Preparative routes to novel rhenium (I) di- and monocarbonyl metal-to-ligand charge transfer chromophores

Complexes containing luminescent Metal-to-Ligand Charge Transfer (MLCT) excited states have been the subject of many studies because of their potential uses as sensors, probes, and photosensitizers for solar energy conversion. Re (I) complexes of this nature are of special interest because of their extraordinary stability. Here I describe new synthetic routes to novel di- and monocarbonyl Re (I) MLCT containing complexes incorporating chelating polypyridines, chelating phosphines, and diphosphine bridges.; New, high yield routes to a new class of long lived luminescent complexes of the type cis-[Re(CO)₂(N-N)(PP)]+ are presented here. All of the excited states are extremely air and light stable, exhibit spectral responses to the red of similar tricarbonyl complexes of Re (I), and possess lifetimes that are abnormally long compared to the energetically similar excited states in the fac-[Re(CO) ₃(bpy)L](+ or 0) series.; In addition, preparative routes to a series of novel Re (I) monocarbonyl complexes of the general formula [Re(CO)(N-N)(P-P))(+ or 0) are also described. The excited states all exhibit spectral responses to the red of similar dicarbonyl complexes of Re (I). Evidence for the substitution mechanism that leads to the new complexes is also included.; Synthesis and characterization of linear oligomeric complexes containing Re (I) tri-, di-, and monocarbonyl units is also presented. These syntheses focused on linear bridging using trans coordination so as to produce an energy “cascade” from the higher energy tricarbonyl units to the lower energy monocarbonyl units.