Amphiphilic terpyridine complexes of ruthenium and rhodium displaying lyotropic mesomorphism

Abstract

New 4′-alkyl-substituted 2,2′:6′,2″-terpyridine (4′R-terpy) compounds have been synthesised from 4′-methyl-2,2′:6′,2″-terpyridine and an appropriate 1-bromoalkane and complexed with ruthenium and rhodium to yield new bis(terpyridine) complexes [Ru(terpy)(4′R-terpy)]²⁺(R = C₁₉H₃₉ or C₃₁H₆₃) and [Rh(terpy)(4′R-terpy)]³⁺(R = C₁₉H₃₉) as chloride and hexafluorophosphate salts. These complexes are amphiphilic being structurally related to surfactant tris(bipyridine)ruthenium complexes. Both ruthenium and rhodium complexes with R = C₁₉H₃₉ and chloride counter ions show lyotropic mesomorphism in water, and the ruthenium complex with R = C₃₁H₆₃ shows mesophase formation in ethylene glycol.