BODIPY Dyads Research Articles

Exciton coupling and energy transfer in oxygen-bridged unsymmetrical BODIPY dyads

Herein, we report the synthesis of unsymmetrical BODIPY dyads through the reaction of phenol oxygen on BODIPYs with α-carbon atoms on bromoBODIPYs. Excited state interactions were observed for the dyads composed of components having similar absorption wavelengths. When dissimilar components were used to construct the dyad, exciton coupling disappeared and an energy transfer causing a large pseudo-Stokes shift was observed. The reported structures are the first examples of oxygen-bridged unsymmetrical BODIPY-BODIPY dyads.

1,8-Naphthalimide-Substituted BODIPY Dyads: Synthesis, Structure, Properties, and Live-Cell Imaging.

A set of 1,8-naphthalimide (NPI)-substituted 4,4-difluoroboradiaza-s-indacene (BODIPY) dyads 1 a-1 c were designed and synthesized by the Pd-catalyzed Sonogashira cross-coupling reaction of ethynyl substituted NPI 1 with the meso-, β-, and α-halogenated BODIPYs a, b, and c, respectively. The BODIPY 1 c exhibits redshifted absorption, which suggests better electronic communication with substitution at the α-position of BODIPY compared with at the meso and β positions, which was further supported by time-dependent DFT calculations. The optical band gap follows the order 1 a>1 b>1 c. The single-crystal X-ray structures of dyads 1 a-1 c are reported, which reflect planar orientations of the BODIPY units with respect to the NPIs. The DFT-optimized structures show good correlation with the experimental data obtained from the single-crystal X-ray structures. The packing diagram of 1 a shows a sheet-like arrangement, 1 b forms a ladder-like structural motif, and 1 c forms a complex 3D structural arrangement. The dyads 1 a-1 c show low cytotoxicity (IC50 >100 μm). The confocal microscopy studies with HeLa and A375 cells (when treated with dyads 1 a-1 c) show that all the dyads easily enter the cell membrane and show significant multicolor intracellular fluorescence covering the entire visible range with clear emissions in blue, green, and red channels.

Excitation energy transfer processes in BODIPY based donor-acceptor system - Synthesis, photophysics, NLO and DFT study

Excited state intramolecular proton transfer (ESIPT) meso flanked BODIPY dyad are synthesized and investigated by using spectroscopic, fluorescence lifetime decay, electrochemical and DFT method. Excitation (λexc = 290 nm) of the Bn-OH-BDY dyad leads to emission (λemi = 545 nm) totally directed by the BODIPY subunits pointing to excitation energy transfer (EET) from the ESIPT to BODIPY core. A large shift of 255 nm has been observed between excitation and emitted light. Attachment of ESIPT unit does not cause any perturbation in the low-energy absorption band of the Bn-OH-BDY dyad. The electrochemical study shows an irreversible peak of single-electron oxidation of ESIPT core at 0.38 eV and reduction of BODIPY core at 1.023 eV. DFT calculation studies show the existence of charge transfer (CT) state from ESIPT to BODIPY core. The results obtained from photophysics, electrochemical study and DFT support EET from excited ESIPT core to BODIPY subunits. The DFT results show dominating electronic contribution to the linear polarizability (α) and first hyperpolarizability (β). NLO response was measured using Z scan technique. The values obtained for nonlinear absorption coefficient (β) in DMSO is −5.95 × 10−12 (m/W) and for third-order susceptibility (χ)3 it is 14.19 × 10−13 (e.s.u). The geometries of the dyad were optimized by using B3LYP/6–311++ G (d,p) level of theory.

BODIPY dyads and triads: synthesis, optical, electrochemical and transistor properties

A series of D–A dyads and D–A–D triads molecular systems based on triphenylamine and 9-ethyl-carbarzole as donor (D) and BODIPY as acceptor (A) has been designed and synthesized. The optoelectronic properties including optical, electrochemical, and charge carrier mobility of these molecules have been investigated. We found that the D–A–D triads exhibited broader absorption, raising the HOMO energy levels and increase hole carrier mobilities. Analysis surface morphology revealed that BODIPY containing carbazole demonstrated smooth film and no macro phase aggregation was observed upon thermal annealing.

Energy transfer and charge separation dynamics in photoexcited pyrene-bodipy molecular dyads.

