First-order Molecular Hyperpolarizability Research Articles

Pseudo-Stilbene- and Azobenzene-Type Systems for Optical Frequency Conversion: Estimating the First-Order Molecular Hyperpolarizability

This study investigates the potential of a set of pseudo-stilbene and azobenzene molecular structures to become optical frequency converters for optical communications based on a detailed exploration of the first-order molecular hyperpolarizability (βHRS), which is the microscopic counterpart of second harmonic generation (SHG). βHRS values were obtained via quantum chemical calculations using the Gaussian 16 software package in solvent and gas-phase media at different wavelengths, i.e., 1064 nm, 1310 nm, and 1510 nm. The latter two wavelengths are of particular interest for optical communications. Our study focused on discerning how the molecular structure influences the βHRS response, explicitly highlighting the influence of the azomethine group (CH=N). The results revealed that the molecular planarity, affected by this group, plays a crucial role in modulating the optical properties. The highest βHRS value in a solvent medium using the CAM-B3LYP/6-311+G(2d,p) level of theory achieved in this work was around 1400 ×10−30cm4startvolt−1, four orders of magnitude higher than KDP (0.2 ×10−30cm4startvolt−1), which is a reference in SHG experiments at 1064 nm. The highest calculated βHRS value at the same level of theory and solvent at 1310 nm and 1550 nm was 631 × 10−30cm4startvolt−1 and 456 × 10−30cm4startvolt−1, respectively. All these values belong to molecular structures with azo-coupling with donor (4-NMe2) and acceptor (4′-NO2) peripheral groups, designated as AB-3.

Studying the first order hyperpolarizability spectra in chalcone-based derivatives and the relation with one- and two-photon absorption transitions.

The first-order molecular hyperpolarizability (β) dispersion was measured in seven chalcone-based molecules utilizing the tunable femtosecond hyper-Rayleigh scattering (tHRS) technique. Additionally, a theoretical model based on photophysical parameters was employed to better understand β dispersion. Due to the distinct substitution patterns of the aryl/heteroaryl rings within the chalcone structure, varying profiles of one- and two-photon absorption spectra and β dispersion were observed. The applied model highlighted two important factors contributing to achieving high β values: (i) the presence of red-shifted one-photon and two-photon absorption bands; and (ii) the number of discernible absorption bands. To contextualize these results with other molecular structures, we employed the HRS figure of merit (FOM). Remarkably, it was revealed that chemically engineered small chalcone molecules exhibit a FOM comparable to larger quadrupolar and octupolar ones. This underscores the significance of tHRS scattering measurements and their correlation with absorptive parameters in the design and characterization of nonlinear optical materials.

Nonlinear Optical Materials: Predicting the First-Order Molecular Hyperpolarizability of Organic Molecular Structures

Experimental nonlinear optics (NLO) is usually expensive due to the high-end photonics and electronic devices needed to perform experiments such as incoherent second harmonic generation in liquid phase, multi-photon absorption, and excitation. Nevertheless, exploring NLO responses of organic and inorganic compounds has already opened a world of new possibilities. For example, NLO switches, NLO frequency converters, and a new way to obtain biological images through the incoherent second harmonic generation (SHG) originate from first-order molecular hyperpolarizability (β). The microscopic effect of the coherent or incoherent SHG is, in fact, the β. Therefore, estimating β without using expensive photonic facilities will optimize time- and cost-efficiency to predict if a specific molecular structure can generate light with double its incident frequency. In this work, we have simulated the β values of 27 organic compounds applying density functional theory (PBE0, TPSSh, wB97XD, B3LYP, CAM-B3LYP, and M06-2X) and Hartree–Fock methods using the Gaussian software package. The predicted β was compared with the experimental analogs obtained by the well-known Hyper–Rayleigh Scattering (HRS) technique. The most reliable functionals were CAM-B3LYP and M06-2X, with an unsigned average error of around 25%. Moreover, we have developed post-processing software—Hyper-QCC, providing an effortless, fast, and reliable way to analyze the Gaussian output files.

