Mean Polarizability Research Articles

Experimental Polarizability Transition Moments of CO2 for Excited Vibrational States.

The Raman spectrum of CO2 from room temperature to 1800 K has been measured in a series of experiments. The differential Raman scattering cross-sections for the fundamental bands at 1285.41 cm-1 and 1388.18 cm-1 have been obtained from reference bands of H2 and N2 as intensity standards. The Raman cross-sections of CO2 hot bands, involving vibrational energy levels up to 5000 cm-1, were derived from those of the fundamental bands. The Raman cross-sections obtained this way were reduced to transition moments of the mean molecular polarizability, which make it possible to simulate the Raman spectrum of CO2 up to 2000 K. This paves the way for local or remote diagnostics of CO2 in hot environments using Raman based techniques.

Polarizability of quasi-1D nanostructures (C60) n in terms of molecular and periodic paradigms

The polarizability exaltation (increase) is typical for oligomers (C60) n . It comprises the superadditive polarizability growth with n. This phenomenon was previously studied only for the molecular models of the (C60) n oligomers. In the present work, we compare the DFT-computed polarizability, obtained for molecules (C60) n and periodic model of quasi-1D covalently-bonded fullerene chains. We found that the increment of the (C60) n mean polarizability growth (95.88 Å3 for n = 6) approaches the value, obtained for the periodic model, 97.49 Å3. According to the periodic computations, polymer (C60) n should be a semiconductor with the direct band gap at the Γ point (the computed energy gap value is 1.41 eV).

The electronic, structural and nonlinear optical properties of licochalcone L in the aqueous solution and gaseous phase: A DFT study

In the present article, various conformers of licochalcone L, a chalcone derivative extracted from the G. inflata root, have been analyzed in the aqueous solution and gaseous phase using calculation based on density functional theory (DFT). Nonlinear optical parameters such as dipole moment (μ), mean polarizability (α), polarizability anisotropy (Δα) and the first order hyperpolarizability (β) have been estimated to examine the NLO properties of the title molecule. These parameters were found to be significantly higher than those of standard molecules, indicating the potential NLO applications of licochalcone L. The analysis of natural bond orbitals (NBO) has been carried out to characterize various intramolecular interactions. The nucleus-independent chemical shift (NICS) technique has been used to investigate the aromaticity. Further, the pKa values have been computed for each hydroxyl group, revealing that the neutral form predominates at physiological pH, while the monoanionic form becomes predominant at pH greater than 9. The impact of solvation on the molecular electrostatic potentials and frontier molecular orbitals has been investigated for the neutral as well as monoanionic form of licochalcone L. A variety of global chemical reactivity descriptors have been calculated to highlight the structure-activity relationship.

Design of High-Performance Inorganic-Organic Hybrid Nonlinear Optical Materials Using Superhalogen Al13 and Dianhydrides.

Novel inorganic-organic hybrid complexes Al13-X (X represents the dianhydrides PMDA, NTCDA, and PTCDA) are theoretically designed and studied using density functional theory (DFT) and time-dependent DFT. These conjugated dianhydrides containing four acceptor carbonyl groups are commonly used as electron acceptor materials. These compounds possess large binding energies, reflecting the sufficient binding of Al13 to the dianhydride molecule. The binding nature of the complexes is of charge transfer type, i.e., electrons are transferred from the aluminum cluster to the dianhydride. All of the aimed complexes have large mean polarizability (α0) and first hyperpolarizability (β0). The β0 values are explained on the basis of electronic transitions in crucial excited states using the TD-DFT method. Additionally, the hole-electron distribution was analyzed, revealing the nature of electronic excitation. Absorption spectra analysis shows that these complexes have an excellent infrared (IR) transparent region (1000-5000 nm). Therefore, these inorganic-organic hybrid complexes with high stability can be considered as potential candidates for new IR nonlinear optical molecules.

Exploring Polyaniline Nanofilaments for Enhanced Optical Recognition of Lead in Water: An Integrated Approach of Experimental and Theoretical Studies

In this study, the behavior of lead adsorbed onto polyaniline composite was examined theoretically with the DFT method and experimentally using spectrophotometry. The synthesis and characterization of polyaniline nanofilaments (PANI) were executed. Density functional theory and Becke's three‐parameter exchange functional approach were employed for quantum mechanical calculations of geometry and energy. The 6.311G** basis set and the Lee‐Yang‐Parr correlation functional method (B3LYP/DFT) were used in a water solution environment to complement the experimental data. Experimental results were visualized using 3D molecular electrostatic potential maps (MEP), which aided in the determination and explanation of various properties, including mean polarizability, total static dipole moment, anisotropy of polarizability, and mean first‐order hyperpolarizability. The findings indicate that Pb‐PANI‐EB shows promise as a potential material for non‐linear optical (NLO) applications. PANI demonstrate efficacy as a sensor capable of detecting Pb concentrations as low as 0.05 ppm. These results justify further exploration of the use of PANI in the development of a fast, economical, robust, and highly sensitive lead (Pb) sensor.

