BODIPY functionalized o-carborane dyads for low-energy photosensitization

Abstract

A new type of organic dyad that can induce low-energy photosensitization has been developed; electron donor and electron acceptor units are boron dipyrromethene (BODIPY) and ortho-carborane (o-Cb), respectively. The new dyads consist of a V-shaped BODIPY-(o-Cb)-BODIPY molecular array in which two BODIPY units are substituted onto two adjacent carbon atoms of the central o-Cb. In the presence of the o-Cb unit, as an electron acceptor, significant fluorescence quenching was observed which indicated that photoinduced electron transfer (PET) had occurred from the end-on BODIPY units to the central o-Cb with PET efficiencies of 63-71%. As a result, the corresponding cationic and anionic species that are responsible for the charge transfer state were detected by the serial spectroelectrochemical studies: cationic BODIPY radicals at 400 nm at the applied voltage of 1.44 V and broad absorption bands of anionic o-Cb radicals in the range of 250-490 nm at -1.84 V. Transient absorption studies further confirmed the BODIPY radical anion at 540 nm and the o-Cb radical anion at 350-475 nm with a structureless broad band.

Carborane–stilbene dyads: the influence of substituents and cluster isomers on photoluminescence properties

“…6,[8][9][10] This quenching takes place due to a rapid photoinduced electron-transfer (PET) process from the excited state S 1 of the fluorophore to the lower energy excited state S x of the cluster, which inhibits the fluorescence emission of the fluorophore. 11 In 2007, our group reported the PL properties of o-carboranyl-functionalized large molecules based on poly(aryl-ether) derivatives, 12,13 In these systems, the influence of the cluster (neutral closo clusters or their conceptually derived anionic nido clusters that are formally obtained by the removal of a B + ) on the fluorescence behavior was investigated. More recently, we developed a set of fluorescent dyads based on carboranes (see compounds 1-2 in Scheme 1) in which the styrene fragment is bound to at least one of the C c atoms through a bridging methylene.…”

Aggregation-induced emission characteristics of o-carborane-functionalized fluorene and its heteroanalogs: the influence of heteroatoms on photoluminescence

“…This result implies that all compounds have a significant electronic coupling between the two organic chromophores in the ground state. 34,35 The solvent dependence of the UV-vis absorption spectra for CDC, CDN, CDO and CDS was hardly observed (Fig. S1, ESI †), further indicating that the ground state was not affected by the solvent polarity.…”

“…46 (2 H, d, J = 8.0 Hz), 7.36-7. 35 (2 H, d, J = 4.0 Hz), 7.30-7.22 (6 H, m), 1.20 (6 H, s). 13 Synthesis of 1,2-di(dibenzothiophene-2-yl)-ortho-carborane, CDS.…”

Boron clusters in luminescent materials

“…143a-b, Scheme 34) for low-energy photosensitization. 52 The new dyads consist of V-shaped molecules in which two BODIPY units are substituted onto two adjacent carbon atoms of the central o-carborane. In the presence of the o-carborane unit, as an electron acceptor, significant fluorescence quenching was observed which indicated that PET (photoinduced electron transfer) had occurred from the end-on BODIPY units to the central o-carborane with PET efficiencies of B63-71%.…”