title: Dynamics of ion-regulated photoinduced electron transfer in BODIPY-BAPTA conjugates.
abstract: Efficient Ca(2+)-switched fluorescent sensors, where fluorescence output is governed by a light-activated ion-gated electron transfer pathway, can be obtained on combining BODIPY chromophores with a readily oxidized biocompatible and selective BAPTA receptor. Herein we report the synthesis and studies of two such conjugates, which vary in the nature of the spacer separating the two electroactive components, namely none (1) or phenyl (2). Single crystal X-ray crystallography and molecular modelling structures and calculations give information on molecular and electronic structure, while steady-state fluorescence experiments show high Ca(2+)-induced fluorescence enhancement factors of 122 and 23 and K(d) values of 0.50 μM and 0.13 μM for 1 and 2, respectively. Notably, studies of the ultrafast photoinduced processes (through transient absorption spectroscopy) give access to electron transfer dynamics in pseudo-physiological media as well as in a polar non-protic solvent and information about the fate of the excited molecules in the presence and absence of calcium. In water, electron transfer rates as high as 3.3 × 10(12) s(−1) and 8.3 × 10(11) s(−1) are measured for the ion-free, directly connected conjugate and the variant incorporating a phenyl spacer, respectively. This electron transfer pathway is efficiently blocked by the presence of an ion, restoring fluorescence.
authors.affiliation: Univ. Bordeaux/CNRS, ISM, 351 cours de la Libération, 33405 Talence Cedex, France.
authors.forename: Pinar
authors.initials: P
authors.lastname: Batat
authors.forename: Guillaume
authors.initials: G
authors.lastname: Vives
authors.forename: Robin
authors.initials: R
authors.lastname: Bofinger
authors.forename: Ren-Wei
authors.initials: RW
authors.lastname: Chang
authors.forename: Brice
authors.initials: B
authors.lastname: Kauffmann
authors.forename: Reiko
authors.initials: R
authors.lastname: Oda
authors.forename: Gediminas
authors.initials: G
authors.lastname: Jonusauskas
authors.forename: Nathan D
authors.initials: ND
authors.lastname: McClenaghan
mesh_terms: D001896:Boron Compounds / Q000737:chemistry*; D002118:Calcium / Q000737:chemistry; D018360:Crystallography, X-Ray; D004533:Egtazic Acid / Q000031:analogs & derivatives* / Q000737:chemistry; D004579:Electron Transport; D007477:Ions / Q000737:chemistry; D008968:Molecular Conformation; D055668:Photochemical Processes; D011789:Quantum Theory; D013050:Spectrometry, Fluorescence
chemical_list: C095489:4,4-difluoro-4-bora-3a,4a-diaza-s-indacene; D001896:Boron Compounds; D007477:Ions; D004533:Egtazic Acid; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium