Showing papers on "Hyperpolarizability published in 2008"
TL;DR: A survey of NLO chromophores and materials incorporating them can be found in this article, where the authors provide a brief introduction explaining overall principles relating to the origin of second-order nonlinear optical properties.
338 citations
22 Jan 2008
TL;DR: In this article, the effect of intramolecular charge transfer on the geometries and the vibrational modes contributing to the linear electro-optic effect of the organic NLO material was analyzed.
Abstract: A comprehensive investigation on the intramolecular charge transfer (ICT) of an efficient π-conjugated potential push–pull NLO chromophore, 4-[ N , N -dimethylamino]-4′-nitro stilbene (DANS), from a strong electron-donor group (dimethylamino- N (CH 3 ) 2 ) to a strong electron-acceptor group (nitro-NO 2 ) through the π-conjugated bridge ( trans -stilbene) has been carried out from their vibrational spectra. The NIR FT-Raman and FT-IR spectra supported by the density functional theory (DFT) quantum chemical computations have been employed to analyze the effects of intramolecular charge transfer on the geometries and the vibrational modes contributing to the linear electro-optic effect of the organic NLO material. It has been observed that the changes in the endocyclic and exocyclic angles result from the charge-transfer interaction of the phenyl ring and the amino group in the electron-donor side of the NLO chromophore. The strongest vibrational modes contributing to the electro-optic effect have been identified and examined from the concurrent IR and Raman activation of ν (C C/C–C) mode, ring C C stretching modes, in-plane deformation modes, nitro modes and the umbrella mode of methyl groups. Furthermore, the splitting of the vinyl stretching modes and the electronic effects such as hyperconjugation and backdonation on the methyl hydrogen atoms causing the decrease of stretching frequencies and infrared intensities have also been analyzed in detail. The effect of frontier orbitals transition of electron density transfer and the influence of planarity between the phenyl rings of the stilbene moiety on the first hyperpolarizability have also been discussed.
185 citations
TL;DR: CPHF is applied for beta and gamma of LiF in different aggregation states: finite and infinite chains, slabs, and cubic crystal, with a dependence on the computational parameters similar to that observed for field-free self-consistent field (SCF) calculations.
Abstract: A computational scheme for the evaluation of the static first (β) and second (γ) hyperpolarizability tensors of systems periodic in 1D (polymers), 2D (slabs), 3D (crystals), and, as a limiting case, 0D (molecules) has been implemented, within the coupled perturbed Hartree–Fock framework (CPHF), in the CRYSTAL code, which uses a Gaussian type basis set. This generalizes to 2D and 3D the work by Bishop et al. (J. Chem. Phys. 114, 7633 (2001)). CPHF is applied for β and γ (the polarizability tensor α is also reported for completeness) of LiF in different aggregation states: finite and infinite chains, slabs, and cubic crystal. Correctness of the computational scheme and its numerical efficiency are documented by the trend of β and γ for increasing dimensionality: for a finite linear chain containing N LiF units, the hyperpolarizability tends to the infinite chain value at large N, N parallel chains give the slab value when N is sufficiently large, and N superimposed slabs tend to the bulk value. High numeric...
180 citations
TL;DR: In this paper, epoxyisophorone ring-opening chemistry was used to incorporate the butylthio group to the phenyltetraene bridge of highly efficient nonlinear optical chromophores in high overall yield.
Abstract: We have successfully utilized epoxyisophorone ring-opening chemistry to efficiently incorporate the butylthio group to the phenyltetraene bridge of highly efficient nonlinear optical chromophores in high overall yield. By following the guidance of Dewar’s rules, the sulfur atom functions as a moderate π-accepting group at a starred position of the conjugated bridge. Several of very critical material parameters of the phenyltetraenic chromophores for device applications have been intrinsically and simultaneously improved through such a simple and straightforward engineering of molecular structures. Compared with the nonsubstituted analogue 2, thiolated chromophore 1 achieves higher molecular hyperpolarizability (34%), enhanced E-O coefficient (38%), significantly improved photochemical stability against 1O2 (by an order of magnitude), and better optical transparency (17 nm blue-shifted λmax absorption spectrum).
