Strongly Coupled Oxasmaragdyrin–BF<sub>2</sub> Chelated Dipyrrin Dyads: Syntheses, X‐ray Structure, Ground‐ and Excited‐State Charge‐Transfer Interactions

Gobeze, Habtom B.; Kumar, Sunit; D’Souza, Francis; Ravikanth, Mangalampalli

doi:10.1002/chem.201604362

Cited by 16 publications

(9 citation statements)

References 92 publications

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“…These results clearly indicate that the electronic absorption of the TPA‐substituted BODIPYs is a function of the acceptor strength. As expected for charge transfer bands, changing the solvent to the more polar benzonitrile caused additional red‐shifting of the charge transfer band to 662 nm, as shown in Figure a …”

Section: Resultssupporting

confidence: 66%

“…As expected for charget ransfer bands, changing the solvent to the more polar benzonitrile caused additional red-shifting of the charge transfer band to 662 nm, as shown in Figure 2a. [21] As shown in Figure 2b(i), the steady-state fluorescences pectrum of BODIPY 1 in toluene was found to be located at 612 nm. Thisp eak was significantly red-shifted from the fluorescence of pristineB ODIPY derivatives, which are known to emit in the 520 nm range.…”

Section: Absorbance and Fluorescencestudiesmentioning

confidence: 83%

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Ultrafast Charge‐Separation in Triphenylamine‐BODIPY‐Derived Triads Carrying Centrally Positioned, Highly Electron‐Deficient, Dicyanoquinodimethane or Tetracyanobutadiene Electron‐Acceptors

Gautam

Misra

Thomas

et al. 2017

Chemistry A European J

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A series of new triphenylamine (TPA)-substituted BODIPYs 1-3 have been designed and synthesized through the Pd-catalysed Sonogashira cross-coupling and [2+2] cycloaddition-retroelectrocyclization reactions in good yields. This procedure yielded highly electron-deficient tetracyanobutadiene (TCBD) or dicyanoquinodimethane (DCNQ) electron-acceptor units centrally located at the TPA-BODIPY system. As a consequence, significant perturbation of the photonic and electronic properties was observed. The triads 2 and 3 showed red-shifted absorption, in addition to a strong charge-transfer-type absorption in the case of 3. The electrochemical studies revealed multi-redox processes involving the TPA, TCBD or DCNQ and BODIPY entities. The computational studies were performed at the B3LYP/6-31G** level to elucidate the geometry and electronic structures. An energy level diagram established for triads 2 and 3 revealed that the photoinduced charge-separation from the BODIPY* is thermodynamically possible. In addition, charge transfer from TPA to TCBD in 2 and DCNQ in 3 was also possible. These charge transfer mechanisms were confirmed by photochemical studies performed using time-resolved emission and femtosecond-transient-absorption studies in solvents of varying polarity. Ultrafast charge-separation has been witnessed in these closely spaced, strongly interacting triads. The charge-separated state returned to the ground state without populating the BODIPY*.

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Section: Resultssupporting

confidence: 66%

Section: Absorbance and Fluorescencestudiesmentioning

confidence: 83%

Ultrafast Charge‐Separation in Triphenylamine‐BODIPY‐Derived Triads Carrying Centrally Positioned, Highly Electron‐Deficient, Dicyanoquinodimethane or Tetracyanobutadiene Electron‐Acceptors

Gautam

Misra

Thomas

et al. 2017

Chemistry A European J

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“…Recent studies have shown the importance of oxasmaragdyrin sensitizer as a compelling material for light-energy-harvesting applications. − For instance, boryl oxasmaragdyrin offers many advantages, such as simpler synthesis and purification processes, low cost, and moisture stability. Besides, very recently, it has been found that such aromatic core-modified expanded porphyrins are efficient hole-transporting materials (HTMs) for perovskite solar cells (PSCs) as they retard charge recombination and transport the photogenerated hole to the counter electrode …”

Section: Introductionmentioning

confidence: 99%

“…On the other hand, boron–dipyrromethene units (BODIPY) are also molecular systems commonly used for efficient light capture, mainly in the far visible or UV region of the electromagnetic spectrum. The photophysical properties of BODIPY and derivatives have been previously studied by Jacquemin’s and Russo’s groups. − The coupling of oxasmaragdyrins with BODIPY through different types of linkers could also enhance the photosensitization properties of the porphyrin derivatives. , Experimentally, the effect of spacers or bridges between chromophores has been studied. Among the bridges that have shown the best results in electronic transfer are those containing acene, thiophene, and phenylethynyl groups.…”

