Expeditious synthetic approach and photophysical properties of fluorescent benzimidazo[1,2-d]dibenzo[b,f][1,4]diazepine derivatives

A short and efficient synthetic route to novel benzimidazo[1,2-d]dibenzo[b,f][1,4]diazepines has been developed using a copper catalyzed intramolecular Ullmann type C-N bond forming reaction as a key step. Copper iodide and 1,10-phenanthroline furnished the desired compounds in good yield. The products are intensely fluorescent with appreciably long lifetimes. Looking at their prospective use as markers for biomacromolecules and in biochemical analysis, we have explored the photophysical properties of these compounds. The spectrophotometric and spectrofluorometric studies reveal that while the absorbance maxima of the compounds are in the UV region, the emission maxima fall in the visible (blue-green) region.