156 citations
TL;DR: It is shown that the use of planar geometry constraints for the molecules, which can somewhat deviate from planarity in the gas phase, leads to sufficient accuracy of predicted values, and is proposed to use the scaled BMK results for prediction of molecular hyperpolarizability at semiquantitative level of accuracy.
Abstract: 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 Moller–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.
155 citations
TL;DR: Results indicate that the differential polarizability and hyperpolarizability frequency shift uncertainties in a Yb lattice clock could be held to well below 10(-17).
Abstract: We present an experimental study of the lattice-induced light shifts on the (1)S(0) --> (3)P(0) optical clock transition (nu(clock) approximately 518 THz) in neutral ytterbium. The "magic" frequency nu(magic) for the 174Yb isotope was determined to be 394 799 475(35) MHz, which leads to a first order light shift uncertainty of 0.38 Hz. We also investigated the hyperpolarizability shifts due to the nearby 6s6p(3)P(0) --> 6s8p(3)P(0), 6s8p(3)P(2), and 6s5f(3)F(2) two-photon resonances at 759.708, 754.23, and 764.95 nm, respectively. By measuring the corresponding clock transition shifts near these two-photon resonances, the hyperpolarizability shift was estimated to be 170(33) mHz for a linear polarized, 50 microK deep, lattice at the magic wavelength. These results indicate that the differential polarizability and hyperpolarizability frequency shift uncertainties in a Yb lattice clock could be held to well below 10(-17).
144 citations
TL;DR: In this article, the first hyperpolarizability of some donor-acceptor oxadiazoles was investigated using ab-initio methods using different basis sets, starting with the minimal basis set, and then split valence sets.
Abstract: The molecular hyperpolarizability of some donor–acceptor oxadiazoles was investigated using ab initio methods. Ab initio optimizations were performed at the Hartree-Fock level using different basis sets, starting with the minimal basis set, and then split valence sets. The first hyperpolarizabilities were calculated at the Hartree-Fock level employing the corresponding basis sets using Gaussian 98W. In general, the first hyperpolarizability is dependent on the choice of method and basis set. In order to understand this phenomenon in the context of molecular orbital picture, we examined the molecular HOMOs and molecular LUMOs generated via HF/6-31G level. It has also been calculated the polarizability, anisotropy of polarizability and ground state dipole moment of all the molecules. Several of these oxadiazoles display significant second-order molecular nonlinearity, β(8.57–195.05 × 10−30 esu) and provide the basis for future design of efficient nonlinear optical materials having the oxadiazole core.
143 citations
TL;DR: Time-dependent Hartree-Fock and Møller-Plesset second-order calculations have been used to unravel the relationships between structure and first hyperpolarizability in spiropyran/merocyanine couples and therefore to design efficient second- order nonlinear optical switching compounds.
Abstract: Time-dependent Hartree–Fock and Moller–Plesset second-order calculations have been used to unravel the relationships between structure and first hyperpolarizability in spiropyran/merocyanine couples and therefore to design efficient second-order nonlinear optical switching compounds. Large first hyperpolarizabilities for the merocyanine form as well as large contrasts of first hyperpolarizability have been obtained when, on the same species, (i) substituents at R1 and R2 positions on the phenolate ring of the merocyanine form are strong acceptor and donor substituents, respectively, (ii) the ethylenic bridge is substituted by donor groups, (iii) the other aromatic part of the system is benzimidazolo rather than indolino or benzothiazolo, and (iv) strong donor substituents are placed on the benzimidazolo moiety.
133 citations
TL;DR: In this article, the structure-property relationship for χ(3) in acceptor-substituted 3,4,5-trimethoxy chalcone derivatives was investigated by performing both Z-scan and transient transmission measurements with 130 fs laser pulses in the near infrared region.
