Rationalization of weak interactions in two fluorescence active imidazo-[1,5-a]-pyridine derivatives: A combined experimental and computational study.

Two bis -bromo substituted imidazo-[1,5- a ]-pyridine derivatives IMPY1 and IMPY2 were synthesized from a 2:1:2 mixture of ortho / meta -bromobenzaldehyde, 2-cyanopyridine and ammonium acetate. The compounds IMPY1 and IMPY2 exhibit blue fluorescence in both THF and methanol solution and their highly fluorescent nature is revealed by the quantum yields Φ F ranging from 9.3 to 10.4%. The crystal structure of the compounds are stabilized by various weak, non-classical hydrogen bonds viz. C−H⋯N, C−H⋯Br and C−H⋯π as well as type II interhalogen and C−Br⋯π halogen bonds. The supramolecular features and electronic property of these compounds have been thoroughly analyzed with the aid of DFT, TD-DFT and molecular electrostatic potential (MEP) analyses. [ABSTRACT FROM AUTHOR]