Third-order Polarizability Research Articles

Exploring the impact of heterocyclic bridges for tuning the amplitudes of Nonlinear optical properties under Gas, IEFPCM and COSMO solvent models

Nonlinear optical (NLO) materials are a distinctive class of materials due to their NLO response and wide range of applications. We present a systematic quantum chemical study for designing triphenylamine based derivatives (1Ph to 3PhDTDZ) by modifying central bridge with various size and types of heterocyclic rings. Density functional theory (DFT) method is used to calculate the NLO properties including linear and third-order NLO polarizabilities (α and γ) by using M06-2X functional coupled with the 6-311G** basis set. The calculation results predict that among the designed compounds, 1PhDTDZ has the highest third-order NLO polarizability of 2347.7 x 10−36 esu and lowest transition energy of 1.828 eV. On the other hand, 3PhDTDZ has a greater amplitude (108.5 x 10−24 esu) of static linear polarizability (αiso). We also computed frequency-dependent third-order NLO polarizability values at various laser wavelengths (1500 nm to 1970 nm). This provides valuable information about the complex interaction between light and matter. Dynamic second hyperpolarizability of electro-optic Pockels effect (EOPE effect, (γ (−ω; ω,0,0)) is calculated at 1500 nm laser wavelength with a larger γ-amplitude of 36708.4 x 10−36 esu. The effect of solvent on α and γ has also been the primary focus of this research. An extensive solvation impact has been studied using integral equation formalism Polarizable Continuum Model (IEFPCM) and Conductor-like Screening Model (COSMO). Magnitudes of αiso and 〈γ〉 have shown variation from gas to solvent methods. While among solvents, amplitudes are seen 3.87 % to 11.29 % greater under the effect of COSMO-methanol than PCM-methanol. The Frontier molecular orbital (FMO) studies found a significant decrease in energy band gaps from 5.75 eV to 2.98 eV. Since our systems exhibit remarkable photovoltaic properties, they can be used as dye-sensitized solar cells (DSSCs). Their open circuit voltage (VOC) ranging from 1 eV to 4 eV. Thus, our designed triphenylamine based derivatives with distinct central heterocyclic bridges showcase remarkable efficiency as NLO materials, with additional benefits of exhibiting good photovoltaic properties.

Quantum chemical framework for designing high-performance ladder-shape NLO molecules and study of implicit vs explicit solvent effects on their NLO properties

Researchers in materials science are greatly fascinated by helicene chemistry due to its excellent optical and structural properties. In this work, we introduced symmetrical substitution of donor and acceptor groups on the [7]helicene ([7]HC-1 to [7]HC-5). DFT analysis is used to explore nonlinear optical (NLO) response for designed compounds. For [7]HC-5, the linear isotropic (αiso) and anisotropic polarizability (αaniso) are 31.59 × 10−24 esu and 59.86 × 10−24 esu, respectively. [7]HC-5 has the highest average third-order NLO polarizability (<γ>) of 47.24 × 10−36 esu which is approximately six times greater than that of para-nitroaniline, a well-known prototype NLO molecule. The effect of implicit and explicit solvents on <γ> and αiso of three selected compounds ([7]HC-1, [7]HC-3, and [7]HC-5) is also evaluated. As compared to explicit and gas phase methods, PCM model predicts an overestimation by an increment of ∼ 4-5 times for selected compounds. TD-DFT calculations show a higher transition dipole moment (4.24) and a lower transition energy (3.414 eV) for [7]HC-5. The higher NLO response is explained based on frontier molecular orbitals (FMOs), electron density difference (EDD), and molecular electrostatic potentials (MEPs). There is a red shift for studied compounds based on UV-visible results. The C-N stretching at 1372 cm-1 for [7]HC-5 indicates the presence of -N(CH3)2. Additionally, we studied photovoltaic parameters and found that [7]HC-5 has the maximum open circuit voltage and the lowest dye regeneration of 2.71 eV and 0.06 eV, respectively.