Superacidic Properties of Protonated PtFn (n = 1–6) and Their Ability to Form Supersalts: DFT Study

AbstractIn the present communication, this study has modeled protonated PtFn (n = 1–6), a new series of superacids. The calculated vertical de‐attachment energy (VDE) of PtFn (n = 1–6) reestablishes the superhalogenic behavior. The vibrational frequency, dissociation energy through the HF channel, and optimized geometries are utilized to discuss the stability of HPtFn (n = 1–6). The deprotonation energy of HPtFn is used to calculate the acidic strength of HPtFn (n = 1–6). The acidity of protonated PtFn (n = 1–6) is directly related to its counterpart superhalogen anions. The computed correlation factor (R2 = 0.9754) shows that VDE is directly associated with acidity. The mechanism of acidity of HPtFn (n = 1–6) is described by using natural bond orbital analysis charges on atoms. The electronic properties of HPtFn (n = 1–6) are calculated using the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy. The nature of chemical reactivity is also determined by the HOMO–LUMO plot of HPtFn (n = 1–6). It has formed the supersalts using superacids HPtFn (n = 1–6) and superbase (OLi3OH), and the nature of supersalts is compared with traditional salt LiF. The most stable conformers of supersalts PtFnOLi3 (n = 2–6) are analyzed for optoelectronic properties. It has computed the dissociation of supersalts through neutral and anions through superhalogns and superalkalis. The computed results show that PtF4OLi3 favors dissociation through anions as in traditional salts. The nonlinear optical parameters are calculated using dipole moment, mean polarizability, anisotropic polarizability, molar reflectivity (MR), order parameters, and hyperpolarizability of PtFnOLi3 (n = 2–4). The estimated nonlinear optical properties parameters are compared with corresponding parameters of traditional salt LiF by the same level theory.

Investigation of nonlinear optical properties of a group of transition metal-decorated B12N12 nanocages: A DFT study

BN nanostructures are a promising group of materials with different technical applications. In this study, the electronic characteristics and NLO response of a group of B12N12 nanocages modified by transition metals have been studied using the DFT approach. Population analysis has been performed to investigate the role of transition metal in the delocalization of electronic charge on the surface of nanostructures. In this regard, molecular electrostatic potential (MEP) maps and density of state (DOS) plots have been surveyed. Based on frontier molecular orbitals (FMOs) energies, the reactivity of considered nanostructures has been discussed in the framework of global reactivity descriptors. NLO properties of considered nanostructures in terms of dipole moment, the mean polarizability, the anisotropy of the polarizability, the first-order hyperpolarizability, and the mean second-order hyperpolarizability have been studied in the gas phase and in the presence of Ethanol as solvent. The correlation between the NLO response of the nanocages and their different electronic characteristics has been studied. Results show that the presence of solvent makes an apparent increase in their NLO response. Electronic transitions responsible for absorption spectra of B12N12 nanocages have been considered, too.

Disentangling the molecular polarizability and first hyperpolarizability of methanol-air interfaces.

Liquid-air interfaces have extensive implications in different areas of interest because the dynamical processes at the interface can be different from those in bulk. Thus, its characterization, understanding, and control may be pivotal in advancing discoveries. However, characterizing the interface requires special and selective tools to avoid signals from the bulk region. This surface specificity and versatility is achieved by using the second harmonic generation (SHG) responses. This study adopts multiscale simulation methods to evaluate the surface SHG responses of methanol-air interfaces with submonolayer resolution tackled by sequentially using classical molecular dynamics simulations under different temperatures and then employing quantum chemistry methods to compute the molecular first hyperpolarizabilities (β). This approach ensures the configurational diversity required to evaluate the average β values. The main achievements are (i) a quasi-absence of surface sensitivity of the mean polarizability 〈α〉 with values about 2% larger than those obtained in bulk, (ii) conversely, smooth variations on the polarizability anisotropy Δα are observed up to the fourth molecular layer at around 20 Å from the interface, and (iii) narrow interfacial effects on the SHG responses, β(-2ω;ω,ω), which are limited to the first molecular layer (∼3.0 Å) and characterized by a high contrast in the βZZZ(-2ω;ω,ω) tensor component between the first and the subsequent layers. Similar trends are obtained at different temperatures or when increasing the number of methanol molecules treated at the quantum chemistry level, indicating the robustness of the approach for describing the dipolar molecular responses of air-liquid interfaces.

