First principles study for the key electronic, optical and nonlinear optical properties of novel donor-acceptor chalcones

Quantum chemical framework for tailoring N/B doped phenalene derivatives to achieve high performance nonlinear optical materials

Nonlinear optical (NLO) response materials are among the smartest materials of the era and are employed to modulate the phase and frequency of the laser. The present study presents a quantum chemical framework for tailoring nitrogen/boron doped derivatives of Dihydrodibenzo [de,op]pentacene through terminal and central core modifications. The derivatives of these compounds have been designed by introducing various π-conjugated connectors as well as B/N heteroatoms in the phenalene rings. Density functional theory (DFT) methods are used to optimize the ground state molecular geometries of designed compounds, represented as 1 to 4 (phenalene derivatives) and 1-BN to 4-BN (B/N doped phenalene derivatives) at the M06-2X/6-311G* level of theory. The highest value of 116.9 × 10-24 esu and 240.2 × 10-24 esu for isotropic and anisotropic linear polarizability is shown by compound 4. Among the designed compounds, 4-BN has achieved the highest γ amplitude of 1858 × 10-36 esu owing to its unique molecular structural design. Further analysis of electronic parameters, such as electron density difference (EDD) maps, the density of states, electrostatic potentials, transition density matrix (TDM) analysis, and frontier molecular orbitals analysis (FMOs), demonstrated the more effective intramolecular charge transfer (ICT) for the best compounds, resulting in a good NLO response. The compounds were also analyzed for their potential in photovoltaic applications based on factors such as open circuit voltage values determined to be between (0.14 eV and 1.82 eV), and light harvesting efficiency (0.425-0.909).

Heterocyclic Donor Moiety Effect on Optical Nonlinearity Behavior of Chrysene-Based Chromophores with Push-Pull Configuration via the Quantum Chemical Approach

Organic-based nonlinear optical (NLO) materials may be used in many optical-electronic systems and other next-generation defense technologies. With the importance of NLO materials, a series of push-pull architecture (D-π-A) derivatives (DTMD2-DTMD6) were devised from DTMR1 through structural alteration of different efficient donor heterocyclic groups. Density functional theory-based computations were executed at the MPW1PW91/6-31G(d,p) level to explore the NLO behavior of the derivatives. To investigate the optoelectronic behavior of the said compounds, various analyses like the frontier molecular orbital (FMO), global reactivity parameters, density of state (DOS), absorption spectra (UV-vis), natural bond orbital, and transition density matrix (TDM) were performed. The derivatives have a smaller band gap (2.156-1.492 eV) and a larger bathochromic shift (λmax = 692.838-969.605 nm) as compared to the reference chromophore (ΔE = 2.306 eV and λmax = 677.949 nm). FMO analysis revealed substantial charge conduction out of the donor toward the acceptor via a spacer that was also shown by TDM and DOS analyses. All derivatives showed promising NLO results, with the maximum amplitude of linear polarizability ⟨α⟩ and first (βtotal) and second (γtotal) hyperpolarizabilities over their reference chromophore. DTMD2 contained the highest βtotal (7.220 × 10-27 esu) and γtotal (1.720 × 10-31 esu) values corresponding with the reduced band gap (1.492 eV), representing potential futures for a large NLO amplitude. This structural modification through the use of various donors has played a significant part in achieving promising NLO behavior in the modified compounds.

Frequency-dependent nonlinear optical response and refractive index investigation of lactone-derived thermochromic compounds

Nonlinear optical (NLO) switchable materials play a crucial role in the fields of electronics and optoelectronics. The selection of an appropriate switching approach is vital in designing such materials to enhance their NLO response. Among various approaches, thermos-switching materials have shown a 4-fold increase in NLO response compared to other photo-switching materials. In this study, we computationally investigated the geometric, electronic, and nonlinear optical properties of reversible lactone-based thermochromic compounds using the ωB97XD/6-311+G (d,p) level of theory. Molecular orbital studies are employed to analyze the electronic properties of the close and open isomers of these compounds, while time-dependent density functional theory (TD-DFT) analysis is utilized to evaluate their molecular absorption. Our findings reveal that the π-electronic conjugation-induced delocalization significantly influences the ON-OFF switchable nonlinear optical response of the lactone-based thermochromic compounds. Notably, among all compounds, the open isomer of lactone 2 exhibits the highest hyperpolarizability value (6596.69 au). Furthermore, we extended our analysis to investigate the frequency-dependent second and third-order hyperpolarizabilities. The most pronounced frequency-dependent NLO response is observed at 532 nm. Additionally, we calculated the refractive index of these thermochromic compounds to further assess their nonlinear optical response. The open isomer of lactone 1 demonstrates the highest refractive index value (3.99 × 10-14 cm2/W). Overall, our study highlights the excellent potential of reversible thermochromic compounds as NLO molecular thermos-switches for future applications.