3-D Supramolecular, quantum computational, and vibrational spectroscopic investigation on L-cysteinium methanesulfonate single crystals

This article reports on molecular modeling using density functional theory (DFT) performed on L-cysteinium methanesulfonate (L-CMS). Calculations were performed on the B3LYP/LanL2DZ level with 6-31 G(d,p) basis set using the Gaussian 09 program package. The optimized structure, HOMO-LUMO, energy gap, electronic properties, MEP, dipole moment, first-order molecular hyperpolarizability (β), chemical potential, global hardness, softness, global electrophilicity, and natural bond orbital analysis of this compound were studied by computational procedures. Intermolecular O-HO, N-HO, and S-HO hydrogen-bonding interactions with different motifs were observed in the crystal structure. Hirshfeld surface analyzes were also performed. Energy frameworks have been constructed to understand the packing of molecules by examining the different intermolecular interaction energies.

Synthesis, structure, Hirshfeld surface analysis, and computational studies of 2-amino-5-nitropyridine-2,4-dinitrophenol cocrystal

A supramolecular cocrystal of 2-ammino-5-nitropyridine (ANP) with 2,4-dinitrophenol (DNP) has been successfully grown by the slow evaporation solution growth technique. The crystal structure of 2-amino-5-nitropyridine-2,4-dinitrophenol (ANDP) was elucidated by the single-crystal X-ray diffraction analysis, and it belongs to a monoclinic system with centrosymmetric space group P21/n. The bulk phase purity and homogeneity of the material were confirmed by powder X-ray diffraction analysis. The functional groups present in the molecule are identified by FT-IR analysis, and the band gap energy was estimated using diffuse reflectance data by the application of the Kubelka–Munk algorithm. The thermal stability of the compound was investigated by carrying out TG–DTA analysis. Theoretical calculations were performed using the density functional theory method to derive the dipole moment and hyperpolarizability. The high value of first-order molecular hyperpolarizability (β) suggests that it is a potential microlevel NLO candidate.

Linear, nonlinear optical properties and structure-property relationships in ESIPT-rhodols

Linear and nonlinear optical (NLO) properties of three ESIPT-rhodol derivatives, spirocyclic and open-forms of 10, 11, and 12 estimated by spectroscopic based mathematical calculations and compared with computed values by using density functional theory (DFT) calculations. The group of global and range-separated hybrid functionals were used for theoretical estimation of NLO properties. Spectroscopic based mathematical calculations were used for estimation of polarizabilty (α), and second-order hyperpolarizability (γ) in series of solvents. Benchmarking strategies were applied to used functionals for investigation of NLO characteristics. BHHLYP and ωB97 functionals performed well in the company of GHs and RSHs functionals to evaluate the NLO characteristics. The resulting NLO characteristics for open 10, 11, and 12 are higher than the consequences observed for close 10, 11, and 12. The computed polarizabilty (α), and second-order hyperpolarizability (γ) follow the trend 10 > 11 > 12, while the first-order hyperpolarizability (β) and molecular hyperpolarizability (µβ) follow the trend 12 > 10 > 11 for both forms. The observed trends in NLO parameters for compounds 10, 11, and 12 are supported by electron correlation analysis.

Synthesis, structural characterization, and Hirshfeld surface analysis of novel NLO active 1-methyl-1,3,5,7-tetraazaadamantan-1-ium 3-carboxy-5-nitrobenzoate hydrate

Single crystals of 1-methyl-1,3,5,7-tetraazaadamantan-1-ium 3-carboxy-5-nitrobenzoate hydrate (I) were grown from an aqueous solution containing hexamethylenetetramine (HMT) and 5-nitroisophthalic acid (5NIPA) by slow evaporation solution growth technique after the mild hydrothermal process. The crystal structure is elucidated by single-crystal X-ray diffraction analysis. It crystallizes in the monoclinic system with acentric space group Cc. The cation and anion present in the adduct are bridged by a water molecule, which is interconnected with CH···O and OH···O hydrogen bonds. The relative second harmonic generation (SHG) efficiency measurements characterized by the Kurtz powder technique reveal that (I) is an active SHG material. The grown crystals were further characterized by FT-IR, UV-DRS, and photoluminescence spectral analysis. Theoretical calculations were performed using density functional theory to derive the dipole moment, polarizability, and first-order molecular hyperpolarizability (β). The intermolecular hydrogen bonding interactions are analysed by Hirshfeld surface analysis and fingerprint plots. Theoretically estimated high β rationalized by the experiment. The molecular electrostatic potential (MEP) maps and Mulliken atomic charge were calculated using density functional theory (DFT) calculations.

