Multiple-state emission and excited-state dynamics of CpRe(CO)2L (L = 3-benzoylpyridine and 4-benzoylpyridine) complexes in fluid and glassy solutions

The photophysical properties of the complexes CpRe(CO)2(3-benzoylpyridine) and CpRe(CO)3(4-benzoylpyridine) are determined by examining their electronic absorption, emission and excitation spectra ans emission lifetimes. The results show that CpRe(CO)2(3-benzoylpyridine) exhibits multiple emission from triplet-centered n,pi* intraligands and metal-to-ligand charge-transfer (MLCT) levels while CpRe(CO)2(4-benzoylpyridine) exhibits only one emission spectra which is assigned to the lowest energy MLCT state. The difference were attributed to the electronic and geometric differences in the excited states.