moment and conductivity measurements. The complexes of the divalent metal ions are non-ionic while those of the trivalent metal ions appear to be 1:1 electrolytes. On the basis of these studies an octahedral geometry is proposed for all of the complexes.
Article
Cobalt(H) complexes of the general composition CoLX2 {where X = Cl, 1/2 SO4, NO3, and SCN; L = 2,3,8,9-tetramethyl-1,4,7,10-tetraazacyclododeca-1,3,7,9-tetraene [N-4] (DAED) or 2,3,8,9-tetraphenyl-5,11-dimethyl-1,4,7,10-tetraazacyclododeca-1,3,7,9-tetraene[N-4] (BDAP)} have been prepared. On the basis of electronic and EPR spectral studies, the chloro, nitrato and thiocyanato complexes were found to have six-coordinate, octahedral geometry and the sulfato complexes were found to have five-coordinate, trigonal-bipyramidal geometry.
Article
Several five- and six-coordinate ferric octaalkylporphyrin (OEP) complexes [Fe(OEP)X, X = ClO4-, SO3CF3-, SbF6-; [Fe(OEP)(3,5-Cl2Py)2]ClO4, Py = pyridine] previously reported to display quantum mechanically admixed intermediate-spin behavior have been spectroscopically examined as possible models for cytochrome c'. The magnetic behavior of the complexes has been confirmed using NMR and EPR spectroscopy. The magnetic circular dichroism (MCD) spectra of these complexes have been investigated in the Soret/visible (300-700 nm) and near-IR (700-2000 nm) regions for the first time and compared to the spectra of high-spin Fe(OEP)Cl and low-spin [Fe(OEP)(HIm)2]Cl and [Fe(OEP)(NMeIm)2]Cl. The MCD spectral features in the Soret/visible region of the four admixed intermediate-spin model complexes are similar in band shape and intensity to the spectrum reported for ferric cytochrome c' from Alcaligenes sp., NCIB 1105 (Yoshimura, T.; Suzuki, S.; Nakahara, A.; Iwasaki, H.; Masuko, M.; Matsubara, T. Biochim. Biophys. Acta 1985, 831, 267-274). The near-IR MCD spectra of these complexes are also very similar to those of cytochrome c' isolated from several bacterial sources (Rawlings, J.; Stephens, P. J.; Nafie, L. A.; Kamen, M. D. Biochemistry 1977, 16, 1725-1729) and are distinctly different from those of known high- and low-spin ferric heme systems or of complexes containing a thermal mixture of high- and low-spin states. These results provide new evidence for the utility of MCD spectroscopy, especially in the near-IR region, as a probe of spin state in ferric heme systems and support the use of the quantum mechanically admixed intermediate-spin ferric porphyrins examined herein as models of cytochrome c'.
Article
Four stable, neutral hexa-coordinated copper(II) complexes with the N2S2*S2 (S* = thioether) donor set have been isolated in the solid state. A dichloro complex of copper(II) has also been prepared with the chromophore CuN2S2*Cl2, where the two thiolates are replaced by two chlorides. These complexes have tetragonal coordination geometry around copper(II) with g| > ghu > ge and A| values within 101–115 G in acetonitrile glass, and show an intense absorption band around 600 nm attributable to thiolate → copper(II) LMCT transition. In acetonitrile the complexes show well-defined cyclic responses in their cyclic voltammograms at room temperature.
Article
New transition metal(II) coordination compounds of tetraaza macrocyclic chiral Schiff bases, derived from 2-hydroxybenzylideneacetylacetone or 4-hydroxybenzylideneacetylacetone and (1R, 2R)-(–)-1,2-diaminocyclohexane, have been prepared and characterised spectroscopically and electrochemically. E.p.r. spectral data for the CuII complexes reveal a strong metal-to-ligand -interaction in their square-planar configuration and the broadening of the g component is due to the strain created by 1R and 2R groups in the cyclohexane rings. The cyclic voltammetric (c.v.) data of the copper complexes show an unusual oxidation state of CuIII, while CoII complexes show a reversible CoII/CoIII redox peak along with an additional peak in the negative potential region characteristic of reversibly bound oxygen. The c.v. results reveal that both CuII and CoII complexes bind axially with added bases. The spectroscopic results reveal that copper, cobalt and nickel complexes are in square-planar geometry, whereas manganese is in octahedral geometry.