The photophysical properties of two pyrene-bodipy molecular dyads, composed of a phenyl-pyrene (Py-Ph) linked to the meso position of a bodipy (BD) molecule with either H-atoms (BD1) or ethyl groups (BD2) at the 2,6 positions, are investigated by stationary, nanosecond and femtosecond spectroscopy. The properties of these dyads (Py-Ph-BD1 and Py-Ph-BD2) are compared to those of their constituent chromophores in two solvents namely 1,2-dichloroethane (DCE) and acetonitrile (ACN). Stationary spectroscopy reveals a weak coupling among the subunits in both dyads. Excitation of the pyrene (Py) subunit leads to emission that is totally governed by the BD subunits in both dyads pointing to excitation energy transfer (EET) from the Py to BD chromophore. Femtosecond fluorescence and transient absorption spectroscopy reveal that EET takes place within 0.3-0.5 ps and is mostly independent of the solvent and the type of the BD subunit. The EET lifetime is in reasonable agreement with that predicted by Förster theory. After EET has taken place, Py-Ph-BD1 in DCE and Py-Ph-BD2 in both solvents decay mainly radiatively to the ground state with 3.5-5.0 ns lifetimes which are similar to those of the individual BD chromophores. However, the excited state of Py-Ph-BD1 in ACN is quenched having a lifetime of 1 ns. This points to the opening of an additional non-radiative channel of the excited state of Py-Ph-BD1 in this solvent, most probably charge separation (CS). Target analysis of the TA spectra has shown that the CS follows inverted kinetics and is substantially slower than the recombination of the charge-separated state. Occurrence of CS with Py-Ph-BD1 in ACN is also supported by energetic considerations. The above results indicate that only a small change in the structure of the BD units incorporated in the dyads significantly affects the excited state dynamics leading either to a dyad with long lifetime and high fluorescence quantum yield or to a dyad with ability to undergo CS.

Synthesis, photophysical, DFT and photodiode properties of subphthalocyanine–BODIPY dyads

In this study, subphthalocyanine–borondipyrromethene conjugates have been successfully designed and synthesized.

Synthesis and photophysical properties of a porphyrin–BODIPY dyad and a porphyrin–o-carborane–BODIPY triad

The photophysical and electrochemical properties of a newly synthesized porphyrin–BODIPY dyad and a porphyrin–o-carborane–BODIPY triad have been investigated.

Synthesis, chemiluminescence and energy transfer efficiency of 2,3-dihydrophthalazine-1,4-dione and BODIPY dyad

The design, synthesis and energy transfer efficiency of a new covalently linked molecular dyad 5, which consists of 2,3-dihydrophthalazine-1,4-dione and BODIPY scaffolds, are reported. It is noteworthy that dyad 5 can induce chemiluminescence upon treatment with alkaline H2O2 in the presence of Fe(III) ions. This reaction triggers chemiluminescence resonance energy transfer (CRET) from 2,3-dihydrophthalazine-1,4-dione unit to BODIPY fluorophore, which act as the donor and the acceptor components, respectively. To our best knowledge, this is the first example of a covalently linked molecular dyad consisting of chemiluminogenic 2,3-dihydrophthalazine-1,4-dione and BODIPY dye. Importantly, dyad 5 can provide a low energy emitting material via the chemiluminescence energy transfer (CRET), which covers almost the entire visible region (400 nm–700 nm) of the electromagnetic spectrum.

Triplet-triplet annihilation upconversion kinetics of C60-Bodipy dyads as organic triplet photosensitizers.

Three new triplet photosensitizers consisting of a bodipy derivative and C60 moieties were synthesized for triplet-triplet annihilation upconversion of perylene. With the extension of the π-conjugated structure of the bodipy derivative, the three photosensitizers exhibited different absorption wavelengths, e.g. 517 nm for B-2, 532 nm for B-4, and 557 nm for B-6. The steady-state and transient absorption, steady-state fluorescence, and upconverted fluorescence emission were investigated to reveal step-by-step the dynamic processes of the above systems. The quantum yields of intramolecular energy transfer, intersystem crossing, and triplet-triplet energy transfer were measured. From the upconverted fluorescence emission spectra, the overall quantum yield of the triplet-triplet annihilation upconversion, ΦUC, was determined to be 5.80% for B-2, 7.95% for B-4, and 4.99% for B-6.

