Structural investigation, theoretical DFT, Hirshfeld surface analysis and catalytic behaviour towards 3,5-DTBC oxidation of two cobalt(ii) complexes with semicarbazone Schiff base ligands

Two novel cobalt(ii) complexes [Co(HL1)(2)](NO3)(2).2.5H(2)O (1) and [Co(HL2)(2)](NO3)(2) (2) (where HL1 = (E)-2-(1-(pyridin-2-yl)ethylidene)hydrazine-1-carboxamide and HL2 = (E)-2-(pyridin-2-ylmethylene)hydrazine-1-carboxamide) have been synthesized and structurally characterized by spectroscopic techniques and single-crystal diffraction analysis. The complexes are close comparable with metals exhibiting the expected distorted octahedral geometry being chelated by two semicarbazone ligands via NNO donor set. The catecholase-like activity of complexes 1 and 2 was evaluated by using 3,5-di-tert-butylcatecholas substrate. The results showed that both the complexes are effective catalysts with K-cat values of 762 and 562, respectively. Theoretical DFT study and Hirschfeld surface analyses were also carried out to reveal the nature of intermolecular contacts and to integrate experimental observations.