Effect of partial substitution of K2O by MgO on the structure, and thermal, physical, optical properties and crystallization behaviour of K2O–MgO–B2O3–P2O5 glasses

In this work, a series of K2O–MgO–B2O3–P2O5 (KMBP) glasses were prepared by the melt-quenching method and the glass-ceramics were prepared by the one-step heat treatment. The thermal, structural, physical and optical properties, as well as the crystallization behaviour of the KMBP system, were investigated in detail using characterization techniques such as DSC, XRD, SEM, FTIR, transmittance spectroscopy and microhardness. As indicated by DSC, the thermostability and glass-forming ability were gradually enhanced through the partial substitution of K2O by MgO. XRD showed that the main crystalline phases of the glass-ceramics (GC) were gradually converted from the P–Mg–K–O based crystalline phases to the P–Mg–O based and the P–Al–O based crystalline phases. The SEM results indicated that tiny grain-like crystals were successfully precipitated from the parent glasses after heat treatment. The deconvoluted FTIR spectra results showed a gradual conversion of the [BO3] and [PO3] units towards the [BO4] and [PO4] units with the increase of the MgO contents. The increase in the degree of glass network polymerization was the essential reason for the increment in the microhardness of the parent glasses. The microhardness of GC featured a trend concordant with the crystallinity of the crystalline phases. The values of metallization criteria (MC) between 0.34 and 0.45, as well as the higher values of third-order nonlinear polarizability (χ(3)) and nonlinear refractive index (nnl) are indicative of the good suitability of the KMBP glasses for the nonlinear optical applications.

Investigation of the third-order optical nonlinear enhancement properties of Ag doped chalcogenide glass films

Chalcogenide glass is widely recognized as an excellent nonlinear optical material. Enhancing its nonlinear optical properties through metal doping has emerged as a prominent research avenue in the field of chalcogenide glass. In this paper, silver (Ag) doped Ge28Sb12Se60 (GSS) chalcogenide glass films with different concentrations were prepared by co-evaporation method. The nonlinear absorption coefficients (β) of different samples were investigated by open-aperture top-hat Z-scan experiments and pump-probe experiments, and the nonlinear refractive index (γ) values were determined using the Tichy-Ticha relation. The results showed that the nonlinear absorption of GSS thin films can be improved by Ag doping. The nonlinear absorption coefficient β exhibits the maximum enhancement of about 2.5 times at 8.3% concentration, with the maximum β reaching 1.83×10−6 m/W. The nonlinear absorption mechanism observed in the thin films can be attributed to free carrier absorption, and the free carrier lifetime is positively correlated with the Ag doping concentration. Within the selected Ag concentration range, the nonlinear refractive index (γ) of Ag doped chalcogenide glass films continues to increase, reaching about 3 times at 30.7% concentration, with the maximum γ being 4.643×10−17 m2/W. Additionally, the third-order nonlinear polarizability (χ(3)) values can be increased from 1.014×10−11 esu to 3.314×10−11 esu with increasing Ag concentration. The research results in present paper are of great significance for further exploration of the optical nonlinear enhancement properties and carrier recombination dynamics in chalcogenide glass.

Designing the electron push-pull chromophores through the joining of triphenylamine and triphenylborane for efficient nonlinear optical and photovoltaic properties

The benzoxadiazole class of organic compounds demonstrates exceptional versatility, particularly in the realm of nonlinear optical (NLO) materials, where their unique properties find impactful applications. In the present study, we have focused on systematically designed six benzoxadiazole (BDZ) derivatives named as BDZ-1 to BDZ-6 by using 2,3,1-benzoxadiazole as a central core/π-spacer between the donor and acceptor. Triphenylamine and triphenylborane are used as donor and acceptor in all derivatives with addition of nitro and methoxy group as substitutions. B3LYP/6-311G* method of density functional theory (DFT) is employed for optimization of purposed systems while M06/6-311G* is used to check the NLO properties. The isotropic polarizability (αiso) and anisotropic polarizability (αaniso) of BDZ-6, were found to be 110.1 × 10−24 esu and 106.3 × 10−24 esu, respectively. Among our designed compounds, the BDZ-6 exhibits the highest third-order NLO polarizability, which was found to be 5954.8 × 10−36 esu corresponding to lowest transition energy of 2.00 eV. Additionally, frontier molecular orbitals (FMOs), molecular electrostatic potential maps (MEPs), electron difference density maps (EDD) and UV–Vis analysis were performed. BDZ-6 shows minimum energy gap of 2.24 eV, while it shows maximum absorption at 620 nm. The density of states (DOS) analysis reveals distinct electronic contributions of various fragments in the formation of HOMO and LUMO orbitals resulting in efficient intramolecular charge transfer (ICT). Photovoltaic findings revealed that BDZ-4 have maximum open circuit voltage of 1.70 eV with minimum dye regeneration value (0.30 eV). Our findings shed light on the design and development of novel NLO materials with BDZ derivatives.

