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ABSTRACT: Four new dinuclear complexes [Ni(μ-L)(μ-OAc)Ni(H(2)O)(2)]NO(3) (), Ni(μ-L)(μ-OBz)Ni(H(2)O)(MeOH)]NO(3)·3MeOH (), [Ni(μ-L)(μ-9-An)Ni(H(2)O)(MeOH)]NO(3) () and [Ni(μ-L)(μ-OAc)Ni(H(2)O)(N(3))]·CH(3)OH () have been prepared from the compartmental ligand N,N',N''-trimethyl-N,N''-bis(2-hydroxy-3-methoxy-5-methylbenzyl)diethylenetriamine (H(2)L) and different carboxylate ligands (OBz = benzoate and 9-An = 9-anthracenecarboxylate), and then magnetically and structurally characterized. The X-ray structures of these complexes reveal that the Ni(2+) ions are bridged by two phenoxo groups belonging to the L(2-) ligand and one syn-syn carboxylate group, giving rise to diphenoxocarboxylate triply bridged dinuclear nickel(ii) complexes. The syn-syn carboxylate bridging group folds the structure with hinge angles (β) in the range 32-36°. The folding of the structure takes place with a concomitant decrease of the O-Ni-O bridging angle (θ) and an increase of the shift carbon atom directly linked to the phenoxo oxygen atom with respect to the Ni-Ni-O plane in the bridging region (τ angle). All the complexes exhibit ferromagnetic interactions between the slightly distorted octahedral Ni(2+) ions. A comparative analysis of the magneto-structural data for and other diphenoxocarboxylate bridged complexes clearly show that not only the θ angle, but also the τ and β angles play a significant role in determining the sign and magnitude of the magnetic exchange coupling in these complexes. The ferromagnetic behaviour observed for has been justified on the basis of their relatively low θ and high β and τ values, all of them decreasing the antiferromagnetic contribution in complexes , as well as the countercomplementarity effects between the diphenoxo and carboxylate bridging ligands. DFT theoretical calculations unequivocally demonstrate that the countercomplementarity mechanism is operative in compounds .
Dalton Transactions 10/2012; · 3.84 Impact Factor
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ABSTRACT: A mononuclear Dy(III) complex with a non-Schiff base compartmental ligand has been prepared and characterised by X-ray crystallography and ac magnetic susceptibility measurements. The complex exhibits SIM behaviour induced by dilution and/or magnetic field with two thermally activated relaxation processes.
Chemical Communications 06/2012; 48(64):7916-8. · 6.17 Impact Factor
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Inorganica Chimica Acta 04/2012; 385:73-80. · 1.85 Impact Factor
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Inorganic Chemistry Communications 01/2012; 19:36-38. · 1.97 Impact Factor
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Polyhedron 01/2012; 33(33):137-144. · 2.06 Impact Factor
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ABSTRACT: The reaction of H(2)L (N,N'-dimethyl-N,N'-bis(2-hydroxy-3-methoxy-5-methylbenzyl)-ethylenediamine) with different copper salts, in methanol and using a H(2)L/Cu = 2 : 3 molar ratio, led to four new bis(μ-diphenoxo)-bridged Cu(3) complexes of general formula [{Cu(S)(μ-L)}(2)Cu(H(2)O)(2n)]X(2) (S = CH(3)OH, n = 1 and X = BF(4)(-) for (1) or ClO(4)(-) for (2); S = Br(3)(-) anion and n = 1 without any X species for (3); S = H(2)O, n = 0 and X = NO(3)(-) for (4)). The use in the same reaction conditions of 4,4'-bipyridine (4,4'-bipy) as connector led to the chain complex [{Cu(μ-4,4'-bipy)(0.5)(μ-L)}(2)Cu(H(2)O)(2n)](ClO(4))(2)·17H(2)O (5). The structure of the centrosymmetric trinuclear unit in (1)-(5) consists of two [Cu(L)] fragments connected through two phenoxo bridging groups to the central copper(II) ion giving rise to a linear arrangement of the copper(II) ions, where the ligand acts in a compartmental form wrapping the metal centre with a N(2)O(2) tetradentate bridging mode. The coordination polyhedron of the symmetrically related external copper atoms exhibits a geometry very close to square-pyramidal, whereas the central copper(II) atom displays either a tetragonally elongated octahedral geometry or a square-planar geometry. Owing to the steric hindrance promoted by the methoxy groups at the phenyl rings, the whole Cu(3) structure is not planar but folded along the line connecting the phenoxo bridging oxygen atoms of the same ligand. Temperature dependence of the magnetic susceptibility of complexes (1)-(5) was measured, showing strong antiferromagnetic interactions between the central and external atoms through the bis(μ-phenoxo) groups. DFT calculations were also performed (a) to support the experimental values of the coupling constant (J(1)) between the nearest-neighbouring copper atoms, (b) to determine the magnitude of the interactions between next-nearest copper(II) atoms (J(2)) and (c) to study magneto-structural correlations for this kind of bis(μ-diphenoxo) trinuclear copper(II) complex.
