EFFECT OF PI-SYSTEM ON LONG-RANGE PHOTOINDUCED ELECTRON-TRANSFER IN THROUGH-RING ALPHA-CYCLODEXTRIN COMPLEXES OF CARBAZOLE-VIOLOGEN LINKED COMPOUNDS

Carbazole-viologen linked compounds, with long spacers (ca. 2 nm), wer e incorporated into two a-cyclodextrins to afford rotaxane-type comple xes. In the presence of a biphenyl unit in the spacer, the fluorescenc e lifetime of the carbazole moiety was reduced by 2 ns as compared wit h the case with a simple alkyl spacer (tau = 12 ns). Contribution of t he superexchange mechanism to long-range electron transfer from the ca rbazole- to the viologen moiety was suggested. (C) 1998 Elsevier Scien ce Ltd. All rights reserved.