Solvent-Induced Formation of Novel Ni(II) Complexes Derived from Bis-Thiosemicarbazone Ligand: An Insight from Experimental and Theoretical Investigations

In this work, we report solvent-induced complexation properties of a new N2S2 tetradentate bis-thiosemicarbazone ligand (H2LI), prepared by the condensation of 4-phenylthiosemicarbazide with bis-aldehyde, namely 2,2’-(ethane-1,2-diylbis(oxy)dibenzaldehyde, towards nickel(II). Using ethanol as a reaction medium allowed the isolation of a discrete mononuclear homoleptic complex [NiLI] (1), for which its crystal structure contains three independent molecules, namely 1-I, 1-II, and 1-III, in the asymmetric unit. The doubly deprotonated ligand LI in the structure of 1 is coordinated in a cis-manner through the azomethine nitrogen atoms and the thiocarbonyl sulfur atoms. The coordination geometry around metal centers in all the three crystallographically independent molecules of 1 is best described as the seesaw structure. Interestingly, using methanol as a reaction medium in the same synthesis allowed for the isolation of a discrete mononuclear homoleptic complex [Ni(LII)2] (2), where LII is a monodeprotonated ligand 2-(2-(2-(2-(dimethoxymethyl)phenoxy)ethoxy)benzylidene)-N-phenylhydrazine-1-carbothioamide (HLII). The ligand LII was formed in situ from the reaction of LI with methanol upon coordination to the metal center under synthetic conditions. In the structure of 2, two ligands LII are coordinated in a trans-manner through the azomethine nitrogen atom and the thiocarbonyl sulfur atom, also yielding a seesaw coordination geometry around the metal center. The charge and energy decomposition scheme ETS-NOCV allows for the conclusion that both structures are stabilized by a bunch of London dispersion-driven intermolecular interactions, including predominantly N–H∙∙∙S and N–H∙∙∙O hydrogen bonds in 1 and 2, respectively; they are further augmented by less typical C–H∙∙∙X (where X = S, N, O, π), CH∙∙∙HC, π∙∙∙π stacking and the most striking, attractive long-range intermolecular C–H∙∙∙Ni preagostic interactions. The latter are found to be determined by both stabilizing Coulomb forces and an exchange-correlation contribution as revealed by the IQA energy decomposition scheme. Interestingly, the analogous long-range C–H∙∙∙S interactions are characterized by a repulsive Coulomb contribution and the prevailing attractive exchange-correlation constituent. The electron density of the delocalized bonds (EDDB) method shows that the nickel(II) atom shares only ~0.8|e| due to the σ-conjugation with the adjacent in-plane atoms, demonstrating a very weak σ-metalloaromatic character.

Theoretical and Spectroscopic Studies of SN Donor Thiosemicarbazone Ligand and Its Pt(II) Complex

Sulphur-nitrogen(SN) donor thiosemicarbazone ligand [(Z)-N-ethyl-2-(5-methyl-2-oxoindolin-3-ylidene)hydrazinecarbothioamide] and its Pt(II) complex were synthesized by condensation method. The compounds were structurally characterized by elemental analysis CHNS, FT-IR, and NMR analysis. The elemental analyses data for the compounds were in good agreement with the theoretical values. The melting point of the complex was higher than the ligand, as expected. The FT-IR spectral data reflect a bidentate bonding of thiosemicarbazone ligand to Pt(II) ion through thioketo sulfur and azomethine nitrogen. The docking results (theoretical results) of these compounds show that the binding energy between DNA and Pt(II) complex was found to be less than that of the Schiff base ligand (L) in the sense that it has higher stability at various stages and angles. The strength of docking between DNA and Pt(II) complex was also found to be that stronger than the Schiff base ligand (L).

Synthesis, structures, and DFT analysis of gold complexes containing thiosemicarbazone ligand

In this study, we report the synthesis of a series of new gold(I) compounds in different solvation mediums. First, gold(I) thiosemicarbazone (TSC) [Au-(TSC)2]Cl was synthesized by reacting [Au(SMe2)]Cl with thiosemicarbazone...