Dalton Transactions 12/2011; 40(46):12462-71. · 3.84 Impact Factor
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ABSTRACT: Conventional reactions of the new multidentate ligand 7-amine-1,2,4-triazolo[1,5-a]pyrimidine (7atp, 1) with copper(II) salts lead to four novel multidimensional coordination complexes [Cu(7atp)(mal)(H(2)O)(2)]·H(2)O (2), [Cu(2)(μ-7atp)(4)(H(2)O)(2)](ClO(4))(4)·3H(2)O (3), {[Cu(7atp)(2)(μ-ox)]·3H(2)O}(n) (4) and {[Cu(7atp)(2)(μ-suc)]·2H(2)O}(n) (5), where ox(2-), mal(2-) and suc(2-) mean oxalate, malonate and succinate, respectively. In these compounds, the 7atp ligand coordinates monodentately through its atom N3, except for compound 3, which displays N3-N4 coordination mode, giving rise to all to structures with diverse topologies and dimensionality. Compound 2 is a mononuclear entity, 3 consists of dinuclear species, 4 is a zig-zag chain with oxalate as a bridging ligand and 5 is a succinate-bridged mono-dimensional system. All polynuclear metal complexes show antiferromagnetic interactions of with J values ranging from -0.12 to -49.5 cm(-1). The ligand donor capabilities have been estimated by topological analyses of the electron density (QTAIM) and electron localization function (ELF), obtained by DFT calculations. The compounds are the first structurally characterized copper(II) complexes containing the 7atp ligand.
Dalton Transactions 12/2011; 41(6):1755-64. · 3.84 Impact Factor
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ABSTRACT: Silver(I) coordination complexes with the versatile and biomimetic ligands 1,2,4-triazolo[1,5-a]pyrimidine (tp), 5,7-dimethyl-1,2,4-triazolo[1,5-a]pyrimidine (dmtp) and 7-amine-1,2,4-triazolo[1,5-a]pyrimidine (7atp) all feature dinuclear [Ag(2)(μ-tp)(2)](2+) building units (where tp is a triazolopyrimidine derivative), which are the preferred motif, independently of the counter-anion used. According to AIM (atoms in molecules) and ELF (electron localization function) analyses, this fact is due to the great stability of these dinuclear species. The complexes structures range from the dinuclear entities [Ag(2)(μ-tp)(2)(CH(3)CN)(4)](BF(4))(2) (1), [Ag(2)(μ-tp)(2)(CH(3)CN)(4)](ClO(4))(2) (2), [Ag(2)(μ-7atp)(2)](ClO(4))(2) (3) and [Ag(2)(μ-dmtp)(2)(CH(3)CN)](PF(6))(ClO(4)) (4) over the 1D polymer chain [Ag(2)(μ-CF(3)SO(3))(2)(μ-dmtp)(2)](n) (5) to the 3D net {[Ag(2)(μ(3)-tp)(2)](PF(6))(2)·∼6H(2)O}(n) (6) with NbO topology.
Dalton Transactions 11/2011; 40(44):11845-55. · 3.84 Impact Factor
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Berichte der deutschen chemischen Gesellschaft 11/2011; 2011(34):5225 - 5232. · 2.94 Impact Factor
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ABSTRACT: The structure of the title ionic compound, (C(5)H(6)N(5))(2)[Cu(C(2)O(4))(2)]·2H(2)O, consists of a centrosymmetric copper(II) oxalate dianion, two monoprotonated mol-ecules of the adenine analog 7-amino-1,2,4-triazolo[1,5-a]pyrimidine (7atp) and two water mol-ecules of crystallization. The Cu(II) ion, located on an inversion center, exhibits a sligthly distorted square-planar coordination geometry, in which two oxalate anions bind in a bidentate fashion. The triazolopyrimidine ligand is protonated at the N atom in position 4, instead of its most basic N atom in position 3. This fact may be explained by the network stability, which is provided through the formation of a two-dimensional wave-like network parallel to (50[Formula: see text]) by N-H⋯O, O-H⋯N and O-H⋯O hydrogen bonds. These nets are further connected via C-H⋯O inter-actions.
