Electronic spectra of a homo-molecular dimer cation, (C6H5CN)2+, are measured by photodissociation spectroscopy in the gas phase. Broad features appeared in the 450–650 nm region are characteristic of π3 → πCN transitions of the C6H5CN+ chromophore. No intense band is observed in the 650–1300 nm region, where other aromatic dimer cations usually show charge resonance bands. Two component molecules of (C6H5CN)2+ cannot take a parallel sandwich configuration suitable for the resonance interaction, because of geometrical constraints due to other stronger interactions.

This work was supported in part by a Grant-in-Aid for Scientific Research (No. 09740450) from the Ministry of Education, Science, Sports and Culture of Japan.

This is a postprint of an article published by Springer Netherlands in Research on Chemical Intermediates, 1998, available online: http://doi.org/10.1163/156856798X00393