Novel fluorescent anthracene–bodipy dyads displaying sensitivity to pH and turn-on behaviour towards Cu(ii) ions

Three bichromophoric compounds containing anthracene and bodipy moieties connected by different spacers have been synthesized and fully characterized. The set of spacers comprises a variety of bridges (short and flexible 1,2-diaminoethane in compound 1a, long and flexible 1,8-diaminooctane in compound 1b and short and rigid piperazine in compound 1c). The new compounds show interchromophoric communication via Electronic Energy Transfer (EET). When anthracene is excited, the energy is efficiently transferred to the bodipy moiety. The emission of the acceptor is partially quenched in dyad 1a but remarkably not in 1b and 1c. In an aqueous environment, the fluorescence of the new compounds display sensitivity to pH (emissive at acidic values and non-emissive at neutral ones), a typical behaviour of photoinduced electron-transfer (PET) probes, but with remarkable differences in the pKa of each compound, attributable to the nature of the linker. Additionally, the behaviour in the presence of several metallic cations (Cu2+, Ni2+, Cd2+, Zn2+) has been studied, and a turn-on response towards Cu2+ in water at neutral pH has been found.

BODIPY dyads from a,c-biladiene salts.

Asymmetric dimers of BODIPY dyes were synthesized from a,c-biladiene salts in good yields; this work constitutes a new versatile approach to the synthesis of BODIPY dyads, which display red-shifted absorptions and emissions in the visible spectral region, higher fluorescence quantum yields and larger Stokes shifts compared with monomeric BODIPYs. The X-ray structure of a 5,5'-dibromo-BODIPY dyad was obtained, and the reactivity of this compound under Suzuki cross-coupling reaction conditions was investigated.

Novel aluminum-BODIPY dyads: intriguing dual-emission via photoinduced energy transfer.

Three novel BODIPY-based heterodinuclear complexes, [salen(3,5-(t)Bu)2Al-(OC6H4-BODIPY)] (6), [salen(3,5-(t)Bu)2Al-(OC6F2H2-BODIPY)] (7), and [(mq)2Al-(OC6H4-BODIPY)] (8) (salen = N,N'-bis(salicylidene)ethylenediamine, BODIPY = 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene, and mq = methyl-8-quinolinolato) were prepared and characterized by multinuclear NMR spectroscopy. The specific structures of 6-8 were also determined by single crystal X-ray analysis. In particular, the salen-based heterodinuclear complexes 6 and 7 exhibited higher thermal stability (Td5 = 309 and 306 °C, respectively) than that of the closely related mononuclear aluminum or BODIPY compounds, except for 8. The UV/vis absorption and PL spectra for 6 and 7 indicated a significant photoinduced energy transfer from the aluminum-salen moiety to the BODIPY group in an intramolecular manner. Theoretical calculations revealed independent transition states of the aluminum-salen moiety or the BODIPY group in the Al(III)-BODIPY dyads, further supporting these experimental results.

Efficient energy transfer in ethynyl bridged corrole–BODIPY dyads

Corrole–BODIPY dyads bridged by ethynyl linkages have been synthesized in high yield. The efficiency and direction of energy transfer has been found to depend on the number of corrole rings and their connection position on the BODIPY core.

Non-covalent functionalization of carbon nano-onions with pyrene–BODIPY dyads for biological imaging

We report a novel approach based on non-covalent interactions for the functionalization of carbon nano-onions (CNOs) with fluorophores.

Solvent switchable dual emission from a bichromophoric ruthenium-BODIPY complex.

A ruthenium(II) polypyridyl-BODIPY dyad is presented which exhibits a solvent switchable dual emission. Intense oxygen sensitive emission from the ruthenium centre and O2 independent emission from the BODIPY centre, are both observed in organic media. In aqueous media, the BODIPY emission is reversibly switched off leaving only a ruthenium centred emission. The materials are interesting both as self-referenced O2 probes and for cell/tissue imaging.

Synthesis and properties of rhenium(I) bridged boron-dipyrromethene dyad

We synthesized the hexa-coordinated Re ( I ) bridged BODIPY dyad 1 in decent yield by thermal reaction of benzimidazole substituted BODIPY 2 with Re ( CO )5 Cl . The dyad 1 was characterized by 1 H , 13 C , 11 B , 19 F NMR, ESI-MS, FTIR, UV-vis, and electrochemical techniques. In Re ( I ) bridged dyad 1, the Re ( I ) ion is hexa-coordinated and coordinates with nitrogen atoms of two benzimidazole units, three axial carbonyl ligands and one chloride atom. The presence of three carbonyl groups in dyad 1 was verified by 13 C NMR and IR spectroscopy. The absorption and steady-state fluorescence spectra of Re ( I ) bridged BODIPY dyad showed a slightly broad and hypsochromically shifted absorption and emission bands compared to BODIPY 2. The electrochemical studies indicated that, the Re ( I ) bridge BODIPY dyad 1 was easy to reduce compared to BODIPY 2 supporting the electron deficient nature dyad upon Re ( I ) ion binding. The molecular structure of dyad 1 was further elucidated by DFT computational studies.

