Thermal and Laser Pyrolysis of Hydrocarbon Anion Radicals

The solid anion radical salts resulting from the reductions of naphthalene, pyrene, perylene, benzo[k]fluoranthene, and biphenyl with lithium, cesium, and potassium metals were either pyrolyzed at 200-380 degrees C or irradiated with a pulsed frequency doubled Nd:YAG laser (532 nm wavelength). For both the pyrolytic and laser photolytic studies the only volatile products were hydrogen and methane. The hydrogen originated from the anionic polymerization of the anion radical. Evidence is presented that suggests that the methane results from a carbene intermediate, which in turn reacts with the H(2). Consistent with the H(2) formation, MALDS mass spectral analysis revealed the presence of dimers, trimers, and higher polymers of the polyaromatic hydrocarbon in the remaining nonvolatile products. There were considerably fewer low molecular weight oliomers produced via the laser photolysis than via the thermolysis.