First-order Hyperpolarizability Values Research Articles

Quantitative Structure-activity Relationship Studies and Nonlinear Optical Properties of 2-Phenylbenzofuran Derivatives: A Density Functional Theory Study

Density Functional Theory calculations, in the ground state of 2-Phenylbenzofuran, were carried out using the GGA-PBE, PBV86 and meta-GGA-TPSS hybrid functionals with 6-31G (d, p) as a basis set. First, theoretical calculations were performed using these functionals to obtain the stable conformer of the molecule. In addition, Mulliken population natural population and natural bond orbital analyses were calculated. The molecular electrostatic potential, band gap energies, global, local chemical reactivity descriptors and non-linear optical (NLO) properties were studied. Additionally, the NLO properties of 2-Phenylbenzofuran and those of its derivatives were investigated by GGA-PBE/6-31G (d,p) level of theory. The first-order hyperpolarizability value of all 2-Phenylbenzofuran derivatives was found within the range extending from 4.00 × 10-30 to 43.57 × 10-30 (esu). It indicated that they possess remarkable NLO properties. In addition, a multiple linear regression procedure was used to envisage the relationships between molecular descriptors and the activity of 2-Phenylbenzofuran derivatives; the quantitative structure-activity relationship (QSAR) studies were performed on them using quantum descriptors. The QSAR was applied to determine a correlation between the various physico-chemical parameters of the studied compounds and their biological activities. The statistical quality of the QSAR models was assessed using statistical parameters, i.e. R2, R2adj and R2cv.

Cation-anion interaction effect on the nonlinear optical behavior of pyridinium-based ionic liquids

Influence of the cation–anion interaction (expressed as internal hydrogen bonds) on the nonlinear optical properties (dipole moment, polarizability, anisotropy of polarizability and first-order hyperpolarizability) for the ionic liquids pyridinium hydrogen sulfate (PHS) and pyridinium bis(dihydrogen phosphate) (P2HP) was investigated in this paper. It was achieved analyzing vibrational modes (FT-IR) and electronic transitions (UV–vis) in PHS and P2HP. Molecular geometry of the title compounds was optimized by means of density functional theory calculations at B3LYP/6–311++G(2d,2p) level.Structural analysis exposed stronger internal hydrogen bonds (H7···O3 and H18···O4) between cationic and anionic fragments in the pyridinium hydrogen sulfate than these (H26···O4 and H25···O12) in pyridinium bis(dihydrogen phosphate). These observations are confirmed by FT-IR and UV–vis methods, where: (i) the infrared bands due to H···O and N–C interactions in P2HP appear at lower frequencies than the same ones in the spectrum of PHS and (ii) the n → π* electron transitions in PHS are more pronounced in comparison with these in P2HP. Based on the weaker cation–anion interaction in P2HP with respect to PHS, the former one is characterized with a remarkably higher first-order hyperpolarizability value. Hence, the ionic liquid P2HP was referred as a better nonlinear optical material than PHS.

Crystal structure, physico-chemical and third order nonlinear traits of the novel (2E)-1-(3,4-dimethoxyphenyl)-3-(4-propoxyphenyl) prop-2-en-1-one (DMPP) chalcone single crystal

Optically highly versatile novel third-order organic nonlinear single crystals of (2E)-1-(3,4-dimethoxyphenyl)-3-(4propoxyphenyl)prop-2-en-1-one (DMPP) which adapts to orthorhombic Pbca space group is crystallized by slow evaporation growth technique. Fourier transform infrared analysis affirms the presence of various functional groups in DMPP. Transparency and lower cut-off wavelength of the crystal were obtained using linear optical properties. The thermal stability without any weight loss is up to 220°C. The molecular structure of DMPP was confirmed by 1H NMR and 13C NMR analysis. From the electrical conductivity studies, the suitability of DMPP chalcone for device fabrication with a very low activation energy value of 0.04 ​at 1 ​MHz and conductivity value of 10−4 ​S/m was observed for the first time. Further B3LYP/6-31G++ level has been used to obtain static first-order and second order hyperpolarizability parameters. The calculated value of first-order hyperpolarizability was calculated to be 96 times better than that of standard urea and several orders better compared to other 3,4 dimethoxy derivatives. The experimental third order nonlinear measurements were done by continuous-wave (cw) 632.8 ​nm laser. From the Z-scan measurements, the calculated imaginary and real third-order nonlinear optical susceptibility are of the order of 10−5 e.s.u. The experimental and computational results disclose that DMPP is a novel third-order optically active single crystal and a noteworthy material for nonlinear optical applications.