Modeling the First-Order Molecular Hyperpolarizability Dispersion from Experimentally Obtained One- and Two-Photon Absorption.

The search for optical materials, particularly organic compounds, is still an attractive and essential field for developing several photonic devices and applications. For example, some applications are based on light scattering with twice the energy of the incoming photon for selected compounds, that is, the nonlinear optical effect related to the second-order susceptibility term from the electronic polarization expression. The microscopic interpretation of this phenomenon is called the first-order molecular hyperpolarizability or incoherent second harmonic generation of light. Understanding such phenomena as a function of the incoming wavelength is crucial to improving the optical response of future materials. Still, the experimental apparatus, hyper-Rayleigh scattering, apparently simple, is indeed a challenging task. Therefore, we proposed a proper alternative to obtain the dispersion of the first-order hyperpolarizability using the well-known one- and two-photon absorption techniques. By the spectral analysis of both the spectra, we gathered spectroscopic parameters and applied them for predicting the first-order hyperpolarizability dispersion. This prediction is based on an n-level energy system, taking into account the position and magnitude of transition dipole moments and the difference between the permanent dipole moment of the n-excited states. Moreover, using the presented method, we can avoid underestimating the first-order hyperpolarizability by not suppressing higher-energy transitions. Quantum chemical calculations and the hyper-Rayleigh scattering technique were used to validate the proposed method.

Second- and third-order nonlinear optical properties of mono-substituted terpenoid-like chalcones

Organic molecules exhibiting second and third-order nonlinear optical properties (NLOP) allow several applications in optics and photonics. Among the class of organic compounds, terpenoid-like chalcones derivatives constitute a suitable choice as nonlinear optical materials, given the possibility of obtaining a wide range of compounds that can be used in biophotonic applications. In this way, here we present a study of the first-order molecular hyperpolarizability and the two-photon absorption (2PA) cross-section of several terpenoid-like chalcones derivatives, aiming for applications in the therapeutic window. The 2PA spectra were evaluated employing the femtosecond tunable Z-Scan technique from 480 nm to 850 nm, and the first hyperpolarizability was determined at 1064 nm using the Hyper-Rayleigh scattering (HRS) technique. Moreover, the first-order molecular hyperpolarizability and the 2PA spectra were modeled by the sum-over-states (SOS) approach and undamped phenomenological model, respectively, providing new insights into the properties and compoundś structure relationship. Results showed that substituent features, such as electron-donating or withdrawing ability, were associated with the 2PA cross-section magnitude. Regarding HRS results, it was possible to compare the difference of state dipole moment from both approaches, combining two experimental routes to determine photophysical parameters of non-fluorescent compounds, revealing the structure-relationship aiming the increase of the NLOP at the near-infrared region.

Synthesis, structural characterization, Hirshfeld surface analysis and third-order nonlinear optical properties of Schiff bases derived from 1,1-diphenylmethylamine

Two Schiff bases namely, (E)-4-((benzhydrylimino) methyl)-N,N-dimethylaniline (I) and (E)-N-(4-isopropylbenzylidene)-1,1-diphenyl methanamine (II) were synthesized by one pot condensation reaction. The structures were confirmed by single-crystal X-ray diffraction (SXRD) analysis. The molecules are associated by C‒H···π and π···π interactions which are responsible for the formation of supramolecular network. The compounds are further characterized by FT-IR, 1H and 13C NMR spectral analysis. The UV–Vis-NIR and photoluminescence spectral data of the compounds were studied to explore the optical transmission and emission properties respectively. The surface morphological changes in the compounds were observed by scanning electron microscopic (SEM) analysis. TG-DTA methods were used to point out the thermal stability of the compounds. The third-order nonlinear optical property was investigated in detail using Z-scan technique. The optimized geometry, molecular electrostatic potential (MEP) maps, Mulliken atomic charge distribution and first-order molecular hyperpolarizability were calculated using density functional theory (DFT) calculations using the B3LYP method with 6–311 G as basis set. Intermolecular interactions were studied using 3D Hirshfeld surface maps and the percentage contributions of various interactions are studied and quantified by 2D fingerprint plots.

