title: Luminescent N,O-chelated chroman-BF2 complexes: structural variants of BODIPY.
abstract: The synthesis and characterization of 5-(chromen-4-one)-dipyrromethane (1), 5-(6-methyl-chromen-4-one)-dipyrromethane (2), 5-(6-isopropyl-chromen-4-one)-dipyrromethane (3) and the respective chromans, 7-[2-pyrrolo]-pyrrole[1,2-a]12H pyrrolino[2,3-b]chroman-4-one (4), 4-methyl-7-[2-pyrrolo]-pyrrole[1,2-a]12H pyrrolino[2,3-b]-chroman-4-one (5) and 4-isopropyl-7-[2-pyrrolo]-pyrrole[1,2-a]12H pyrrolino[2,3-b]-chroman-4-one (6) have been described. Chroman derivatives 4-6 have been used in the synthesis of highly stable, fluorescent, borondifluoride complexes (7-9). All the compounds have been fully characterised by various physicochemical techniques viz., elemental analyses, IR, HRMS, NMR ((1)H, (13)C), electronic absorption, emission (solution and solid state), electrochemical and thermal studies. Crystal structures of dipyrromethanes 1 and 2, chroman derivative 6 and boron complexes 7-9 have been determined by X-ray single crystal analyses. Structural studies revealed that the formation of 4-6 takes place by DDQ mediated C-N coupling. The higher stability of 4-6 relative to their respective dipyrrins has been supported by theoretical studies.
authors.affiliation: Department of Chemistry, Faculty of Science, Banaras Hindu University, Varanasi-221 005, UP, India.
authors.forename: Roop Shikha
authors.initials: RS
authors.lastname: Singh
authors.forename: Mahendra
authors.initials: M
authors.lastname: Yadav
authors.forename: Rakesh Kumar
authors.initials: RK
authors.lastname: Gupta
authors.forename: Rampal
authors.initials: R
authors.lastname: Pandey
authors.forename: Daya Shankar
authors.initials: DS
authors.lastname: Pandey