Article
A 14-membered macrocyclic Schiff base derived from 3-salicylideneacetylacetone ando-phenylenediamine acts as a tetradentate and strongly conjugated ligand to form a cationic solid complex with CuCl2. U.v.-vis. and e.s.r. spectral data reveal a strong ligand to metal -interaction in the square planar complex. C.v. data reveal that the title ligand is able to stabilize the copper(III) oxidation state more effectively than comparable saturated or partially unsaturated macrocyclic ligands and confers a weaker tendency for reduction of copper(II) to copper(I) and copper(0). While the inclusion of a PPh3 ligand suppresses the Cu0 CuI CuII oxidation, imidazole and pyridine strongly enhance the CuII CuIII oxidation of the complex.
Article
Two new, Schiff base ligands containing cyclobutane and thiazole rings, 4-(1-methyl-1-mesitylcyclobutane-3-yl)-2-(2,4-dihydroxybenzylidenehydrazino)thiazole (L1H) and 4-(1-methyl-1-mesitycyclobutane-3-yl)-2-(2-hydroxy-3-methoxybenzylidenehydrazino)thiazole (L2H) and their mononuclear complexes with a 1:2 metal-ligand ratio have been prepared with acetate salts of CoII, CuII, NiII and ZnII in EtOH. The structures of the ligands and their complexes have been established by microanalyses, i.r., u.v.–vis., 13C- and 1H-n.m.r. spectra, and by magnetic susceptibility measurements. The complexes are mononuclear. Thermal properties of the ligands and complexes have been studied by t.g.a. and d.s.c. techniques. Antimicrobial activities of the ligands and their complexes have been tested against eight different microorganisms. Some of the complexes and L1H were found to be active against some of the microorganisms studied.
Article
A series of new macrocyclic dioxotetraamine ligands having 2-methylfuran pendent(s), 4-(2-methylfuran)-1,4,7,10-tetraazacyclotridecane-11,13-dione (H2L1), 4,7-bis(2-methylfuran)-1,4,7,10-tetraazacyclotri-decane-11,13-dione (H2L2), 1-(2-methylfuran)-1,4,8,11-tetraazacyclotetradecane-5,7-dione (H2L3) and 1,11bis(2-methylfuran)-1,4,8,11-tetraazacyclotetradecane-5,7-dione (H2L4), have been synthesized and characterized. The solution behaviours of the copper(II) complexes of the four ligands have been studied with ESR, cyclic voltammetry (CV) and UV-vis techniques. A red-shift has been observed for the maximum absorption band of the electronic spectra of CuL1, CuL3 and CuL2, CuL4 in comparison to those of the corresponding unsubstituted copper(II) complexes CuL01 and CuL02, respectively. Electrochemical studies suggest that the introduction of 2-methylfuran pendant(s) to the macrocyclic dioxotetraamines destabilizes the CuIII ion comparing with the unsubstituted species for both of the two kinds of macrocycles (13-membered and 14-membered macrocycles). The copper(II) complex of (H2L2), has been isolated as a single crystal and the crystal structure determined by X-ray diffraction analysis. It is interesting that the complex has an N-meso chiral nitrogen configuration. The CuII atom is in five coordination environment with four basal nitrogen atoms and one axial oxygen atom from H2O, and it adopts a distorted square pyramidal configuration.
Article
Pyridine adducts of copper(II) complexes with thiosemicarbazones and semicarbazones have been synthesized and characterized using elemental analyses, molar conductance, IR spectra, magnetic measurements, electronic and ESR spectra. Copper(II) adducts show quasi-reversible responses (ΔEp=100 mV) in cyclic voltammograms with E1/2=0.510–0.535 V versus Ag|AgCl at room temperature in N,N-dimethylformamide, attributable to a CuIII/CuII couple. The spectral studies support the distorted octahedral geometry of these copper(II) adducts. The nucleolytic cleavage activity of all the copper(II) adducts was carried out on double-stranded pBR 322 circular plasmid DNA by using the gel electrophoresis experiment in the presence and absence of oxidant (H2O2). In the absence of oxidant a less discernible DNA cleavage was observed, whereas in the presence of oxidant (H2O2) all adducts showed increased nuclease activity.
