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Luminescence data are reported for W(CO)5L complexes, where L = 4-acetylpyridine, 4-benzoylpyridine, 4-cyanopyridine and 4-formylpyridine, as solids, and in fluid solution. Photosubstitution quantum yields (for the dissociation of L) have been recorded for these W(CO)5L complexes in several solvents using various irradiation wavelengths. Apparent activation energies for the W(CO)5L complexes in several solvents have been measured from the temperature dependencies of the emission and photoreactivity processes. Quenching of the emission and photoreactivity processes are reported for several quenchers; the results are used to bracket the energies of the emitting state for each complex. Two low-lying metal to ligand change-transfer excited states are implicated in the radiative decay process. Possible excited state schemes for these W(CO)5L complexes are discussed in accordance with the experimental observations. Excited state absorption and primary photoproduct spectra have been recorded for the W(CO)5L complexes in methylcyclohexane and benzene by monitoring techniques. A common photoproduct is inferred, its spectrum being close to that of W(CO)5S, where S denotes solvent, following pulse laser photolysis of W(CO)6 as previously reported by us. (Author)

Laser pulse photolysis at 353 nm of tungsten hexacarbonyl in room temperature methylcyclohexane produces an intermediate, proposed to be W(CO)5S, S denoting solvent, with an absorption maximum at 425 nm and epsilon max. = 7,500 m to the -1 power cm. In the presence of added L = 4-acetylpyridine, the intermediate reacts completely to form W(CO)5L as final product. The rate of disappearance of the intermediate is pseudo first order, with kapp linear in (L) at low concentration but approaching a limiting value at higher concentrations. The proposed mechanism is one of reversible dissociation of W(CO)5S to W(CO)5 and S with rate constants k sub 1 and K sub -1 followed by scavenging of the W(CO)5 by the L, with rate constant k sub 2. At 20 C k sub 1 = 1,900,000 s to the -1 power and the corresponding activation quantities are E sub 1* = 3.9 kcal mole and (* sub 1 - E sub 2* = 2.6 kcal mole. The nature of the primary photolysis step is discussed.

The complex W(CO)5L,L = 4 cyanopyridine, is found to emit in room temperature methycyclohexane solution. The emission is centered around 630 nm and is 105 plus or minus 10 nsec in lifetime, gamma, at 25 C. Added 0.1 M ethanol does not change the charcteristics, and in this medium 1/gamma = 2.61x10 to the 8th power exp(-1960/RT). The mission is quenched by anthracene, as is also the photosubstitution reaction whereby L is replaced by ethanol ( phi = 0.028 plus or minus 10% at room tmperature), Stern-Volmer plots of gamma/gamma and of phi/phi vs. quencher concentration are linear, the common slope giving a bimolecular quenching rate constant of 3.7x10 to the 9th power M sec. The charge transfer (CT) emitting state is clearly implicated in the photochemistry; between the emission spectrum and the anthracene triplet state energy, the energy of the CT state is bracketed as between 14.7 and 20 kk. (Author)