title: Solvent-Driven Conformational Exchange for Amide-Linked Bichromophoric BODIPY Derivatives.
abstract: The fluorescence lifetime and quantum yield are seen to depend in an unexpected manner on the nature of the solvent for a pair of tripartite molecules composed of two identical boron dipyrromethene (BODIPY) residues attached to a 1,10-phenanthroline core. A key feature of these molecular architectures concerns the presence of an amide linkage that connects the BODIPY dye to the heterocyclic platform. The secondary amide derivative is more sensitive to environmental change than is the corresponding tertiary amide. In general, increasing solvent polarity, as measured by the static dielectric constant, above a critical threshold tends to reduce fluorescence but certain hydrogen bond accepting solvents exhibit anomolous behaviour. Fluorescence quenching is believed to arise from light-induced charge transfer between the two BODIPY dyes, but thermodynamic arguments alone do not explain the experimental findings. Molecular modelling is used to argue that the conformation changes in strongly polar media in such a way as to facilitate improved rates of light-induced charge transfer. These solvent-induced changes, however, differ remarkably for the two types of amide.
authors.affiliation: Department of Dyestuff Technology, Institute of Chemical Technology, Mumbai, 400019, India.
authors.forename: Shrikant
authors.initials: S
authors.lastname: Thakare
authors.affiliation: Molecular Photonics Laboratory, School of Chemistry, Newcastle University, Bedson Building, Newcastle upon Tyne, NE1 7RU, UK.
authors.forename: Patrycja
authors.initials: P
authors.lastname: Stachelek
authors.affiliation: Bio-Organic Division, Bhabha Atomic Research Centre, Mumbai, 400085, India.
authors.forename: Soumyaditya
authors.initials: S
authors.lastname: Mula
authors.affiliation: Department of Dyestuff Technology, Institute of Chemical Technology, Mumbai, 400019, India.
authors.forename: Ankush B
authors.initials: AB
authors.lastname: More
authors.affiliation: Bio-Organic Division, Bhabha Atomic Research Centre, Mumbai, 400085, India.
authors.forename: Subrata
authors.initials: S
authors.lastname: Chattopadhyay
authors.affiliation: Laser and Plasma Technology Division, Bhabha Atomic Research Centre, Mumbai, 400085, India.
authors.forename: Alok K
authors.initials: AK
authors.lastname: Ray
authors.affiliation: Department of Dyestuff Technology, Institute of Chemical Technology, Mumbai, 400019, India.
authors.forename: Nagaiyan
authors.initials: N
authors.lastname: Sekar
authors.affiliation: Laboratoire de Chimie Organique et Spectroscopies Avancées (LCOSA), Ecole Européenne de Chimie, Polymères et Matériaux, Université de Strasbourg, 25 rue Becquerel, 67087, Strasbourg Cedex 02, France.
authors.forename: Raymond
authors.initials: R
authors.lastname: Ziessel
authors.affiliation: Molecular Photonics Laboratory, School of Chemistry, Newcastle University, Bedson Building, Newcastle upon Tyne, NE1 7RU, UK. anthony.harriman@ncl.ac.uk.
authors.forename: Anthony
authors.initials: A
authors.lastname: Harriman
keywords: BODIPY; boron; charge transfer; conformational exchange; dyes/pigments; fluorescence; isomerisation