LASER FLASH-PHOTOLYSIS STUDY OF 10,10-DIMETHYL-9-ANTHRYLIDENE, A CARBENE WITH NEARLY DEGENERATE SINGLET AND TRIPLET-STATES

10,10-Dimethyl-9-anthrylidene (DMA) was studied by laser flash photolysis (LFP) techniques. LFP of the requisite diazo precursor in pentane or carbon tetrachloride produced transient spectra attributed to the hydrocarbon and monochlorinated diarylmethyl radicals, respectively. In the presence of pyridine and oxygen, ylides were formed upon LFP of 10,10-dimethyl-9-diazoanthrone. However, ylides are not formed in acetonitrile or acetone. The carbene itself was not detected by transient absorption spectroscopy. The absolute rate constants for reaction of DMA with pyridine, methanol and triethylsilane are 1.96 x 10(9), 1.8 x 10(10), and 1.0 x 10(8) l mol-1 s-1, respectively. It is concluded that the singlet and triplet states of DMA are essentially degenerate.