Nonlinear optical properties of novel crystalline complexes of cobalt (II) and nickel (II) with 4-bromo-3-methyl-1H-pyrazole: combined experimental and computational study

Two new isostructural cobalt [Co(II)(C4H5BrN2)4(Cl)2], I and nickel [Ni(II)(C4H5BrN2)4(Cl)2], II complexes were synthesized for linear and nonlinear optical (NLO) responses using the finite field method. The synthesized complexes were characterized using elemental analysis, infrared and H-NMR spectroscopy, TG/DSC analysis, and X-ray crystallography. The crystal analysis indicates that both complexes I and II are mononuclear, and crystallize in the monoclinic space group P21/c. The metal ion in each complex is six coordinated with four nitrogen atoms (from 4-bromo-3-methyl-1H-pyrazole ligand) and two chloride ligands adopting octahedral coordination geometry. Furthermore, the computational predictions for molecular geometries and average third-order nonlinear polarizabilities of I and II are made in current study. The average theoretically predicted third-order nonlinear polarizabilities 〈γ〉 of I and II are 95.50 × 10−36 and 91.25 × 10−36 esu, respectively. The 〈γ〉 amplitudes values of complexes I and II are ∼5.26 and ∼5.0 times greater than the prototype NLO molecule of para-nitroaniline (p-NA) at same level of theory, which indicates their decent potential as efficient NLO materials.

Electrically controlled liquid crystal nonlinear optical devices prepared by multi-layer composite structures

In this study, a multi-layer composite structure is used to prepare nonlinear optical devices from multi-walled carbon nanotubes (MWCNTs)/liquid crystal (LC) composite systems. Their third-order optical nonlinearity is investigated. The MWCNTs were coated and modified to improve their dispersion in the solvent. The coated and modified MWCNTs were characterized by IR absorption spectroscopy and transmission electron microscopy (TEM). The nonlinear optical (NLO) properties of the devices prepared by the multi-layer composite structures with varying design parameters were studied. The conventional devices were also prepared by mixed doping method for comparison with the proposed devices. Both devices underwent Z-scan testing. The third-order nonlinear polarizability of the conventional hybrid-doped devices was calculated with a value of 5.39 × 10-10 esu. The third-order nonlinear polarizability of the proposed devices prepared by the multi-layer composite structures has a value of 2.97 × 10-9 esu, which is about five times the corresponding value for the hybrid-doped devices. So, the devices prepared by the multi-layer composite structures have better NLO properties. Moreover, the third-order nonlinear polarizability of the proposed devices was further increased up to 3.88 × 10-9 esu, which is an increase of almost 31% after applying voltage to these devices prepared by the multi-layer composite structures. The limiting threshold of S-CTAB/MWCNTs@BHR33400 is 0.245 J/cm2 after voltage application. Applying voltage plays a role in promoting the NLO properties of the devices. Using the multi-layer composite structure to prepare the liquid crystal nonlinear optical devices can significantly improve the NLO properties of the devices. Such prepared devices can be electrically tuned, providing new avenues for preparing nonlinear optical devices.

