Consecutive Photolyses of Naphthalenedicarboxylic Anhydrides in Low Temperature Matrixes:  Experimental and Computational Studies on Naphthynes and Benzocyclopentadienylideneketenes

The generation of 1- and 2-naphthynes by the photolyses of 1,2- and 2,3-naphthalenedicarboxylic anhydrides (1, 2), respectively, was investigated by means of Fourier transformed infrared (FT-IR) and ultraviolet−visible (UV−Vis) absorption spectroscopies and theoretical calculations. Consecutive decarboxylation and decarbonylation of 1 were quantitatively analyzed on the basis of UV−Vis absorption spectra. The quantum efficiencies of these processes were estimated as 2 × 10-4 and 0.1, respectively. An isotopomer experiment showed that a cyclopropanone intermediate formed by the decarboxylation showed four CO stretching bands due to anharmonic resonance. Benzocyclopentadienylideneketene was formed from 1-naphthyne and CO, whereas 2-naphthyne did not react with CO to form the corresponding ketene. This different behavior was discussed on the basis of the geometries and energies calculated at the B3LYP/6-31G** level. Moreover, it was shown that the UV−Vis absorption spectra of reactive intermediates generated in the argon matrix were described well by computations based on INDO/S and time-dependent density functional theory (TD-DFT) methods.