Acta Chimica Slovaca (ACS) publishes papers on fundamental and applied aspects of chemistry, biochemistry, chemical technology, chemical engineering and process control, biotechnology and food technology. Welcome are also topics which include chemical aspects of materials, physical chemistry and chemical physics, analytical chemistry, macromolecular chemistry and biomedical engineering.

Influence of the counter-anions on the [Ni(Him)6]2+ complex cation (Him = imidazole)

A. Koščíková *, L. Krešáková, J. Černák

Department of Inorganic Chemistry, Institute of Chemistry, P. J. Šafárik University, Moyzesova 11, 041 54 Košice, Slovakia

E-mail: * andrea.koscikova@student.upjs.sk

Abstract: Four ionic Ni(II) complexes containing the [Ni(Him)6]2+ (Him = imidazole) complex cation were prepared: [Ni(Him)6](CO3)·5H2O (1), [Ni(Him)6](ac)2·H2O (2, ac = acetate), [Ni(Him)6](NO3)2 (3), and [Ni(Him)6]SiF6 (4); complexes 2 and 4 are new. The prepared complexes were characterized chemically and spectroscopically. Results of X-ray single crystal studies have shown that all four complexes exhibit ionic crystal structures comprising [Ni(Him)6]2+ complex cations, the respective anion(s), and in case of 1 and 2, additional solvate water molecules. Ni(II) central atoms in all complexes 1-4 are hexa-coordinated by six N-atoms originating from monodentate Him ligands. While in 1 and 4 the NiN6 chromophore is quite a regular octahedron with only one independent Ni-N bond, as imposed by local symmetry, in 2 and 3 the octahedra are slightly deformed. On the other hand, significant differences were observed in the orientation of Him rings within the respective coordination polyhedra.

Keywords: Crystal structure, hexa-coordination, imidazole, nickel(II)

Acta Chimica Slovaca, Vol. 19, No. 1, 2026, pp. 1—9, DOI: 10.2478/acs-2026-0001