Section: Introductionmentioning

confidence: 99%

“…27−32 The coupling of oxasmaragdyrins with BODIPY through different types of linkers could also enhance the photosensitization properties of the porphyrin derivatives. 23,33 Experimentally, the effect of spacers or bridges between chromophores has been studied. Among the bridges that have shown the best results in electronic transfer are those containing acene, 34 thiophene, 35 and phenylethynyl 36 groups.…”

Section: Introductionmentioning

confidence: 99%

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Assessment of BODIPY–Oxasmaragdyrin Dyads for Dye-Sensitized Solar Cells: Aromaticity, Photosensitization Capability, and Charge Transport

Borges-Martínez

Álvarez

Montenegro-Pohlhammer

et al. 2019

J. Phys. Chem. C

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Dye-sensitized solar cells (DSSC) are presented as an alternative among renewable energies where the dye plays an important role to obtain an effective device. Our goal in this work is to examine the influence of several bridging functional groups between the BODIPY and oxasmaragdyrin systems forming dyads (D), as potential components of DSSC, on the aromatic, photophysical, and charge transport properties. A set of 11 dyads made of the oxasmaragdyrin with 2,6-dimethoxyphenyl and methylamine groups in two of their meso carbons (S) and the 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY, B) moieties that differ in the binding bridge between them has been analyzed with density functional theory (DFT). The geometries were optimized with the B3LYP/6-311G(d,p) level of theory employing D3 Grimme′s correction, and a set of six functionals (B3LYP, BHandHLYP, CAM-B3LYP, PBE0, wB97X, TPSSh) was evaluated for reference systems in time-dependent DFT calculations. We found that TPSSh presents the best agreement with the available data of UV–vis spectra, so it was used for calculation of the electronic absorption spectra of the 11 oxasmaragdyrins and 11 dyads. When the bridge between S and B consists of one (D3), two (D5), or three acetylene units (D6), a strong absorption band in the infrared region around 1000 nm can be achieved. These bands correspond to charge-separated excited states that favor a panchromatic absorption in that region. The aromaticity index NICS(0) computed at the macrocycle center ring critical point using the GIAO/B3LYP/6-311G(d,p) level of theory shows in all these systems an aromatic character for the oxasmaragdyrin macrocycle (from −10.7 to −12.4 ppm). We also found that all dyads present a favorable electron injection toward the semiconductor TiO2 because the LUMO energy of the dyad is higher than the conduction band of the semiconductor (−4.3 eV) used in a solar cell. Besides, the HOMO energy of the dyads D3, D5, and D6 is lower than the redox potential (−4.8 eV) of a mediator as the I–/I3 – system used to recover it after circulation of electrons. Nonequilibrium Green′s function-based calculations performed for a couple of dyads, with (D6) and without (D4) a significant charge transfer band, connected to Au electrodes show that D6 was to be a better conductor, in agreement with the charge transfer results obtained from the photophysical properties. Finally, the Gibbs free energy for the formation of the dyads here investigated is calculated. All of them are shown to be exergonic reactions (ΔG solution < 0), which suggests that these systems could be synthesized.

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Triplet BODIPY and AzaBODIPY Derived Donor‐acceptor Dyads: Competitive Electron Transfer versus Intersystem Crossing upon Photoexcitation

