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![Spin density populations and dihedral angles of the two tetramers: 4a and 4c. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]](profile/M-Bouachrine/publication/230131106/figure/fig2/AS:267694427602963@1440834733293/Spin-density-populations-and-dihedral-angles-of-the-two-tetramers-4a-and-4c-Color.png)
Spin density populations and dihedral angles of the two tetramers: 4a and 4c. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]
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P3mt1 and P3mt2 were electrochemically synthesized using two different electrolyte supports H2SO4 and TEABF4, respectively. First, it was deduced from density functional theory (DFT) calculations that the electronic and steric effects govern polymerization mechanism of the radical monomers. Second, DFT combined with experimental spectroscopic analy...
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... polymerization mechanisms continue in the same reactivity protocol based on the spin density at the terminus carbon sites of each oligomer (4a, 4c, 5a, and 5c) (Figs. 6 and 7). The most probable hexamers are 6a and 6c and their optimization geometries are presented in Figure 8. Spin density populations and dihedral angles of the two pentamers: 5a and 5c. [Color figure can be viewed in the online issue, which is available at www.interscience. wiley.com.] At this stage and concerning the calculated spin ...
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... The DFT were performed using the Gaussian 09 package [22]. It is noted that the use of this method as well as this basis set appears to be adequate approach for the study of physicochemical properties of these compounds and most organic compounds [23][24][25][26][27][28][29]. This method introduces electron correlation effects at a lower cost in the computation's time. ...
... Vibrational properties including infrared and Raman simulated spectra were accomplished. So, we think that this approach permit to describe deeply the correlation structure-properties and consequently to modulate the properties of appropriate organic optoelectronic devices [21][22][23]. ...
... The B3LYP hybrid functional combines Becke's three-parameter functional [28] for the exchange with the non-local correlation potential of Lee-Yang-Parr [29]. In fact, these basis sets have been successfully applied to some conjugated polymers systems [23,30,31]. Therefore, the optimized geometries were calculated for the various charged states (cationic, anionic, and neutral). ...
This work aims at completing theoretically the oligomerization mechanism, vibrational and optical properties of soluble oligomer obtained from anodic oxidation of p-chloro-anisole (OPClAn) with a view to get some insight into structure–property relationships. The obtained results were compared with those of oligomers from p-fluoro-anisole (OPFAn) and p-phenylene (OPP). Spectroscopic characterization based on infrared absorption, Raman scattering, optical absorption, photoluminescence (PL) and decays of time-resolved photoluminescence (TR-PL) in chloroform solution and in film states of OPClAn was performed. Further investigations on conformational, geometrical parameters, and electronic structures of these compounds were carried out by applying Density Functional Theory (DFT) calculation based on B3LYP with 6-31G(d,p) and 3-21G* as basis sets. The optimized structures, HOMO–LUMO gaps (ΔH–L), in addition to the ionization potentials (IPs) and electron affinities (EAs) were calculated. The ΔH–Ls, Egs, IPs and EAs of the oligomers were obtained by extrapolating those of the oligomers to the inverse chain length for n = 13. From the combined results, we have evoked an oligomerization mechanism consistent with the OPClAn prepared material. Furthermore, we have shown that introducing electron-donating/withdrawing substituents on oligo-phenylene backbone can tune the HOMO and LUMO levels and thereby control the opto-electronic properties of the designed oligomers.
... Moreover, density functional theory (DFT) has proved to be successful in predicting and reproducing geometrical and optoelectronic properties of a variety of organic compounds, and in addition, more accurate than semi empirical and ab initio methods. [10][11][12] Recently, we have chemically synthesized and characterized by various experimental spectroscopic techniques a new graft copolymer based on poly (N-vinylcarbazole) (PVK) and poly(3-methylthiophene) (PMeT). Two samples named PVK-3MeT1 and PVK-3MeT2 were prepared with two different polymerization yields, in the doped and chemically de-doped states. ...
In this article, we present quantum chemical calculations, based on density functional theory (DFT), performed to investigate the geometries and the opto-electronic properties of a new synthesized graft copolymer based on poly(N-vinylcarbazole) (PVK) and poly(3-methylthiophene) (PMeT) named PVK-3MeT. First, we have theoretically computed and compared the structural, optical, and vibrational parameters of both neutral and doped states. In addition, the excited state was theoretically obtained by the ab initio RCIS/STO-3G method. To assign the absorption and emission peaks observed experimentally, we computed the energies of the lowest singlet excited state with the time-dependent density functional theory (TD-DFT) method. Electronic parameters such as the HOMO-LUMO band gap, the ionization potential (IP), and electron affinity (EA) are extracted. Calculations show that the PVK-3MeT copolymer is nonplanar in its ground neutral state. Meanwhile, upon doping or photoexcitation, an enhancement of the planarity is observed, resulting on a decrease of the inter-ring torsion angle between 3-methylthiophene units. Such modifications in the geometric parameters induce a dramatic change on the HOMO and LUMO orbitals in the doped or excited states. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.