Article
Ternary complexes of copper(ii) with beta -ketoesters [beta -keto=ethyl acetoacetate (HETAA) and ethyl benzoylacetate (HETBA)] and diamines [diam=N,N,N',N'-tetramethylethylenediamine (Me(4)en), N,N,N'-trimethylethylene- diamine (Me(3)en), N,N,N'-triethylethylenediamine (Et(3)en) and N-methyl-1,4-diazacycloheptane (medach)] of general formula Cu(beta -keto)(diam)X, where X-=ClO4, BPh4, NO3, Cl or Br, have been prepared. Their structure and chromotropicity have been characterized using spectral analyses, electrochemical and magnetic susceptibility measurements. Complexes having perchlorate, tetraphenylborate and nitrate as anions show a remarkable change from reddish violet to green in different solvents and anions with increasing donor strength of the solvent or anion. Complexes having chloride and bromide as anions are highly influenced by the acceptor property rather than the donor property of the solvent. The spectral studies revealed the possibility of using these complexes as Lewis acid-base color indicators for both solvent and anion donor strength. Cyclic voltammetric measurements on the complexes in different solvents showed that the reduction process is mainly diffusion controlled and quasi-reversible or irreversible. Such behavior has been explained according to the ECE mechanism (E=electrochemical step, C=chemical step). The solvent effect has been rationalized in terms of the thermo- dynamics and kinetics of the redox processes. A correlation has been found between the copper(ii) reduction potential and the spectral data in different solvents.
Article
Reaction of 2 equiv of Li[NH-2,6-C(6)H(3)R(2)] with [(Me(4)taa)ZrCl(2)] (Me(4)taaH(2) = tetramethyldibenzotetraaza[14]annulene) gives the bis(amido) derivatives [(Me(4)taa)Zr(NH-2,6-C(6)H(3)R(2))(2)] [R = Pr(i) (1) and Me (2)]. Addition of Me(4)taaH(2) to [Zr(N-2,6-C(6)H(3)Pr(i)(2))(NH-2,6-C(6)H(3)Pr(i)(2))(2)(py)(2)] also affords 1. The reaction of 2 equiv of aryl or alkyl amines H(2)NR with the bis(alkyl) complex [(Me(4)taa)Zr(CH(2)SiMe(3))(2)] is the most versatile method for preparing [(Me(4)taa)Zr(NHR)(2)] (R = 2,6-C(6)H(3)Pr(i)(2), 2,6-C(6)H(3)Me(2), Ph, or Bu(t)). Reaction of 1 equiv of Me(4)taaH(2) with the binuclear complexes [(Bu(t)NH)(2)Zr(&mgr;-NBu(t))(2)Zr(NHBu(t))(2)] or [(py)(HN-2,6-C(6)H(3)Me(2))(2)Zr(&mgr;-N-2,6-C(6)H(3)Me(2))(2)Zr(NH-2,6-C(6)H(3)Me(2))(2)(py)] gives the asymmetrically substituted derivatives [(Me(4)taa)Zr(&mgr;-NR)(2)Zr(NHR)(2)] [R = Bu(t) (6) or 2,6-C(6)H(3)Me(2) (8)], which have been crystallographically characterized.
Article
Solvatochromic mixed ligand complexes of copper(II) with malonate and diamine derivatives, Cu(n)(RMal)(diam)(n)X(m) (where n=1 or 2, m=1-4, RMal, malonic acid (H(2)Mal), diethylmalonate (HDEtMal) or diethylethoxyethylenemalonate (DEtEMal), and diam, ethylenediamine (en), 1,3-propylenediamine (1,3-pn), N,N,N'-trimethylethylenediamine (Me(3)en), N,N,N'-triethylethylenediamine (Et(3)en), N,N,N',N'-tetramethylethylenediamine (Me(4)en), N,N,N',N'-tetramethylpropylenediamine (Me(4)pn), or N-methyl-1,4-diazacycloheptane (medach); and X=ClO(4)(-) or Cl(-)), has been synthesized and characterized by spectroscopic, magnetic, molar conductance and electrochemical measurements. The mass spectra along with the analytical data of the complexes show peaks with m/e corresponding to a bridged binuclear structure for the chloride complexes, while perchlorate complexes showed either mononuclear structure for DEtMal and DEtEMal or bridged binuclear structure for Mal complexes. These results correspond to IR spectral data, which indicated that the modes of ester and carboxylato coordination sites are mono- and/or bidentate. The d-d absorption bands in weak donor solvents suggest square-planar and distorted square pyramidal-trigonal bipyramid geometries for the perchlorate and chloride complexes; respectively. On the other hand, an octahedral structure is identified for complexes in strong donor solvents. Perchlorate complexes show a drastic color change from violet to green as the donation ability of solvent increases, whereas chloride complexes are highly affected by the acceptor properties of the solvent. Cyclic voltammetric measurements on the complexes, proposed a quasi-reversible or irreversible and mainly diffusion controlled reduction process. Such behavior has been explained according to the ECE mechanism. A linear correlation has been found between the Cu(II) reduction potential and the spectral data. Molecular orbital calculations were performed for the ligands on the bases of PM3 level and the results corresponded to the experimental data. The data are discussed in terms of chromotropic concept and its applications as a Lewis acid-base color indicator.