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ABSTRACT: The crystal structures of six compounds involving the divalent cations of Mn, Zn and Cd, the anionic form of the heterocycle 4,6-dimethyl-1,2,3-triazolo[4,5-d]pyrimidin-5,7-dione (Hdmax) and bipyridyl based spacer ligands are reported. The most important feature of these structures is the presence, in all cases, of a topologically identical 1-D polymeric superstructure (tape), involving tetra- or hexaaqua complex cations and triazolopyrimidine anions, built through hydrogen bonds. Adding these results to others previously published, we may consider these tapes as robust supramolecular synthons where a defined/clear case of molecular recognition between these two moieties takes place.
Dalton Transactions 07/2012; 41(34):10390-5. · 3.84 Impact Factor
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ABSTRACT: Studies on the anti-proliferative activity in vitro of seven ternary nickel (II) complexes with a triazolopyrimidine derivative and different aliphatic or aromatic amines as auxiliary ligands against promastigote and amastigote forms of Leishmania infantum and Leishmania braziliensis have been carried out. These compounds are not toxic for the host cells and two of them are effective at lower concentrations than the reference drug used in the present study (Glucantime). In general, the in vitro growth rate of Leishmania spp. was reduced, its capacity to infect cells was negatively affected and the multiplication of the amastigotes decreased. Ultrastructural analysis and metabolism excretion studies were executed in order to propose a possible mechanism for the action of the assayed compounds. Our results show that the potential mechanism is at the level of organelles membranes, either by direct action on the microtubules or by their disorganization, leading to vacuolization, degradation and ultimately cell death.
Journal of inorganic biochemistry 03/2012; 112:1-9. · 3.25 Impact Factor
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Polyhedron 01/2012; 33(33):137-144. · 2.06 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: Seven ternary nickel(II) complexes (three previously described and four firstly described here) with an azapurine derivative (the anionic form of 4,6-dimethyl-1,2,3-triazolo[4,5-d]pyrimidin-5,7-dione) have been synthesized and spectroscopically characterized, and the crystal structures of three of them have been solved by X-ray diffraction. Studies in vitro and in vivo on the antiproliferative activity of these complexes against Trypanosoma cruzi (epimastigote, amastigote, and trypomastigote forms) have been carried out, displaying in some cases significantly higher antitrypanosomatid activity and lower toxicity than the reference drug for Chagas' disease, benznidazole (N-benzyl-2-(2-nitro-1H-imidazol-1-yl)acetamide). Ultrastructural analysis and metabolism excretion studies were also executed in order to propose a possible mechanism of action for the assayed drugs.
Journal of Medicinal Chemistry 10/2010; 53(19):6964-72. · 4.80 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: The asymmetric unit of the title compound, C(12)H(9)N(2) (+)·ClO(4) (-)·C(6)H(6)N(4)O·2H(2)O, contains a monoprotonated 4,7-phenanthrolinium (47phen) cation, a perchlorate anion balancing its charge, a neutral mol-ecule of 5-methyl-1,2,4-triazolo[1,5-a]pyrimidin-7(4H)-one (HmtpO) and two inter-stitial water mol-ecules. In the crystal structure, the acidic H atoms of 47phenH(+) and HmtpO form strong hydrogen bonds with the water mol-ecules, which in turn act as hydrogen-bond donors, forming links between them and towards the carbonyl O atom of HmtpO, the non-protonated N atom of 47phen(+) and one of the O atoms of the anion.
Acta Crystallographica Section E Structure Reports Online 01/2010; 66(Pt 2):o459-60. · 0.35 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: Anti-proliferative effects are described for newly synthesised copper (II) complexes of two triazolo-pyrimidine derivatives (1,2,4-triazolo-[1,5-a]pyrimidine, tp, and 5,7-dimethyl 1,2,4-triazolo-[1,5-a]pyrimidine, dmtp) against to Trypanosoma cruzi and Leishmania (Viannia) peruviana. Of the compounds assayed, those that presented the ligand tp and auxiliary ligand 1,10-phenanthroline (C24b, C49) were most highly active against to T. cruzi with IC(50) within the range of the reference drug benznidazole. These compounds, together with C35 were the most effective against L. (V.) peruviana with an IC(50) greater than that presented by reference drugs (Pentostam and Glucantim). These compounds were not toxic to the host cell. IC(25) diminished the infection capacity and severely reduced the multiplication of intracellular forms of T. cruzi, and L. (V.) peruviana. In the case of T. Cruzi, the transformation to trypomastigote was seriously depressed. Copper (II) complexes C24b, C49 and C35, acted on the energy metabolism of the parasites at the level of the NAD(+)/NADH balance and at the level of the organelle membranes, causing degradation and cell death.
