The influence of the relative position of the thiophene and pyrrole rings in donor–acceptor thienylpyrrolyl-benzothiazole derivatives. A photophysical and theoretical investigation (original) (raw)
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The Journal of Physical Chemistry A, 2007
A comprehensive study has been made in solution at room temperature (293 K), low temperature (77 K), and in thin films (Zeonex matrixes) of the spectral and photophysical properties of six arylthienyl-and bithienylbenzothiazole derivatives functionalized with different donor groups. Similar experiments have been carried out with two related precursors (containing the arylthienyl and aryl-bithienyl conjugated systems), and results are compared. Singlet-singlet and triplet-triplet absorption spectra, emission spectra together with lifetimes and quantum yields have been obtained, and from these data the rates for all the radiative and nonradiative processes determined, providing information on the dominant decay processes. The arylthienyl-benzothiazole derivatives show high fluorescence quantum yields (φ F ) with negligible internal conversion (φ IC ), whereas the bithienyl-benzothiazoles display lower but still significant φ F values, but now radiationless processes (φ IC and φ ISC ) are competitive. A comparison with the analogous oligothiophenes is made. Singlet oxygen yields were also determined and the triplet energy transfer to 3 O 2 to produce 1 O 2 was found to be highly efficient with values of S ∆ () φ ∆ /φ T ) varying from 0.4 to 1.
Tetrahedron, 2011
Keywords: Heterocyclic azo dyes Thienylpyrrole Benzothiazole Nonlinear optical (NLO) materials Reverse polarity First hyperpolarizability (b) Thienylpyrroles as auxiliary donors Redox properties Density functional theory (DFT) Thermal stability a b s t r a c t Two series of related donoreacceptor conjugated heterocyclic azo dyes based on the thienylpyrrole system, functionalized with benzothiazol-2-yl (5e6) or benzothiazol-6-yl acceptor groups (7) through an N]N bridge, have been synthesized by azo coupling using 1-alkyl(aryl)thienylpyrroles (1) and benzothiazolyl diazonium salts (2e4) as coupling components. Their optical (linear and first hyperpolarizability), electrochemical, and thermal properties have been examined. Optimized ground-state molecular geometries and estimates of the lowest energy single electron vertical excitation energies in dioxane solutions were obtained using density functional theory (DFT) at the B3LYP/6-31þG(d,p) level. Hyper-Rayleigh scattering (HRS) in dioxane solutions using a fundamental wavelength of 1064 nm was employed to evaluate their second-order nonlinear optical properties. Of these systems, the benzothiazol-2-yl-diazenes 5e6 exhibit the largest first hyperpolarizabilities (b¼460e660Â10 À30 esu, T convention) compared to benzothiazol-6yl-diazenes 7 (b¼360e485Â10 À30 esu, T convention). Good to excellent thermal stabilities were also obtained for all azo dyes (235e317 C). This multidisciplinary study showed that modulation of the optical and electronic properties can be achieved by introduction of the benzothiazole acceptor group in the thienylpyrrole system through position 2 or 6 of the benzothiazole heterocycle.
2019
Three series of isomeric 2-pyridyl 4-aryl thiazoles have been synthesized by reacting 2/3/4-pyridine thioamides derived from the corresponding nitriles with various 4-substituted phenacyl bromides using Hantzsch thiazole synthesis. Amongst the three isomeric series, 2-pyridyl and 4-pyridyl isomers are found to exhibit better photophysical properties than 3-pyridyl series. 4-Pyridyl isomer with methoxy substituent on phenyl ring is found to exhibit high luminescence quantum yield. The relationship between the structure and the photophysical properties have been studied using DFT calculations.
Proceedings of SPIE - The International Society for Optical Engineering, 2011
Two series of novel push-pull heterocyclic azo dyes have been synthesized and characterized. The two series of compounds were based on different combinations of -conjugated bridges (bithiophene and thienylpyrrole) which also act simultaneously as donor groups, together with diazo(benzo)thiazolyl as acceptor moieties. Their thermal stability and electrochemical behavior were characterized, while hyper-Rayleigh scattering (HRS) was employed to evaluate their second-order nonlinear optical properties. The results of these studies have been critically analyzed together with several thienylpyrrole azo dyes reported earlier from our laboratories in which the thienylpyrrole system was used as the donor group functionalized with aryl and (benzo)thiazolyldiazene as acceptor moiety. The measured molecular first hyperpolarizabilities and the observed linear optical and redox behavior showed strong variations in function of the heterocyclic spacers used (bithiophene or thienylpyrrole) and were also sensitive to the acceptor strength of the diazenehetero(aryl) moiety.
