First-order Molecular Hyperpolarizability Research Articles

Generic Classification Scheme for Second-Order Dipolar Nonlinear Optical Organometallic Complexes That Exhibit Second Harmonic Generation.

The molecular design rules of organic nonlinear optical (NLO) materials are well established, especially those pertaining to the first-order molecular hyperpolarizability, β, which governs second-harmonic generation (SHG): a phenomenon that is responsible for the frequency doubling processes in many optical applications. The availability of these rational guidelines has propelled the development of new organic SHG chromophores. Conversely, the development of organometallic SHG-active complexes has not been steered so clearly. Many reports on individual series of complexes suggest a singular correlation between their structure and SHG properties. Several reviews have catalogued such results, but these have only distinguished compounds by chemical type, while their SHG properties are described one-by-one for each chemical. We herein propose a generic classification scheme that can systematically rationalize dipolar SHG properties for all organometallic complexes. This classification method stands to provide the holistic information that is needed to generate a rational set of guidelines for the systematic molecular design of dipolar SHG-active organometallic chromophores. Our scheme shows that only a simple set of molecular design rules is required to relate the chemical structure of an organometallic complex to its second-order dipolar SHG properties. This is despite the fact that these molecular design rules are rooted in a complicated panoply of ligand- and crystal-field theory, resonance structures, intramolecular charge transfer considerations, metal oxidation states, and metal coordination attributes. While the roots of these rules can be derived at the individual chemical level, their derivation via our workflow of simple decision-making processes which connect these rules within a simple classification scheme, stands to facilitate a rational molecular design approach toward the materials discovery of organometallic complexes for SHG applications.

Supramolecular architecture and computational studies of nicotinohydrazide and furan-2-carbohydrazide crystals

Single crystals of N'-(1-(Benzo[d][1,3]dioxol-5-yl]ethylidene) nicotinohydrazide (I) and N'-(1-(benzo[d][1,3]dioxol-5-yl)ethylidene)furan-2-carbohydrazide (II) were grown by slow evaporation solution growth technique. (I) and (II) belong to the triclinic and monoclinic systems with centrosymmetric space groups Pī and C2/c respectively. The molecules are associated by weak CH⋯O, NH⋯N, CH … π and π-π stacking interactions, which are responsible for the formation and strengthening of the supramolecular assembly. Inter- and intramolecular hydrogen-bonding interactions support the supramolecular architecture in the crystal packing. The band gap energy is estimated by the application of the Kubelka–Munk algorithm. Theoretical calculations were performed using density functional theory (DFT) to derive the optimized geometry, dipole moment, first-order molecular hyperpolarizability and HOMO–LUMO energies. The distributions of the various atoms were probed by Mulliken population analysis. Hirshfeld surface analysis given an idea about the close contacts associated with molecular interactions. Fingerprint plots of the Hirshfeld surfaces were used to locate and analyze the percentage of hydrogen bonding interactions.

Spectroscopic investigations using density functional theory on 2-methoxy- 4(phenyliminomethyl)phenol: A non linear optical material

Single crystals of 2-methoxy-4(phenyliminomethyl)phenol were grown from ethanol by slow evaporation solution growth technique. Single crystal X-ray diffraction experiment reveals the crystallization in orthorhombic system having non-centrosymmetric space group C2221. Geometrical optimization by density functional theory method was carried out using Gaussian program and compared with experimental results. Detailed experimental and theoretical vibrational analyses were carried out and the results were correlated to find close agreement. Thermal analyses show the material is thermally stable with a melting point of 159 °C. Natural bond orbital analysis was carried out to explain charge transfer interactions through hydrogen bonding. Relatively smaller HOMO-LUMO band gap favors the non linear optical activity of the molecule. Natural population analysis and molecular electrostatic potential calculations visualize the charge distribution in an isolated molecule. Calculated first-order molecular hyperpolarizability and preliminary second harmonic generation test carried out using Kurtz-Perry technique establish 2-methoxy-4(phenyliminomethyl)phenol crystal as a good non linear optical material. Z-scan proposes the material for reverse saturable absorption.

