Molecular Assemblies and Spin-Crossover Behaviour of Cobalt(ɪɪ) Complexes with Terpyridine Incorporating Different Nitrogen Positions in Pyridine Rings

Cobalt(ii) complexes with terpyridine-type ligands, [Co(n-pyterpy)2](ClO4)2 (n = 3 (1), 4 (2)), were prepared and characterised. Different positions of the nitrogen atom in the terpyridine ligands influenced their assembly properties in the crystal structures. Complex 1 showed a 2D network structure consisting of 1D chains connected by intermolecular N⋯HC interactions. On the other hand, complex 2 consisted of two different cobalt ion sites (Co1 and Co2) with slightly different coordination environments. Complex 2 showed 1D chains with no interchain interactions. Such differences are discussed with the cooperativities estimated by their spin crossover behaviours.