Synthesis, Crystal Structure and Photoluminescent Properties of Novel 9-Cyano-pyrrolo[1,2-a][1,10]phenanthrolines

Novel 9-cyano-pyrrolo[1,2-a][1,10]phenanthrolines 6a–d were obtained by an efficient one-pot regioselective reaction between 1,10-phenanthrolinium bromides 2a–d and acrylonitrile as a dipolarophile, in the presence of triethylamine and tetrakis-pyridino-cobalt(II) dichromate (TPCD) as oxidizing agents. The optical properties of the compounds were investigated through UV–Vis spectrophotometry and steady-state photoluminescence measurements, while their structures were elucidated by single-crystal X-ray diffraction. The structural characterization revealed that the molecular structures of the four compounds were stabilized by hydrogen bonds and π–π interactions.