Drug metabolism letters. 02/2009; 3(1):35-44.
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Acta Crystallographica Section C Crystal Structure Communications 09/2006; 62(Pt 8):o489-91. · 0.52 Impact Factor
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Francisco J Corpas,
Juan B Barroso,
Alfonso Carreras, Miguel Quirós,
Ana M León,
María C Romero-Puertas,
Francisco J Esteban,
Raquel Valderrama,
José M Palma,
Luisa M Sandalio,
Manuel Gómez,
Luis A del Río
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ABSTRACT: The cellular and subcellular localization of endogenous nitric oxide (NO.) in leaves from young and senescent pea (Pisum sativum) plants was studied. Confocal laser scanning microscopy analysis of pea leaf sections with the fluorescent probe 4,5-diaminofluorescein diacetate revealed that endogenous NO. was mainly present in vascular tissues (xylem and phloem). Green fluorescence spots were also detected in the epidermal cells, palisade and spongy mesophyll cells, and guard cells. In senescent leaves, NO. generation was clearly reduced in the vascular tissues. At the subcellular level, by electron paramagnetic resonance spectroscopy with the spin trap Fe(MGD)(2) and fluorometric analysis with 4,5-diaminofluorescein diacetate, NO. was found to be an endogenous metabolite of peroxisomes. The characteristic three-line electron paramagnetic resonance spectrum of NO., with g = 2.05 and a(N) = 12.8 G, was detected in peroxisomes. By fluorometry, NO. was also found in these organelles, and the level measured of NO. was linearly dependent on the amount of peroxisomal protein. The enzymatic production of NO. from l-Arg (nitric oxide synthase [NOS]-like activity) was measured by ozone chemiluminiscence. The specific activity of peroxisomal NOS was 4.9 nmol NO. mg(-1) protein min(-1); was strictly dependent on NADPH, calmodulin, and BH(4); and required calcium. In senescent pea leaves, the NOS-like activity of peroxisomes was down-regulated by 72%. It is proposed that peroxisomal NO. could be involved in the process of senescence of pea leaves.
Plant physiology 10/2004; 136(1):2722-33. · 6.53 Impact Factor
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ABSTRACT: Reaction of [(dach)Pd(NO3)2] entities (dach = (R,R)-1,2-diaminocyclohexane, (S,S)-1,2-diaminocyclohexane) and 4,7-phenanthroline (phen) providing, respectively, 90 and 120 degrees bond angles, leads to the formation of two novel positively charged homochiral cyclic trinuclear metallacalix[3]arene species [((R,R)-1,2-diaminocyclohexane)Pd(phen)]3(NO3)6 (2a) and [((S,S)-1,2-diaminocyclohexane)Pd(phen)]3(NO3)6 (2b). These species have been characterised by 1)H NMR and X-ray diffraction methods (2b), showing that they possess accessible cavities suited for supramolecular recognition processes. We prove, indeed, from 1H NMR studies the inclusion of mononucleotides inside the cavity of the trinuclear species [(ethylenediamino)Pd(phen)]3(6+) (1), [((R,R)-1,2-diaminocyclohexane)Pd(phen)]3(6+) (2a) and [((S,S)-1,2-diaminocyclohexane)Pd(phen)]3(6+) (2b) in aqueous solution. Association constants (K(ass)) range from 85 +/- 6 M(-1) for the interaction between [(ethylenediamine)Pd(phen)]3(6+) and adenosine monophosphate to 37 +/- 4 M(-1) for the interaction between [(1,2-diaminocyclohexane)Pd(phen)]3(6+) and thymidine monophosphate. We invoke the synergy of electrostatic, anion-pi and pi-pi interactions to explain the recognition of mononucleotides inside the cavity of the metallacalix[3]arenes.