DFT studies of the structural, chemical descriptors and nonlinear optical properties of the drug dihydroartemisinin functionalized on C60 fullerene

Density Functional Theory (DFT) calculations where performed to study the structural, electronic and nonlinear optical properties, global reactivity descriptors and the solubility of the dihydroartemisinin drug and its functionalization on C60 fullerene. The results of this study show that the geometrical parameters of the studied molecule do not change significantly after its functionalization. Furthermore, the values of the binding and reaction energies are all negative meaning that the binding of dihydroartemisinin to C60 is energetically favorable and the synthesis of our complex structure is possible. By comparing the solvation energies, we found that the functionalization of C60 fullerene improves the solubility of dihydroartemisinin in water. The gap value of functionalized fullerene is about 2.5 eV indicating that it can be considered as a semiconductor material. Finally, the functionalization considerably improves the nonlinear optical properties and the high values of first order hyperpolarizability led us to conclude that our molecules are promising material for nonlinear optical devices.

Spectroscopic calculations, Hirshfeld surface analysis, and molecular docking studies of anticancer 6-(4-Aminophenyl)-4-(4-methoxyphenyl)-2-methoxynicotinonitrile

The title compound 6-(4-Aminophenyl)-4-(4-methoxyphenyl)-2-methoxynicotinonitrile was deliberated by proton nuclear magnetic resonance, ultraviolet-visible, and Fourier transform infrared spectroscopy techniques. The theoretical optimized geometrical parameters (bond lengths, bond angles and dihedral angles), vibrational wavenumbers, and the non-linear optical properties were calculated using the density functional theory with the Becke, 3-parameter, Lee–Yang–Parr functional method. Hirshfeld surface and two-dimensional fingerprint plot analyses have been performed to study the nature of intermolecular interactions within the crystal structure. The ultraviolet-visible spectrum, global chemical reactivity descriptors, the highest occupied molecular orbital and the lowest unoccupied molecular orbital energies in acetonitrile solvent have performed by Time-Dependent Density Functional Theory approach. The molecular electrostatic potential used to predict the reactive sites indicates that the nitrogen atom of the nitrile group is prone to electrophilic attack, and the hydrogen atoms belonging to the amino group to nucleophilic attack. The first-order hyperpolarizability value indicates that the title compound is a useful claimant as non-linear optical material studies. The reduced density gradient function based on electron density provides a simple, clear, and practical method to research non-covalent interactions was investigated. Molecular docking studies of the title compound have been performed, which suggests that the title molecule may act as a potential anticancer agent.

New Insights into the Structure and Reactivity of Uracil Derivatives in Different Solvents-A Computational Study.

Ab initio calculations were carried out to understand the reactivity and stability of some uracil derivatives, cytosine, 1-methyl cytosine, and cytidine in solvents, water, dimethyl sulfoxide (DMSO), n-octanol, and chloroform. Geometries were fully optimized at MP2 and B3LYP using the 6-31+G(d,p) basis set by applying the Solvation Model on Density (SMD) in solvent systems. The syn conformer of cytidine (cytidine II) is the most stable conformer in the gas phase, while the anticonformer (cytidine IV) is most stable in all of the solvents. Solvation free energy and polarizability values in different solvents decrease in the order water > DMSO > n-octanol > chloroform, while dipole moment, first-order hyperpolarizability, and HOMO–LUMO energy gap values follow the order of polar protic solvent (water and n-octanol) > polar aprotic solvent (DMSO) > nonpolar solvent (chloroform). The solvation free energy, dipole moment, polarizability, and first-order hyperpolarizability values also follow the order of cytosine > 1-methyl cytosine > cytidine. To illustrate that the molecular properties correlate well with the reactivity of the molecules, ab initio calculations were carried out for the reaction of uracil derivatives with Br2 in the gas phase, water, DMSO, n-octanol, and chloroform. All ground and transition state geometries were fully optimized at B3LYP/6-31+G(d,p), and energies were also calculated at G3MP2 for cytosine and 1-methyl cytosine. For cytosine and 1-methyl cytosine, Gibbs energies of activation decrease with the polarity of the solvent that is chloroform > n-octanol > DMSO > water, while the Gibbs energies of activation for the reaction with cytidine decrease in the order of water > DMSO > n-octanol > chloroform. These results suggest that solvent polarity is very important for the stability and reactivity of uracil derivatives. Hydrogen bonding may also play an important role mainly for cytidine. Free energies of activation decrease with the size of the molecule, i.e., cytosine > 1-methyl cytosine > cytidine.