Fine‐Tuning Dual Emission and Aggregation‐Induced Emission Switching in NPI–BODIPY Dyads

Three new NPI-BODIPY dyads 1-3 (NPI = 1,8-naphthalimide, BODIPY = boron-dipyrromethene) were synthesized, characterized, and studied. The NPI and BODIPY moieties in these dyads are electronically separated by oxoaryl bridges, and the compounds only differ structurally with respect to methyl substituents on the BODIPY fluorophore. The NPI and BODIPY moieties retain their optical features in molecular dyads 1-3. Dyads 1-3 show dual emission in solution originating from the two separate fluorescent units. The variations of the dual emission in these compounds are controlled by the structural flexibilities of the systems. Dyads 1-3, depending on their molecular flexibilities, show considerably different spectral shapes and dissimilar intensity ratios of the two emission bands. The dyads also show significant aggregation-induced emission switching (AIES) on formation of nano-aggregates in THF/H2O with changes in emission color from green to red. Whereas the flexible and aggregation-prone compound 1 shows AIES, rigid systems with less favorable intermolecular interactions (i.e., 2 and 3) show aggregation-induced quenching of emission. Correlations of the emission intensity and structural flexibility were found to be reversed in solution and aggregated states. Photophysical and structural investigations suggested that intermolecular interactions (e.g., π-π stacking) play a major role in controlling the emission of these compounds in the aggregated state.

A dioxadithiaazacrown ether–BODIPY dyad Hg2+ complex for detection of l-cysteine: fluorescence switching and application to soft material

A Hg2+ coordinate complex of a 1,4-dioxa-7,13-dithia-10-azacyclopentadecane–BODIPY dyad recognises l-cysteine (cys) via reversible complexation/decomplexation and show switching of fluorescence upon sequential addition of Hg2+ and cys in solution as well as in hydrogel.

Experimental and theoretical study of enol-keto prototropic tautomerism and photophysics of azomethine-BODIPY dyads.

In this study we report about two novel azomethine–BODIPY dyads 1 and 2. The two dyads have been, respectively, synthesized by covalent tethering of tautomeric ortho-hydroxy aromatic azomethine moieties including N-salicylideneaniline (SA) and N-naphthlideneaniline (NA) to a BODIPY fluorophore. Both of the two dyads 1 and 2 show enol-imine (OH) structures dominating in the crystalline state. Dyad 1 in the enol state is the most stable form at room temperature in most media, while enol–keto prototropic tautomerism of the NA moiety in solution is preserved in dyad 2, which can be reversibly converted between enol and keto forms in the environment's polarity. Visible illumination of dyad 2 in the enol state excites selectively the BODIPY fragment and then deactivates radiatively by emitting green light in the form of fluorescence, while the emission intensity of 2 in the keto state is quenched on the basis of the proton-coupled photoinduced electron transfer (PCPET) mechanism. This allows large fluorescence modulation between the two states of dyad 2 and generates a novel tautomerisable fluorescent switch. Theoretical calculations including calculated energies, potential energy surfaces (PESs) and intrinsic reaction coordinate (IRC) analysis further support that the single proton transfer reaction from an enol form to a transition state (TS) and from the TS to a keto form for 2 is easier to occur than that for 1, which accounts for the fluorescence quenching of 2 in methanol. The agreement of the experimental results and theoretical calculations clearly suggests that fluorescent and tautomeric components can be paired within the same molecular skeleton and the proton tautomerization of the latter can be designed to regulate the emission of the former. In addition, preliminary experiments revealed that 1 can be potentially used as a simple on/off fluorescent chemosensor which exhibited higher selectivity for Cu(2+) over other common cations.

Resonance energy transfer-enhanced rhodamine–styryl Bodipy dyad triplet photosensitizers

Broadband visible light-absorbing triplet photosensitizers with rhodamine as the energy donor and styryl Bodipy as the energy acceptor/spin converter were prepared.