et al. 2019

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The bis-iodo β-pyrrole-substituted BF 2 -chelated dipyrromethene, I 2 BODIPY, and its structural analogue BF 2 -chelated aza dipyrromethene, I 2 azaBODIPY, carrying a nitrogen at the mesoposition instead of carbon, were synthesized and characterized as new set of triplet sensitizers using different techniques. These sensitizers were further functionalized with fullerene, C 60 , at the central boron atom to build donor-acceptor conjugates. Using spectral, electrochemical, and computational methods, these conjugates were characterized, and the energy levels were established. Intersystem crossing to populate the triplet state was observed upon excitation of I 2 BODIPY and I 2 azaBODIPY, however, the measured rates of k ISC were found to be nearly two orders of magnitude higher for I 2 azaBODIPY (k ISC~1 0 11 s À 1 ) compared to I 2 BODIPY (k ISC~1 0 9 s À 1 ). The energetics, k ISC , and position of HOMO and LUMO levels was found to control the ability of the dyad to undergo electron transfer, although the donor-acceptor distances were virtually the same in both I 2 BODIPY-C 60 and I 2 azaBODIPY-C 60 conjugates. Freeenergy calculations revealed that the photoinduced electron transfer process was thermodynamically feasible from only the singlet excited states in both conjugates. Consequently, electron transfer from the 1 I 2 BODIPY* in competition with intersystem crossing was witnessed in the case of I 2 BODIPY-C 60 dyad while in the case of I 2 azaBODIPY-C 60 dyad, excitation of azaBODIPY led to a short-lived charge transfer state involving the catechol bridge followed by populating the low-lying 3 I 2 azaBODIPY* state without promoting the process of charge separation involving C 60 . The lifetime of the charge-separated states was in the ns range in the I 2 BODIPY-C 60 conjugate both in polar and nonpolar solvents.[a] S. subsequently reacted with NIS to make 1 d bearing iodo entities on the pyrrole rings. Finally, 1 d was reacted with C 60 in the presence of sarcosine in dry toluene to yield the dyad 1, according to Prato reaction. [16] The synthesis of 2 and the control compounds is given in Scheme 2. First, the BF 2 chelated (3,5-diphenyl-1H-pyrrol-2-yl) (3,5-diphenylpyrrol-2-ylidene)-amine, azaBODIPY was synthesized by literature methods. [17] This compound was further reacted with NIS in dry chloroform:acetic acid mixture to yield I 2 azaBODIPY, 2 b. In a separate experiment, azaBODIPY was reacted with 3,4-dihydroxybenzaldehyde in the presence of AlCl 3 to obtain the formyl phenyl dioxyboron derivative, 2 c. 2 c was further reacted with NIS to obtain 2 d. Finally, the electron acceptor fullerene was appended by reacting 2 d with fullerene and N-methyl glycine in dry toluene. It may be pointed here that reacting 1 b and 2 b directly with 3,4-dihydroxybenzaldehyde in the presence of AlCl 3 to obtain 1 d and 2 d resulted in complex reaction mixture due to the likely reaction of AlCl 3 with iodo entities.The newly synthesized compounds were fully characterized by MALDI-TOF-mass, 1 H and 13 C NMR techniques (see s...

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Strongly Coupled Oxasmaragdyrin–BF₂ Chelated Dipyrrin Dyads: Syntheses, X‐ray Structure, Ground‐ and Excited‐State Charge‐Transfer Interactions

Cited by 16 publications

References 92 publications

Ultrafast Charge‐Separation in Triphenylamine‐BODIPY‐Derived Triads Carrying Centrally Positioned, Highly Electron‐Deficient, Dicyanoquinodimethane or Tetracyanobutadiene Electron‐Acceptors

Ultrafast Charge‐Separation in Triphenylamine‐BODIPY‐Derived Triads Carrying Centrally Positioned, Highly Electron‐Deficient, Dicyanoquinodimethane or Tetracyanobutadiene Electron‐Acceptors

Assessment of BODIPY–Oxasmaragdyrin Dyads for Dye-Sensitized Solar Cells: Aromaticity, Photosensitization Capability, and Charge Transport

Triplet BODIPY and AzaBODIPY Derived Donor‐acceptor Dyads: Competitive Electron Transfer versus Intersystem Crossing upon Photoexcitation

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Strongly Coupled Oxasmaragdyrin–BF2 Chelated Dipyrrin Dyads: Syntheses, X‐ray Structure, Ground‐ and Excited‐State Charge‐Transfer Interactions

Cited by 16 publications

References 92 publications

Ultrafast Charge‐Separation in Triphenylamine‐BODIPY‐Derived Triads Carrying Centrally Positioned, Highly Electron‐Deficient, Dicyanoquinodimethane or Tetracyanobutadiene Electron‐Acceptors

Ultrafast Charge‐Separation in Triphenylamine‐BODIPY‐Derived Triads Carrying Centrally Positioned, Highly Electron‐Deficient, Dicyanoquinodimethane or Tetracyanobutadiene Electron‐Acceptors

Assessment of BODIPY–Oxasmaragdyrin Dyads for Dye-Sensitized Solar Cells: Aromaticity, Photosensitization Capability, and Charge Transport

Triplet BODIPY and AzaBODIPY Derived Donor‐acceptor Dyads: Competitive Electron Transfer versus Intersystem Crossing upon Photoexcitation

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Strongly Coupled Oxasmaragdyrin–BF₂ Chelated Dipyrrin Dyads: Syntheses, X‐ray Structure, Ground‐ and Excited‐State Charge‐Transfer Interactions