# Electronic energy transfer and collection in luminescent molecular rods containing ruthenium(II) and osmium(II) 2,2 ': 6 ',2 ''-terpyridine complexes linked by thiophene-2,5-diyl spacers

Encinas, Susana and Flamigni, Lucia and Barigelletti, Francesco and Constable, Edwin C. and Housecroft, Catherine E. and Schofield, Emma R. and Figgemeier, Egbert and Fenske, Dieter and Neuburger, Markus and Vos, Johannes G. and Zehnder, Margareta. (2002) Electronic energy transfer and collection in luminescent molecular rods containing ruthenium(II) and osmium(II) 2,2 ': 6 ',2 ''-terpyridine complexes linked by thiophene-2,5-diyl spacers. Chemistry - A European Journal, 8 (1). pp. 137-150.

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Official URL: https://edoc.unibas.ch/76366/

The electronic absorption spectra, luminescence spectra and lifetimes (in MeCN at room temperature and in frozen n-C3H7CN at 77K). and electrochemical potentials (in MeCN) of the novel dinuclear [(tpy)Ru(3)Os(tpy)](4+) and trinuclear [(tpy)Ru(3)Os(3)Ru(tpy)](6+) complexes (3=2,5-bis(2,2:6,2-terpyridin-4-yl)thiophene) have been obtained and are compared with those of model mononuclear complexes and homometallic [(tpy)Ru(3)Ru(tpy)](4+), [(tpy)Os(3)Os(tpy)](4+) and [(tpy)Ru(3)Ru(3)Ru(tpy)](6+) complexes. The bridging ligand 3 is nearly planar in the complexes, as seen from a preliminary X-ray determination of [(tpy)Ru(3)Ru(tpy)][PF6](4), and confers a high degree of rigidity upon the polynuclear species. The trinuclear species are rod-shaped with a distance of about 3 nm between the terminal metal centres. For the polynuclear complexes, the spectroscopic and electrochemical data are in accord with a significant intermetal interaction. All of the complexes are luminescent (Phi in the range 10(-4) - 10(-2) and tau in the range 6-340 ns, at room temperature), and ruthenium- or osmium-based luminescence properties can be identified. Due to the excited state properties of the various components and to the geometric and electronic properties of the bridge, Ru -> Os directional transfer of excitation energy takes place in the complexes [(tpy)Ru(3)Os(tpy)](4+) (end-to-end) and [(tpy)Ru(3)Os(3)Ru(tpy)](6+) (periphery-to-centre). With respect to the homometallic case. for [(tpy)Ru(3)Os(3)Ru(tpy)](6+) excitation trapping at the central position is accompanied by a fivefold enhancement of luminescence intensity.