Intramolecular Energy Transfer in Ruthenium(II)-Chromium(III) Chromophore-Luminophore Complexes. Ru(bpy)2[Cr(cyclam)(CN)2]24+

A new trinuclear Ru(II)-Cr(III) chromophore-luminophore complex, Ru(bpy)2[Cr(cyclam)(CN)2]24+, has been synthesized and characterized. Visible light absorption by the Ru(bpy)22+ chromophore leads to emission from the Cr(cyclam)(CN)2+ luminophore, as a consequence of very efficient (≥99%) and fast (subnanosecond time scale) chromophore-luminophore exchange energy-transfer process. The emission is intense (Φ = 5.3 × 10−3in H2O) and long-lived (τ = 260 μs in H2O). The photophysical properties of the luminophore are slightly perturbed by interaction with the chromophore, resulting in a sharper emission band shape and shorter radiative and radiationless lifetimes. The presence of a Ru(II) → Cr(III) intervalence transfer state, hardly detectable in the ground-state spectrum, is clearly revealed by the excited-state absorption spectrum of the chromophore-luminophore complex. © 1992, American Chemical Society. All rights reserved.