Unravelling the optoelectronic and biological properties of phenanthroimidazo [1,2‐c] quinazoline‐based donor‐acceptor materials

Imidazo[1,2‐c]quinazoline, a class of fused imidazole and quinazoline acceptor units, is widely established as biologically and broadly spectral active materials, while their optoelectronic properties were seldom investigated in the literature. In this context, this research work introduced two donors of varying strength, such as triphenylamine (TP) and phenothiazine (PZ) units, into the phenanthroimidazo [1,2‐c] quinazoline acceptor unit to form donor‐acceptor type luminescence materials such as TPQZ and PZQZ, respectively and were characterized by NMR and mass spectroscopy. Both these materials exhibited intramolecular charge transfer (ICT) type absorption (∼380–450 nm) and emission (∼540–600 nm) characteristics, which attributed to the electronic transition occurring from the HOMO of the TP/PZ donor to the LUMO+1 and LUMO+2 of the imidazo [1,2‐c] quinazoline acceptor unit, as predicted using DFT calculations. Increasing the electron donor strength was not only limited to fine‐tuning the π→π* based localized (∼400–450 nm) to ICT (∼450–650 nm) emission characteristics in both the solution and solid‐state conditions but also found to improve the zone of inhibition to 16 mm against Staphylococcus aureus / Bacillus subtilis bacterial species. The scope of realizing the luminescence nature of this acceptor unit is further expanded towards tagging biological samples such as E. coli. Overall, this work opens up a new paradigm in developing luminescent materials utilizing imidazo[1,2‐c]quinazoline acceptor unit for optoelectronic and biological applications.