Photophysical studies of donor, acceptor substituted tetrahydrodibenzo[a,i]phenanthridines

Highly luminescent, 5-aryl-7,8,13,14-tetrahydrodibenzo[ajlphenanthridines (THDPs) in Donor(D)-pi-Acceptor(A), A-pi-A, A-pi-A-pi-A1 configurations were synthesized in good to moderate yields by simple, two step reactions. All the phenyl rings were found to be in near-coplanar configuration due to the enforced planarity by the ethylene bridge. As a result, efficient pi-conjugation was maintained throught the molecule. UV-visible absorption and fluorescence spectra of THDP became shifted to longer wavelengths upon substitution of different moieties at 5-Aryl position. A maximum of 200 nm red shifted fluorescence with respect to parent compound was observed for the nitro substituent. However, tradeoffs in spectral shifts were noticed when two strongly electron withdrawing groups such as nitro and cyano groups were present simultaneously. Presence of one or more acceptors induced the intramolecular electron transfer processes, and the photophysical properties of THDP core was tuned by different substituents. Application of this fluorophore has also been demonstrated by means of DNA interaction studies. (C) 2016 Elsevier Ltd. All rights reserved.