Crystal structures and spectroscopic properties of copper(II)–dipicolinate complexes with benzimidazole ligands

• Published in: Transition metal chemistry (Weinheim) Vol. 43; no. 6; pp. 507 - 516
• Main Authors: Masárová, Petra, Kuchtanin, Vladimír, Mazúr, Milan, Moncol, Ján
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.09.2018
• Subjects: Catalysis; Chemistry; Chemistry and Materials Science; Inorganic Chemistry; Organometallic Chemistry; Physical Chemistry
• ISSN: 0340-4285; 1572-901X
• DOI: 10.1007/s11243-018-0236-2

The syntheses, crystal structures and spectroscopic properties of three Cu(II)–dipicolinate complexes with benzimidazole ligands, namely [Cu(bzim)(dipic)(MeOH)] ( 1 ), [Cu 2 (2-Etbzim) 2 (dipic) 2 ] n ·0.5 n H 2 O ( 2 ) and [Cu 2 (2- i Prbzim) 2 (dipic) 2 ] n ( 3 ), where dipic = dipicolinate, bzim = 1-H-benzimidazole, 2-Etbzim = 2-ethyl-1-H-benzimidazole and 2-iPrbzim = 2-isopropyl-1-H-benzimidazole, are reported. Crystal structure studies revealed different coordination modes of the dipicolinate ligands; tridentate chelating for monomeric complex 1 , and both tridentate chelating and bridging for similar polymeric complexes 2 and 3 . Polymers 2 and 3 both contain two units, in which the Cu(II) central atoms Cu1 and Cu2 have different coordination polyhedra. The first unit {Cu(dipic) 2 } with Cu1 is connected to the second via two bidentate carboxylate groups of an μ 3 -bridging dipicolinate. In the second unit, Cu2 is coordinated by two imidazole nitrogen atoms from 2-ethyl-1-H-benzimidazole ( 2 ) or 2-isopropyl-1-H-benzimidazole ( 3 ) ligands. Complex 2 is of higher symmetry and has a localized Cu(II) atom Cu2 in a special position on the twofold axis. EPR spectra of all three Cu(II) complexes, which were measured at both room temperature and 98 K, indicate distorted tetragonal coordination spheres for all the Cu(II) atoms. The g -factor relation ( g // >  g ┴  > 2.0023) is consistent with a d x 2 - y 2 ground electronic state in each case.