title: Multistep energy and electron transfer in a "V-configured" supramolecular BODIPY-azaBODIPY-fullerene triad: mimicry of photosynthetic antenna reaction-center events.
abstract: A new photosynthetic antenna-reaction-center model compound composed of covalently linked BF2 -chelated dipyrromethene (BODIPY), BF2 -chelated azadipyrromethene (azaBODIPY), and fullerene (C60 ), in a "V-configuration", has been newly synthesized and characterized by using a multistep synthetic procedure. Optical absorbance and steady-state fluorescence, computational, and electrochemical studies were systematically performed in nonpolar, toluene, and polar, benzonitrile, solvents to establish the molecular integrity of the triad and to construct an energy-level diagram revealing different photochemical events. The geometry obtained by B3LYP/6-31G* calculations revealed the anticipated V-configuration of the BODIPY-azaBODIPY-C60 triad. The location of the frontier orbitals in the triad tracked the site of electron transfer determined from electrochemical studies. The different photochemical events originated from (1) BODIPY* were realized from the energy-level diagram. Accordingly, (1) BODIPY* resulted in competitive ultrafast energy transfer to produce BODIPY-(1) azaBODIPY*-C60 and electron transfer to produce BODIPY(.) (+) -azaBODIPY-C60 (.) (-) as major photochemical events. The charge-separated state persisted for few nanoseconds prior populating (3) C60 *, which in turn revealed an unusual triplet-triplet energy transfer to produce (3) azaBODIPY* prior returning to the ground state. These findings delineate the importance of multimodular systems in energy harvesting, and more importantly, their utility in building multifunction performing optoelectronic devices.
authors.affiliation: Department of Chemistry, University of North Texas, 1155 Union Circle, 305070, Denton, TX 76203-5017 (USA).
authors.forename: Venugopal
authors.initials: V
authors.lastname: Bandi
authors.forename: Fiona P
authors.initials: FP
authors.lastname: D'Souza
authors.forename: Habtom B
authors.initials: HB
authors.lastname: Gobeze
authors.forename: Francis
authors.initials: F
authors.lastname: D'Souza
mesh_terms: D001372:Aza Compounds / Q000737:chemistry; D001672:Biocompatible Materials / Q000737:chemistry* / Q000378:metabolism; D001896:Boron Compounds / Q000737:chemistry*; D055664:Electrochemical Techniques; D004579:Electron Transport; D037741:Fullerenes / Q000737:chemistry*; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry / Q000378:metabolism; D011789:Quantum Theory; D055672:Static Electricity; D013816:Thermodynamics
chemical_list: C095489:4,4-difluoro-4-bora-3a,4a-diaza-s-indacene; D001372:Aza Compounds; D001672:Biocompatible Materials; D001896:Boron Compounds; D037741:Fullerenes; D045322:Photosynthetic Reaction Center Complex Proteins
keywords: BODIPY; azaBODIPY; charge separation; electron transfer; fullerenes