Supramolecular and intramolecular energy transfer with ruthenium-anthracene donor-acceptor couples: Salt bridge versus covalent bond

摘要

The formation of hydrogen-bonded cation-anion adducts between the complex [Ru(bpy)_2(biimH_2)]~(2+) (bpy = 2,2'-bipyridine; biimH_2 = 2,2'-biimidazole) and anthracene-9-carboxylate in dichloromethane solution was investigated by 1H NMR, optical absorption, and luminescence spectroscopy. The experimental data indicates that more than one anthracene-9-carboxylate anion can interact closely with the dicationic ruthenium complex. Energy transfer from the photoexcited ruthenium complex to anthracene-9-carboxylate in 1:1 adducts of these two components was investigated by transient absorption spectroscopy and compared to intramolecular energy transfer in a covalently linked ruthenium-xylene-anthracene dyad with a comparable donor-acceptor distance. A ruthenium(II) biimidazole complex forms closely interacting cation-anion adducts with anthracene-9-carboxylate. Energy transfer within these adducts and a covalent donor-bridge-acceptor system is compared.