Abstract: By performing both Z-scan and transient transmission measurements with 130 fs laser pulses in the near infrared region, we investigated structure-property relationships for χ(3) in acceptor-substituted 3,4,5-trimethoxy chalcone derivatives. We determined all nonlinear parameters, including two-photon absorption (2PA) cross section, 2PA-induced excited-state absorption (ESA) cross section, microscopic second-order hyperpolarizability, and lifetime of the excited state in these molecules. We found that the microscopic second-order hyperpolarizability γR and 2PA cross section σ2PA in chalcone derivatives increase as the acceptor strength of the molecules increases, which demonstrates an enhancement in optical nonlinearities by simple structural variations. We evaluated the one-photon, two-photon, and effective three-photon figures of merit for acetone solutions of chalcone derivatives at irradiance of 100 GW/cm2. Furthermore, we observed optical limiting behavior in these compounds, which result from both 2P...
108 citations
TL;DR: It is found that the carbon nanotubes serve as both electronic bridges and acceptors, leading to a donor-nanotube paradigm for the effective design of large first hyperpolarizabilities.
Abstract: Studies of the nonlinear electronic response of donor/acceptor substituted nanotubes suggest a behavior that is both surprising and qualitatively distinct from that in conventional conjugated organic species. We find that the carbon nanotubes serve as both electronic bridges and acceptors, leading to a donor-nanotube paradigm for the effective design of large first hyperpolarizabilities. We also find that tuning the donor orientation, relative to the nanotube, can significantly enhance the first hyperpolarizability.
106 citations
TL;DR: In this paper, the linear and second-order nonlinear optical properties of two anil derivatives and their variations upon switching between the enol-imine and keto-amine forms were investigated.
Abstract: This paper addresses the linear and second-order nonlinear optical properties of two anil derivatives and in particular their variations upon switching between the enol-imine and keto-amine forms. Quantum chemical evaluations of the first hyperpolarizabilities, accounting for both solvent and electron correlation effects, are compared with hyper-Rayleigh scattering and electric field-induced second harmonic generation measurements. For both compounds, the E/K first hyperpolarizability ratios are larger than 2, demonstrating that the enol forms present the largest responses but also that the switching is associated with a substantial β contrast.
TL;DR: In this paper, the authors present the results of their calculations of the geometric parameters, vibrational spectra and hyperpolarizability of a non-linear optical material, l -histidine bromide.
TL;DR: The calculation of optimized molecular structure and molecular hyperpolarizability of four new acridine-benzothiazolylamine chromophores display significant second–order molecular nonlinearity, β and provide the basis for future design of efficient nonlinear optical materials having the acridines-benZothiazol-2-yl-amino core.
Abstract: The calculation of optimized molecular structure and molecular hyperpolarizability of four new acridine-benzothiazolylamine chromophores (1-4) [2-nitro-6-(piperid-1-yl) acridine (1), 6-(benzothiazol-2-yl-amino)-2-nitro-acridine (2), 6-(6-ethylcarboxylate-benzothiazol-2-yl-amino)-2-nitroacridine (3), 6-(6-(beta-hydroxyethyl-benzothiazol-2-yl-amino)-2-nitroacridine (4)] have been investigated using ab initio methods. Ab initio optimization were performed at the Hartree-Fock level using STO-3G basis set. The first hyperpolarizabilities have been calculated at the Hartree-Fock method with 6-31G and 6-311G basis sets using Gaussian 98W. In general, the first hyperpolarizability is dependent on the choice of method and basis set. To understand this phenomenon in the context of molecular orbital picture, we examined the frontier molecular orbital energies of all the molecules by using HF/6-31G, 6-311G levels. The polarizability, anisotropy of polarizability and ground state dipole moment of all the molecules have also been calculated. These acridine-benzothiazolylamine chromophores display significant second-order molecular nonlinearity, beta (60.2-137.0 x 10(-30) esu) and provide the basis for future design of efficient nonlinear optical materials having the acridine-benzothiazolylamine core.
TL;DR: In this article, the third-order nonlinear optical properties of chalcone derivatives have been investigated by Z-scan technique using 7 ns laser pulses at 532 nm and the results suggest that the nonlinear properties of the chalcones have been improved when they are used as dopants in polymer matrix.
