Ruthenium polypyridine complexes of tris-(2-pyridyl)-1,3,5-triazine-unusual building blocks for the synthesis of photochemical molecular devices

The mononuclear compounds bis-(2,2'-bipyridine)ruthenium(II)-(tris(2-pyridyl)triazine) [(bpy)(2)Ru(tpt)](PF6)(2) 1 and bis-(4,4'-di-tert-butyl-2,2'-bipyridine)ruthenium(II)-(tris(2-pyridyl)triazine) [(tbbpy)(2)Ru(tpt)](PF6)(2) 2 have been synthesised and fully characterised. The attempted syntheses of heterodinuclear complexes with the tris(2-pyridyl) triazine (tpt) ligand as bridging ligand and various palladium(II)- and platinum(II)-dichloro complexes using the ruthenium complexes as starting materials resulted in a partial hydrolysis of the triazine based bridging ligand in case of 2 and an unselective decomposition in case of 1. Compound 2 reacts with Pd(DMSO)(2)Cl-2 and Pt(DMSO)(2)Cl-2 substituting three ligands from the metal centres of these precursors with partial hydrolysis of the triazine moiety of the bridging ligand yielding the dinuclear complexes bis-(4,4'-di-tert-butyl-2,2'-bipyridine)ruthenium(II)-N-((picolinamido)(pyridin-2-yl)methylene)picolinamide)chloro-palladium(II) [(tbbpy)(2)Ru(tptO)PdCl](PF6)(2) 3 and bis-(4,4'-di-tert-butyl-2,2'-bipyridine) ruthenium(II)-N((picolinamido)(pyridin-2-yl)methylene)picolinamide)chloro-platinum(II) [tbbpy)(2)Ru(tptO)PtCl](PF6)(2) 4. The newly formed bridging ligand coordinates in a bidentate fashion at the ruthenium centre and acts as a tridentate ligand for the second metal centre. The structures of all the complexes have been fully characterised and their photophysical properties are reported. A similar reaction sequence using the (4'-(p-bromophenyl)-2,2':6',2 ''-terpyridine)ruthenium(II)-(tris(2-pyridyl)triazine) complex [(BrPhtpy)Ru(tpt)](PF6)(2) 5 and Pd(CH3CN)(2)Cl-2 as starting materials did not yield the hydrolysed bridging ligand but the expected dinuclear complex [(BrPhtpy)Ru(tpt)PdCl2](PF6)(2) 6 suggesting that the coordination of two pyridine rings of the tpt by the ruthenium centre is essential for the stabilisation of the tpt frame work. Preliminary investigations show that the dinuclear ruthenium-palladium and - platinum complexes are not active catalysts in the light-driven hydrogen production.