Growth, NBO, and vibrational studies combined with intramolecular hydrogen bond interaction of L-Valine lead (II) nitrate complex: DFT

The slow evaporation method was used to grow a new semi-organic L-Valine lead (II) nitrate (LVLN) single crystal. Powder X-ray diffraction was used to examine the crystalline quality of the grown crystal LVLN. Fourier-transform infrared (FT-IR) spectroscopy was used to identify characteristic vibrations, which were then compared to simulated spectra at density functional theory (DFT) method. The lower cut-off wavelength was measured to be 262 nm by UV-visible spectral analysis. Thermal stability and its decompositions were investigated for the title compound using thermogravimetric and differential thermal analyses (TG/DTA). Results of DFT calculations with B3LYP functional and a 6-31++G(d,p) basis set were helpful to identify the ground state molecular geometries, vibrational frequencies, Mulliken population analysis on an atomic charge, HOMO–LUMO analysis, first-order molecular hyperpolarizability (β) properties, and other molecular properties for LVLN. The intramolecular interactions existing inside the crystal have been investigated by Hirshfeld surface evaluation.

Non-Linear Optical Properties and Global Reactivity Descriptors by ab initio Hartree-Fock (H.F.) Calculations of Simple Coumarins

In this present analysis, the measurement of optimized molecular structure and molecular hyperpolarizability (βtotal) of simple coumarin molecules were investigated using the HF method at 6-311G basis set level Gaussian09W. The measured nonlinear optical parameters (NLO); polarizability (α), the anisotropy of the polarizability (Δα), and first-order molecular hyperpolarizability (βtotal) of the studied coumarins indicate promising optical properties. The energy difference between HOMO and LUMO helped determine the molecular descriptors; global hardness (η), softness (σ) electronegativity (χ) Chemical potential (μ), and electrophilicity index (ω) in gas and different solvents. The molecular hyperpolarizability (βtotal) and descriptors that have been calculated in the solvent medium were taken into consideration through the Polarizable Continuum Model (PCM), This study shows the high static hyperpolarizability exhibited by HNR, FXT, and CNT and offers the potential the materials may have for NLO devices. The molecular descriptors, hardness, and chemical potential values are high for CNT and UCAcompared to other studied coumarins. This suggested that CNT and CA have the most significant chemical potential resistance to change the number of electrons among the other molecules.

Synthesis, crystal growth, characterization and DFT investigation of a nonlinear optically active cuminaldehyde derivative hydrazone.

Single crystals of (E)-N'-(4-isopropylbenzylidene)isonicotinohydrazide monohydrate (IBIHM) were grown from ethanol by the slow evaporation from solution growth technique at room temperature. The structure was elucidated by single-crystal X-ray diffraction analysis and crystallized in the orthorhombic system with noncentrosymmetric space group P212121. Optical studies reveal that the absorption was minimum in the visible region and the band-gap energy was estimated using the Kubelka-Munk algorithm. The functional groups were identified by Fourier transform infrared spectral analysis. A scanning electron microscopy study revealed the surface morphology of the grown crystal. Investigation of the intermolecular interactions, crystal packing using Hirshfeld surface analysis and single-crystal X-ray diffraction confirm that the close contacts were associated with molecular interactions. Fingerprint plots of Hirshfeld surfaces are used to locate and analyze the percentage of hydrogen-bonding interactions. The second-harmonic generation efficiency of the grown specimen was superior to that of the reference material, potassium dihydrogen phosphate. The grown crystals were further characterized by mass spectrometry and elemental analysis. Theoretical studies using density functional theory (DFT) greatly substantiated the experimental observations. Large first-order molecular hyperpolarizability (β) of about ∼70× was observed for IBIHM. The efficiency of IBIHM in terms of nonlinear optical response was verified and the molecule displayed greater chemical stability and reactivity.