Acta Crystallographica Section E Structure Reports Online 11/2011; 67(Pt 11):m1531-2. · 0.35 Impact Factor
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ABSTRACT: Conventional reactions of the versatile multidentate ligand 5-methyl-1,2,4-triazolo[1,5-a] pyrimidin-7(4H)-one (HmtpO) with metallic(II) perchlorate salts lead to three novel multidimensional complexes [Cu(HmtpO)(2)(H(2)O)(3)](ClO(4))(2)·H(2)O (1), {[Cu(HmtpO)(2)(H(2)O)(2)](ClO(4))(2) ·2HmtpO}(n) (2) and {[Co(HmtpO)(H(2)O)(3)](ClO(4))(2)·2H(2)O}(n) (3). We have tested the antiparasital activity in vitro and in vivo of the three new complexes against Trypanosoma cruzi showing very promising results and overcoming clearly the reference drug commonly used for the Chagas disease treatment, benznidazole.
Journal of inorganic biochemistry 06/2011; 105(6):770-6. · 3.25 Impact Factor
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ABSTRACT: Conventional reactions of the versatile multidentate ligand 5-methyl-1,2,4-triazolo[1,5-a]pyrimidin-7(4H)-one (HmtpO) with metallic(II) salts lead to three novel multidimensional complexes [Cu(HmtpO)(2)(H(2)O)(3)](ClO(4))(2)·H(2)O (1), {[Cu(HmtpO)(2)(H(2)O)(2)](ClO(4))(2)·2HmtpO}(n) (2) and {[Co(HmtpO)(H(2)O)(3)](ClO(4))(2)·2H(2)O}(n) (3). In each compound, the triazolopyrimidine ligand shows a different and unusual coordination mode, giving rise to structures with diverse topologies and dimensionality. Compound 1 is a monomeric complex, in which HmtpO shows both N3-monodentate and N1,O71-bidentate modes. 2 is a bidimensional framework with the ligand showing a N3,O71 bidentate-bridging mode. The structure of 3 consists of 1D chains, in which HmtpO displays a N1,N3,O71-tridentate-bridging mode. It should be noted that these coordination modes of the HmtpO ligand are unique in the case of compounds 2 and 3. On the other hand, the magnetic properties of the polynuclear complexes 2 and 3 have been studied showing weak ferromagnetic and antiferromagnetic behaviour, respectively.
Dalton Transactions 05/2011; 40(19):5180-7. · 3.84 Impact Factor
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Dalton Transactions 01/2011; DOI 10.1039/C1DT10603A. · 3.84 Impact Factor
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ABSTRACT: In the title complex, [Zn(NCO)(2)(C(7)H(8)N(4))(2)], the Zn(II) ion exhibits a distorted tetra-hedral coordination geometry. The coordination environment is formed by two 5,7-dimethyl-1,2,4-triazolo[1,5-a]pyrimidine (dmtp) ligands, coordinated through the N atom in position 3, and two cyanate anions inter-acting by their N atoms. Supra-molecular dimers are generated by stacking inter-actions between the pyrimidine rings of two ligands related by an inversion center [centroid-centroid distance = 3.5444 (18) Å].
Acta Crystallographica Section E Structure Reports Online 01/2011; 67(Pt 3):m345. · 0.35 Impact Factor
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ABSTRACT: A series of one-dimensional Ni(2)Ln cationic complexes have been prepared by assembling the in situ generated dinuclear mesocate [Ni(2)(mbpb)(3)](2-) building block [H(2)mbpb is the ligand 1,3-bis(pyridine-2-carboxamide)benzene] with Ln(3+) metal ions (Ln(3+) = Gd, Tb, Dy). The crystal-field potentials for the two types of site symmetries found for these 3d-3d-4f complexes (LnO(7) and LnO(8)) are quite different, which has a direct influence on the depopulation of the Stark sublevels, the magnetic anisotropy, and the magnetic properties.