TL;DR: In this article, the authors employed density functional theory and time-dependent density functional theories with hybrid functional B3LYP to investigate several physical and chemical properties of N-methyle-3,4-fulleropyrrolidine (NMFP), including geometry, electron population, infrared (IR), Raman and electronic absorption spectra.
Abstract: Density functional theory and time-dependent density functional theory with hybrid functional B3LYP are employed to investigate several physical and chemical properties of N-methyle-3,4-fulleropyrrolidine (NMFP), including geometry, electron population, infrared (IR), Raman and electronic absorption spectra. The analysis of the natural bond orbital (NBO) suggests that there are about 0.16 electrons transferred from the moiety –C3NH7 of NMFP to fullerene cage. The strongest IR and Raman spectra are from different modes with frequencies of 2955 and 1490 cm−1, respectively. The calculated isotropic polarizability, polarizability anisotropy invariant and hyperpolarizability are 521.6, 65.3 and −68 (a.u.), respectively. The calculated electronic absorption spectra agree well with the experimental measurement. The solvent cyclohexane did not significantly affect the overall spectral shape but the absorption intensity and low-energy-band locations. The first absorption band in visible region comes from n σ π → π ∗ transitions, and the bands near 437 and 451 nm are both related to the ligand-to-fullerene charge transfer processes. The second absorption band in near-UV region is dominated by typical π → π ∗ transitions.
TL;DR: In this paper, the nonlinear optical rectification (OR) in the asymmetric double triangular quantum wells (DTQWs) is investigated theoretically, and the dependence of OR on the right-well width of the DTQWs is studied, and influence of the applied electric field on OR is also taken into account.
Abstract: The nonlinear optical rectification (OR) in the asymmetric double triangular quantum wells (DTQWs) is investigated theoretically. The dependence of OR on the right-well width of the DTQWs is studied, and the influence of the applied electric field on OR is also taken into account. The analytical expression of the OR susceptibility is analyzed by using the compact density-matrix approach and the iterative method and the numerical calculations are presented for the typical GaAs/AlxGa1-xAs asymmetric DTQWs. The results show that the OR susceptibility obtained in this coupled system can reach the magnitude of 10-3 m/V, 2-3 orders of magnitude higher than that in single quantum systems. Moreover, the OR susceptibility is not a monotonic function of the width of the right well, but has complex relationship with it. The calculated results also reveal that an applied electric field has a great influence on the OR susceptibility. Applying an appropriate electric field to a quasi-symmetric or symmetric DTQW can result in a larger OR susceptibility as compared with that obtained in an optimal asymmetric DTQW without electric field.
TL;DR: Although the final states for one- and two-photon transitions are not the same in these centrosymmetric molecules, the Z-scan studies reveal coincidences in one- photon absorption with features in the frequency dependencies of both real and imaginary parts of the cubic hyperpolarizability.
Abstract: The wavelength dependence of the cubic nonlinearity of ligated platinum-terminated polyynes trans,trans-{(p-MeC6H4)3P}2(p-MeC6H4)Pt(C≡C)nPt(p-C6H4Me){P(p-C6H4Me)3}2 (n = 3−6, 8, 10, 12) has been examined by femtosecond Z-scan studies in the wavelength range 520−1500 nm and the results rationalized by density functional theory calculations on the model complexes trans,trans-(H3P)2(C6H5)Pt(C≡C)nPt(C6H5)(PH3)2 (n = 2−8, 10, 12). Although the final states for one- and two-photon transitions are not the same in these centrosymmetric molecules, the Z-scan studies reveal coincidences in one-photon absorption with features in the frequency dependencies of both real and imaginary parts of the cubic hyperpolarizability, as well as inflections in the frequency dependencies of the real part of γ that correspond to resonances in the imaginary part of γ. The theoretical studies suggest that the linear absorption spectra are dominated by X1Ag → n1B3u transitions, with the first state of B3u symmetry playing a steadily d...