Spectroscopic, electronic properties analysis for 2, 6-Bis (phenylamino)-4-(iminophenyl) benzoquinone molecule and molecular docking clarification for its anticancer activity detected by strong inhibition of NQO1 enzyme

Quinone compounds have been the subject of extensive research due to their remarkable efficiency and prospective use as drugs and in a variety of fields. In this study, we report the spectroscopic characterization, electronic structure, ADMET evaluation, and molecular docking assessment of 2,6-Bis(phenylamino)-4-(iminophenyl)benzoquinone as an anticancer drug. By using DFT investigations, the vibrational wavenumbers were calculated and utilized to assign vibrational bands, which were found to be in good accordance with the experimentally observed data. The analysis of the UV-Vis spectra revealing an absorption peak from electronic transitions HOMO→LUMO at 547 nm is found to be in good conformity with its experimental value. The HOMO and LUMO frontier molecular orbitals and their associated energies highlighted the mechanism of charge transfer within the molecule and revealed a small energy gap. The chemically reactive sites identified by the MEP surface helped predict the spots of the molecule's biological activity. According to NBO analysis, the π C9-C10 → π* C11-C12 interaction has the maximum energy stability with 23.74 Kcal/mol., due to π electron delocalization within the ring. At the same level of theory, third-order NLO polarizability was found to be 4-fold stronger than the third-order of P-NA (a prototype NLO molecule). The potential for a safe oral bioavailability drug was identified by computing ADMET parameters and evaluating drug-likeness based on Lipinski's rule of five. The molecular docking study found that the molecule binding to NQO1 receptor protein with superior binding energy -8.69 kcal/mol than previously studied Quinone derivatives. Additionally, molecular dynamics simulations were performed to test the dynamic behavior of the ligand-NQO1 complex. The complex was stable in the binding pocket of the receptor proteins, according to the analysis of the simulation outcomes such as RMSD and RMSF. These results suggests using this molecule as a potential anticancer drug due to its high capability to inhibit the NQO1 enzyme.

Acid catalyzed one-pot approach towards the synthesis of curcuminoid systems: unsymmetrical diarylidene cycloalkanones, exploration of their single crystals, optical and nonlinear optical properties.

In the present study crystalline unsymmetrical diarylidene ketone derivatives BNTP and BDBC have been prepared by two sequential acid catalyzed aldol condensation reactions in a one pot manner. The crystal structures of both compounds were confirmed by single crystal X-ray diffraction analysis which revealed the presence of H-bonding interactions of type C-H⋯O, along with weak C-H⋯π and weak π⋯π stacking interactions that are involved in the crystal stabilization of both organic compounds. Hirshfeld surface analysis is carried out for the broad investigation of the intermolecular interactions in both compounds. The quantum chemical investigation was performed on the optimized molecular geometries of BNTP and BDBC to calculate optical and nonlinear optical (NLO) properties. The density functional theory (DFT) study showed that the third-order NLO polarizabilities of compounds BNTP and BDBC are found to be 226.45 × 10-36 esu and 238.72 × 10-36 esu, respectively, which indicates noticeable good NLO response properties. Additionally, the BNTP and BDBC molecules also showed the HOMO-LUMO orbital gaps of 5.96 eV and 6.06 eV, respectively. Furthermore, the computation of UV-visible spectra of the titled compounds indicated a limited and/or no absorption above the 400 nm region, directing a good transparency and NLO property trade-off for both synthesized compounds that may play a significant contribution in the future for optoelectronic technologies.

Spectroscopic characterization (IR, UV-Vis), and HOMO-LUMO, MEP, NLO, NBO Analysis and the Antifungal Activity for 4-Bromo-N-(2-nitrophenyl) benzamide; Using DFT Modeling and In silico Molecular Docking

In this study, the density functional theory was used to explore the spectral and electronic properties of the title molecule, as well as a molecular docking technique to evaluate its antifungal activity. The fundamental vibrations were assigned based on the calculated vibrational spectra. The maximum absorption peak in the UV–Visible spectra was detected at 238.165 nm and caused by electronic transitions from HOMO to LUMO+1. The calculated quantum chemical parameters indicated considerable chemical activity, such as a small band gap and high electrophilicity value. The title molecule has a high level of electrophile nature, as revealed by its high electrophilicity value (7.32 eV) and MEP analysis. The third-order NLO polarizability analysis demonstrated significant potential for NLO applications. NBO analysis was conducted to analyze a complete molecular description and intermolecular interactions resulting from hyper-conjugative interactions and charge delocalization of the molecule. The calculated physicochemical properties of Lipinski's rule revealed a favorable character of drug-likeness. The molecular docking study confirmed the strong inhibitory potential (-8.05 Kcal/Mol) for the title molecule against 14α-demethylase, the main target enzyme for antifungal medications. In the reported protein-ligand interaction, the presence of a halogen bond with the bromine atom indicated the halogenated character of the studied molecule. These findings point to a high level of antifungal activity.