Inorganic Chemistry 02/2010; 49(4):1826-33. · 4.60 Impact Factor
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ABSTRACT: Eight new multidimensional metal(II) complexes [Zn(tp)2(NCS)2] (1), [Ni(tp)2(H2O)2(m-tp)2Ni(NCS)4]n (2), [Co(tp)2(H2O)2(m-tp)2Co(NCS)4]n (3), [Cd(tp)2(NCS)2]n (4), [Mn(tp)2(NCS)2(H2O)2] (5), [Zn(tp)2(NCO)2] (6), [Cd(tp)(NCO)2]n (7) and [Cd(tp)(N3)2]n (8) have been synthesized by conventional reactions of the 1,2,4-triazolo[1,5-a]pyrimidine with metallic(II) salts in the presence of thiocyanate, cyanate and azide as auxiliary ligands. X-Ray diffraction studies on these compounds show that species 1, 5 and 6 are mononuclear units in which zinc and manganese have tetrahedral and octahedral coordination geometry, respectively. Complexes 2 and 3 are isostructural and consist of neutral chains with triazolopyrimidine bridging ligands through N1, N3 nitrogen atoms. Compound 4 exhibits a 2D rectangular-grid-like structure and complexes 7 and 8 are cyanate-bridged chains formed by defective cubanes. Magnetic and luminescent properties of these materials have also been studied.
CrystEngComm 01/2010; 12:3038-3045. · 3.84 Impact Factor
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ABSTRACT: Complexes with the ligand 4,6-dimethyl-1,2,3-triazolo-[4,5-d]-pyrimidin-5,7-dionato (dmax(-)) and the auxiliary chelating-bridging ligand bipyrimidine (bpym) have been synthesized and structurally characterized for the divalent cations of Zn, Cd and Cu. For Zn and Cd, dinuclear complexes with the formulae [Zn(2)(dmax)(4)(H(2)O)(2)(bpym)].2H(2)O and [Cd(2)(dmax)(4)(H(2)O)(4)(bpym)].6H(2)O have been isolated whereas for Cu, the one-dimensional polymer {[Cu(2)(dmax)(4)(bpym)].5H(2)O}(n) has been obtained. Bpym acts as a chelating-bridging ligand in the three compounds, joining couples of metal ions. Two crystallographically and chemically different dmax(-) ligands are present in each of these complexes, one monodentately linked via the triazole N atom furthest from the pyrimidine ring (N2) and the other either monodentately linked via the triazole N atom closer to a carbonyl group (N1, Zn and Cd compounds) or in bridging N1-N2 mode (Cu compound), in the latter case generating an one-dimensional polymer with alternating bpym and (dmax)(2) bridges. The magnetic interaction across the bpym bridge gives rise to a strong antiferromagnetic interaction (2J = -201 cm(-1)), whereas that across the (dmax)(2) bridge is negligible and cannot be reliably determined (obscured by the strong one). The hydrogen bonds between water molecules and the triazolopyrimidine derivative build the 3-D structure of the compounds.
Dalton Transactions 12/2009; · 3.84 Impact Factor
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ABSTRACT: Eight new complexes containing the versatile multidentate ligand 5-pyrimidyl-tetrazolate (pmtz), namely [Cu(mu(3)-pmtz)](n) (1), [Pd(2)(mu-pmtz)(2)Cl(2)] (2), [Ni(pmtz)(en)(2)]Cl x 2 H(2)O (3), [Cu(tren)(pmtz)(ClO(4))] (4), [Co(2)(tren)(2)(mu-pmtz)(mu-O(2))](ClO(4))(3) x 3 H(2)O (5), [Fe(2)(pmtz)(4)(H(2)O)(2)(mu-O)] x 5 H(2)O (6), [(UO(2))(4)(mu-pmtz)(2)(mu-OH)(2)(mu(3)-O)(2)(H(2)O)(4)] x 6 H(2)O (7) and [Dy(2)(pmtz)(4)(mu-pmtz)(H(2)O)(6)](pmtz) x 6 H(2)O (8), have been prepared by either conventional solution or hydrothermal techniques and characterised by single-crystal X-ray diffraction. Those compounds prepared under hydrothermal conditions ((1), (2), (7) and (8)) exhibit chelating/bridging coordination modes that connect two or three metal ions generating polynuclear species. Thus, compound is a 2D polymer where the ligand exhibits a new chelating/bridging kappa(2)N(1),N(7):kappaN(2):kappaN(3) coordination mode, whereas complexes (2) and (7) are dinuclear and tetranuclear species, respectively, in which the ligand displays a kappa(2)N(1),N(7):kappaN(2) coordination mode. The increase of the metal size favours the adoption of the kappa(2)N(1),N(7):kappa(2)N(4),N(11) bis(chelating)bridging mode. This is the case of compound (8) that contains bulky Dy(III) metal ions. Despite the large size of the UO(2+) metal ion, the pmtz ligand in (7) does not adopt the expected bis(chelating)bridging mode because the uranyl cation hydrolyzes to the highly stable bis(mu(3)-oxo) tetranuclear unit. Conventional mild solution conditions lead to complexes containing monodentate or chelating coordination modes. Thus, compounds (3) and (6) are mononuclear and mu-oxo dinuclear species, respectively, which contain kappa(2)N(1),N(7) chelating pmtz ligands. Compound (4) is mononuclear with the ligand acting in a new monodentate form through the N(1) atom of the tetrazolato ring, whereas (5) is a dinuclear complex where pmtz adopts a new exo-bidentate N(2),N(3) bridging coordination mode. Variable-temperature magnetic measurements of (6) indicate that the oxo-bridge mediates a very strong antiferromagnetic interaction between the iron(III) ions with a J = -222.7 cm(-1). Luminescence measurements show that the pmtz ligands act as "antenna" for energy absorption and transfer to the uranyl emissive state.
