The complex W(CO)4(4-Me-phen)
(4-Me-phen = 4-methyl-1,10-phenanthroline) has been
determined to be luminescent and act as a spectroscopic probe in
UV-curable trimethylolpropane triacrylate/poly(methyl methacrylate) thin films.
Electronic absorption and luminescence characteristics have been measured for this complex in
room-temperature solutions
and low-temperature (80 K) glasses and in 10 mil thin films of the
unexposed and exposed
acrylate resins. In each environment dual luminescence bands were
observed which are
attributed to triplet-centered metal-to-ligand charge-transfer
(3MLCT) excited states. For
the unexposed photoresist these transitions were recorded at 520 and
750 nm and in the
exposed material these are moved to 525 and 715 nm, respectively.
The lowest energy
emission band undergoes a substantial blue-shift and intensifies
greatly on polymerization;
this phenomenon provides a useful molecular probe of the acrylate
cross-linking process.
These changes in emission characteristics are associated with a
rigidochromic effect imparted
on the lowest lying and solvent sensitive b2 →
b2(π*) 3MLCT electronically excited
state in
this complex. The complex W(CO)5(4-CN-py)
(4-CN-py = 4-cyanopyridine) was also
investigated as a spectroscopic probe in the acrylate system but
appears unsuitable for this
purpose as it was found to degrade significantly in the
resin.
ChemInform Abstract Electronic absorption, emission, and excitation spectra and emission lifetimes of (I) in ether/isopentane/ethanol (5:5:2) glasses at 80 rc C and benzene at 293 K are recorded. Details of the emission assignments and excited-state dynamics of the title system are discussed.
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