Cu(II) and Zn(II) Complexes with Dinitrobenzoates and Pyrazolyl Ligands: Structural and Thermal Stability Influence of N–H Moiety

Abstract

The synthesis and characterization of air-stable Cu(II) and Zn(II) complexes with 3,5-dinitrobenzoate (DNB) and 3,5-dimethylpyrazole (L1) or bis(3,5-dimethylpyrazol-1-yl)methane (L2) are described. Three of these complexes exhibit a monomeric structure, while the Cu(II) complex with L2 is a trinuclear complex. Density functional theory calculations were performed to understand the unexpected formation of the three-centered compound. In agreement with the X-ray crystal structure, the N–H moiety present in L1 was identified as possible driving force to obtain monomeric structures, while L2, without it, can favor the trinuclear complex formation. Thermal studies were carried for the complexes, and it was observed that the presence of the azole ligand allows the decomposition of the complexes at lower temperatures due to the presence of acidic protons, being especially important for L1.