Relativistic normal coupled-cluster theory analysis of second- and third-order electric polarizabilities of Zn I

We present precise values of electric polarizabilities for the ground state of Zn due to second-order dipole and quadrupole interactions, and due to third-order dipole-quadrupole interactions. These quantities are evaluated in the linear response theory framework by employing a relativistic version of the normal coupled-cluster (NCC) method. The calculated dipole polarizability value is compared with available experimental and other theoretical results including those are obtained using the ordinary coupled-cluster (CC) methods in both finite-field and expectation value evaluation approaches. We also give a term-by-term comparison of contributions from our CC and NCC calculations in order to show differences in the results from these two methods. Moreover, we present results from other lower-order methods to understand the role of electron correlation effects in the determination of the above quantities. A machine learning based scheme to generate optimized basis functions for atomic calculations is developed and applied here. From the analysis of the dipole polarizability result, accuracy of the calculated quadrupole and third-order polarizability values are ascertained, for which no experimental values are currently available.

Phenothiazine metal-organic framework materials with excellent third-order nonlinear properties

The third-order nonlinear optical material with excellent performance is a molecule with a large π-conjugated structure for absorption structure and a high degree of delocalization. Nitrogen-sulfur derivatives have lone pairs of electrons in their N and S atoms, which makes them have a strong intramolecular charge transfer ability, which is conducive to the formation of donor-acceptor molecules. In this paper, phenothiazine is used as the matrix structure of the third-order nonlinear optical material, modified, and then metal coordination is performed to obtain [Zn(Py)2Cl2]n and [Cd(Py)2Cl2]n. Its structure is characterized by infrared spectroscopy, single crystal X-ray diffraction and powder X-ray diffraction. The morphology of the material was characterized by scanning electron microscopy. The photophysical properties, thermal properties and third-order nonlinear properties were tested, and the theoretical verification was carried out with the DFT calculation method, and the relationship between the structure and the third-order nonlinear properties was summarized. The experimental results show that phenothiazine has good electron donating ability, the two-photon absorption coefficient β is between 1.334–38.400 × 10−10 m/W, and the third-order nonlinear polarizability χ(3) is between 2.752–79.247 × 10−11 esu, The second-order hyperpolarizability γ of the ligand molecule is 5.213 × 10−34 esu. The χ(3) values of [Zn(Py)2Cl2]n and [Cd(Py)2Cl2]n are 4 orders of magnitude higher than ordinary α-quartz (χ(3) = 2.6 × 10−14 esu).

Single crystal exploration, supramolecular behaviour, Hirshfeld surface analysis, linear and non-linear theoretical optical properties of Schiff bases derived from Benzene sulfonamides

The current research work is about the efficient synthesis of three crystalline Schiff bases derived from benzene sulfonamides named as (E)-4-((3-ethoxy-2-hydroxybenzylidene)amino)benzenesulfonamide (ASES), (E)-4-((3-ethoxy-2-hydroxybenzylidene)amino)-N-(5-methylisoxazol-3-yl)benzenesulfonamide (SMB), (E)-4-((2-hydroxy-3-methoxybenzylidene)amino)-N-(5-methylisoxazol-3-yl)benzenesulfonamide (SES) and their characterization by single-crystal X-rays diffraction (SC-XRD) studies. The molecular configuration of ASES and SMB is stabilized by intramolecular O-H⋯N bonding, whereas C-H⋯O intramolecular H-bonding is responsible for the stabilization of the molecular configuration of SES. The N-H⋯O intermolecular H-bonding is the main aspect of the supramolecular behaviour of ASES, while the N-H⋯O and C-H⋯O intermolecular H-bonding are the major features of the supramolecular behaviour of SMB and SES, respectively. The S-O⋯π interaction performs a significant role in the stabilization of the molecular assembly of the SMB, whereas the C-H⋯π interaction stabilizes the molecular assembly of SES. The role of weak off-set π⋯π interaction in all three compounds is also explored. The non-covalent interactions of strong as well as comparatively weak nature are further comprehensively explored by Hirshfeld surface (HS) analysis for the further exploration of the molecular assembly. Furthermore, we have also applied quantum chemical methods to calculate the linear and nonlinear optical (NLO) properties of synthesized compounds. The average linear polarizability <α> values for ASES, SMB, and SES are found to be 34.83 × 10−24 esu, 40.14 × 10−24 esu, and 42.67 × 10−24 esu, respectively, while the third-order NLO average polarizability <γ> amplitudes of ASES, SMB, and SES are found to be reasonably larger, amounting to 58.89 × 10−36 esu, 83.35 × 10−36 esu, and 69.69 × 10−36 esu at the M06-2X/6-311G* levels of theory, respectively. A comparison of average NLO polarizabilities shows that the <γ> amplitudes of SMB and SES are 41% and 18% larger than that of ASES, respectively, which are also 3 and 2.5 times larger than that of para-nitroaniline (p-NA) as calculated using the same methodology. We believe that the above-synthesized compounds will have decent potential to be used as NLO materials.

