Quantum chemical studies on tuning the second-order nonlinear optical molecular switching of triarylborane derivatives (original) (raw)
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Molecules, 2019
Herein, we report the quantum chemical results based on density functional theory for the polarizability (α) and first hyperpolarizability (β) values of diacetylene-functionalized organic molecules (DFOM) containing an electron acceptor (A) unit in the form of nitro group and electron donor (D) unit in the form of amino group. Six DFOM 1-6 have been designed by structural tailoring of the synthesized chromophore 4,4-(buta-1,3-diyne-1,4-diyl) dianiline (R) and the influence of the D and A moieties on α and β was explored. Ground state geometries, HOMO-LUMO energies, and natural bond orbital (NBO) analysis of all DFOM (R and 1-6) were explored through B3LYP level of DFT and 6-31G(d,p) basis set. The polarizability (α), first hyperpolarizability (β) values were computed using B3LYP (gas phase), CAM-B3LYP (gas phase), CAM-B3LYP (solvent DMSO) methods and 6-31G(d,p) basis set combination. UV-Visible analysis was performed at CAM-B3LYP/6-31G(d,p) level of theory. Results illustrated that much reduced energy gap in the range of 2.212-2.809 eV was observed in designed DFOM 1-6 as compared to parent molecule R (4.405 eV). Designed DFOM (except for 2 and 4) were found red shifted compared to parent molecule R. An absorption at longer wavelength was observed for 6 with 371.46 nm. NBO analysis confirmed the involvement of extended conjugation and as well as charge transfer character towards the promising NLO response and red shift of molecules under study. Overall, compound 6 displayed large <α> and β tot , computed to be 333.40 (a.u.) (B3LYP gas), 302.38 (a.u.) (CAM-B3LYP gas), 380.46 (a.u.) (CAM-B3LYP solvent) and 24708.79 (a.u.), 11841.93 (a.u.), 25053.32 (a.u.) measured from B3LYP (gas), CAM-B3LYP (gas) and CAM-B3LYP (DMSO) methods respectively. This investigation provides a theoretical framework for conversion of centrosymmetric molecules into non-centrosymmetric architectures to discover NLO candidates for modern hi-tech applications.
Journal of Molecular Structure, 2019
The effects of the electron-donating capacity altered by heteroatom substituents on the electronic structures, photophysical properties, and excited-state intramolecular proton transfer (ESIPT) processes of 3HX analogues (3HF, 3HQ, 3HTF, and 3HSO where X = O, NH, S, and SO 2 , respectively) have been investigated by both static calculations and dynamic simulations using density functional theory (DFT) and time-dependent DFT (TD-DFT) methods at B3LYP/TZVP level for ground state (S 0) and excited-state (S 1), respectively. The static results indicate that the intramolecular hydrogen bonds of all molecules are strengthened in the S 1 , confirmed by the red-shift of IR vibrational spectra and the topology analysis. Heteroatom substitutions cause the red-shift on enol absorption and keto emission spectra of 3HX with relatively larger Stoke shift corresponding to their HOMO−LUMO gaps compared with that of 3HF. Frontier molecular orbitals (MOs) show that upon the photoexcitation, the charge redistribution between the proton donor and proton acceptor groups have induced the ESIPT process. Moreover, the potential energy curves (PECs) of proton transfer (PT) processes of all molecules reveal that the PT processes of all molecules are most likely to proceed in the S 1 state because of low barriers and exothermic reaction. The chance of ESIPT for all molecules is in this order: 3HSO > 3HTF > 3HF > 3HQ. The results of dynamic simulations confirm that the ESIPT processes of all molecules easily occur with the ultrafast time scale (48, 55, 60, 70 fs for 3HSO, 3HTF, 3HF, and 3HQ, respectively). Furthermore, the PT time is anti-correlated with the electronegativity of heteroatoms in 3HX, supported by Mulliken analysis. The ESIPT process of 3HSO is the fastest among 3HX in accordance with its highest intramolecular hydrogen bond strength, lowest PT barrier, and highest exothermic reaction. Nevertheless, after the ESIPT is complete, the twisted structure of 3HSO has initiated the conical intersection, leading to no keto emission observed in the experiment.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2013
