Unusual Nitrosyl¿Nitrosyl Interaction in Coordination Polymers of Ni(II) and Co(II) Complexes with α,ω-bis(benzotriazoloxy)alkane System

Abstract

[eng] A novel type of NO⋯NO supramolecular interaction is reported for the first time. Three new polymeric coordination complexes, two nickel(II) complexes, {[Ni(μ-L1)2(NCS)2]}n, (1) {[Ni(μ-L2)2(NCS)2]}n, (2) and a cobalt(II) complex {[Co(μ-L3)2(NCS)2]}n (3) have been synthesized with the organic ligand α,ω- bis(benzotriazoloxy)alkane (L1 = 1,3-bis(benzotriazol-1-yl)-1,3-dioxapropane; L2 = 1,5-bis (benzotriazol-1- yl)-1,5-dioxapentane; L3 = 1,6-bis(benzotriazol-1-yl)-1,6-dioxahexane) and thiocyanate as counterions. The complexes were characterized by various physical measurements such as elemental analysis, FT-IR, UV-Vis, NMR and mass spectroscopy. The single crystal X-ray analysis revealed that complexes 1 and 2 have a 1D coordination polymer helical structure whereas complex 3 has a 2D polymer anti corrugate structure. Complexes 2 and 3 were found to be involved in packing in the crystal structures by a very unusual anti-parallel strong NO⋯NO interaction. In addition, the π-acidity of the triazole ring moiety increased upon the coordination of the Ni ion which led to the establishment of lone pair-π (lp-π) interactions. Moreover, all of the complexes show different intermolecular interactions (H-bonds, π-π, lone pair-π and anti-parallel NO⋯NO) whose energetics and role in the crystal packing have been evaluated with theoretical DFT calculations.