External field intensity and wavelength dependency from IR to deep UV of linear and nonlinear optical properties of 1-butyl-3-methylimidazolium dicyanamide ionic liquid

The electronic structure, inter-ionic interactions and charge transfer, polarizability, and first-order and second-order hyperpolarizabilities of 1-butyl-3-methylimidazolium dicyanamide ionic liquid have been explored via modeling at M06-2X/6-311++G(d,p) level of theory. External field intensity dependence of electronic properties was investigated by utilization of field intensity from 0.0001 to 0.002 au applied in the direction of anion-cation. Interionic interactions have been characterized through the reduced density gradient method to reveal and distinguish hydrogen bonding and other non-covalent interactions. Extraordinary bonding interactions were observed between the anion and ring system of the cation. Electronic excitation characteristics were analyzed based on the inter-fragment charge transfer method to distinguish charge transfer contributions from local excitations. Static and dynamic nonlinear optical parameters namely the total dipole moment μ, the mean polarizability α(0,0) and α(−ω; ω), the anisotropy of polarizability Δα(0,0) and Δα(−ω; ω) the first hyperpolarizability in the direction of dipole moment β(0,0,0), β(−ω; ω,0), and β (−2ω; ω,ω), the average second hyperpolarizability γ(0;0,0,0), γ(−ω; ω,0,0) and γ(−2ω; ω,ω,0) have been calculated for specific laser wavelengths corresponding to the UV, visible, and infrared region. Thus, a novel way of mapping the field intensity and wavelength dependence of NLO properties was achieved. The hyperpolarizability calculations indicate that 1-butyl-3-methylimidazolium dicyanamide has a significant potential to be used in electro-optics Pockels effect, second-harmonic generation, and electro-optical Kerr effect applications. NLO property maps indicate that the wavelength dependence in the IR and visible region is almost ignorable when compared with that of the UV region where the first hyperpolarizabilities can increase by ten thousand and the second hyperpolarizabilities can reach up to ten billion times.

Wettability and Surface Tension of Imidazolium, Ammonium, and Phosphonium Bis(fluorosulfonyl)amide Ionic Liquids: Comparison between Pentyl, Ethoxyethyl, and Ethylthioethyl Groups.

This study particularly compares the surface tensions and contact angles for molten bis(fluorosulfonyl)amide salts of imidazolium, ammonium, and phosphonium cations with the pentyl, ethoxyethyl, or ethylthioethyl group. The examined substrate plates for contact angle measurements include silicate glass, platinum, copper, graphene, and polytetrafluoroethylene (PTFE). In addition, quantum chemistry calculations were performed to obtain the optimized structures of the cations and anions of the ionic liquids (ILs) that were studied here along with some typical anions and their dipole moments, mean polarizabilities, and charge distributions. All ILs showed the same order of contact angles with respect to the substrates: PTFE > graphene ≈ copper ≈ platinum > silicate glass. By comparing the three functional groups, i.e., pentyl, ethoxyethyl, and ethylthioethyl, the ILs with the ethylthioethyl group featured a higher work of adhesion than the respective ILs with the pentyl or ethoxyethyl group. The values of the surface tensions of the ILs followed the same trend for the three functional groups. Based on the Fowkes theory, it was found that the larger surface tensions of the ILs with the ethylthioethyl group compared with pentyl and ethoxyethyl groups were because of the increase in both dispersive and nondispersive components. The quantum chemistry calculations of the ions showed a larger dipole moment and mean polarizability for the cations with the ethylthioethyl group as compared with the pentyl and ethoxyethyl groups. This is consistent with the analysis results of the surface tensions based on the Fowkes theory. By comparing other anions, the dispersive component of the surface tension of the ILs with bis(fluorosulfonyl)amide was large, which is attributed to the small dipole moment of the anion.