Insights into the nonlinear optical (NLO) response of pure Aum (2 ≥ m ≤ 7) and copper-doped Au m -xCu x clusters.

A series of small pure Aum (2 ≥ m ≤ 7) and copper-doped Aum−xCux clusters was evaluated by density functional theory (DFT) at the CAM-B3LYP/LANL2DZ level for their geometric, electronic, and nonlinear optical (NLO) properties. The charge transfer for the Au cluster significantly improved by reducing the HOMO–LUMO energy gap from 3.67 eV to 0.91 eV after doping with Cu atoms. The doping of Cu also showed noteworthy impacts on other optical and NLO properties, including a decrease in the excitation energy and increase in the dipole moment and oscillator strength. Furthermore, changes in the linear isotropic and anisotropic polarizabilities (αiso and αaniso) and first and second NLO hyperpolarizabilities (βstatic, γstatic) were also observed in the pure and Cu-doped clusters, which enhanced the NLO response. The nonlinear optical properties of the clusters were evaluated by calculating the static and frequency dependent second- and third-order NLO polarizabilities at 1064 nm wavelength. Among all the doped structures, the Au3Cu1 cluster showed the largest static first hyperpolarizability of β(total) = 4.73 × 103 au, while the Au1Cu6 cluster showed frequency dependent first hyperpolarizability of β(−2w;w,w) = 1.26 × 106 au. Besides this, large static and frequency-dependent second hyperpolarizability values of 6.30 × 105 au and 1.05 × 10 au were exhibited by Cu7 and Au1Cu6, respectively. This study offers an effective approach to design high-performance NLO materials utilizing mixed metal clusters which might have broad applications in the fields of optoelectronics and electronics.

Insighting the functionally modified C60 fullerenes as an efficient nonlinear optical materials: A quantum chemical study

It is well-known that π-conjugation plays an important role to tune the nonlinear optical (NLO) response of donor-π-conjugated-acceptor compounds. Fullerenes (C60) are one of a few compounds who are abounded with π-conjugation and perhaps are the largest π-conjugation compounds. In the present study, we systematically designed C60 derivatives (2 (fulleropyrrolidine) and 2a-2c (fulleropyrrolidine tetrathiafulvalene derivatives where 2a, 2b and 2c are with n = 0, n = 1 and n = 2) through the use of pyrrolidine and tetrathiafulvalene moieties. We applied density functional theory (DFT) methods to calculate their respective geometrical structures, electronic properties, linear and nonlinear optical response properties along with their respective UV–Visible spectra using CAM-B3LYP functional and 6-31G* basis set. The isotropic polarizability (αiso) and anisotropic polarizability (αaniso) of 2c was found to be 131.52 × 10-24 and 47.01 × 10-24 esu, respectively. Amongst our designed compounds, the maximum second-order nonlinear optical polarizability amplitude (β//) of 2c was found to be 15.69 × 10-30 esu. Interestingly, 2c shows the highest third-order nonlinear polarizability amplitude <γ> of 284.29 × 10-36 esu that is about three times higher than parent compound 1. Additionally, frontier molecular orbitals (FMOs), molecular electrostatic potential maps (MEPs), transition density matrix (TDM) analysis indicate more effective charge redistribution from donor moiety to acceptor fragments. The density of states (DOS) diagrams reveal distinct electronic contributions of various fragments in the formation of HOMO and LUMO orbitals resulting in efficient intramolecular charge transfer (ICT) and robust third-order NLO response properties of functionalized fullerene derivatives. The current study may arouse the attention of the scientific society to utilize the extensive π-conjugation of functionalized fullerenes for designing efficient NLO materials.

