INTERVALENCE ELECTRON-TRANSFER IN PENTAAMMINERUTHENIUM COMPLEXES OF DIPYRIDYLPOLYENES, DIPYRIDYLTHIOPHENE, AND DIPYRIDYLFURAN

Intervalence transitions have been observed between pentaamminerutheni um(II) and -ruthenium(III) groups linked by dipyridylpolyenes, dipyrid ylthiophene, and dipyridylfuran. For all compounds, the comproportiona tion constants have been determined, to obtain corrected spectra of th e mixed-valence forms, and the intervalence band profiles have been ob tained by spectral deconvolution. The longest dipyridylpolyenes (with 3 and 4 double bonds) give only ill-defined bands, which does not allo w us to reach definitive conclusions on the decay law of the electroni c interaction with distance. On the contrary, dipyridylthiophene and - furan present a better resolution of the intervalence transition, whic h is ascribed to a better coplanarity and rigidity.