LUMINESCENCE RIGIDOCHROMISM OF FAC-CLRE(CO)3(4,7-PH2PHEN) (4,7-PH2PHEN = 4,7-DIPHENYL-1,10-PHENANTHROLINE) AS A SPECTROSCOPIC PROBE IN MONITORING POLYMERIZATION OF PHOTOSENSITIVE THIN-FILMS

The complex fac-ClRe(CO)3(4,7-Ph2phen) (4,7-Ph2phen = 4,7-diphenyl-1,10-phenanthroline) has been found to be strongly luminescent and able to act as a spectroscopic probe in technologically important photosensitive thin films. UV-curable trimethylolpropane triacrylate/poly(methyl methacrylate) (TMPTA/PMMA) and bisphenol-A-novalac/diglycidyl diglycidyl ether of bisphenol-A epoxy resins have been investigated containing the organometallic probe. In each case, the luminescence from these thin films is attributed to a lowest energy triplet-centered metal-to-ligand charge-transfer (MLCT) excited state that arises from the complex. Importantly, the MLCT luminescence characteristics (energy position, band intensity, and lifetime) vary greatly when these acrylate and epoxy resins are exposed to UV light and polymerize. These changes in emission properties are attributed to a luminescence rigidochromic effect and are associated with the varying nature of solvation and dipolar interactions about the metal complex during these cross-linking polymerization reactions.