Solvatochromic effect on UV–vis absorption and fluorescence emission spectra, second- and third-order nonlinear optical properties of dicyanovinyl-substituted thienylpyrroles: DFT and TDDFT study

The nonlinear optical properties of dicyanovinyl-thienylpyrroles 1–6 compounds were investigated by the determining of the first-order molecular static hyperpolarizability (β) and the second-order molecular static hyperpolarizability (γ) in the ground state by using the HSEh1PBE/6-311G(d,p) level of density functional theory (DFT). The photophysical behavior of compounds 1 and 5 in polar and non-polar solvents was studied by using UV–vis absorption and fluorescence emission spectroscopies. In order to investigate the effects of these solvents, the time-dependent density functional theory (TD-DFT) calculations with the polarizable continuum model (PCM) in the excited state were performed. The UV–Vis absorption and fluorescence emission spectra for compound 5 were also simulated using TD-HSEh1PBE/6-311G(d,p) level, and the major contributions to the electronic transitions for compounds 1–6 were obtained. The β0 value (18.74×10−30esu) calculated by using HSEh1PBE/6-311G(d,p) for compound 2 is 1.49 times lower than the experimental value (28×10−30esu), and 2.34 times greater than pNA value (8×10−30esu). The β and γ parameters for compound 2 is lower than 1 and 3–6 due to electron donating pyrrole ring and electron accepting dicyanovinyl group. Moreover, we used the hybrid DFT methods (B3LYP, M062X, CAM-B3LYP and BHandHLYP) to show the accuracy for first static hyperpolarizability values for compounds 1–6. The β0 parameter for compound 5 in both polar and non-polar solvents was examined by using two level model.

Theoretical study of nonlinear optical properties of cobalt bis (dicarbollide) derivatives: the effect of substituents

In the present work, molecular first-order hyperpolarizability ( $$\beta _{\mathrm{tot}}$$ ) and dipole moment (d) are obtained at B3LYP/6–31G(d,p) level of theory by coupled perturbed Hartree–Fock method within the static approach. The investigated molecules are a series of substituted cobalt bis (dicarbollide) derivatives: Hydrogens bonded to the two carbon atoms are replaced by acceptor and donor electron substituents. Correlations between the Hammett electronic parameters of the substituents and the molecular properties are tested. Among them, the named push–pull compounds produced the largest calculated values of $$\beta _{\mathrm{tot}}$$ and d. The UV–Vis spectra are reported for all studied compounds.

Combined theoretical and experimental studies on the molecular structure, spectral and Hirshfeld surface studies of NLO tris(thiourea)zinc(II) sulfate crystals

Transparent single crystals of tris(thiourea)zinc(II) sulfate (ZTS) were grown by slow evaporation technique at room temperature from an aqueous solution containing zinc sulfate and thiourea in the molar ratio 1:3. The experimental and theoretical studies on the molecular structure and vibrational spectra of ZTS were investigated by single crystal X-ray diffraction, FT-IR and density functional theory (DFT). The recorded X-ray diffraction bond parameters are compared with theoretical values calculated at B3LYP/LANL2DZ level. The observed vibrational patterns were compared with the computed wave numbers. The energy and oscillator strength calculated by TD-DFT results complement with the experimental findings. The first-order molecular hyperpolarizability, polarizability, dipole moment and HOMO–LUMO band gap energies were derived. The molecular stability and bond strength were investigated by applying the natural bond orbital analysis (NBO). Information about the size, shape, charge density distribution and site of chemical reactivity of the molecule has been obtained by mapping electron density with molecular electrostatic potential (MEP) using the same level of basis set. Intermolecular hydrogen bonding was investigated by means of the Hirshfeld surfaces, and the role of the NH⋯O interactions as driving force for crystal structure formation has been demonstrated. The percentages of hydrogen bonding interactions are analyzed by Fingerprint plots of Hirshfeld surface.