Dalton Transactions 06/2004; · 3.84 Impact Factor
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ABSTRACT: A set of enantiomerically pure cyclic multinuclear complexes with the formula cis-[a(2)PdL](n) (n+) [a(2)=(R,R)-1,2-diaminocyclohexane (R,R-dach), (S,S)-1,2-diaminocyclohexane (S,S-dach); n=4, 6; LH=2-hydroxypyrimidine (2-Hpymo), 4,6-dimethyl-2-hydroxypyrimidine (2-Hdmpymo) and 4-hydroxypyrimidine (4-Hpymo)] were obtained by reaction of cis-[a(2)Pd(H(2)O)(2)](2+) and LH in aqueous media. The polynuclear complexes were studied by (1)H NMR spectroscopy and X-ray crystallography. These studies revealed that the N1,N3-bridging mode exhibited by the pyrimidine moieties is ideally suited for formation of inorganic analogues of calixarenes (metallacalixarenes) in a self-assembly process. The most stable species are the tetranuclear metallacalix[4]arenes, which are obtained in all cases. Hexanuclear species, namely, [a(2)Pd(2-dmpymo)](6) (6+), were also isolated and fully characterised. (1)H NMR experiments show conversion of [a(2)Pd(2-dmpymo)](6) (6+) to [a(2)Pd(2-dmpymo)](4) (4+) on heating. Analogously to organic calixarenes, these systems are also capable of incorporating hard metal ions at the oxo surface. Additionally, investigations on the receptor properties of these metallacalixarenes towards mononucleotides showed that enantioselective recognition processes occur in aqueous media.
Chemistry 10/2003; 9(18):4414-21. · 5.93 Impact Factor
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ABSTRACT: The preparation, X-ray structure, and spectroscopic and magnetic properties of [Cu(NCS)(μ-NCS)(Hmtpo)(H2O)]2 (where Hmtpo= 4H,7H-5-methyl-7-oxo[1,2,4]triazolo[1,5-a]pyrimidine) are described. This compound crystallizes in triclinic space group P1̄, with unit cell dimensions a = 8.408(2) Å, b = 10.581(3) Å, c = 7.927(2) Å, α = 89.45(2)°, β = 77.44(2)°, γ = 69.75(2)°, and Z = 1 (binuclear unit). The structure was refined to final R = 0.033 for 2143 data with I ≥ 3.0σ(I). The structure is comprised of polymeric 1-D copper(II) complexes supported by two different kinds of thiocyanate bridges. The coordination geometry around each of the metal centers is a distorted octahedron (N3S + O + S*). The equatorial positions are occupied by a monodentate Hmtpo ligand, coordinated via N3, two bridging thiocyanate groups coordinated in a “symmetric” end-to-end fashion, and the N-donor atom of an asymmetric end-to-end thiocyanate bridge. Finally, a water molecule and a weakly bonded S-donor atom from the asymmetric end-to-end thiocyanate bridge, with a Cu···S separation of 2.959(1) Å, occupy the apical sites. The presence of two “symmetric” thiocyanate bridges with short Cu−SCN and Cu−NCS distances of 2.402(1) and 1.938(3) Å, respectively, results in a Cu−Cu separation of 5.499(1) Å. The magnetic susceptibility data measured in the 11−290 K temperature range shows a strong antiferromagnetic coupling between the copper ions through the “symmetric” thiocyanate bridges. Fitting the data to the Bleaney−Bowers equation gives the exchange parameter 2J = −148.2 cm-1, which is many times higher than those previously found in other copper(II) thiocyanate bridged complexes, and g = 2.20. The unprecedented equatorial−equatorial disposition of the thiocyanate bridging entities appears to be responsible for the magnetic behavior of this compound.
