Luminescence of some simple tetracoordinate organoboron complexes in solution. Fluorescence from ligand to ligand CT states

The Lewis base-Lewis acid adducts with the Lewis bases pyrazine, triphenyphosphine, neocuproine (2,9-dimethy1-1,10-phenanthroline), cuproine (2,2'-diquinolyl) and triphenylborane as Lewis acid were prepared. Their electronic spectra are characterized by low-energy electronic transitions which are attributed to phenyl (BPh3) to Lewis base, ligand to ligand charge transfer (LLCT) transitions. These Lewis base-BPh3 complexes display a distinct blue to green fluorescence in solution which originates from the lowest-energy LLCT singlets. (C) 2016 Elsevier B.V. All rights reserved