Synthesis and Photophysical Properties of Novel Donor-Acceptor N-(Pyridin-2-yl)-Substituted Benzo(thio)amides and Their Difluoroboranyl Derivatives

J Phys Chem A. 2016 Jun 23;120(24):4116-23. doi: 10.1021/acs.jpca.6b04004. Epub 2016 Jun 10.

Abstract

The unprecedented N-pyridin-2-yl substituted benzo(thio)amides were prepared and subsequently converted into the cyclic difluoroboranyl (BF2) derivatives. Mass spectrometry, multinuclear NMR, IR, and elemental analysis confirmed the structure of these compounds. UV/vis and fluorescence spectroscopy as well as first-principle calculations were used to study their properties. For the first time, the influence of both the O/S replacement and presence/absence of the BF2 moiety on the photophysical properties of compounds exhibiting charge transfer properties were examined experimentally and theoretically. We show that the sulfur-containing compound has a much smaller emission quantum yield than its oxygen counterpart. The fluorescence quantum yield is much higher upon formation of the difluoroboranyl complex.