Cu(II) and Zn(II) Complexes with Dinitrobenzoates and Pyrazolyl Lig-ands: Structural and Thermal Stability Influence of N-H Moiety.

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. DFT 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 complexes 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 pres-ence of acidic protons, being this especially important for L1.