TL;DR: These properties are essential for the practical use of Dronpa or other GFP-like fluorescent proteins as second-order nonlinear fluorophores for symmetry-sensitive nonlinear microscopy imaging and as nonlinear optical sensors for electrophysiological processes.
Abstract: The second-order nonlinear optical properties of green fluorescent proteins (GFPs), such as the photoswitchable Dronpa and enhanced GFP (EGFP), have been studied at both the theoretical and experimental levels. In the case of Dronpa, both approaches are consistent in showing the rather counterintuitive result of a larger second-order nonlinear polarizability (or first hyperpolarizability, β) for the protonated state, which has a higher transition energy, than for the deprotonated, fluorescent state with its absorption at lower energy. Moreover, the value of β for the protonated form of Dronpa is among the highest reported for proteins. In addition to the pH dependence, we have found a wavelength dependence in the β values. These properties are essential for the practical use of Dronpa or other GFP-like fluorescent proteins as second-order nonlinear fluorophores for symmetry-sensitive nonlinear microscopy imaging and as nonlinear optical sensors for electrophysiological processes. An accurate value of the ...
TL;DR: It is found that the new lithium salt electride, Li-H 3C 4N 2...Na 2, has a very large beta 0 value, which is a new record and comes from its small transition energy and large difference in the dipole moments between the ground state and the excited state.
Abstract: A new lithium salt electride with an excess electron pair is designed, for the first time, by means of doping two sodium atoms into the lithium salt of pyridazine. For this series of electride molecules, the structures with all real frequencies and the static first hyperpolarizability (β0) are obtained at the second-order Moller−Plesset theory (MP2). Pyridazine H4C4N2 becomes the lithium salt of pyridazine Li−H3C4N2 as one H atom is substituted by Li. The lithium salt effect on hyperpolarizability is observed as the β0 value is increased by about 170 times from 5 to 859 au. For the electride effect, an electride H4C4N2···Na2 formed by doping two Na atoms into pyridazine, the β0 value is increased by about 3000 times from 5 to 1.5 × 104 au. Furthermore, combining these two effects, that is, lithium salt effect and electride effect, more significant increase in β0 is expected. A new lithium salt electride Li−H3C4N2···Na2 is thus designed by doping two Na atoms into Li−H3C4N2. It is found that the new lithiu...
TL;DR: The wavelength-dependent molecular first hyperpolarizability β of the zwitterionic nonlinear optical (NLO) chromophore picolinium quinodimethane (PQDM) is determined by hyper-Rayleigh scattering (HRS) and used to test and improve theoretical β dispersion models.
Abstract: The wavelength-dependent molecular first hyperpolarizability β of the zwitterionic nonlinear optical (NLO) chromophore picolinium quinodimethane (PQDM) is determined by hyper-Rayleigh scattering (HRS) and used to test and improve theoretical β dispersion models. Experimental HRS data are obtained over a very wide fundamental wavelength range (780−1730 nm), spanning the entire range of two-photon resonance with the intramolecular charge-transfer (ICT) transition and reaching the onset of a higher energy resonance. Reliable calibration against the pure solvent (dimethylformamide, DMF, and DMF-d7 at the longest wavelengths) was achieved over the full spectral range as a result of the high sensitivity of the HRS setup. Extremely high resonant β values are obtained (up to 4560 × 10-30 esu at 1360 nm) and also away from resonance β remains very large (1210 × 10-30 esu at 1730 nm). The two-photon resonance with the ICT band shows a pronounced red shift (∼33 nm in second-harmonic wavelength) relative to the absor...
TL;DR: In this article, single crystals of 3-nitroaniline (C6H6N2O2) were grown by using slow evaporation solution growth technique at room temperature using methanol as a solvent.
Abstract: Single crystals of 3-nitroaniline (C6H6N2O2) also called as m-nitroaniline (m-NA) have been grown by adopting slow evaporation solution growth technique at room temperature using methanol as a solvent. To reveal the microscopic nonlinear optical properties, the first-order hyperpolarizability (β) was evaluated by using the density functional theory (DFT) quantum chemical calculations at B3LYP/3–21 G (d,p) level. According to the results of DFT calculations, the grown crystals exhibit non-zero β values and it might have microscopic nonlinear optical behavior which is seven times more than that of urea. Terahertz (1 THz=1012 Hz) radiation was also generated in the title organic nonlinear optical crystal using ultra short femtosecond laser.