Synthesis, Molecular Structure, Spectral, Thermal, and DFT Studies of an Organic Crystal: 1-(benzo[d][1,3]dioxol-5-yl)-3-phenylprop-2-en-1-One

The synthesis, characterization, thermal stability, optical spectroscopic, FT-IR, and theoretical studies of a novel 1-(benzo[d][1,3]dioxol-5-yl)-3-phenylprop-2-en-1-one (BDP) is reported. Structure is elucidated by single-crystal X-ray diffraction analysis. The crystal belongs to monoclinic system with centrosymmetric space group P21/c with four molecules in the unit cell. The various mode of vibration present in the molecule are confirmed by FT-IR analysis and the experimental pattern is compared with theoretical one. The crystal is transparent in the entire visible region having a lower optical cut-off ∼390 nm and the observed values are compared with theoretical values. The surface morphology of the specimen was analyzed by scanning electron microscopy (SEM). The TG/DTA study reveals the purity of the materials and no decomposition is observed up to the melting point. Theoretical calculations were performed to derive the optimized geometry, average polarizability (α), dipole moment (μ), first-order molecular hyperpolarizability (β), HOMO–LUMO, chemical hardness (η), softness (S), and electronegativity (χ) by using B3LYP/6-31G(d,p) level of theory. The atomic charge distributions of the various atoms present in BDP are obtained by Mulliken charge population analysis.

Synthesis, Crystal Growth, Characterization, and Theoretical Studies of 3-(4-fluorophenyl)-1-(4-methylphenyl)prop-2-en-1-one

Single crystals of 3-(4-fluorophenyl)-1-(4-methylphenyl)prop-2-en-1-one (FMPP) have been grown by mixed solvent system ethanol and chloroform 2:1 (v/v) at room temperature. Single crystal X–ray diffraction reveals that FMPP belongs to monoclinic system with four molecules in the unit cell. The structure and the crystallinity of the material were further confirmed by FT-IR, FT-Raman, and powder X–ray diffraction analyses. The band gap energy is estimated by Kubelka–Munk algorithm using DRS data. Theoretical calculations were performed to derive the optimized geometry and the first-order molecular hyperpolarizability (β) values. The as-grown crystal is further characterized by GC-Mass, SEM, and thermal analyses.

Growth, hyperpolarizability, characterization and theoretical studies of NLO active tris(allylthiourea)mercury(II) chloride

Single crystals of tris(allylthiourea)mercury(II) chloride (TATMC) have been grown by slow evaporation solution growth technique. It belongs to the trigonal system with noncentrosymmetric space group R3c and the cell parameters are, a=b=11.4443(3)Å, c=28.1142(6)Å, V=3188.85(14)Å3, α=β=90°, γ=120° and Z=6. Powder X-ray diffraction pattern reveals the crystallinity of the as-grown specimen and it closely resembles the simulated one from the single crystal XRD data. Good reflectance in the visible region is observed and the band gap energy is estimated using diffuse reflectance data by the application of Kubelka–Munk algorithm. The functional groups are identified by Fourier transform infrared spectral analysis and compared with theoretical spectrum. The crystal is stable up to the melting point and the mechanistic behavior is ascertained by microhardness studies. The second harmonic generation efficiency of TATMC is estimated by Kurtz and Perry powder technique. The first-order molecular hyperpolarizabilities of some tris(allylthiourea) complexes have been evaluated using density functional theory (DFT) employing B3LYP functional, LanL2DZ as basis set and results rationalized. The optimized geometry closely resembles the ORTEP. The Hirshfeld surface analysis is carried out using HF method with 3-21G as basis set. Investigation of the intermolecular interactions and crystal packing via Hirshfeld surface analysis, derived by single crystal XRD data, reveals the close contacts associated with strong interactions.

Synthesis, growth, spectral studies, first-order molecular hyperpolarizability and Hirshfeld surface analysis of isonicotinohydrazide single crystals

Single crystals of (E)-N′-((4-fluorophenyl)(phenyl)methylene)isonicotinohydrazide dihydrate were grown by the slow evaporation solution growth technique.