10/1997;
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ABSTRACT: The formation of the mononuclear Pt(II) compound cis-[Pt(NH(3))(2)(Hmtpo-N(3))(2)](NO(3))(2).2H(2)O (1) (Hmtpo = 4,7-dihydro-5-methyl-7-oxo[1,2,4]triazolo[1,5-a]pyrimidine) upon reaction of Hmtpo with cisplatin is reported. Subsequent reactions of 1 with Pd(II) electrophiles of the type [Pd(am)(2)(H(2)O)(2)](NO(3))(2) ((am)(2) = en, bpy) in neutral aqueous media afford heterobinuclear complexes of formula [(NH(3))(2)Pt(&mgr;-mtpo-N(3),N(4))(2)Pd(am)(2)](NO(3))(2), where (am)(2) = bpy (2) and en (3). On the other hand, reaction of 1 with the platinum electrophile [Pt(bpy)(H(2)O)(2)](2+) yields the binuclear compound [(mtpo-N(3))(NH(3))(2)Pt(&mgr;-mtpo-N(3),N(4))Pt(bpy)(OH)](NO(3)).6H(2)O (4). The compounds have been structurally characterized by 1-D and 2-D (1)H NMR spectroscopy and X-ray crystallography (1, 2, and 4). Compound 1 crystallizes in the triclinic space group P&onemacr; with unit cell dimensions a = 7.859(1) Å, b = 11.811(2), c = 12.986(2) Å, alpha = 73.69(1) degrees, beta = 84.53(1) degrees, gamma = 85.80(1) degrees, and Z = 2. Compound 2 crystallizes in the monoclinic space group P2(1)/c with unit cell dimensions a = 13.752(1) Å, b = 12.5658(8) Å, c = 19.215(1) Å, beta = 118.08(1) degrees, and Z = 4. Compound 4 crystallizes in the triclinic space group P&onemacr; with unit cell dimensions a = 10.282(2) Å, b = 14.133(3) Å, c = 14.794(3) Å, alpha = 110.63(3) degrees, beta = 97.83(3) degrees, gamma = 108.48(3) degrees, and Z = 2. The structure of 1 consists of mononuclear cis-[Pt(NH(3))(2)(Hmtpo-N(3))(2)](2+) cations, in which the Hmtpo ligands are coordinated through N(3) in a monodentate fashion. In compound 2, two mtpo moieties bridge the metal centers through N(3) and N(4), giving rise to a Pt-Pd separation of 3.083(1) Å. On the other hand, only one bridging mtpo moiety is present in 4, which accounts for a lengthening in the M-M separation to 3.337(1) Å. The environment around the metal centers consists of four nitrogens, except for one Pt nucleus in compound 4, which presents a rare example of a terminal OH group. The (1)H NMR studies show clearly that these structures are retained in solution. Finally, a bidentate bridging mode through N(1)/N(3) is postulated for the species generated in solution by the reaction of 1 with the electrophile [Pt(NH(3))(2)(H(2)O)(2)](2+), which may lead to tetranuclear or polymeric species.
Inorganic Chemistry 08/1997; 36(15):3277-3283. · 4.60 Impact Factor
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ABSTRACT: A condensation reaction between two cis-[PtCl2(Hmtpo)2] (where Hmtpo= 4,7-H-5-methyl-7-oxo[1,2,4]triazolo[1,5a]pyrimidine) molecules takes place in neutral aqueous media, giving [Pt2(μ-mtpo)4]·4H2O (1). The X-ray structure of the recrystallization product of 1 in DMSO:EtOH (1:1) (DMSO = dimethyl sulfoxide), namely, [Pt2(μ-mtpo)4]·2DMSO (2) has been determined. Compound 2 crystallizes in the orthorhombic space group Pbcn with unit cell dimensions a = 14.207(3) Å, b = 15.187(3) Å, c = 17.165(3) Å, and Z = 4. The molecular structure shows that the two Pt atoms are bridged by four mtpo ligands. Thus, it presents two face to face PtN4 units with a Pt···Pt 2.744(2) Å separation. Compound 1 has also been characterized by 1H and 195Pt NMR. The very short Pt(II)···Pt(II) contact suggests an interaction between the two metal centers, supported by the great deshielding observed for the platinum nuclei in the 195Pt NMR spectrum (δ = −2005 ppm) compared to a Pt(II) in a typical N4 environment. In order to make an approach to the possible bonding nature of the Pt(II)···Pt(II) interaction, a theoretical analysis has been performed on the basis of the properties of the electronic charge density distribution, derived from ab initio MO calculations for the model compound {Pt2[NHCHN(C(CH2)(CH3))]4} using RHF/LANL2DZ and B3LYP/LANL2DZ wave functions; both take into account relativistic effects and the second electronic correlation also. A significant directional interaction between the two metal centers has been found. Thus, a bond critical point appears between the two platinum nuclei, with a density of charge ρb = 0.056 e·bohr-3, which is half of that found for the platinum nitrogen bond. Moreover, a value of the energy density, Ed(rb) < 0 (Ed(r) = −0.0175 hartree·bohr-3), at this point, shows the bonding nature of the interaction.
