title: Metal complexes of a pentadentate N2O3bis(semicarbazone) Schiff-base. A case study of structure-spectroscopy correlation.
abstract: Schiff condensation of 2,6-diformyl 4-methylphenol with semicarbazide hydrochloride in 1:2 molar ratio produces the bis(semicarbazone) ligand, herein called H3L. A comprehensive spectroscopic analysis of the compound was performed by (1)H and (13)C NMR, FTIR and electronic spectroscopies. Assignments to the UV-vis spectrum of H3L were supported by semi-empirical quantum mechanics ZINDO/S calculations. The ligand H3L forms monoclinic crystals in the space group P21/c and its structure is stabilized by classic hydrogen bonds with propanone molecules. It promptly reacts with first row metal ions to produce the following coordination compounds: [Co2(L)(μ-NO3)]·DMF, [Ni2(H2L)(μ-CH3COO)(CH3COO)2]·2H2O, [Cu2(L)(μ-NO3)(H2O)2]·H2O, [Cu2(L)(μ-CH3COO)(H2O)2]·H2O and [Cu2(H2L)(μ-Cl)Cl2]·3H2O, that have different compositions, depending on the degree of deprotonation of the ligand upon coordination. Electronic and EPR spectroscopies as well as effective magnetic moment measurements of the complexes were used in an attempt to better understand their mode of coordination, the microsymmetry around the metal ions and magnetic properties.
authors.affiliation: Departamento de Química, Universidade Federal do Paraná, Cx. Postal 19081, 81531-980 Curitiba, PR, Brazil.
authors.forename: Mayara Hissami
authors.initials: MH
authors.lastname: Inoue
authors.affiliation: Departamento de Química, Universidade Federal do Paraná, Cx. Postal 19081, 81531-980 Curitiba, PR, Brazil.
authors.forename: Ronny Rocha
authors.initials: RR
authors.lastname: Ribeiro
authors.affiliation: Instituto de Física, Universidade Federal de Goiás, Cx. Postal 131, 74001-970 Goiânia, GO, Brazil.
authors.forename: José Ricardo
authors.initials: JR
authors.lastname: Sabino
authors.affiliation: Departamento de Química, Universidade Federal do Paraná, Cx. Postal 19081, 81531-980 Curitiba, PR, Brazil. Electronic address: fsnunes@ufpr.br.
authors.forename: Fábio Souza
authors.initials: FS
authors.lastname: Nunes
keywords: 2,6-Diformyl-4-methylphenol semicarbazone; Crystal structure; Magnetic moments; NMR, electronic and EPR spectroscopies; ZINDO/S