TL;DR: Amaranth (E123, Food Red 9, FD & C Red 2) is a sulfonated azo dye used as a color additive in foodstuffs, pharmaceuticals and cosmetics as discussed by the authors.
Abstract: Amaranth (E123, Food Red 9, FD & C Red 2) is a sulfonated azo dye used as a color additive in foodstuffs, pharmaceuticals and cosmetics. FT-IR and FT-Raman spectra of amaranth were recorded and analyzed. Density functional theory (DFT) calculations were performed to derive the equilibrium geometry, vibrational wavenumbers, intensities and first hyperpolarizability. The results of the optimized molecular structure gave clear evidence for the intramolecular charge transfer (ICT) and intramolecular hydrogen bonding in the molecule. Azo stretching wavenumbers are lowered owing to conjugation and π-electron delocalization. Time-dependent density functional theory (TD-DFT) calculations of the electronic spectra were performed on the optimized structure and compared with the experimental UV-visible spectrum. Vibrational spectra, natural bonding orbitals (NBO) analysis and optimized geometry indicate CH·N hydrogen bonding in the molecule. The first hyperpolarizability of the molecule was calculated. The optical nonlinearity of the dye is due to the donation of the electron density from the hydroxyl group of the conjugated system via naphthalene (2) ring into π*-orbital of the azo moiety. Copyright © 2008 John Wiley & Sons, Ltd.
TL;DR: State-average complete active space self-consistent field (SA-CASSCF) calculations suggest that changing the environmental polarity is a promising strategy for tuning alpha and beta in such types of chromophores, which experimentally exhibit large nonlinear optical response.
Abstract: State-average complete active space self-consistent field (SA-CASSCF) calculations are performed on the energetically lowest two electronic states of a novel alkyl-substituted 4-quinopyran twisted π-system electro-optic chromophore. In the gas phase, the ground-state electronic configuration is diradicaloid (D), and the first excited state is zwitterionic (Z). When an external dipolar field is applied to simulate polar solvation, the relative energies of D and Z are dramatically perturbed. At sufficient field strengths, the relative ordering of the states is inverted so that Z becomes the ground state. As the energy difference between the D and Z states falls, the magnitudes of the longitudinal static polarizability (α) and hyperpolarizability (β) increase appreciablyin certain cases, by 2 orders of magnitude. These computational results are interpreted and supported by qualitative state correlation diagrams constructed from qualitative molecular orbital theory and are in agreement with recent experimenta...
TL;DR: A series of H-shaped second-order nonlinear optical (NLO) chromophores with two parallel and nonconjugated D−π−A units have been synthesized, in which a 9,10-dihydroanthracene is employed as molecular backbone.
Abstract: A series of H-shaped second-order nonlinear optical (NLO) chromophores with two parallel and nonconjugated D−π−A units have been synthesized, in which a 9,10-dihydroanthracene is employed as molecular backbone. The measurement results of hyper-Rayleigh scattering (HRS) and UV−vis spectra show that the first molecular hyperpolarizability (β) values of H-shaped chromophores are remarkably increased compared with the corresponding mono-D−π−A unit reference compounds (the enhancements per azo D−π−A unit from 1.2 to 3.0 are observed), without causing a large shift of the absorption band to longer wavelength. Therefore, it gives an available way of solving the trade-off between nonlinearity and transparency in designing NLO chromophores. Furthermore, some main-chain fluoro-containing polyimides embedded with the H-shaped chromophores have also been prepared. The elemental investigation results show that the polyimides exhibit a higher macroscopic nonlinear optical coefficient (d33 = 35.0 to ∼70.2 pm/V), good th...