The effects of lateral electric field and dimensionality on the electronic properties of 2D-core/shell quantum disk emerged in finite confining potential

This study explores the influence of lateral electric fields and dimensionality on the physical properties of core/shell quantum disks subjected to a finite confinement potential. By solving the Schrodinger equation using the finite elements method within the effective mass approximation, we investigate the impurity polarizability, diamagnetic response, and dipole moment of the nanostructure. Our findings highlight the substantial impact of these parameters on the physical properties, which are optimized through excitation adjustments. We observe that the electron-impurity mean distance, polarizability, and diamagnetic response exhibit significant changes under the influence of the geometrical confinement regime either weak or strong, the orientation of the applied electric field either positive or negative, and the inner and outer radii of the core/shell. These observations demonstrate the potential for decreasing and/or improving these properties. The insights gained from this study provide crucial knowledge for advancing nanoelectronic devices. By optimizing the impurity polarizability, diamagnetic response, and electron-impurity mean distance in core/shell quantum disks under lateral electric fields, the sensitivity and detection capabilities of these sensors can be significantly improved.

The effect of central transition metals and electron-donating substituent on the performances of dye/TiO2 interface for dye-sensitized solar cells applications

Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) approaches were applied to explore the effect of central transition metals and the dye/TiO2 interface on dye-sensitized solar cell (DSSC) performance and supply a promising way to estimate and screen possible candidates for DSSC applications. The interaction properties, bonding characteristics, sensitized mechanisms, charge transfer, frontier molecular orbitals, energy gap, partial densities of states (PDOS), non-covalent interactions (NCI), and electronic absorption spectra were examined and analyzed to provide the photovoltaic characteristics of Sc, Cu, and Ti tetrasulfonic acid phthalocyanine sensitizer@TiO2 interface in both gas phase and polar solvent as acetonitrile.The interfacial of TiPc-(SO3H)4 with TiO2, which facilitates the driving force for the electron injection of photosensitizers (ΔGinj), increases the charge separation, open-circuit voltage (Voc), and high light-harvesting efficiency (LHE) values. However, minimize the charge recombination, lifetime of the excited state (τ), regeneration driving force (ΔGreg). Our results reveal that TiPc-(SO3H)4@TiO2 is superior to those of ScPc-(SO3H)4, CuPc-(SO3H)4, TiPc-(SO3H)4 and Pc-(SO3H)4/TiO2, indicating the novel TiPc-(SO3H)4@TiO2 interface could be promising candidates for DSSC photovoltaic devices performance. In addition, the static mean polarizability and first hyperpolarizability of all six dyes elucidated that the TiPc-(SO3H)4@TiO2 interface can be regarded as a potential performer in non-linear optical (NLO) properties. These theoretical identifications may provide novel perspectives and instructions for future experimental researchers to promote the synthesis and application of TiPc-(SO3H)4@TiO2 interfaces to improve the photo-to-current conversion efficiency.

Structural, spectroscopic, electronic, Hirshfeld, QTAIM and biological predications of a hybrid 2,6-dichloropurine compound: A detailed density functional theoretical study

Extensive research into the optimized structure, spectroscopic and biological properties of 2,6-dichloropurine (6DCP) was conducted using IR/Raman and NMR techniques, as well as theoretically using the DFT approach with B3LYP, CAM-B3LYP, and PBEPBE function levels at 6-311++G(d, p) basis set. The computational results from DFT approaches such as geometrical, IR/Raman and NMR spectra were compared with the experimental results. All our theoretical calculations were in good agreement with observed data. The electronic HOMO-LUMO, H-bonding and strong conjugative interactions across different molecular entities are discussed to reveal the accompanying pharmaceutical intermediate. The molecular properties such as chemical reactivity descriptors, mapped ESP, dipole moment, mean polarizability, and first order hyperpolarizability of the title molecule were calculated by quantum mechanical calculations. The high value of the electronic dipole moment and polarizability estimate for the 6DCP molecule may improve its biological activity. The NBO study has enabled researchers to investigate hyper-conjugate interactions, intramolecular bonding, and strong H-bonding interactions. Strong H-bonding interaction energies of 120.47 kcal/mol have been performed at the DFT/PBEPBE level.

