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Issue 11, 2000
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Switching of the inter-component photoinduced electron- and energy-transfer properties of a Ru(II)–aza-crown–Re(I) complex; effects of changing temperature, and of incorporation of Ba2+ ion into the macrocyclic spacer between the chromophores

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Abstract

The binuclear complex [{Ru(bipy)2}(μ-L1){Re(CO)3(H2O)}][PF6]3 (Ru-crw-Re), and its mononuclear counterpart [Ru(bipy)2(L1)][PF6]2, were synthesised. The bridging ligand L1 contains two bipyridyl binding sites which are attached via methylene spacers to each of the N atoms of a diaza-18-crown-6 macrocycle spacer (crw), such that addition of a metal ion to the macrocycle affects the pathway linking the two chromophores. The absorption spectra, luminescence spectra and excited-state lifetimes, and electrochemical properties of acetonitrile solutions of these complexes were investigated. Luminescence studies on Ru-crw-Re showed the presence of two competing types of photoinduced intramolecular process involving the Re-based excited state as a donor, viz.: (i) electron transfer from an amine group(s) of the aza-crown ether; and (ii) Re→Ru energy transfer. These processes were monitored by time-resolved luminescence spectroscopy both at room temperature and at 77 K, and in the presence and absence of a cation (Ba2+) hosted within the aza-crown macrocyclic unit. In fluid solution at room temperature, there is no photoinduced Re→Ru energy transfer; instead photoinduced electron transfer occurs in the absence of Ba2+ (kel = 1.2 × 1010 s−1), which is inhibited by the presence of Ba2+. In frozen solvent (77 K), only Re→Ru photoinduced energy transfer occurs, with ken = 2 × 108 s−1 in the absence of Ba2+ and kenBa = 7 × 106 s−1 in the presence of Ba2+. Thus, Re→Ru energy transfer is strongly affected by Ba2+ being hosted within the aza-crown cavity, i.e. a switching effect. The role of the diverse factors affecting the two processes is discussed in detail.

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Supplementary files

Article information


Submitted
28 Feb 2000
Accepted
12 Apr 2000
First published
12 May 2000

J. Chem. Soc., Dalton Trans., 2000, 1783-1792
Article type
Paper

Switching of the inter-component photoinduced electron- and energy-transfer properties of a Ru(II)–aza-crown–Re(I) complex; effects of changing temperature, and of incorporation of Ba2+ ion into the macrocyclic spacer between the chromophores

S. Encinas, K. L. Bushell, S. M. Couchman, J. C. Jeffery, M. D. Ward, L. Flamigni and F. Barigelletti, J. Chem. Soc., Dalton Trans., 2000, 1783
DOI: 10.1039/B001594F

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