Determination of the structural, electronic, optoelectronic and thermodynamic properties of the methylxanthine molecules theophylline and theobromine.

RHF and DFT (wB97XD and B3LYP) methods with the 6-31++G** basis set have been used to study structural, optoelectronic and thermodynamic properties of Theophylline and Theobromine. Dipole moment, average polarizability, anisotropy, first-order molecular hyperpolarizability, second-order molecular polarizability, HOMO and LOMO energy gap, molar refractivity, chemical hardness, chemical softness, electronic chemical potential, electronegativity, electrophilicity index, dielectric constant, electric susceptibility, refractive index and their thermodynamic properties have equally been calculated. To understand the vibrational analysis of our system, IR and RAMAN frequencies were calculated and described. Results reveal that molecules can have applications in linear and nonlinear optical devices, photonic devices and in molecular electronics. Equally, from dipole moment, average polarizability, anisotropy, first-order molecular hyperpolarizability, second-order molecular polarizability, HOMO and LOMO energy gap, molar refractivity, chemical hardness, chemical softness, electronic chemical potential, electronegativity, electrophilicity index and literature we suggest that Theophylline and Theobromine be consider as candidates for the treatment of COVID-19 and other respiratory diseases.Electronic supplementary materialThe online version of this article (10.1007/s11082-020-02617-w) contains supplementary material, which is available to authorized users.

Crystal growth, structural, nonlinear optical and theoretical investigations of Benzilic acid crystals

Organic single crystals of Benzilic Acid (BA) were grown by slow solvent evaporating method by using acetone as solvent. The unit cell parameter values and the crystal system are recognized by using single crystal XRD technique. The optical assessment of BA molecules is observed by with UV-Vis spectral analysis as the ultraviolet range between 200 and 400 nm and the visible region between 400 and 800 nm. The nonlinear optical (NLO) properties such as second harmonic efficiency nature of BA crystal were analyzed using Nd:YAG laser. The laser-induced damage threshold assessment of BA crystal is measured as 2.76 GW/cm2. From the Density Functional Theory (DFT), the molecular structural feature and vibrational frequencies were defined by using the Gaussian system along with comparisons of experimental frequencies. Using the DFT method, the derived vibrational frequency values showed an admirable accord with experimental frequencies. The charge interactions within the BA molecules are confirmed by HOMO and LUMO energy value. The first-order molecular hyperpolarizabilities, dipole moment, polarizability and Mulliken charge analysis of the BA molecule are also evaluated.

Supramolecular cocrystals of O-H...O hydrogen-bonded 18-crown-6 with isophthalic acid derivatives: Hirshfeld surface analysis and third-order nonlinear optical properties.

Two cocrystals of 18-crown-6 with isophthalic acid derivatives, 5-hydroxyisophthalic acid and trimesic acid, have been successfully grown by the slow evaporation solution growth technique. Crystal structures of (18-crown-6)·6(5-hydroxyisophthalic acid)·10(H2O) (I) and (18-crown-6)·2(trimesic acid)·2(H2O) (II) elucidated by single crystal X-ray diffraction reveal that both cocrystals pack the centrosymmetric triclinic space group P{\overline 1}. The molecules are associated by strong/weak hydrogen bonds, π...π and H...H stacking interactions. Powder X-ray diffraction analyses, experimental and simulated from single-crystal diffractogram data have been matched. The vibrational patterns in FT-IR spectra are used to identify the functional groups. The band gap energy is estimated by the application of the Kubelka-Munk algorithm. Hirshfeld surfaces derived from X-ray diffraction analysis reveal the type of molecular interactions and their relative contributions. The constructed supramolecular assembly of crown ether cocrystal is thoroughly described. Both cocrystals exhibit a significant third-order nonlinear optical response and it is observed that (I) possesses a significant first-order molecular hyperpolarizability whereas it is negligible for (II).

