GROUND-STATE AND EXCITED-STATE PROPERTIES OF MONOMETALLIC AND BIMETALLIC COMPLEXES BASED ON RHENIUM(I) TRICARBONYL CHLORIDE - EFFECT OF AN INSULATING VS A CONDUCTING BRIDGE

The preparation and properties of monometallic and bimetallic complexes of rhenium(I) tricarbonyl chloride coordinated to 4,4'-dimethyl-2,2'-bipyridine ((CH3)2bpy), 2,2'-bipyrimidine (bpm), 2,3-bis(2-pyridyl)pyrazine (bpp), and 1,2-bis(4'-methyl-2,2'-bipyridyl-4-yl)ethane (Mebpy-Mebpy) are described. The CO stretching frequencies were in accord with facial geometry for the complexes. The NMR properties revealed that protons on the carbon atoms a to the coordinating nitrogen atoms of coordinated heterocycles were deshielded and shifted downfield. Electrochemically, one or two irreversible oxidations, a reversible reduction assignable to reduction of the heterocyclic ligand, and a second reduction (irreversible) at a potential more negative than that of the first were observed. The monometallic complexes displayed dπ*→π* transitions in the 360-380-nm region. The transition red-shifted to 454 nm for [(bpp)(Re(CO)3Cl)2] and to 480 nm for [(bpm)(Re(CO)3Cl)2] but remained at 366 nm for [(Mebpy-Mebpy)(Re(CO)3Cl)2], Emission was observed at room temperature for [((CH3)2bpy)Re(CO)3Cl], [(Mebpy-Meb-py)Re(CO)3Cl], [(bpp)Re(CO)3Cl], and [(Mebpy-Mebpy)(Re(CO)3Cl)2], Their emission maxima were located near 600 nm except for [(bpp)Re(CO)3Cl]. Its emission maximum was observed at 700 nm. © 1990, American Chemical Society. All rights reserved.