Optical, vibrational, NBO, first-order molecular hyperpolarizability and Hirshfeld surface analysis of a nonlinear optical chalcone

The synthesis of (1E,4E)-1,5-di-p-tolylpenta-1,4-dien-3-one (DTDO) was done and its single crystals were grown by slow evaporation solution technique from 4-methylbenzaldehyde, acetone solution at room temperature. Crystal structure is determined by single crystal X-ray diffraction analysis and reveals that it belongs to the monoclinic system with four molecules in the unit cell (space group C2). The emission of green light from the sample confirms the second harmonic generation (SHG) of the specimen responsible for nonlinear optical property. The various vibration patterns of the specimen have been investigated by Fourier transform infrared and Fourier transform Raman spectroscopy. Optimized molecular geometry, vibrational patterns of DTDO are derived from density functional theory (DFT) calculations and the results are compared with experimental one. The molecular stability and bond strengths were investigated by applying the natural bond orbital analysis. Information about the size, shape, charge density distribution and site of chemical reactivity of the molecule has been obtained by mapping electron density with molecular electrostatic potential (MEP). Highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy gaps were calculated. The other molecular properties like charge transfer are explained using Mulliken population analysis and the first-order molecular hyperpolarizability (β) of the specimen is also estimated and SHG efficiency of DTDO was found to be 3.9 times that of KDP. Fingerprint plots and Hirshfeld surfaces were used to locate and analyze the molecular surface and bonding interactions in various methodologies utilized in the establishment of the relative energies.

Synthesis, growth, structure, and characterization of (2E,6E)-2-(4-bromobenzylidine)-6-(4-methoxybenzylidine)cyclohexanone

Single crystals of (2E, 6E)-2-(4-bromobenzylidine)-6-(4-methoxybenzylidine)cyclohexanone are grown by slow evaporation solution growth technique from ethanol at room temperature. The single crystal-X-ray diffraction study reveals that as-grown crystal belongs to triclinic system and the cell parameters are, a = 9.3720(3) A, b = 11.0500(7) A, c = 18.1790(3) A, and V = 1,734.90(13) A3. The structure and the crystallinity of the material were further confirmed by nuclear magnetic resonance spectroscopy and powder X-ray diffraction analysis. Simulated XRD pattern closely resembles the powder XRD profile with lowered intensities. FT-IR and FT-Raman spectral analyses reveal the various modes of vibrations. The crystal is transparent in the visible region having a lower optical cut-off at ~503 nm with band gap energy of 2.55 eV, estimated by the application of Kubelka–Munk algorithm. Theoretical calculations were performed using the Hartree–Fock method at level with 6-31G(d,p) as the basis set for to derive the optimized geometry and first-order molecular hyperpolarizability (β) values. The as-grown specimens were further characterized by dielectric and mechanical studies.

Crystal growth, characterization and theoretical studies of alkaline earth metal-doped tetrakis(thiourea)nickel(II) chloride

The influence of Sr(II)-doping on the properties of tetrakis(thiourea)nickel(II) chloride (TTNC) has been described. The reduction in the intensity observed in powder X-ray diffraction of doped specimen and slight shifts in vibrational frequencies of doped specimens confirm the lattice stress as a result of doping. Surface morphological changes due to doping of the Sr(II) are observed by scanning electron microscopy. The incorporation of metal into the host crystal lattice was confirmed by energy dispersive X-ray spectroscopy. Lattice parameters are determined by single crystal XRD analysis. The thermogravimetric and differential thermal analysis studies reveal the purity of the materials and no decomposition is observed up to the melting point. The nonlinear optical properties of the doped and undoped specimens were studied. Theoretical calculations were performed using the Density functional theory (DFT) method with B3LYP/LANL2DZ as the basis set. The molecular geometry and vibrational frequencies of TTNC in the ground state were calculated and the observed structural parameters of TTNC are compared with parameters obtained from single crystal X-ray studies. The atomic charge distributions are obtained by Mulliken charge population analysis. The first-order molecular hyperpolarizability, polarizability and dipole moment were derived.

