Planar, Fluorescent Push–Pull System That Comprises Benzofuran and Iminocoumarin Moieties

Węcławski, Marek K.; Meiling, Till Thomas; Leniak, Arkadiusz; Cywiński, Piotr; Gryko, Daniel T.

doi:10.1021/acs.orglett.5b02042

Cited by 18 publications

(6 citation statements)

References 44 publications

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“…It is worth emphasizing, however, that the absorption of dye 1 is bathochromically shifted by 20 nm compared to that of dye 2 , which underlines a better electronic communication between the aryl substituents and the core in the case of the former compound, due to a smaller dihedral angle between core and substituents. On the other hand, the λ max of the non‐symmetrical dye 4 is located at 451 nm, bathochromically shifted of about 50 nm compared to the spectra of previously reported analogous compounds bearing an iminocoumarin moiety . This is related to the increase in electron‐donating character of benzofuran, which is now weakly conjugated with an electron‐rich indole moiety.…”

Section: Figuresupporting

confidence: 64%

“…[15,16,17] This property can, in principle, increase charge mobility after photo-annealing, whereas, at the same time, soluble precursor dyes can be deposited from solutions. [18] The structure of dye 4 was confirmed by 1 Ha nd 13 CNMR spectroscopy and MS. In particular, to ensure ar easonable electronic communication, we focusedo nh eterocyclic substituents bearing five-membered rings.…”

mentioning

confidence: 89%

“…However, the reaction of 5 with ethyl 1‐ tert ‐butyloxycarbonyl‐indole‐3‐carboxylate led to the unexpected formation of heterocycle 4 , comprised of vertically linked benzofuran and coumarin moieties. This process resembles the formation of the furo[4′,3′,2′:4,5]naphtho[1,2,3‐ de ]chromen‐7‐imine skeleton from aryl acetonitriles and compound 5 , previously described by us . The structure of dye 4 was confirmed by 1 H and 13 C NMR spectroscopy and MS.…”

Section: Figurementioning

confidence: 99%

“…In particular, to ensure ar easonable electronic communication, we focusedo nh eterocyclic substituents bearing five-membered rings. [18] This is related to the increasei ne lectron-donating charactero fb enzofuran, which is now weakly conjugated with an electron-rich indole moiety. [15,16] The doubleK noevenagel condensation of 1,5-di-(benzoyloxy)anthraquinone 5 with variouse ster derivatives of thiophene, benzothiophene, and indole was performed (Scheme 1).…”

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confidence: 99%

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π‐Conjugated Organic–Inorganic Hybrid Photoanodes: Revealing the Photochemical Behavior through In Situ X‐Ray Absorption Spectroscopy

Hsu

Węcławski

Koszarna

et al. 2018

Chemistry A European J

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Small-molecule organic semiconductors exhibit great potential for the photoelectrochemical oxidation of water because of their n-type semiconductor nature and their tunable bandgaps. In this work, several head-to-tail bis-coumarins were synthesized and their photophysical properties characterized. Their characteristics as n-type semiconductors were modified by varying the electronic character of substituents at positions 1a nd 7, which enabled the energy level of the LUMO and the photoinduced charge-carrier-transfer efficiency to be modulated.X -Ray absorption near-edge structure (XANES) spectroscopy confirmed that the charge transfer is ac rucial factor contributing to the resulting activity of the photoanode. The photoactivity of the photoanodes towards water oxidation was revealed to be governed by both the LUMO energy level and transfer efficiency of the photoinduced charge carriers. Amongt he studied molecules, ab is-coumarin with benzothiophenyl substituents showed the greatest potential as light absorber for photoelectrochemicalw ater oxidation. Solar irradiation, as ar enewable and inexhaustible energy source,h as significant potential to replace carbon-based fuels, which currentlya re the major energy source for humanity. [1] However,t he low efficiency in the conversion of solar energy to usable energy sourcesh as hindered developments thus far. The proposition of af easible strategy to increaset he efficiency of solar energy conversion is, therefore, of paramount importance. Among various approaches, photoelectrochemical water splitting is ap romising, versatile technique to realize the highly efficient conversion of solar energy into chemical fuels. [2] The half reaction at the photoanode [i.e.,oxygen evolution reaction (OER)] is the kineticb arrieri nt his process due to the requirement of af our-electron transfer process (4 OH À ! 2O 2 + 2H 2 O + 4e À ). [3] Furthermore, with respectt ot he photoanode,t he light absorber in chargeo fc onverting the solar energy into chemical potential must be also carefully considered. Several stable semiconductors comprised of abundant elements with wide bandgaps such as TiO 2 , [4] Fe 2 O 3 , [5] and BiVO 4 [6,7] have been fabricated as photoanodes for water oxidation. However,t hese materials still suffer from the limitations of both low photocurrents and photovoltages due to their narrow light-absorption regions. For these reasons, reduction and/or modification of the bandgaph ave become desirable research outcomes over the past few years.Considering that the bandgap reduction and/or modification in inorganic materials is limited, [8] the use of organics mall-molecule dyes offers ap otentials olution to this barrier due to their semiconductor nature and tunable bandgap. [9] In an ideal photoanode for water oxidation, the generated electric field of the n-type semiconductor,t hrough band bending, would facilitate the migration of holes towards the reactive interface. [2] Althougho rganic semiconductors can be categorized into ptype, n-type and ambipolar semicondu...

