Synthesis, structure, and spectroscopy of an encapsulated nickel(II) complex of the unsymmetrical macrobicyclic ligand 1-methyl-8-amino-3,13-dithia-6,10,16,19-tetraazabicyclo[6.6.6]icosane (AMN4S2sar)

Abstract

The nickel(II) complex of the encapsulating ligand 1-methyl-8-amino-3,13-dithia-6,10,16,19-tetraazabicyclo[6.6.6]-icosane, [Ni(AMNSsar)], is reported. Crystals of the complex are monoclinic, space group P2/c, with Z = 4, a = 9.167(6) A, b = 19.885(4) A, c = 13.068(8) A, β = 95.37(3)°, and R = 0.055. The low-temperature (−10 K) single-crystal absorption spectrum and ligand field analysis of the complex are reported. The spin-forbidden A → E, A transitions were observed at low temperature, and from the spectroscopic analysis, a significant differential nephelauxetic effect is shown to occur resulting in much lower values for the Racah B and C parameters for these spin-forbidden transitions in relation to the spin-allowed transitions.