Chemically Modified Quinoidal Oligothiophenes for Enhanced Linear and Third-Order Nonlinear Optical Properties.

In the present investigation, quantum chemical calculations have been performed in a systematic way to explore the optoelectronic, charge transfer, and nonlinear optical (NLO) properties of different bis(dicyanomethylene) end-functionalized quinoidal oligothiophenes. The effect of different conformations (linking modes of thiophene rings) on conformational, optoelectronic, and NLO properties are studied from the best-performed dimer to octamer. The optical and NLO properties of all the selected systems (1–7) are calculated by means of density functional theory (DFT) methods. Among all the designed compounds, the largest linear isotropic (αiso) polarizability value of 603.1 × 10–24 esu is shown by compound 7 which is ∼12, ∼16, ∼9, ∼11, ∼10, and ∼4 times larger as compared to compounds 1–6, respectively. A relative investigation is performed considering the expansion in third-order NLO polarizability as a function of size and conformational modes. Among all the investigated systems, system 7 shows the highest value of static second hyperpolarizability ⟨γ⟩ with an amplitude of 7607 × 10–36 esu at the M06/6-311G** level of theory, which is ∼521, ∼505, ∼38, ∼884, ∼185, and ∼15 times more than that of compounds 1–6, respectively. The extensively larger ⟨γ⟩ amplitude of compound 7 with higher oscillator strength and lower transition energy indicates that NLO properties are remarkably dependent upon linking modes of thiophene rings and its chain length. Furthermore, to trace the origin of higher nonlinearities, TD-DFT calculations are also performed at the same TD-M06/6-311G** level of theory. Additionally, a comprehensive understanding of the effect of structure/property relationship on the NLO polarizabilities of these investigated quinoidal oligothiophenes is obtained through the inspection of Frontier molecular orbitals, the density of states (TDOS and PDOS), and molecular electrostatic potential diagrams including the transition density matrix. Hence, the current examination will not just feature the NLO capability of entitled compounds yet additionally incite the interest of experimentalists to adequately modify the structure of these oligothiophenes for efficient optical and NLO applications.

Experimental and computational study of naphthalimide derivatives: Synthesis, optical, nonlinear optical and antiviral properties

The nonlinear optical (NLO) and antiviral properties of naphthalimide Schiff base compounds (5a–c) were experimentally and computationally investigated. The synthesized compounds (5a–c) were successfully characterized via UV–Vis, FTIR, 1H NMR, fluorescence spectroscopy, and elemental analysis. The calculated average third-order NLO polarizabilities (˂γ˃) of 5a, 5b, and 5c were found to be 5, 9, and 21 times greater than the ˂γ˃ amplitude of p-NA, respectively. The computed results revealed the potential of the synthesized compounds for NLO applications. Additionally, molecular docking studies of the synthesized compounds with two crucial SARS-CoV-2 proteins were performed to examine their biochemical properties. Compound 5c exhibited a higher binding affinity with the spike protein compared to that with Mᴾᴿᴼ. The results obtained herein indicate the potential of the synthesized naphthalimide derivatives for optoelectronic and drug design applications.

An Efficient Synthesis, Spectroscopic Characterization, and Optical Nonlinearity Response of Novel Salicylaldehyde Thiosemicarbazone Derivatives.