Dalton Transactions 11/2009; · 3.84 Impact Factor
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ABSTRACT: The double stranded Cu(II)2-metallacyclic complex of formula [Cu2(mbpb)2].2H2O (1) and the triple stranded Ni(II)2-metallacyclic complexes of formula [Ni2(Hmbpb)3]PF6.21H2O (2), [Co(H2O)6][Ni2(mbpb)3)]THF.10H2O (3) and {Ag2(H2O)[Ni2(mbpb)3]}.11H2O (4) (where H2mbpb is the bisbidentate dinucleating bridging ligand 1,3-bis(pyridine-2-carboxamide) benzene) have been synthesised and characterised by single-crystal X-ray diffraction. Within the dinuclear molecules, metal ions are bridged by either fully or semideprotonated bisbidentate ligands, which are coordinated through the pyridine and amidato nitrogen donor atoms. In complex 4 the triple stranded dinuclear Ni2 units are connected to the Ag+ cations through O-amidato bridges and Ag-pi(benzene) interactions to afford a 1D bimetallic chain. Cu2 (1) and Ni2 (2-4) complexes exhibit ferromagnetic coupling between the metal ions through the bridging ligand with J(Cu-Cu) = 21.1 cm(-1) and J(Ni-Ni) in the range of 2.9-3.6 cm(-1), respectively. Amongst copper(II) dinuclear complexes bearing m-phenylenediamidato bridges, complex 1 exhibits the stronger ferromagnetic exchange coupling reported so far. DFT calculations firstly confirm that the spin polarisation mechanism is responsible for the ferromagnetic coupling, and secondly allows us to predict stronger ferromagnetic couplings in Cu(II)(2) complexes with larger tetrahedral distortions of the CuN4 coordination environment.
Dalton Transactions 10/2009; · 3.84 Impact Factor
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ABSTRACT: The reaction of K(2)TzC (H(2)TzC = tetrazole-5-carboxylic acid) and either MnCl(2) x 4 H(2)O or CuCl(2) x 2 H(2)O under hydrothermal conditions leads to the formation of three new polynuclear complexes of formula [Mn(TzC)(H(2)O)(2)](n) 1 and [M(2)(TzC)(2)(H(2)O)(6)] x nH(2)O (M = Mn(II) 2, n = 4 and Cu(II) 3, n = 2). Complex 1 displays a 1D planar zig-zag chain structure where the ligand is disorderd into two positions and exhibits two mu(3)-chelating/bridging tetradentate coordination modes, one through the two carboxylate oxygen atoms and the neighbouring nitrogen atom of the tetrazolate ring and the other one through three neighboring nitrogen atoms belonging to the tetrazole ring and one of the carboxylate oxygen atoms. The structure of 2 and 3 consists of centrosymmetric dinuclear molecules, in which the ligands exhibit a mu(2)-chelating/bridging coordination mode through one of the carboxylate oxygen atoms and two neighbouring nitrogen atoms of the tetrazolate ring, generating a planar M(N-N)(2)M hexagon. Variable-temperature magnetic susceptibility studies reveal a weak antiferromagnetic interaction for 1 (J = -1.5 cm(-1)). In spite of the coplanarity of the tetrazolate and metal coordination planes in 2 and 3, they exhibit very weak antiferromagnetic interactions. DFT calculations have been performed in order to explain this unexpected magnetic behaviour.
Dalton Transactions 09/2009; · 3.84 Impact Factor
