Construction of spin-crossover dinuclear cobalt(II) compounds based on complementary terpyridine ligand pairing.

The self-assembly of multinuclear SCO complexes is appealing in which unique properties may be discovered due to enhanced intramolecular and intermolecular interactions. In this work, three dinuclear cobalt(II) complexes, named Co-1, Co-2, and Co-3, were prepared based on a complementary terpyridine ligand pair strategy. The complexes were accurately synthesized by the solvothermal method in which dinuclear complexes were directional assemblies from cobalt(II) ions, terpy bearing 2,6-dimethoxyphenyl substituents at the terpyridyl 6,6''-positions, and ditopic terpy built with different linkers (alkynyl for 1, diynyl for 2, and phenyl for 3).

Ligand symmetry significantly affects spin crossover behaviour in isomeric [Fe(pybox)] complexes.

The understanding of the correlation between the spin-state behaviour and the structural features in transition-metal complexes is of pronounced importance to the design of spin crossover compounds with high performance. However, the study of the influence of ligand symmetry on the spin crossover properties is still limited due to the shortage of suitable structural systems. Herein we report the magneto-structural correlations of three mononuclear Fe(ii) isomers with respect to their ligand symmetry.