Excited-state behavior of ortho-phenylenes

J Org Chem. 2011 Nov 4;76(21):9188-91. doi: 10.1021/jo201842q. Epub 2011 Oct 12.

Abstract

The excited-state properties of unsubstituted ortho-phenylene oligomers have been studied using TD-DFT. Calculations of vertical transitions at the helical ground-state geometries are in good qualitative agreement with the experimental UV-vis spectra. In the excited state, the spring-like compounds compress; for the longer oligomers, this compression is localized at one end of the oligomer. This behavior explains the unusual experimentally observed hypsochromic shifts in fluorescence spectra with increasing oligomer length.