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

N(4)-Methyl-4-nitroacetophenone thiosemicarbazone (H4NO2Ac4M, 1) and its nickel(II) complex ([Ni(4NO2Ac4M)2], 2) were obtained and fully characterized. Compound 1 crystallizes in the triclinic P1¯ 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-d6, and the 1-Z,E isomer in CDCl3. 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-d6) 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-d6 as well as in the powder. Compound 2-cis(Z-Ni-Z)→2-cis(E-Ni-E) conversion probably occurs during crystallization.

X-ray structural studies of N(4)-methyl-4-nitroacetophenone thiosemicarbazone, H4NO2Ac4M (1) and its nickel(II) complex, [Ni(4NO2Ac4M)2] (2) revealed that the 1-E,E isomer of the thiosemicarbazone and the 2-cis (E-Ni-E) isomer of the complex are formed in the crystal. NMR data along with Hartree–Fock (HF) and Density Functional Theory (DFT) calculations suggest that the 1-E,E isomer probably exists in DMSO-d6, and the 1-Z,E isomer in CDCl3. NMR data along with HF and DFT calculations suggest the presence of 2-cis(Z-Ni-Z) in DMSO-d6 as well as in the powder, indicating 2-cis(Z-Ni-Z) → 2-cis (E-Ni-E) conversion during crystallization.Figure optionsDownload as PowerPoint slide