About the Speaker
Professor Bhisma Kumar Patel is a professor at the Department of Chemistry at IIT Guwahati. Previously he has served as Head, Department of Chemistry and Dean of Student's Affairs at IIT Guwahati. His research areas encompass C-H Activations (Metal and Metal free), Tandem and Cascade Catalytic Synthesis, Organic Reaction Mechanisms, Heterocyclic Synthesis, Organo and Organometalic Catalysis, Theoretical Investigation on Selectivity in Organic Reactions, Green Chemistry, Organic Tribromide Mediated Organic Synthesis, Metal Catalysed Oxidative Transformations and Hypervalent Iodine Mediated Organic Transformations among others. He is a fellow of the Indian Academy of Sciences and the National Academy of Sciences and recipient of Costal Chemical Research Society Award (CCRS-2016), Samanta Chandra Sekhar Award by Odisha Bigyan Academy, 2015, Bronze Medal by Chemical Research Society (CRSI) of India, 2014 and R. C. Tripathy Young Scientist Award by Orissa Chemical Society (OCS), 1998.
Title of the Talk
"Access to Multifunctional AIEEgens via Annulations".
Ruthenium(II) catalyzed oxidative C-H / O-H and C-H / S-H annulations have been demonstrated by us using different directing arenes viz. 2-arylquinolinone, 2-arylbenzoxazinone, quinoline-4(1H)-thiones and quinoxaline with internal alkynes. Regiospecific annulations have been observed for directing arenes via the assistance of weaker carbonyl or thio carbonyl groups in the presence of a stronger nitrogen-directing site. Multifaceted application potential of AIEEgens in bio-imaging, theranostic, chemo/bio sensors, mechanochromic, solar cells and organic photoelectronic opens up a new research paradigm to develop and design more such compounds. Herein, quinoxaline N-directed Ru(II)-catalyzed oxidative annulation of 2-arylquinoxalines with internal alkynes leads to the formation of highly luminescent annulated quaternary ammonium salts in the presence of Cu(OAc)2.H2O oxidant. While the synthesized compounds exhibit emissions in green to yellow region with large Stoke shifts and reasonable quantum yields, their DFT calculation display 3D twisted conformation bearing donor-p-acceptor (D-p-A) configuration, where the two phenyl moieties could serve as donors and the extended quinoxaline core as the acceptor. Single crystal analysis of the quaternary salt, depicts the presence of multiple intermolecular non-covalent and weak π-π interactions that are possibly responsible for the luminescent behavior in crystalline as well as solid state. Advent of AIEE in quinoxalinium salt in DMF/water is due to the presence of intramolecular motion (RIM) and their restriction in aggregated state. AIEEgen unveils mechanochromism on changing from crystalline to amorphous state upon grinding, where a few of such compounds are utilized for development of latent fingerprints on an adhesive tape. Furthermore, a representative group of synthesized luminescent quinoxalinium salts portray dose dependent cell growth inhibition of HeLa cells with concomitant cell arrest in G1 phases. Hence, these AIEE luminogens are not only attractive as luminescent “light-up” probes for cell imaging, but also important as anticancer agents.