We present a kinetic and theoretical study of electrophilic aromatic substitution (SEAr) involving 2-(2′,4′,6′-trinitrophenyl)-4,6-dinitrobenzotriazole 1-oxide 1 with a series of 5-R-substituted indoles 2a-e (R = CN, Cl, H, Me and NH2) in acetonitrile at 20 °C. Single electron transfer (SET) mechanism was proposed and confirmed by the agreement between the rate constants (k) and the oxidation potentials (Epox) of these series of indoles. Using Mayr's equation, the electrophilicity parameter (E) of 1 at C-7 position is derived and compared with the same parameter estimated using empirical equation E versus. pKa. Density Functional Theory (DFT) calculations were performed to confirm the suggested reaction mechanisms and elucidate the origin of the electrophilic reactivity of 1. Notably, a linear correlation (R2 = 0.9957) between the experimental nucleophilicity (N) and the theoretical model of nucleophilicity (ω−1) determined in this work of various 5-R-substituted indoles has been obtained and discussed.
Mayr and Parr's approaches were combined with the correlation N vs ω−1 established in the present work, to evaluate the empirical electrophilicity parameter (E) of 2-(2′,4′,6′-trinitrophenyl)-4,6-dinitrobenzotriazole 1-oxide and the unknown nucleophile specific parameters (N and sN) of four new 5-R-substituted indoles (R = NO2, F, H and N(CH3)2) in acetonitrile.
In this paper, news donor–Acceptor (D–A) structures involving carbazole as electron donor units and furan, aniline and hydroquinone as electron acceptors has been theoretically studied using the density functional theory (DFT) with the hybrid B3LYP exchange correlation function and the 6-31G (d) basis set. Thus, structural parameters, electronic properties, HOMO–LUMO gaps, Molecular orbital densities, Ionization Potential (IPs), Electronic Affinities (EAs) are theoretically predicted. However, the charge transfer process between the carbazole/bicarbazole electron donor unit and the electron acceptor one is supported by analyzing the optical absorption spectra of the obtained compounds and the localization of occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO).
In this work, we have analyzed the vibrational, optical and emission properties of soluble copolymer denoted poly(2,5-di-butoxyethoxy-1,4-phenylene-alt-2,5-thienylene) (PBuPT) by combining experimental and theoretical studies. Extrapolated Ionization Potentials (IPs), Electron Affinities (EAs) and energy gaps were determined employing Density Functional Theory (DFT) method. Theoretical analyses have been performed in order to understand deeply the interesting role played by the intra-molecular S⋯O interactions in determining the planarity of the copolymer. Further, an intra-molecular charge transfer for the copolymer has been proposed through the alternating donor–acceptor conjugated systems. In addition, vibrational, optical and emission spectra of three repeat units model compound have been simulated and compared to the experiments. Based on these results, we have described attentively the structure–property relationships of those samples which could be exploited as an active layer in organic optoelectronic devices.
Poly(3-methyl-thiophene) (P3MTh) is synthesized via oxidative coupling of the basic monomer using TiCl4 as oxidant in chloroform medium. Experimental analyses (infrared, optical absorption measurements and thermal analysis) are combined with theoretical calculations, based on Density Functional Theory (DFT), not only to confirm the polymer formation but also to predict the final structure of the resulting compound. Furthermore, the relationship between structure–property is carried out.
The magnetic properties of two types of poly[(3-methoxy)4,6-toluene] (P3mt1 and P3mt2) are studied before and after doping with iodine or organic acids (CF3COOH or CH3SO3H) in a range of temperature varying from 110 to 460K. Under 250K and independent of the state, the magnetic susceptibility χ obeys Curie law dependence. Up to this temperature, χ is governed by a Pauli law contribution. This fact can be related to localized or delocalized spin. Furthermore, iodine doping induces distortion in the polymers that affects the ESR line distribution. In the case of organic acids doping process, a hyperfine structure with hyperfine coupling constant values between 2.2 and 2.8G is observed. As the spin concentration decreases, we deduce that in the case of P3mt2, there is a de-doping process.
Poly(para-hydroquinone) (PPHQ) was prepared by chemical oxidation reaction using titanium tetrachloride (TiCl4) as an oxidant. Solid-state nuclear magnetic resonance (CPMAS 13C-NMR), infrared absorption, optical absorption, thermal analysis (TGA and DTA), and electron paramagnetic resonance techniques were used to characterize the obtained PPHQ polymer. The correlation between different experimental results justifies the chemical structure and proves the vibrational and optical properties of this polymer. Theoretical calculations based on ab initio density functional theory and semiempirical Austin Model 1 methods were accomplished to elucidate the structure–property relationship of PPHQ polymer. From oligomer 8-hydroquinone, we have predicted the experimentally observed results. This oligomer is considered as model structure, which reproduces the PPHQ polymer characteristics and elucidates the TiCl4 effect on the properties of the polymer under study. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