TL;DR: The infrared absorption, Raman spectra and SERS spectra of p-amino acetanilide have been analyzed with the aid of density functional theory calculations and reveal that the PAA molecule is planar, while secondary amide group is twisted with respect to the phenyl ring, upon hydrogen bonding.
TL;DR: It is found that, as a function of the donor atoms, the diradical character of these complexes varies from 0.0 to 0.884 and is associated with substantial variations of gamma, which is in good agreement with the structure-property relationship obtained for pure hydrocarbon systems.
Abstract: Hybrid density functional theory method is applied for investigating the diradical character dependence of the second hyperpolarizability (γ) of square planar nickel complexes involving several types of bidentate ligands [o-C6H4XY, where X = Y = O, NH, S, Se, and PH as well as (X, Y) = (NH, NH2) and (S, NH2)]. It is found that, as a function of the donor atoms, the diradical character of these complexes varies from 0.0 to 0.884 and is associated with substantial variations of γ ranging from 14 × 103 to 819 × 103 au. In particular, the largest γ values are associated with intermediate diradical characters in good agreement with the structure−property relationship obtained for pure hydrocarbon systems. Increasing the electronegativity of the X and Y donor groups of the ligands leads to larger diradical characters as a result of the enhancement of the double bond nature of the C=X(Y) bonds, which further stabilizes the diradicals on both-end benzene rings. This demonstrates that the electronegativities of th...
TL;DR: In this paper, the synthesis, growth, crystal structure determination, and hyperpolarizability studies of larginium-4-nitro phenolate monohydrate (LARP) single crystals for the first time in the literature were presented.
Abstract: This report presents the synthesis, growth, crystal structure determination, and hyperpolarizability studies of l-argininium-4-nitro phenolate monohydrate (LARP) single crystals for the first time in the literature. Density functional theory at the B3LYP/HF6-31G (d,p) level has been used to compute the first-order hyperpolarizabilty of LARP. The second harmonic generation efficiency of the title compound is very high. Planar molecular structure and better conditions for electron conjugation and charge transfer result in larger values of β for this title crystal.
TL;DR: The introducing of electron-donors significantly enhances the first hyperpolarizabilities of (naphthylimido)hexamolybdate derivatives comparing with the electron-acceptors as the electronic field could generate a large static electronic field and give the large contribution to NLO response.
Abstract: The static first hyperpolarizabilities and origin of nonlinear optical (NLO) properties of [(2-methylnaphthyl)imido]hexamolybdates derivatives have been investigated by density functional theory (DFT). The [(2-methylnaphthyl)imido]hexamolybdate has considerable large first hyperpolarizability, 6.780 x 10(-30) esu, and it is larger than that of [(2,6-dimethylphenyl)arylimido]hexamolybdate due to the double aromatic rings in the naphthylimido ligand. The naphthylimido ligand acts as an electron-donor and the polyanion acts as an electron-acceptor. The substituent position on the naphthylimido is a key factor to determine the first hyperpolarizability of (naphthylimido)hexamolybdate derivatives. The derivative, which the iodine atom locates on the para nitrogen on the naphthylimido ligand, has the largest betao(o) value among the iodine-substituted derivatives. It suggests that the iodine atom is quasi linear with nitrogen and Mo, which is bonded to thenitrogen atom, could generate a large static electronic field and give the large contribution to NLO response.The introducing of electron-donors significantly enhances the first hyperpolarizabilities of (naphthylimido)hexamolybdates comparing with the electron-acceptors as the electron-donating ability is significantly enhanced when the electron-donor is attached to the naphthylimido segment. The present investigation provides important insight into NLO properties of (arylimido)molybdate derivatives.
TL;DR: In this article, the second-order nonlinear optical (NLO) response has been determined experimentally by the EFISH technique and found to be similar but slightly lower than that of related [Ir(ppy)2(5-R-1,10-phenanthroline)][PF6] (ppy=cyclometallated 2-phenylpyridine), characterized by one of the highest secondorder NLO response ever reported for a metal complex.
TL;DR: In this paper, a global modeling of sum frequency generation (SFG) spectra of the self assembly of alkanethiols is presented, where all CH modes are modelled together.