Structure and electronics in dimeric boron π expanded azine and salphen complexes

Although boron-based fluorophores incorporating nitrogenous chelating ligands have received much attention, there has been little work on examples of boron-salphen and azine derivatives. In this report, we present several π expanded boron salphen type complexes, incorporating both bis(2-hydroxynaphthaldehyde)azine as well as ortho, meta and para variants of the analogous 2-hydroxynaphthaldehyde salphen compounds. For the azine, we observed only the formation of a single BF₂ adduct, while for the naphth-phen compounds dimeric BF₂ binding was observed. All new compounds were fully characterized via X-ray diffraction, and both DFT and TDDFT studies were carried out to probe the electronic structures of these fluorophores.