12/1996;
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Polyhedron 29(1):372-378. · 2.06 Impact Factor
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ABSTRACT: The crystal structure of the ionic compounds (tpH)n[CdnCl3n] and (dmtpH)2[CdCl4] · 2H2O is described, where tp = 1,2,4-triazolo-[1,5-a]pyrimidine and dmtp = 5,7-dimethyl-1,2,4-triazolo-[1,5-a]pyrimidine. Both compounds are monoclinic, space groups P21/c and C2/c, respectively. Unit cell parameters are a = 13.7860(7), b = 9.4013(5), c = 17.6679(9) Å, β = 98.672(1)° for the first compound and a = 11.7543(7), b = 12.6823(7), c = 6.6836(4) Å, β = 96.710(1)° for the second. In both cases, the heterocycles are protonated at the nitrogen atom at position 3. For dmtp, the charge of the cation is neutralized by the simple tetrahedral [CdCl4]2− anion, whereas for tp, a polymeric [CdnCl3n]n− anion is present, formed by aligned face-sharing CdCl6 octahedra.
Journal of Molecular Structure. 882:30-34.
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ABSTRACT: This article covers all the research work published until September 1998 about the coordination chemistry of 1,2,4-triazolo-[1,5-a]pyrimidine derivatives. The revision is mainly focused in the structural features of the compounds, obtained from single crystal X-ray diffraction. The references are classified according to the present metal atoms. These kind of ligands display a broad versatility when binding metal ions, monodentate binding through the endocyclic nitrogen atom at position 3 being however their main coordinating behaviour. Dimeric and polymeric structures are observed when a bidentate binding through N3–N4 or N3–N1, respectively, takes place. N1–O7 chelating binding mode has also been observed in a few cases. In some cases, dimers or polymers are also generated when the present auxiliary ligands are the ones that bridge the metal centres.
Coordination Chemistry Reviews.
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ABSTRACT: The reaction between [(η6-p-cymene)Ru(H2O)3]X2 and 4,7-phenanthroline (phen) leads to the formation of the rectangular tetranuclear complexes [(η6-p-cymene)4Ru4(μ-4,7-phen-N4,N7)2(μ-OH)4]X4 (X = NO3, 1a; SO3CF3, 1b) which have been structurally characterised by X-ray crystallography. 1H NMR spectroscopic studies suggest the presence of a partially dissociated dinuclear species of type [(η6-p-cymene)2Ru2(μ-4,7-phen-N4,N7)(solv)4]4+ in equilibrium with the tetranuclear cyclic species found in the solid state. The temperature effect for this equilibrium was studied by variable temperature 1H NMR experiments in D2O and MeOD. The results reveal that the proportion of the tetranuclear species increases with the polarity of the solvent which favour stacking interactions between the phenanthroline moieties. In addition, the reactivity of the tetranuclear species towards the nucleosides guanosine (Guo), cytidine (Cyt), 2′-deoxythymidine (Thy) and 2′-deoxyadenosine (dAdo) has been monitored by 1H NMR as a potential model for the interaction of the 1 species with the probable DNA target. The results reveal that the 1 systems are able to bind the nucleobases endocyclic nitrogen atoms of Guo Cyt, and dAdo.
Journal of Inorganic Biochemistry.
