Syntheses, characterization and DFT studies of two new homo-dinuclear zinc(II) complexes based on pyrazole and 3,5-dimethylpyrazole ligands

Abstract

Two new homo-dinuclear zinc(II) complexes, bis(µ-pyrazolato-) bis[(formato)(pyrazole)zinc(II)], [{Zn(OCHO)(pzH)}2(µ-N2H3C3)2] (1) and bis(µ-3,5-dimethylpyrazolato)bis[(formato)(-3,5-dimethylpyrazole) zinc(II)], [{Zn(dmpzH)(OCHO)}2(µ-N2H7C5)2] (2), were synthesized through the reactions of zinc(II) formate dihydrate, Zn(OCHO)2·2H2O with pyrazole (pzH = C3H4N2) and 3,5-dimethylpyrazole (dmpzH = C5H8N2), respectively, in toluene at room temperature. These dinuclear complexes have been characterized using different analytical techniques; elemental and thermogravimetric analyses, IR and 1H-NMR spectroscopies, single-crystal X-ray diffraction and DFT studies. Compound 1 crystallized in the P space group of the triclinic crystal system with unit cell parameters a = 8.205(3) Å, b = 8.864(5) Å, c = 14.486(7) Å, α = 104.929(14)°, β = 91.214(11)° and γ = 106.921(8)°. Compound 2 crystallized in the P21/c space group of the monoclinic crystal system with cell parameters a = 8.400(3) Å, b = 11.020(4) Å, c = 14.930(5) Å, α = γ = 90° and β = 106.3(10)°. Pseudo-tetrahedral coordination geometries were observed around the zinc(II) centers in both complexes, constructed by one oxygen atom from a formate anion and three nitrogen atoms from one pzH and two pyrazolato in 1 or one dmpzH and two 3,5-dimethylpyrazolato in 2. The bulk of these materials are consolidated by weak and strong N-H···O, C-H···O, C-N···O and C-H···π, N-H···π and C-O···O intra/intermolecular interactions resulting to zigzag networks containing empty voids. DFT studies on both compounds revealed their optimized structures, frontier molecular orbitals, theoretical IR frequencies and the global reactivity descriptors.