Experimental and computational perspectives on linear and non-linear optical parameters of an orthorhombic crystal for optical limiting applications

4-Dimethylaminopyridinium 3,5-dinitrobenzoate (DMAPDNBA), a charge transfer complex, was synthesized and successfully grown by slow evaporation solution growth technique. Single-crystal X-ray diffractogram reveals that the material crystallizes in orthorhombic system with non-centrosymmetric space group P212121 with cell parameters a = 5.92 A, b = 13.77 A, c = 18.64 A, and V = 1519 A3. Powder XRD and FTIR spectral investigation were carried out to analyse the crystallinity of the material and for assigning vibrations to identify the different functional groups existing within the material. The optical transmittance in the visible and near IR (400–800 nm) regions with lower cutoff wavelength of 227 nm, luminescence spectrum, and the optical band gap of 5.45 eV sufficiently fulfilled the requirement for non-linear optical applications. The thermal exploration analysis (TG–DSC) confirmed the stable nature of the compound up to 190 °C, and dielectric constant measurement of the obtained sample enhanced the property of non-linear optical activity at higher frequencies. The mechanical property of DMAPDNBA was evaluated using Vickers’s hardness test which confirmed that the material belonged to the soft category. The frequency conversion efficiency of the grown sample was measured to be eightfold that of the reference potassium dihydrogen phosphate, which exploits the potentiality of the charge transfer complex to be used as a promising candidate for various laser-assisted NLO applications. Third-order non-linearity was measured adopting Z-Scan technique, and the optical limiting/switching efficiency of the complex was verified with the optical limiting threshold value of 10.64 J/cm2 and figure of merit property, confirming the capability of the material for switching applications. The threshold value of laser damage was found to be 1.74 GW/cm2. Theoretical investigations were performed using density functional theory (DFT-B3LYP) approach to estimate and predict various linear and non-linear optical properties of the DMAPDNBA complex. The first-order hyperpolarizability value of the DMAPDNBA molecule was found to be 19 times that of the standard organic crystal, urea. In short, all the above findings designate the candidature of the charge transfer complex, DMAPDNBA, for photonic applications.

5-Methyl-4-[3-(2-oxopyrrolidin-1-yl)propyl]-2,4-dihydro-3H-1,2,4-triazol-3-one: Synthesis, Characterization, and DFT Study

5-Methyl-4-(3-(2-oxopyrrolidin-1-yl)propyl)-2,4-dihydro-3H-1,2,4-triazol-3-one was synthesized and characterized by X-ray, FTIR and NMR spectroscopic techniques. The molecular geometry and spectral parameters of the title compound were also computed by the DFT/B3LYP76-311++G(d,p) method, and the theoretical data showed a good agreement with the experimental ones. The differences between the theoretical and experimental IR and NMR spectra supported the presence of inter- and intramolecular C-H⋯O and intermolecular N-H⋯O hydrogen bonds, which were revealed by X-ray analysis. Nonlinear optical (NLO) properties of the title compound were analyzed by the DFT/B3LYP/6-311++G(d,p) method by calculating the mean polarizability (α) and first-order hyperpolarizability values (β) (α = 22.0746454×10−24, β = 10.1110649×10−31 esu). As compared with the corresponding data for urea (α = 4.9067×10−24, β = 7.8782×10−31 esu), these values suggest promising NLO properties.

Quantum Mechanical Studies of Three Aromatic Halogen-Substituted Bioactive Sulfonamidobenzoxazole Compounds with Potential Light Harvesting Properties

Three different organic compounds, 2-phenyl-5-(4-trifloromethyl phenyl sulfonamido) benzoxazole (PTPS), 2-(4-chlorobenzyl)-5-(2,4-dinitrophenylsulfonamido)benzoxazole (CNSB) and 2-(4-fluorobenzyl)-5-(2,4-dinitrophenylsulfonamido)benzoxazole (FBPS), were synthesized. To find their energetically stable conformation, geometry optimization was done using density functional theory with the level B3LYP/cc-pVDZ. Electron distribution of the system was studied using molecular electrostatic potential map. Different intermolecular interactions arising from hyperconjugative effect were investigated using the natural bond orbital (NBO) formalism. Nonlinear optical properties were further studied using first-order hyperpolarizability values. The three compounds may be important in the development of novel inhibitor molecules of Topoisomerase II enzyme, as lead compounds. Light harvesting efficiency of PTPS is 0.9342, which shows that it is having potential applications in the design of new DSSC's.