Int J Quantum Chem, 1998
The electronic spectra of phenylmethylene, 3-pyridylmethylene, furfurylmethylene, and theinylmethylene derivatives of 2-aminothiazole have been investigated. Gaussian analysis for the spectra indicates the existence of four electronic transitions in the 350᎐220 nm region. Geometry optimization using AM1 method followed by INDOrS-CI calculations was carried out. The results confirmed the absence of n᎐ * Ž . transitions. The coefficients of configuration interaction CI wave functions defined the Ž . type of electronic transitions, which are of major charge transfer CT character. The anticonformer is the predominant one. The gap energies of the studied compounds are of the same order, which indicates that their reactivities are expected to be the same.
Photophysical properties and excited state dynamics of 4,7-dithien-2-yl-2,1,3-benzothiadiazole
Physical chemistry chemical physics : PCCP, 2017
The relationships between the photophysics and structural properties of 4,7-dithien-2-yl-2,1,3-benzothiadiazole as a function of solvent polarity are investigated both experimentally and by computational methods. Stationary fluorescence measurements are consistent with a model envisaging the presence of three types of conformers in equilibrium in the ground state. They are characterized by different relative orientations of the thiophene rings. Due to a low rotational barrier, the sample in solution is characterized by a distribution of relative internal orientations. By applying the Kawski method, we evaluate the average dipole moment of ground and excited states of the three types of conformers. The ground state dipole moments are small and similar for the three types of conformers. On the contrary, dipole moments differ substantially in the excited state. X-ray diffraction of a single crystal confirms the presence of an orientational disorder of thiophene rings. Transient absorpt...
Photophysical properties of 2,5-diphenyl-thiazolo[5,4- d ]thiazole
Journal of Photochemistry and Photobiology A: Chemistry, 2001
2,5-Diphenyl-thiazolo[5,4-d]thiazole (DTTz) was prepared and its photophysical properties were determined by optical absorption and steady-state spectroscopy, both in solution and in the solid state. Solvents with different properties (polarity, dielectric constant and refractive index) were employed and the solvatochromic effect and Stokes's shift were analyzed by Lippert's equation. The fluorescence emission was a mirror image of the excitation (absorption) spectrum, indicating that no geometric distortion takes place upon excitation. Larger Stokes's shifts with significant broadening of the fluorescence emission were obtained in the presence of strong concentrated acidic solutions. There was also a simultaneous decrease of the fluorescence quantum yield. Quantum mechanical calculation shows that this molecule is planar in the electronic ground state and its dipole moment is null in this state. Quantum mechanics successfully simulates the spectral profile. The lower electronic transition is characterized as a-*. Charge densities determined by quantum mechanical calculation demonstrate that protonation occurs on the nitrogen atom of the heterocyclic ring. Although no excimer emission was detected in concentrated solutions and in the solid state, an exciton splitting of the absorption or excitation spectra was observed. This was explained on the basis of the excitonic spectral splitting by the-stage molecular configuration of the molecules in the solid state with parallel dipole moments.
2-Arylthienyl-Substituted 1,3-Benzothiazoles as New Nonlinear Optical Chromophores
European Journal of Organic Chemistry, 2006
A series of nonlinear optical chromophores 6 containing a substituted benzothiazole ring have been synthesized and characterized. 1,3-Benzothiazoles 6 were prepared by treating various formyl derivatives of thienyl compounds with ortho-aminobenzenethiol in fair to excellent yields. These in turn were prepared by Suzuki coupling between aryl and thienyl precursors. The electronic interactions between donor and acceptor end groups in the conjugated 1,3-benzothiazoles 6 are revealed by the intense and markedly solvatochromic CT transitions. The solvatochromic behaviour of compounds 6 was determined by linear regression analyses of absorption maxima in several solvents, where benzothiazole 6f was found to be a very appropriate indicator dye