This work presents the characterization of (2R,3R,4R,5S)-1-(2-hydroxyethyl)-2-(hydroxymethyl)piperidine-3,4,5-triol (abbreviated as HEHMPT) by quantum chemical calculations and spectral techniques. The spectroscopic properties are investigated by FT-IR, FT-Raman and UV-Vis techniques. The FT-IR and FT-Raman spectra of the title compound have been recorded in the region 4000-400 cm-1 and 4000-100 cm-1 respectively. The UV-Vis absorption spectrum of the HEHMPT that dissolved in water is recorded in the range of 100-400 nm. The structural and spectroscopic data of the molecule are obtained from B3LYP and M06-2X with 6-31G(d,p) basis set calculations. The theoretical wavenumbers are scaled and compared with experimental FT-IR and FT-Raman spectra. The complete assignments are performed on the basis of the normal coordinate analysis (NCA), experimental result and potential energy distribution (PED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method, interpreted in terms of fundamental modes. The stable geometry of the compound has been determined from the potential energy surface scan. The stability of molecule is analyzed by NBO analysis. The molecule orbital contributions are studied by using the total (TDOS), partial (PDOS), and overlap population (OPDOS) density of states. The electronic properties like UV spectral analysis and HOMO-LUMO energies are reported. The calculated HOMO and LUMO energies show that charge transfer interactions taking place within the molecule. Mulliken population analysis on atomic charges is also calculated.
The Journal of chemical physics, 2008
The donor/acceptor (D/A) substituted π-conjugated organic molecules possess extremely fast nonlinear optical (NLO) response time that is purely electronic in origin. This makes them promising candidates for optoelectronic applications. In the present study, we utilized four hybrid density functionals (B3LYP, B97-2, PBE0, BMK), Hartree–Fock, and second order Møller–Plesset correlation energy correction, truncated at second-order (MP2) methods with different basis sets to estimate molecular first hyperpolarizability (β) of D/A-substituted benzenes and stilbenes (D = OMe, OH, NMe2, NH2; A = NO2, CN). The results of density functional theory (DFT) calculations are compared to those of MP2 method and to the experimental data. We addressed the following questions: (1) the accurate techniques to compare calculated results to each other and to experiment, (2) the choice of the basis set, (3) the effect of molecular planarity, and (4) the choice of the method. Comparison of the absolute values of hyperpolarizabilities obtained computationally and experimentally is complicated by the ambiguities in conventions and reference values used by different experimental groups. A much more tangible way is to compare the ratios of β’s for two (or more) given molecules of interest that were calculated at the same level of theory and measured at the same laboratory using the same conventions and reference values. Coincidentally, it is the relative hyperpolarizabilities rather than absolute ones that are of importance in the rational molecular design of effective NLO materials. This design includes prediction of the most promising candidates from particular homologous series, which are to be synthesized and used for further investigation. In order to accomplish this goal, semiquantitative level of accuracy is usually sufficient. Augmentation of the basis set with polarization and diffuse functions changes β by 20%; however, further extension of the basis set does not have significant effect. Thus, we recommend 6-31+G* basis set. We also show that the use of planar geometry constraints for the molecules, which can somewhat deviate from planarity in the gas phase, leads to sufficient accuracy (with an error less than 10%) of predicted values. For all the molecules studied, MP2 values are in better agreement with experiment, while DFT hybrid methods overestimate β values. BMK functional gives the best agreement with experiment, with systematic overestimation close to the factor of 1.4. We propose to use the scaled BMK results for prediction of molecular hyperpolarizability at semiquantitative level of accuracy.