A combined experimental (XRD, FT-IR, UV-VIS and NMR) and theoretical (NBO, NLO, local & global chemical activity) studies of methyl 2-((3R,4R)-3-(naphthalen-1-yl)-4-(phenylsulfonyl) isoxazolidin-2-yl) acetate

Methyl 2-((3R,4R)-3-(naphthalen-1-yl)-4-(phenylsulfonyl) isoxazolidin-2-yl) acetate (3e) was synthesized and characterized by XRD, FT-IR, UV–Vis and NMR techniques. All theoretical computations were calculated by using density functional theory (DFT) B3LYP method with the help of 6-311G(d,p) basis set. Theoretical calculations help to obtain detailed information about local & global chemical activities, molecular and chemical properties which are reveal the electrophilic and nucleophilic nature. Accordingly, global (FMOs, hardness & softness parameters) and local (MEP, FF, net charges) chemical activity descriptors were examined. To determine the non-linear optical behaviours of title compound; the total dipole moment, mean polarizability and first-order hyperpolarizability values have been examined.

Vibrational spectroscopic characterization, electronic absorption, optical nonlinearity computation and terahertz investigation of (2E) 3-(4-ethoxyphenyl)-1-(3-bromophenyl) prop-2-en-1-one for NLO device fabrication

The present study spotlights the key structure-property features of a chalcone derivative (2E) 3-(4-ethoxyphenyl)-1-(3-bromophenyl) prop-2-en-1-one (E3BC) for future applications in nonlinear optical devices through dual approach involving experimental and theoretical techniques. The sample has been characterized by 1H NMR, FT-IR, FT-Raman and terahertz spectroscopies. The experimental results are supported by computational studies using density functional theory. To analyse the 1H NMR spectra, theoretical calculations on chemical shifts were done by GIAO method. Complete vibrational assignments of the vibrational modes have been made on the basis of the potential energy distribution in terms of internal coordinates. The low frequency vibrational modes between 0.2 and 1.8 THz were examined via terahertz time domain spectroscopy. The UV–vis spectrum was recorded in methanol solution. The energies, absorption wavelengths and oscillator strengths of electronic singlet-singlet transitions were determined by time dependent density functional theory. The calculated HOMO-LUMO energy gap is small which reveals that the charge transfer takes place within the molecule and it can be exploited for the nonlinear optical applications. Information about the charge density distribution and the sites of chemical reactivity of the molecule has been obtained by mapping electron density with molecular electrostatic potential. The MEP surface around the bromine atom exhibited the dual nature. Along the C-Br axis the positive electrostatic potential (the σ-hole) is present while the remainder of the surface is negative. Hence bromine atom can interact electrostatically with both nucleophiles and electrophiles. For other atoms no atom-specific effects are found. The stability of the molecule arising from hyper conjugative interactions and charge delocalization has been interpreted using natural bond orbital analysis. The study indicates that the intramolecular charge transfer (n → σ∗, n → π∗ and π → π∗) can induce nonlinearity in the molecule and validates E3BC's candidature to be used as a nonlinear optical active material. In order to understand the nonlinear optical activity of the molecule the calculations of electronic dipole moment, polarizability, anisotropy of polarizability as well as first and second hyperpolarizabilities are performed using finite field approach implemented in the DFT method. The findings suggested that the first order hyperpolarizability of titled molecule is 139 times greater than the value of urea. The high value of first order hyperpolarizability shows that E3BC can be a potential candidate in the nonlinear optical applications. The vibrational contribution to the above properties has also been computed using the self-consistent field wave functions within the double harmonic oscillator approximation.

