The Least Stable Isomer of BN Naphthalene: Toward Predictive Trends for the Optoelectronic Properties of BN Acenes

The least stable
isomer of the parental BN naphthalene series has
been synthesized in a simple four-step sequence. Its experimental
electronic structure characterization via UV-PES, cyclic voltammetry,
and UV–vis spectroscopy in direct comparison with three other
known BN naphthalene isomers has established two guiding principles
for predicting the electronic structures of BN acene compounds: (1)
Orientational BN isomers have similar HOMO–LUMO gaps. (2) For
each pair of orientational BN isomers, the more thermodynamically
stable compound has the lower HOMO energy. Furthermore, we demonstrate
that BN/CC isosterism in the context of BN-9,1-Naph can
impact crystal packing to favor a cofacial π-stack motif.