In this study, seven derivatives of salicylaldehyde thiosemicarbazones (1–7) were synthesized by refluxing substituted thiosemicarbazide and salicylaldehyde in an ethanol solvent. Different spectral techniques (UV–vis, IR, and NMR) were used to analyze the prepared compounds (1–7). Accompanied by the experimental study, quantum chemical studies were also carried out at the M06/6-311G(d,p) level. A comparative analysis of the UV–visible spectra and vibrational frequencies between computational and experimental findings was also performed. These comparative data disclosed that both studies were observed to be in excellent agreement. Furthermore, natural bond orbital investigations revealed that nonbonding transitions were significant for the stability of prepared molecules. In addition, frontier molecular orbital (FMO) findings described that a promising charge transfer phenomenon was found in 1–7. The energies of FMOs were further used to determine global reactivity parameters (GRPs). These GRP factors revealed that all synthesized compounds (1–7) contain a greater hardness value (η = 2.1 eV) and a lower softness value (σ = 0.24 eV), which indicated that these compounds were less reactive and more stable. Nonlinear optical (NLO) evaluation displayed that compound 5 consisted of greater values of linear polarizability ⟨α⟩ and third-order polarizability ⟨γ⟩ of 324.93 and 1.69 × 105 a.u., respectively, while compound 3 exhibited a larger value of second-order polarizability (βtotal) of 508.41 a.u. The NLO behavior of these prepared compounds may be significant for the hi-tech NLO applications.

Exploring the optoelectronic and third-order nonlinear optical susceptibility of cross-shaped molecules: insights from molecule to material level

In the present investigation, we use a dual computational approach (at single molecular and solid-state levels) to explore the optoelectronic and nonlinear optical (NLO) properties of cross-shaped derivatives. The solid-state electronic band structures of the compounds 1-3 (the derivatives of tetracarboxylic acid in cross-shaped having the core of benzene (1), pyrazinoquinoxaline (2), and tetrathiafulvalene (3)) are calculated. The calculated band gaps for compounds 1-2 are found to be direct bad gaps and compound 3 to be indirect bad gap with energy gaps of 2.749, 1.765, and 0.875eV, respectively. The important optical properties including refractive index, absorption coefficients, loss functions, and extinction coefficient of these semiconductors are calculated at bulk level to seek their potential applications as efficient optoelectronic materials. Additionally, we use the Lorentz approximation to calculate the third-order NLO susceptibilities of compounds 1-3 using the molecular hyperpolarizability and solid-state parameters. The calculated third-order NLO susceptibilities of compounds 1-3 are found to be 6.92 × 10-12, 64.0 × 10-12, and 26.3 × 10-12esu, respectively. Thus, the present study not only provides a way to connect the calculated third-order molecular NLO polarizability to NLO susceptibilities for compounds 1-3 through Lorentz approximation but also highlights the importance of central core modifications on their NLO susceptibilities.

Enhanced linear and nonlinear optical response of superhalogen (Al7) doped graphitic carbon nitride (g-C3N4)

• Effect of Al 7 on g-C 3 N 4 is investigated for the second- and third-order NLO polarizabilities. • Doping reduces the band gap by about 50 % in the single doped system. Similarly, linear optical properties increase from 55 to 108 %. • The single doped system exhibited the first and second hyperpolarizability of about 39 and 5 times greater than the pure g-C 3 N 4 . In this study, pure and superhalogen doped g-C 3 N 4 clusters are computed with the CAM-B3LYP method of DFT to investigate the electronic and optical properties. Single Al 7 @g-C 3 N 4 and double doped 2Al 7 @g-C 3 N 4 systems are investigated. The doping of the superhalogen cluster on g-C 3 N 4 especially in a single doped system significantly improves the charge transfer properties by reducing the band gap energies from 6.42 eV to 3.23 eV. The average and total first hyperpolarizabilities ( β o and β total ) remarkably increase from 82 to 3204 au and 136–5340 au, whereas average second hyperpolarizability ( γ o ) increases from 14 × 10 4 to 64 × 10 4 au due to their lower transition energies. The selected systems were also compared with the external reference molecule p -NA which is a well-known reference molecule for NLO applications. TD-DFT simulations reveal that among pure, single, and double doped systems, the only single doped system shows significantly better outcomes including interaction energies, vertical ionization potential, HOMO-LUMO energies, and UV–vis absorption. The single doped system shows high absorption in the far-red region that use in lasers. The entitled systems especially single doped systems have the potential to use them as an efficient NLO material.