Variation in coordinative property of two different N2O2 donor Schiff base ligands with nickel(II) and cobalt(III) ions: characterisation and single crystal structure elucidation

Relative stability of the cis and trans isomers of octahedral cobalt(iii) complexes of the type [Co(N2O2)X2] with tetradentate salen type Schiff bases: a combined theoretical and experimental study

Energies of cis and trans isomers of a series of octahedral cobalt(iii) complexes with salen type Schiff bases have been estimated by DFT calculations.

A combined experimental and computational study on supramolecular assemblies in hetero-tetranuclear nickel(ii)-cadmium(ii) complexes with N2O4-donor compartmental Schiff bases

Two new hetero-tetranuclear nickel(ii)/cadmium(ii) complexes, a cubane [(CH₃CO₂)₂Ni₂(L¹)₂Cd₂(NCS)₂] (1) and a linear tetramer [(DMSO)₂NiL²Cd(NCS)(μ_1,3-SCN)Ni(DMSO)L²Cd(NCS)₂] (2) {where H₂L¹ = N,N'-bis(3-methoxysalicylidene)propane-1,3-diamine and H₂L² = N,N'-bis(3-ethoxysalicylidene)propane-1,3-diamine are potential octadentate compartmental Schiff bases}, were synthesized and characterized. The structures of both complexes were confirmed by single crystal X-ray diffraction studies. Complex 1 contained a Ni₂Cd₂O₄ cubane core, whereas complex 2 featured an end-to-end thiocyanate-bridged tetranuclear moiety. Furthermore, complex 1 showed C-HH-C interactions, whereas a unique Sπ interaction was observed in complex 2. Theoretical studies were performed using several computational tools such as NBO and AIM analyses. Both complexes showed photoluminescence in DMSO medium at room temperature upon irradiation with ultraviolet light. The lifetimes of the excited states were ∼27 ns.

Potency of photoinduced electron transfer and antioxidant efficacy of pyrrole and pyridine based Cu(II)-Schiff complexes while binding with CT-DNA

Here we report a systematic and comparative study to define a correlation between the structure and function of a series of simple, biologically active small inorganic Schiff base copper complexes for the occurrence of charge transfer phenomenon in calf thymus DNA (CT-DNA) using transient absorption spectroscopy corroborated with magnetic field effect. Four copper(II) Schiff base complexes with differently substituted heterocyclic ligands with antioxidant activity have been used. The binding constants of the order of ∼ 10(4) support the moderate binding affinity of the complexes towards CT-DNA. The methyl-substituted pyrrole complex shows maximum binding affinity (Kb: 8.33 × 10(4)) compared to others. The occurrence of photoinduced electron transfer (PET) from CT-DNA to pyrrole containing complexes has been confirmed by identifying the corresponding transient radical ions whereas the extent of PET with pyridine substituted complexes is too small to be observed. The increase of the yield of radical ions in presence of magnetic field depicts that the initial spin correlation in geminate radical ion pair is triplet. The difference between experimental and calculated B½ values, the measure of hyperfine interactions (HFI) present in the system, arises due to hole hopping through intrastrand and interstrand DNA bases. The unsubstituted pyrrole complexes cleave DNA much more than the methyl-substituted one. Therefore, the probability of intrastrand superexchange increases with methyl-substituted complexes, that reduces the rate of hole hopping and hence the B½ value.

Nickel(II)-Schiff base complex recognizing domain II of bovine and human serum albumin: spectroscopic and docking studies

It has been spectroscopically monitored that a mononuclear nickel(II)-Schiff base complex {[NiL]·CH(3)OH=NSC} exhibits greater binding affinity for bovine serum albumin (BSA) than that of its human counterpart (HSA). Moreover the modes of binding of NSC with the two serum albumins also differ significantly. Docking studies predict a relatively rare type of 'superficial binding' of NSC at domain IIB of HSA with certain mobility whereas for BSA such phenomena has not been detected. The mobile nature of NSC at domain IIB of HSA has been well correlated with the spectroscopic results. It is to be noted that thermodynamic parameters for the NSC interaction also differ for the two serum albumins. Occurrence of energy transfer between the donor (Trp of BSA and HSA) and acceptor (NSC) has been obtained by means of Förster resonance energy transfer (FRET). The protein stability on NSC binding has also been experimented by the GuHCl-induced protein unfolding studies. Interestingly it has been found that NSC-HSA interaction enhances the protein stability whereas NSC-BSA binding has no such impact. Such observations are indicative of the fact that the conformation of NSC is responsible in recognizing the two serum albumins and selectively enhancing protein stability.

Tris{2-[(furan-2-meth-yl)imino-meth-yl]-4-methyl-phenolato}cobalt(III)

In title compound, [Co(C(13)H(12)NO(2))(3)], the Co(III) ion is six-coordinated by three bidentate Schiff base ligands in a distorted octa-hedral environment. Adjacent complex mol-ecules are linked through C-H⋯O hydrogen bonds.

Redetermination of 6,6'-dimeth-oxy-2,2'-[hexane-1,6-diylbis(nitrilo-dimethyl-idyne)]diphenol

The title compound, C(22)H(28)N(2)O(4), contains two independent centrosymmetric mol-ecules (A and B). In the previous structure determination [Xia et al. (2007 ▶). Acta Cryst. E63, o259] both A and B were modelled as neutral mol-ecules with the H atoms of the the O-H groups included in calculated positions. In this redetermination, the transferrable H atoms were located in difference maps and freely refined, indicating that one mol-ecule (A) crystallizes in the neutral (nonzwitterionic) form and the other in the zwitterionic form, namely 6,6'-dimeth-oxy-2,2'-[hexane-1,6-diylbis(nitrilo-dimethyl-idyne)]-di-phenol-6,6'-dimeth-oxy-2,2'-[hexane-1,6-diylbis(nitrilio-di-methyl-idyne)]diphenolate (1/1). This finding is supported by significant differences in the C-O(H) (A) and C-O(-) (B) bond lengths. In the crystal, the zwitterionic mol-ecules (B) are involved in inter-molecular N-H⋯O hydrogen bonds forming one-dimensional chains along [001]. Each independent mol-ecule forms an intra-molecular O-H⋯N (A) or N-H⋯O (B) hydrogen bond. In mol-ecule B, one of the -CH(2)- groups is disordered over two sets of sites with refined occupancies of 0.659 (8) and 0.341 (8).