Crystal growth, characterization and theoretical studies of 4-aminopyridinium picrate

Single crystals of 4-aminopyridinium picrate (APP) were grown by slow evaporation of a mixed solvent system methanol–acetone (1:1, v/v) containing equimolar quantities of 4-aminopyridine and picric acid. Structure is elucidated by single crystal XRD analysis and the crystal belongs to monoclinic system with four molecules in the unit cell (space group P21/c) and the cell parameter values are, a=8.513Å (±0.015), b=11.33Å (±0.02), c=14.33Å (±0.03) and β=104.15° (±0.019), V=1340A3 (±6) with refined R factors R1=0.0053 and wR2=0.0126. The electron density mapping is interpreted to find coordinates for each atom in the crystallized molecules. The various functional groups present in the molecule are confirmed by FT-IR analysis. UV–visible spectral analysis was used to determine the band gap energy of 4-aminopyridinium picrate. Powder X-ray diffraction pattern reveals the crystallinity of the as-grown crystal and it closely resembles the simulated XRD from the single crystal XRD analysis. Scanning electron microscopy reveals the surface morphology of the grown crystal. Optimized geometry is derived by Hartree–Fock theory calculations and the first-order molecular hyperpolarizability (β), theoretically calculated bond length, bond angles and excited state energy from theoretical UV–vis spectrum were estimated.

Synthesis, crystal growth, characterization and theoretical studies of 4-aminobenzophenonium picrate

Single crystals of 4-aminobenzophenonium picrate (4ABPP) were grown by slow evaporation of a mixed solvent system methanol–acetone (1:1,v/v) containing equimolar quantities of picric acid and 4-aminobenzophenone. The proton and carbon signals are confirmed by nuclear magnetic resonance spectroscopy. The various functional groups present in the molecule are identified by FT-IR analysis. Optimized geometry, first-order molecular hyperpolarizability (β), polarizability (α), bond length, bond angles and excited state energy from theoretical UV were derived by Hartree–Fock calculations. The complete assignment of the vibrational modes for 4-aminobenzophenonium picrate was performed by the scaled quantum mechanics force field (SQMFF) methodology using potential energy distribution. Natural bond orbital (NBO) calculations were employed to study the stabilities arising from charge delocalization and intermolecular interactions of 4ABPP. The atomic charge distributions of the various atoms present in 4ABPP are obtained by Mulliken charge population analysis. The as-grown crystal is further characterized by thermal and optical absorbance studies.

Synthesis, growth, structure, spectral, thermal and first-order molecular hyperpolarizability of benzophenone-2-furoyl hydrazone single crystal

Single crystals of benzophenone-2-furoyl hydrazone are grown by slow evaporation solution growth technique from ethanol at room temperature. It belongs to monoclinic system with the space group P21/c and the cell parameters are, a=6.1631(3)Å, b=13.1397(8)Å, c=18.0030(11)Å and V=1457.72(14)Å3. NMR spectral studies reveal the structure and powder XRD indicates the crystallinity of the specimen. The characteristic functional groups present in the molecule are confirmed by Fourier transform infrared spectroscopy. The crystals are transparent in the visible region having a lower optical cut-off at ∼406nm and the band gap energies are estimated by the application of Kubelka–Munk algorithm. Thermal analysis by TG/DTA indicates the stability of the material. The scanning electron microscopy studies reveal the surface morphology of the as-grown crystal. Theoretical calculations were performed using Hartree–Fock method with 6-31G(d,p) as the basis set for to derive the optimized geometry, dipole moment and first-order molecular hyperpolarizability (β) values.

