Ditopic, flexible hydrazone-based building blocks with pendant 2,2 ':6 ',2 ''-terpyridine metal-binding domains

The synthesis and characterization of three new bis(2,2':6',2'-terpyridine) (tpy) ligands containing different hydrazone spacers between the metal-binding domains are described. Treatment of 1,4-benzenedi-carbaldehyde bis(2,2':6',2 ''-terpyridin-4'-ylhydrazone) (1) with [(tpy)RuCl3] in the presence of N-ethylmorpholine results in the formation of [(tpy)Ru(mu-1)Ru(tpy)](4+). Single crystal X-ray diffraction data for [(tpy)Ru(mu-1)Ru(tpy)][PF6](4) center dot 8MeCN confirm the ability of the hydrazone-based ligand to bridge two ruthenium(H) centres, providing proof-of-principle for the application of this class of flexible ligand in the design of coordination polymers.