N(4)-Methyl-4-nitroacetophenone thiosemicarbazone and its nickel(II) complex: Experimental and theoretical structural studies

Abstract

N(4)-Methyl-4-nitroacetophenone thiosemicarbazone (H4NO 2Ac4M, 1) and its nickel(II) complex ([Ni(4NO 2Ac4M) 2], 2) were obtained and fully characterized. Compound 1 crystallizes in the triclinic P 1 ¯ space group and adopts the 1- E , E configuration in relation to the imino and thioamide groups, respectively. NMR data along with HF/6-31G ∗ and DFT/BLYP/6-31G ∗ theoretical calculations of energies and of 1H and 13C NMR chemical shifts for the optimized geometries of 1 suggest that the 1- E , E isomer probably exists in DMSO- d 6, and the 1- Z , E isomer in CDCl 3. Compound 2 crystallizes in the monoclinic C2/ c space group. The thiosemicarbazones coordinate through the N–S chelating system, with the sulfurs in cis position to each other. In the crystal the two ligands adopt the E configuration in relation to the imino group, 2- cis ( E - Ni- E ). However, solid state (powder) as well as solution (DMSO- d 6) NMR data along with HF/6-31G ∗ and DFT/BLYP/6-31G ∗ calculations of 1H and 13C chemical shifts for the optimized geometries of 2 suggest the presence of 2- cis ( Z - Ni- Z ) in DMSO- d 6 as well as in the powder. Compound 2- cis ( Z - Ni- Z )→ 2- cis ( E - Ni- E ) conversion probably occurs during crystallization.