Theoretical study of optoelectronic properties of the molecule 2-cyano-3-[4-(diphenylamino)phenyl] acrylic acid

2-Cyano-3-[4-(diphenylamino)phenyl]acrylic acid is one of the most important dyes used in DSSC. In this work, the RHF and DFT (B3LYP and WB97XD) methods along with the 6-31+G** have been used to study the structural, optoelectronic and thermodynamic properties of the 2-cyano-3-[4-(diphenylamino)phenyl]acrylic acid. The dipole moment (µ), polarizability (α0), anisotropy of polarizability (Δα), hyperpolarizability (β0), HOMO and LOMO energy, energy gap (Egap), dielectric constant (e), electric susceptibility (χ), refractive index (η) and thermodynamic properties of this molecule have been calculated using the same levels of theory. The entropy and enthalpy have also been calculated. In order to understand the vibrational analysis of our system, the IR and RAMAN frequencies were calculated and described. The dipole moment average polarizability and first-order molecular hyperpolarizability of the studied molecule indicate that the compound is a good candidate as nonlinear optical materials.

Multiple strong hydrogen bonded supramolecular cocrystals of 18-crown-6 with 5-nitroisophthalic acid: Solvent effect and optical nonlinearities

Novel cocrystals of 18-crown-6 (18C6) with 5-nitroisophthalic acid (5NIPA) have been prepared by reaction in a solution of CH3OH–H2O (2:3, v/v) and C2H5OH–H2O (2:3, v/v) systems. The cocrystals 18-crown-6.5-nitroisophthalic acid. CH3OH.2(H2O) (I) and 18-crown-6.5-nitroisophthalic acid.3(H2O) (II) have been characterized by X-ray diffraction and constructed supramolecular assembly is thoroughly investigated. CH3OH incorporation inducing centrosymmetric crystallization and acentric crystal packed supramolecular construction in presence of ethanol are the highlights of the study. Intermolecular interactions are quantified by Hirshfeld surface analysis. First-order molecular hyperpolarizability estimated by theoretical calculations indicate a significant microlevel nonlinearity in both cases and Z-scan studies suggest a promising third-order nonlinear optical behaviour. Supramolecular assembly afford multiple strong O–H ….O hydrogen bonds creating a facile atmosphere for optical nonlinearity and mainly these O ….O hydrogen bonds stabilize the structure.

Structural studies of 3-[(E)-[(2E)-2-methyl-3-phenylprop-2-en-1-ylidene] amino]-1-phenylthiourea: Combined experimental and computational studies

A novel N4-phenylthiosemicarbazone,3-[(E)-[(2E)-2-methyl-3-phenylprop-2-en-1-ylidene] amino]-1-phenylthiourea, abbreviated as NPCN, has been synthesized and characterized by elemental analysis and FT-IR, FT-Raman, 1H NMR, 13C NMR and electronic spectral methods. Single crystals of the title compound were grown by slow evaporation method. Single crystal X-ray diffraction analysis shows that the title compound belongs to monoclinic system in P21/c space group with cell parameters a = 14.697(2) Å, b = 18.890(2) Å, c = 12.3992(14) Å, α = γ = 90° and β = 110.213(4) °. DFT calculations were done using B3LYP/6-311++G (d, p) level basis set and the results were compared with the experimental results. The intermolecular interaction in crystal structure of the compound was investigated by Hirshfeld surface analysis and 2D fingerprint plots. The HOMO-LUMO band gap energies, molecular electrostatic potential (MESP), first-order molecular hyperpolarizability and dipole moment were calculated. NLO activity of the compound was also determined experimentally using urea as reference.

Synthesis, structural characterization and Hirshfeld surface analysis of 4-hydroxyanilinium picrate hydrate

Abstract Structure characterization of single crystals of 4-hydroxyanilinium picrate hydrate (HAPH) by single-crystal X-ray diffraction (XRD) analysis shows that the compound C12H12N4O9 crystallizes in monoclinic space group P21/c. The band gap energy is estimated and photoluminescence studies exhibit fluorescent emission. High value of first-order molecular hyperpolarizability (β) estimated by theoretical calculation reveals good nonlinear optical (NLO) character of the material and the behaviour is rationalized. Intra- and intermolecular interactions are quantified by Hirshfeld surface analysis derived from single crystal XRD data.