Experimental and theoretical studies of a thiourea derivative: 1-(4-chloro-benzoyl)-3-(2-trifluoromethyl-phenyl)thiourea

The 1-(4-chloro-benzoyl)-3-(2-trifluoromethyl-phenyl)thiourea compound was synthesized by a two-step reaction and a single crystal of it was obtained by recrystallization method. Its structure was elucidated by elemental analyzes, FT-IR, 1H NMR, and 13C NMR techniques, and its molecular and crystal structure was also determined by single-crystal X-ray diffraction analysis. The Hirshfeld surface analyzes of the crystal structure indicate that the most important contributions for crystal packing are from H···H (23.8%), H···S/S···H (14.5%), H···F/F···H (14.3%), C···H/H···C (14.2%), and Cl···F/F···Cl (9.0%). In addition, energy-framework calculations are used to analyze and visualize the three-dimensional topology of the crystal packing. The electrostatic energy framework is dominant over the dispersion energy framework. The density functional theory method with the basis set of B3LYP/6-311G(d,p) has been employed to obtain the optimized structural geometry, Mulliken charges, molecular electrostatic potential, frontier molecular orbitals, the total density of states, reduced density gradient analysis and natural bond orbitals. The experimental crystal structure parameters and optimized structure parameters are very similar. The HOMO–LUMO energy gap of the compound is 3.5307 eV. Different global chemical reactivity descriptor parameters were also calculated. Nonlinear optical properties such as anisotropy of polarizability, mean polarizability, static dipole moment, and first-order hyperpolarizability values were theoretically determined. The Fukui functions as electron density-based local reactivity descriptors were also calculated to explain the chemical selectivity or the reactivity site in the molecule. Molecular docking studies were also carried out to determine the inhibitory action of the title compound against the main protease (6LU7) of a new coronavirus (COVID-19).

Dielectric characterization studies of hydrogen-bonded polar liquids in nonpolar medium using cavity perturbation technique

The dielectric characteristics of polar substances like propan-1-ol, propionaldehyde, isopropyl amine & its equimolar ternary mixtures in benzene are examined at discrete microwave frequency region using the cavity perturbation technique at 6.218 GHz (J-band), 9.880 GHz (X-band), 16.331 GHz (P-band) and 24.951 GHz (K-Band) at room temperature. The minimum energy geometry optimization is performed at 6-311G+ (d, p), 6-311G++ (d, p) basis set with DFT(B3LYP) method for both pure as well as ternary mixtures of propan-1-ol, propionaldehyde & isopropyl amine liquid systems. The dipole moment(s) of these combinations are evaluated using Higasi's approach and verified with theoretical data. The average relaxation times of the ternary solutions are calculated using the Cole-Cole plots. The mean molecular polarizability values of distinct systems of propan-1-ol, propionaldehyde, isopropyl amine, and their ternary solutions are calculated with Lippincott-δ function model. The findings are described through the molecular association between the components by hydrogen bonding.

Density Functional Theory and Ab Initio Hartree-Fock Computational Study of 2-[1-Acetyl-3-Methyl-4,5-Dihydro-1H-1,2,4-Triazol-5-One-4-Yl]-Phenoxyacetic Acide

In the present theoretical study, the 2-[1-acetyl-3-methyl-4,5-dihydro-1H-1,2,4-triazol-5-one-4-yl]-phenoxyacetic acide was optimized by B3PW91 and HF methods 6-311+G (d.p) basis set using the Gaussian G09W program. The molecular structure, HOMO and LUMO energy analysis, electronic transitions, total static dipole moment, the mean polarizability, the anisotropy of the polarizability, the mean first-order hyperpolarizability, electronegativity, chemical hardness, molecular electrostatic potential maps (MEP) and Mulliken charges of 2-[1-acetyl-3-methyl-4,5-dihydro-1H-1,2,4-triazol-5-one-4-yl]-phenoxyacetic acide molecule have been investigated by using B3PW91 and HF methods with the 6-311+G (d, p) basis set. The calculated IR data of titled compound were calculated in gas phase by using of 6311+G (d, p) basis sets of B3PW91 and HF methods and are multiplied with appropriate adjustment factors. Theoretical infrared spectrums are formed from the data obtained according to B3PW91 method. In the identification of calculated IR data was used the veda4f program. 1H-NMR and 13C-NMR spectral data values were calculated according to the method of GIAO using the program package Gaussian G09W Software. Experimental data were obtained from the literature. Experimental and theoretical values were inserted into the graphic according to equitation of δ exp=a+b. δ calc. The standard error values were found via SigmaPlot program with regression coefficient of a and b constants. In addition, in vitro antioxidant properties of this compound was investigated.