Growth, crystalline perfection, spectral, thermal and theoretical studies on imidazolium l-tartrate crystals

Transparent optical quality single crystals of imidazolium l-tartrate (IMLT) were grown by conventional slow evaporation solution growth technique. Crystal structure of the as-grown IMLT was determined by single crystal X-ray diffraction analysis. Thermal analysis reveals the purity of the crystal and the sample is stable up to the melting point. Good transmittance in the visible region is observed and the band gap energy is estimated using diffuse reflectance data by the application of Kubelka–Munk algorithm. The powder X-ray diffraction study reveals the crystallinity of the as-grown crystal and it is compared with that of the experimental one. An additional peak in high resolution X-ray diffraction (HRXRD) indicates the presence of an internal structural low angle boundary. Second harmonic generation (SHG) activity of IMLT is significant as estimated by Kurtz and Perry powder technique. HOMO–LUMO energies and first-order molecular hyperpolarizability of IMLT have been evaluated using density functional theory (DFT) employing B3LYP functional and 6-31G(d,p) basis set. The optimized geometry closely resembles the ORTEP. The vibrational patterns present in the molecule are confirmed by FT-IR coinciding with theoretical patterns.

Synthesis, spectral, thermal, optical and theoretical studies of (2E,6E)-2-benzylidene-6-(4-methoxybenzylidene)cyclohexanone

Single crystals of (2E,6E)-2-benzylidine-6-(4-methoxybenzylidine)cyclohexanone are grown by slow evaporation of ethanolic solution at room temperature. The characteristic functional groups present in the molecule are confirmed by Fourier transform infrared and Fourier transform Raman analyses. The scanning electron microscopy study reveals the surface morphology of the material. Thermogravimetric/differential thermal analysis study reveals the purity of the material and the crystal is transparent in the visible region having a lower optical cut-off at ∼487nm. The second harmonic generation efficiency of as-grown material is estimated by Kurtz and Perry technique. Optimized geometry has been derived using Hartree–Fock calculations performed at the level 6-31G (d,p) and the first-order molecular hyperpolarizability (β) is estimated. The specimen is further characterized by nuclear magnetic resonance spectroscopy.

Crystal growth and second harmonic generation efficiency of a chalcone derivative

Single crystals of (2E,6E)-2-(4-fluorobenzylidine)-6-(4-methoxybenzylidine)cyclohexanone (FBMBC) have been grown by a slow evaporation solution growth technique from ethanol at room temperature. The single crystal X-ray diffraction study reveals that the FBMBC belongs to triclinic system and the cell parameters are a=9.790(6)Å, b=12.08(7)Å, c=14.09(9)Å and V=1577Å3. The structure and the crystallinity of the material were further confirmed by powder X-ray diffraction analysis. The various functional groups present in the molecule are confirmed by Fourier transform infrared spectral analysis. The scanning electron microscopy study reveals the surface morphology of the as-grown crystal. Thermogravimetric/differential thermal analysis studies reveal the purity of the material and the crystals are transparent in the visible region having a low optical cut-off at ∼475nm. The second harmonic generation efficiency of FBMBC is estimated by the Kurtz and Perry technique. Theoretical calculations were performed using the Hartree–Fock method with 6-31G(d,p) as the basis set to derive the optimized geometry and the first-order molecular hyperpolarizability (β) values.

Nonlinear optical analyses of organic N-(9-Anthrylmethylidene) methylamine Schiff base

The organic NLO Schiff base of N-(9-Anthrylmethylidene) methylamine was synthesized by condensation process. The material was characterized through Powder XRD, FT-IR, and Raman techniques. The various planes of reflection are identified from the Powder XRD pattern. The formation of Schiff base is confirmed through FT-IR and Raman analysis. The intra molecular charge transfer interaction and the existence of the first-order molecular hyperpolarizability (β) are identified from the red shift of the UV–Vis analysis. The structure of the molecule was optimized by density functional theory (DFT) using B3LYP method with 6-31G basis set. The NBO analysis is used to interpret the delocalization. The dipole moment and first hyperpolarizability values were also computed by HF/6-31G. These values indicate that the compound is a good candidate with nonlinear optical properties. This is the first time report on the existence of a second harmonic generation (SHG), χ2, efficiency that has been identified by Powder Kurtz–Perry method.