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Section: Figuresupporting

confidence: 64%

mentioning

confidence: 89%

Section: Figurementioning

confidence: 99%

mentioning

confidence: 99%

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π‐Conjugated Organic–Inorganic Hybrid Photoanodes: Revealing the Photochemical Behavior through In Situ X‐Ray Absorption Spectroscopy

Hsu

Węcławski

Koszarna

et al. 2018

Chemistry A European J

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“…The obvious key elements to the construction of such structures are the push–pull π‐conjugated building blocks . Such molecules possessing high dipole moments are a key class of dye widely employed both in practical applications as well as in various types of research . Their popularity stems from the appreciable combination of optical properties, such as high fluorescence quantum yield, large Stokes shift, and polarity‐sensitive fluorescence .…”

Section: Introductionmentioning

confidence: 99%

The Coumarin‐Dimer Spring—The Struggle between Charge Transfer and Steric Interactions

Kielesiński

Morawski

Sobolewski

et al. 2017

Chemistry A European J

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The synthesis of a weakly coupled, strongly polarized coumarin dimer has been achieved for the first time. The three-step strategy comprises the Skattebøl formylation followed by the Knoevenagel reaction and the formation of a tertiary amide by using a peptide-type procedure. The molecule consists of two different coumarin moieties: One is a classical donor-acceptor system and the second one possesses a weaker amide donor at the 7-position. The polarized coumarin dimer can form an electronically conjugated structure possessing an electric dipole larger than that of 7-(dimethylamino)coumarin-3-carboxylic acid. The limited flexibility of the inter-coumarin connection results in stable conformers of different electric dipole moments and complex photophysics. In the solid state, this compound has a strongly bent conformation with the two coumarin units forming an angle of around 74°. In solution, two conformers are in equilibrium. The existence of the molecule as two conformers in the ground state has been confirmed by optical studies, and further corroborated by molecular calculations. The fluorescence spectra possess a unique feature: A charge-transfer band (ca. 550 nm) is visible only in nonpolar or weakly polar solvents. Optical spectroscopy studies coupled with molecular calculations allowed us to rationalize this phenomenon: The large amplitude of intramolecular motions is responsible for the conformational isomerization as well as producing a conical intersection between the potential energy surfaces of the excited singlet state and the ground state, which opens an internal conversion channel that effectively competes with the fluorescence of the conformers.

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Environment‐Responsive 8‐CF₃‐BODIPY Dyes with Aniline Groups at the 3 Position: Synthesis, Optical Properties and RI‐CC2 Calculations

et al. 2017

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The spectroscopic and the photophysical properties of isomeric environment-sensitive BODIPYd erivatives in different solvents are reported. The simultaneous presence of the stronge lectron-acceptorC F 3 and electron-donor NH 2 group in the structure of BODIPY,a sw ell as the positiono f the NH 2 group on the aryl ring, showedasignificante ffect on the spectroscopic and fluorescence characteristics of the BODIPY chromophore, both experimentally and theoretically. The comparison of meta and para derivatives (1a and 1b) shows that, in both cases, they have av ery low quantum yield (F f )a nd fluorescencel ifetime (t f )i nt he solvents used (except for n-hexane), therefore, they are potentially suitable as turn-onf luorescences ensors. The twisted intramolecular charge transfer (TICT) mechanism was adopted to explain solvate-induced fluorescence quenching. Besides this, there is as trong pH dependence on the photophysical behavior of the two isomers, which could also lead to applications as pH sensors. On the other hand, only 1a can be au seful probe for CO 2 sensing.O wing to aw eaker electron-donor character of the NHCOMe group in comparison with the NH 2 group, the position of the fluorescence "off-on" threshold of BODIPY 1c and 1d is shifted to the side of more polar solvents than for 1a and 1b.

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Planar, Fluorescent Push–Pull System That Comprises Benzofuran and Iminocoumarin Moieties

Cited by 18 publications

References 44 publications

π‐Conjugated Organic–Inorganic Hybrid Photoanodes: Revealing the Photochemical Behavior through In Situ X‐Ray Absorption Spectroscopy

π‐Conjugated Organic–Inorganic Hybrid Photoanodes: Revealing the Photochemical Behavior through In Situ X‐Ray Absorption Spectroscopy

The Coumarin‐Dimer Spring—The Struggle between Charge Transfer and Steric Interactions

Environment‐Responsive 8‐CF₃‐BODIPY Dyes with Aniline Groups at the 3 Position: Synthesis, Optical Properties and RI‐CC2 Calculations

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Planar, Fluorescent Push–Pull System That Comprises Benzofuran and Iminocoumarin Moieties

Cited by 18 publications

References 44 publications

π‐Conjugated Organic–Inorganic Hybrid Photoanodes: Revealing the Photochemical Behavior through In Situ X‐Ray Absorption Spectroscopy

π‐Conjugated Organic–Inorganic Hybrid Photoanodes: Revealing the Photochemical Behavior through In Situ X‐Ray Absorption Spectroscopy

The Coumarin‐Dimer Spring—The Struggle between Charge Transfer and Steric Interactions

Environment‐Responsive 8‐CF3‐BODIPY Dyes with Aniline Groups at the 3 Position: Synthesis, Optical Properties and RI‐CC2 Calculations

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Environment‐Responsive 8‐CF₃‐BODIPY Dyes with Aniline Groups at the 3 Position: Synthesis, Optical Properties and RI‐CC2 Calculations