A Theoretical Study on Charge Transfer and Hyperpolarizability of (S)-2-amino-3-(3,4-dihydroxyphenyl)-2-methyl-propanoic Acid

The DFT approach was used to investigate the antihypertensive molecule (S)-2-amino-3-(3,4-dihydroxyphenyl)- 2-methyl-propanoic acid at the B3LYP/6-311++G(d,p) level of theory. The electron-hole analysis of three excited states has been performed, in which the maximum charge transfer length (2.727Å) has been calculated for the first excited state and the minimum for the third excited state (1.626 Å). On the other hand, the electron-hole overlap is found to be almost negligible for the first excited state and it is found to be maximum for the second excited state. The variation of thermodynamic properties with temperature is studied. The correlation graphs are obtained between the thermodynamic quantities (heat capacity, enthalpy, entropy) and temperature with a very high value of R2 (>0.99). The values of dipole moment, mean polarizability, anisotropy of polarizability, first hyperpolarizability and second hyperpolarizability are found to be 3.5250 Debye, 12.6980×10−24esu, 19.8162×10−24esu, 0.9017×10−30esu and -0.0412×10−35esu, respectively. These values are higher than the value of urea.

Distributed Polarizability Model for Covalently Bonded Fullerene Nanoaggregates: Origins of Polarizability Exaltation.

Polarizability exaltation is typical for (C60)n nanostructures. It relates to the ratio between the mean polarizabilities of (C60)n and C60: the first one is higher than the n-fold mean polarizability of the original fullerene. This phenomenon is used in the design of novel fullerene compounds and the understanding of its properties but still has no chemical rationalization. In the present work, we studied the distributed polarizability of (C60)2 and isomeric (C60)3 nanoaggregates with the density functional theory method. We found that polarizability exaltation increases with the size of the nanostructure and originates from the response of the sp2-hybridized carbon atoms to the external electric field. The highest contributions to the dipole polarizability of (C60)2 and (C60)3 come from the most remote atoms of the marginal fullerene cores. The sp3-hybridized carbon atoms of cyclobutane bridges negligibly contribute to the molecular property. A similar major contribution to the molecular polarizability from the marginal atoms is observed for related carbon nanostructures isomeric to (C60)2 (tubular fullerene and nanopeanut). Additionally, we discuss the analogy between the polarizability exaltation of covalently bonded (C60)n and the increase in the polarizability found in experiments on fullerene nanoclusters/films as compared with the isolated molecules.

Polarizability of Kekulene, Septulene, and Nearest Non-Planar Polycyclic Aromatic Hydrocarbons

The polarizability of polycyclic aromatic hydrocarbons (PAHs) is an important property that relates to their abundance in natural environments. To assess the differences in the mean polarizability of planar and non-planar polycyclic aromatic hydrocarbons (PAHs), we computationally studied the PAH series of circulenes (kekulene C48H24, [13]circulene C52H26, and septulene C56H28), a number of the nearest helicenes, and their “expanded” isomers. We mean under “nearest” a close number of aromatic rings: 11 (C46H26), 12 (C50H28), 13 (C54H30), and 14 (C58H32). For these PAHs, we performed the quantum chemical calculations of thermodynamic and polarizability parameters with the PBE/3ζ density functional theory method, which is widely used in the theoretical chemistry of fullerenes and PAHs. The calculated mean polarizabilities (in Å3) ranged from 80.1 for [11]helicene to 135.5 for septulene, and while the circulenes and expanded helicenes had similar values, the mean polarizability of the normal helicenes was markedly lower. In all four pairs of helical PAHs, the expanded helicene was energetically considerably more favorable than its standard helicene isomer. Herewith, the ratio of their polarizabilities was equal to 1.3.

Nonlinear optical activity of piperazine-1,4-diium bis(sulfanilate) compound

The present work investigates the NLO activity of the piperazine-1,4-diium bis(sulfanilate) molecule using density functionaltheory (DFT). The optimized molecular geometry and the vibrational wavenumber are calculated using DFT/B3LYP method with 6-311G (d,p) basis set.The possible hydrogen bonding interaction and charge delocalization are analyzed using natural bond orbital (NBO) analysis. Charge transfer interactionis identified using molecular electrostatic potential (MEP). Frontier molecular orbital (FMO) analysis illustrates that charge is transferred from sulfanilate anion and piperazinium cation. The electronic absorption transitions with different solvents are carried out by the time-dependent density functional theory (TD-DFT) method. The Fukui functional analysis is carried out to find the possible sites for the nucleophilic and electrophilic attack. The dipole moment (μ), mean polarizability (Δα), first order (β) and second order hyperpolarizability (γ) are calculated by DFT calculation. The NLO properties are relatively high when compared with urea, indicating the potential NLO application of PADSA.