The theoretical investigation of global reactivity descriptors, NLO behaviours and bioactivity scores of some norbornadiene derivatives

In this study, global reactivity descriptors such as ionization potential, electron affinity, electronegativity, chemical hardness, softness and electrophilicity index of norbornadiene derivatives which include some halogen atoms and atom groups, have been investigated with DFT/BPV86/B3LYP/B3PW91 methods with 6-31G(d,p) basis set. To determine the non-linear optical behaviours of the structures, the total dipole moment, polarizability,and first-order hyperpolarizabilityvalues have been examined at the same theoretical level. It has been determined that thiol-bonded groups on comparison with others have a much better NLO material property. In addition, the potentials of the structures as drug-active compounds have been inspected with Lipinski’s rule of 5 and bioactivity scores. Thiol and hydroxyl-bonded groups have a good drug-likeness and bioactivity score relative to the others.

Crystal growth, physical properties, and theoretical investigation on organic acentric single crystal towards efficient second-order NLO applications: Triphenylguanidine

A novel organic nonlinear optical crystal Triphenylguanidine (TPG) was grown by the solvent evaporation method. Single-crystal X-ray diffraction (XRD) studies showed that the TPG compound crystallizes in orthorhombic crystal system with Pna21 space group and the corresponding lattice planes of reflections were indexed using powder XRD studies. Fourier transform infrared and Fourier transform Raman studies revealed the presence of various functional groups in the TPG crystal. The molecular structure of TPG was also confirmed using the NMR studies. UV–Vis studies validate the aptness of TPG crystal towards nonlinear optical applications. TPG crystal shows blue emission from photoluminescence studies. The mechanical stability of the grown crystal was identified using Vickers microhardness studies. Dielectric studies were carried out as a function of frequency at room temperature. Powder SHG effective nonlinearity of TPG crystal is about 2.3 times that of standard KDP. The thermal stability of TPG crystal was investigated by the TG-DTA studies. Using Gaussian 03 program the HOMO–LUMO energy gap and first-order hyperpolarizability value for TPG molecule were calculated. The calculated first-order hyperpolarizability value of TPG molecule is 17 times that of urea.

Zintl superalkalis as building blocks of supersalts.

Alkali metal cations and halogen anions are common components of ionic salts. Recently, a new class of salts termed supersalts was reported, each of which contains a superalkali and a superhalogen that mimic an alkali metal cation and a halogen anion, respectively. Using three different functionals, namely B3LYP, wB97X, and M06-2X, we theoretically investigated a new subset of supersalts composed of Zintl-based superalkalis and inorganic superhalogens via computational modeling. The calculated dipole moment and first-order hyperpolarizability values for these supersalts indicate that they present nonlinear optical (NLO) behavior. The supersalts of Zintl superalkalis (Ca2P7, Sr2P7, Ba2P7) and superhalogens (BF4, BeF3, NO3) studied here were found to be stable. Graphical Abstract Using the first-principles calculation, a new class of supersalts by using Zintl-based superalkalis and inorganic superhalogens has been designed.

Experimental and quantum chemical studies of a new organic proton transfer compound, 1H-imidazole-3-ium-3-hydroxy-2,4,6-trinitrophenolate

A new proton transfer compound, 1H-imidazole-3-ium-3-hydroxy-2,4,6-trinitrophenolate (IMHTP), was crystallized by slow evaporation-solution growth technique. 1H and 13C NMR spectral studies confirm the molecular structure of the grown crystal. Single crystal X-ray diffraction study confirms that IMHTP crystallizes in monoclinic system with space group P21/c. Thermal curves (TG/DTA) show that the material is thermally stable up to 198 °C. The crystal emits fluorescence at 510 nm, proving its utility in making green light emitting materials in optical applications. The stable molecular structure was optimized by Gaussian 09 program with B3LYP/6-311++G(d,p) level of basis set. The frontier molecular orbital study shows that the charge transfer interaction occurs within the complex. The calculated first-order hyperpolarizability value of IMHTP is 44 times higher than that the reference material, urea. The electrostatic potential map was used to probe into electrophilic and nucleophilic reactive sites present in the molecule.

Growth, thermal, vibrational studies and quantum chemical calculations of 2,6-dibromo-4-nitrophenol: a new nonlinear optical crystal

Good-quality single crystals of 2,6-dibromo-4-nitrophenol have been grown by slow evaporation solution growth technique using ethanol as solvent. The lattice parameters of the grown crystal were confirmed from single-crystal XRD analysis. Quantum chemical calculations were carried out using DFT /B3LYP/6-31 G(d,p) method. The optimized geometrical parameters have been obtained from the computational technique, and the result shows good agreement with the experimental XRD data. Both the experimental and theoretical vibrational spectrum confirms the presence of functional groups. Optical absorption behaviour of the grown crystal was examined by recording the optical spectrum and band gap energy was also estimated. Theoretical investigation shows that the title compound exhibits non-zero first-order hyperpolarizability values and has microscopic non-linear optical behaviour which is 22 times more than that of urea. The calculated HOMO and LUMO energies reveal the charge transfer characteristic of the title compound. Frequency conversion property of the grown crystal was investigated using Kurtz and Perry powder technique.

