Photophysical and redox properties of dinuclear Ru and Os polypyridyl complexes with incorporated photostable spiropyran bridge

Belser, P., De Cola, L., Hartl, F. ORCID: https://orcid.org/0000-0002-7013-5360, Jukes, R.T.F. and Bozic, B. (2009) Photophysical and redox properties of dinuclear Ru and Os polypyridyl complexes with incorporated photostable spiropyran bridge. Inorganic Chemistry, 48 (4). pp. 1711-1721. ISSN 0020-1669 doi: 10.1021/ic800963u

Abstract/Summary

Aimed at creating a true photoswitchable energy transfer system, four dinuclear complexes containing ruthenium(II) and osmium(II) metal centers bridged by spiropyran-type linkers were designed and investigated. The bridge in its closed spiropyran form was shown to be a good insulator for energy transfer between the Ru-bpy donor and the Os-bpy acceptor (bpy = 2,2'-bipyridine). On the basis of properties of previously reported photochromic nitrospiropyrans substituted with a single polypyridine metal center, conversion of the bridge to the open merocyanine form was envisaged to result in efficient electronic energy transfer by a sequential ("hopping") mechanism. In contrast to the expectations, however, the studied closed-form dinuclear complexes remained stable independently of their photochemical or electrochemical activation. This difference in reactivity is attributed to the replacement of the nitro group by a second polypyridine metal center. We assume that these changes have fundamentally altered the excited-state and redox properties of the complexes, making the ring-opening pathways unavailable.