New Zn(II) complexes with N2S2 Schiff base ligands. Experimental and theoretical studies of the role of Zn(II) in disulfide thiolate-exchange

Abstract

a b s t r a c tDescribed are the synthesis and characterization of two, potentially tetradentate, N 2 S 2 Schiff-base ligands, containing a disulfide bond, N, and L 2 and the complexes 1 and 2 have been characterized spectroscopically, and the crystal and molecular structures of the two complexes have been determined by single crystal X-ray diffraction. The coordination geometry around Zn(II) centers in both complexes is a distorted tetrahedron. In addition, DFT calculations (B3LYP/LANL2DZ/6-311++G(d,p)) support the structure of 1. Cyclic voltammetric studies demonstrate that Zn(II) shifts the reduction potential of the disulfide ligands L 1 and L 2 to less negative values thus making them more susceptible to reductive cleavage of the disulfide bond. The results of semi-empirical PM6 calculations offer key insight into the nature of the transition state for this reaction.

Molecular design and synthesis of new dithiocarbazate complexes; crystal structure, bioactivities and nano studies

“…Formation of the S-S bond is a consequence of S-H oxidation which is a phenomenon which frequently happen in the amino acid cysteine (Scheme 1). 45 The S-S bond length in hydrogen disulde is 2.06Å, however, formation of this bond with a length of 2.045Å in the L is close to the length of the bond in other compounds. 53 The torsion angle S1 0 -S1-C8-S2 (À8.86(8)Å) shows that the molecule is not planar and is twisted.…”

“…42 The absence of this signal in the spectra of the complexes conrms that coordination occurs through the phenolic oxygen. 43 Also the singlet signal assigned to the imine hydrogen in the L spectrum (8.54 ppm) shis down eld aer complexation 44,45 while satellites appear around this signal in compounds 4-6 which correspond to coupling of this hydrogen with 117 Sn and 119 Sn isotopes, 46 all of which indicate coordination of this nitrogen atom.…”

2-[(1E)-[(Z)-2-({[(1Z)-[(E)-2-[(2-Hydroxyphenyl)methylidene]hydrazin-1-ylidene]({[(4-methylphenyl)methyl]sulfanyl})methyl]disulfanyl}({[(4-methylphenyl)methyl]sulfanyl})methylidene)hydrazin-1-ylidene]methyl]phenol: crystal structure, Hirshfeld surface analysis and computational study

“…These molecules are effective ligands for a variety of metals and the motivation for complexation largely stems from the promising biological activity exhibited by the derived metal complexes (Low et al, 2016;Ravoof et al, 2017;Yusof et al, 2020). However, these Schiff bases are susceptible to oxidation resulting in the formation of a disulfide bond, as has been observed previously (Amirnasr et al, 2014;Sohtun et al, 2018). This is the case in the present report where the title compound, (I), was the side-product from the synthesis of the Schiff base, 4-methylbenzyl-2-(2-hydroxybenzylidene) hydrazinecarbodithioate (Ravoof et al, 2010).…”

Copper(II) Schiff Base Complexes with Catalyst Property: Experimental, Theoretical, Thermodynamic and Biological Studies

“…41,57 Ssmall differences between the theoretical and experimental vibrational frequencies can be related to (i) the environmental condition (gas phase and solid state) and (ii) from the fact that the experimental values are anharmonic frequencies while the calculated values are harmonic. 58…”