Theoretical Chemistry Accounts, 2009
In this paper, we present an alternative picture for the electronic structure of dihalogen molecules and for the physical origin of the ''charge-shift bonding'' effect. Absolute energies, binding energies, quadrupole moments and harmonic frequencies are determined for a hierarchy of methods from Hartree-Fock (HF), many forms of generalized valence bond (GVB) wavefunctions to Multi-Reference-MP2. All valence electron pairs are explicitly correlated in the GVB wavefunctions. It is shown that HF charge densities for the fluorine molecule are extremely inaccurate. This fact causes the HF canonical orbital basis for this molecule to be inadequate in low order correlation treatments in spite of the fact that there are no ''near degeneracies'' at the equilibrium distance. The accurate description charge fluctuation lone pair repulsions are essential for a proper assessment of the fluorine molecule binding energy, bond distance and harmonic frequency. These properties are well described by lifting the perfectpairing restriction in a full-valence orbital optimized GVB-RCI (restricted-configuration-interaction) wavefunction. The accurate calculation of electron-electron cusps is of lesser importance in the description of the electronic structure of the fluorine molecule than usually considered. An analysis of the lone pair GVB natural orbitals provides a clear-cut understanding on the differences between fluorine and the other dihalogen molecules. Within our model, we conclude that among the dihalogen molecules the charge-shift bonding concept is meaningful only for the fluorine molecule.
Russian Journal of Physical Chemistry A, 2014
In this study, quantum chemical calculations of geometric parameters, conformational, natural bond orbital (NBO) and nonlinear optical (NLO) properties, vibrational frequencies, 1 H and 13 C NMR chemical shifts of the title molecule [C 9 H 7 F 5 N 2 O 3 ] in the ground state have been calculated with the help of Density Functional Theory (DFT-B3LYP/6 311++G(d,p)) and Hartree Fock (HF/6 311++G(d,p)) methods. The optimized geometric parameters, vibrational frequencies, 1 H and 13 C NMR chemical shifts values are compared with experimental values of the investigated molecules. Comparison between experi mental and theoretical results showed that B3LYP/6 311++G(d,p) method is able to provide more satisfac tory results. In order to understand this phenomenon in the context of molecular orbital picture, we examined the molecular frontier orbital energies (HOMO, HOMO 1, LUMO, and LUMO + 1), the energy difference (ΔE) between E HOMO and E LUMO , electronegativity (χ), hardness (η), softness (S) calculated by HF/6 311++G(d,p) and B3LYP/6 311++G(d,p) levels. The molecular surfaces, Mulliken, NBO, and Atomic polar tensor (APT) charges of the investigated molecule have also been calculated by using the same methods.
To our knowledge, the theoretical calculations of monohydroxymethyl-TTFs 4a-d have not been reported except in our work. Organic molecule containing extended π-conjugated electrons have characterized by large values of molecular first hyperpolarizabilities show enhanced NLO properties. Monohydroxymethyl-TTFsmolecules can show large first order hyperpolarizabilities (β) related to an electronic intra-molecular charge-transfer excitation between the ground and excited states. The redistribution of electron density (ED) in various bonding, antibonding orbitals and E(2) energies have been calculated by natural bond orbital (NBO) analysis and natural localized molecular orbital interactions to give clear evidence of stabilization originating from the hyperconjugation of various intra-molecular interactions.
Journal of physical chemistry and functional materials, 2019
In this study, the chemical reactivity, stability and electronic properties of Propylbenzene (C9H12) and 2-chloro-5-(trifluoromethyl) aniline (C7F3NH5Cl) molecules have been investigated by using the Density Functional Theory (DFT) and Hartree Fock Theory (HFT) methods with difference basis sets like (B3LYP/3-21G, 6-31+G(dp), 6-31G,6-311G). The Lowest Unoccupied Molecular Orbitals (LUMO), and Highest Occupied Molecular Orbitals (HOMO) energies can be used to characterize the kinetic stability and chemical reactivity in chemical structure for these molecules.