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. 2021 Nov 23;11(60):37726-37743.
doi: 10.1039/d1ra06902k.

Co(ii), Ni(ii), Cu(ii) and Cd(ii)-thiocarbonohydrazone complexes: spectroscopic, DFT, thermal, and electrical conductivity studies

R Fouad  1 , Ibrahim A Shaaban  2   3 , Tarik E Ali  2   1 , Mohammed A Assiri  2 , S S Shenouda  4
Affiliations

Co(ii), Ni(ii), Cu(ii) and Cd(ii)-thiocarbonohydrazone complexes: spectroscopic, DFT, thermal, and electrical conductivity studies

R Fouad et al. RSC Adv. .

Abstract

New and stable coordinated compounds have been isolated in a good yield. The chelates have been prepared by mixing Co(ii), Ni(ii), Cu(ii), and Cd(ii) metal ions with (1E)-1-((6-methyl-4-oxo-4H-chromen-3-yl)methylene)thiocarbonohydrazide (MCMT) in 2 : 1 stoichiometry (MCMT : M2+). Various techniques, including elemental microanalyses, molar conductance, thermal studies, FT-IR, 1H-NMR, UV-Vis, and XRD spectral analyses, magnetic moment measurements, and electrical conductivity, were applied for the structural and spectroscopic elucidation of the coordinating compounds. Further, computational studies using the DFT-B3LYP method were reported for MCMT and its metal complexes. MCMT behaves as a neutral NS bidentate moiety that forms octahedral complexes with general formula [M(MCMT)2Cl(OH2)]Cl·XH2O (M = Cu2+; (X = ½), Ni2+, Co2+; (X = 1)); [Cd(MCMT)2Cl2]·½H2O. There is good confirmation between experimental infrared spectral data and theoretical DFT-B3LYP computational outcomes where MCMT acts as a five-membered chelate bonded to the metal ion through azomethine nitrogen and thiocarbonyl sulphur donors. The thermal analysis is studied to confirm the elucidated structure of the complexes. Also, the kinetic and thermodynamic parameters of the thermal decomposition steps were evaluated. The measured optical band gap values of the prepared compounds exhibited semiconducting nature. AC conductivity and dielectric properties of the ligand and its complexes were examined, which showed that Cu(ii) complex has the highest dielectric constant referring to its high polarization and storage ability.

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Conflict of interest statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Scheme 1
Scheme 1. Synthesis of transition metal complexes.
Fig. 1
Fig. 1. Equilibrium geometries of suggested tautomers for MCMT and their relative energies (ΔE) using B3LYP/6-31G(d) calculations.
Fig. 2
Fig. 2. Optimized geometries and relative energy for the proposed coordination sites for the ligand to Cu(ii) ion. * S-5 has an imaginary frequency (i.e., transition state).
Fig. 3
Fig. 3. DFT-B3LYP/6-31G(d) optimized geometries of the suggested geometrical isomers for Co(ii), Ni(ii), and Cu(ii) complexes.
Fig. 4
Fig. 4. HOMO and LUMO frontier molecular orbitals for MCMT ligand and its Co(ii) complex as predicted using B3LYP/6-31G(d) calculations.
Fig. 5
Fig. 5. 1H-NMR spectra of Cd(ii) complex in (a) DMSO-d6 and (b) D2O.
Fig. 6
Fig. 6. UV-Vis spectra of transition metal complexes in DMF as the solvent.
Fig. 7
Fig. 7. ESR spectrum of Cu(ii) complex.
Fig. 8
Fig. 8. XRD pattern of MCMT, Cu(ii), and Cd(ii) complexes.
Fig. 9
Fig. 9. (αthν)0.5versus hv of: (a) MCMT ligand; (b) Co(ii) complex; (c) Ni(ii) complex; (d) Cu(ii) complex; (e) Cd(ii) complex.
Fig. 10
Fig. 10. Frequency dependence of the ac conductivity for MCMT and Co(ii), Ni(ii), Cu(ii), and Cd(ii) complexes.
Fig. 11
Fig. 11. ln σacversus ln(2πf) for MCMT and Co(ii), Ni(ii), Cu(ii), and Cd(ii) complexes.
Fig. 12
Fig. 12. Frequency dependence of the dielectric constant ε1 for MCMT, Co(ii), Ni(ii), Cu(ii), and Cd(ii) complexes.
Fig. 13
Fig. 13. Frequency dependence of the dielectric loss ε2 for MCMT, Co(ii), Ni(ii), Cu(ii), and Cd(ii) complexes.
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