Vibrational spectroscopic and DFT calculation studies of 2-amino-7-bromo-5-oxo-[1]benzopyrano [2,3-b]pyridine-3 carbonitrile

The vibrational spectra of 2-amino-7-bromo-5-oxo-[1]benzopyrano [2,3-b]pyridine-3 carbonitrile were recorded using fourier transform-infrared and fourier transform-Raman spectrometer. The optimized structural parameters, vibrational frequencies, Mulliken atomic charge distribution, frontier molecular orbitals, thermodynamic properties, temperature dependence of thermodynamic parameters, first order hyperpolarizability and natural bond orbital calculations of the molecule were performed using the Gaussian 09 program. The vibrational frequencies were assigned on the basis of potential energy distribution calculation using the VEDA 4.0 program. The calculated first order hyperpolarizability of ABOBPC molecule was obtained as 6.908×10−30 issue, which was 10.5 times greater than urea. The nonlinear optical activity of the molecule was also confirmed by the frontier molecular orbitals and natural bond orbital analysis. The frontier molecular orbitals analysis shows that the lower energy gap of the molecule, which leads to the higher value of first order hyperpolarizability. The natural bond orbital analysis indicates that the nonlinear optical activity of the molecule arises due to the π→π∗ transitions. The Mulliken atomic charge distribution confirms the presence of intramolecular charge transfer within the molecule. The reactive site of the molecule was predicted from the molecular electrostatic potential contour map. The values of thermo dynamic parameters were increasing with increasing temperature.

The vibrational studies and theoretical investigation of structure, electronic and non-linear optical properties of Sudan III [1-{[4-(phenylazo) phenyl]azo}-2-naphthalenol

Sudan III [1-{[4-(phenylazo) phenyl]azo}-2-naphthalenol] is non-ionic fat-soluable dye used as an additive in gasoline, oils and plastics. The molecular structure, molecular electrostatic potential, NBO analysis, linear and non-linear optical properties of Sudan III have been investigated using density functional theory (DFT) calculation with 6-311G(d,p) basis set. To investigate the tautomeric stability, optimization calculations at B3LYP/6-311G(d,p) level were performed for the azo (OH) and hydrazo (NH) forms of the title compound. The calculated first-order hyperpolarizability value is comparable with the reported values and attractive object for future studies of non-linear optics. FT-IR (4000–400cm−1) and FT-Raman (3500–50cm−1) spectra of Sudan III have been recorded. The vibrational frequencies determined experimentally are compared with those obtained theoretically and a vibrational assignment and analysis of the fundamental modes of the compound is performed. The scaled frequencies resulted in good agreement with the observed spectral patterns.

Growth and nonlinear optical studies of N-acetyl-L-cysteine crystal

Crystals of N -acetyl-L-cysteine have been grown by slow evaporation solution growth technique using water as solvent. Cell parameters of the crystals were confirmed by powder X-ray diffraction. Functional groups were identified and their vibrational activity was studied by investigating the FTIR spectrum. Decomposition nature of the grown material was studied in thermal analysis. Transparent nature of the crystal in UV-VIS-NIR region was examined by optical absorption spectrum. Frequency conversion process was tested and the title crystal has two times larger relative second harmonic conversion efficiency compared to the standard KDP. Static and dynamic values of first-order hyperpolarizability were calculated and also the electronic excitation mechanism was analyzed.

Static first order hyperpolarizabilities of DNA base pairs: A configuration interaction study

We have investigated the role of H-bonding on the static first-order hyperpolarizabilities of DNA base pairs, namely, adenine–thymine (AT) and guanine–cytosine (GC). To interpret the effect of long-range dipolar interaction on this optical coefficient, the configuration interaction method has been implemented in these systems. Remarkably, the static first-order hyperpolarizability values gradually increases for the AT base pair as one increases the H-bonding distance between the DNA bases, whereas a reverse trend is observed for the GC base pair where the hyperpolarizability values pass through a minimum.