The effect of the CPP size on the nonlinear optical properties of the new necklace-type molecules formed by carborane and [n]Cycloparaphenylenes(n = 8-11)

The new necklace-type molecules were formed by [8-13]CPP and carborane, which further manipulated the size of the macroring, revealing the effect of size on its luminescence behavior. In this work, the effects of ring size on the absorption spectrum, electron excitation and nonlinear optical properties of the compounds were investigated in detail, aiming to reveal an effective way to improve the optical properties of these necklace-type compounds. The absorption spectra of the compounds showed that the size of the CPP ring had little effect on the spectral shape and position, but the electron transition information showed that there were the significant charge transfer within the CPP ring and a gradual enhancement of interfragment charge transfer from the CPP ring to carborane. The increasing order of polarizability, first and second hyperpolarizability values of these compounds with the increase of CPP size indicated that increasing the size of the CPP ring was an effective way to increase the nonlinear optical properties of necklace-type molecules. Among the frequency dependent hyperpolarizability values, the γ(-ω;ω,0,0) value increased by a factor of 4 from complex 1 to 6 with the increase of CPP ring size, which indicated that increasing the size of the CPP ring was an effective way to increase the optical Kerr effect of necklace-type molecules. Therefore, these the new necklace-type nolecules formed by carborane and [n]Cycloparaphenylenes would be excellent nonlinear optical materials in the field of the all-optical switch.

Photoswitchable nonlinear optical properties of azobenzene-based supramolecular complexes: insights from density functional theory

Density functional theory (DFT) calculations were performed for a series of supramolecular assemblies containing azobenzene (Azo-X where X = I, Br and H) and alkoxystilbazole subunits to evaluate their electronic, linear and nonlinear optical properties. These assemblies are derivatives of azobenzene, obtained by the substitution of electron-withdrawing and electron-donating groups onto the molecular skeleton. The interaction energies (E_int) of all the designed supramolecular complexes (IA-IF, IIA-IIF and IIIA-IIIF) range from -1.0 kcal mol^-1 to -7.7 kcal mol^-1. The electronic properties of these hydrogen/halogen bond driven supramolecular assemblies such as vertical ionization energies (VIE), HOMO-LUMO energy gap (G_H-L), excitation energies, density of states (DOS) and natural population (NPA) analyses were also computed. The non-covalent interaction index (NCI) and quantum theory of atoms in molecules (QTAIM) analyses were also performed to validate the nature of inter- and intra-molecular interactions in these complexes. A substantial enhancement in the first hyperpolarizability (β₀) values of the designed supramolecular complexes was observed, which is driven by the charge transfer from the pyridyl moiety of alkoxystilbazole to Azo-X. The highest β₀ value of 1.3 × 10⁴ au was observed for the supramolecular complex of p-nitro substituted azobenzene with alkoxystilbazole (ID complex). Moreover, the results show that the substitution of electron-withdrawing groups on Azo-X can also bring larger β₀ values for such complexes. It was confirmed on a purely theoretical basis that both the types of noncovalent interactions present and the substituent group incorporated influence the nonlinear optical (NLO) response of the systems. Furthermore, the β₀ values of the E (trans) and Z (cis) forms were compared to demonstrate the two-way photoinduced switching mechanism.

DFT investigations and molecular docking as potent inhibitors of SARS-CoV-2 main protease of 4-phenylpyrimidine

In this work, quantum chemical descriptors and a vibrational analysis of 4-Phenylpyrimidine (4-PPy) were also investigated. Through conformational analysis, the most stable conformer can be determined. The geometry of the molecular structure was optimized by using the density functional theory (DFT) at the B3LYP/6-311++G(d,p) level. The theoretically obtained FT-IR and FT-Raman spectral data agree with the experimental results. UV-Vis was done in the gas phase along with different solvents by the TD-DFT method and the PCM solvent model. Molecular electrostatic potential, natural bond orbital analysis, nonlinear optical properties, and global chemical reactivity parameters were described through the DFT method. Besides, the chemical implications of a molecule were explained using an electron localization function and a local orbital locator. We attempted to detect the antiviral activity of the 4-PPy compound by predicting molecular docking into coronavirus 2 (SARS-n-CoV-2) protein structures (6LU7, 6M03, and 6W63), because COVID-19 is known to have serious adverse effects in all areas of human life worldwide, and possible drugs need to be investigated for this. The results of the docking simulation demonstrate good affinities for binding to the receptors.

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.

Designing of gigantic first-order hyperpolarizability molecules via joining the promising organic fragments: a DFT study

A suitable substitution of carbazole with a π-spacer group like cyanoethynylethene offers exciting future opportunities in terms of smart nonlinear optical material. In the quest of better organic nonlinear optical material, we have designed a series of derivatives based on carbazole and cyanoethynylethene fragment combinations in a unique fashion by employing the density functional (DFT) methods. The calculated time-dependent density functional theory (TD-DFT) calculations infer that the gigantic first static hyperpolarizability (β_tot) values are due to a lower energy gap and higher transition dipole moment for the crucial electronic transition. Furthermore, to see the in-depth execution for enhanced second-order nonlinear optics and the structure property relationship on nonlinear optics (NLO) behavior, we have performed frontier molecular orbitals (FMO), density of state (DOS), and transition density matrix (TDM). Furthermore, CAM-B3LYP functional-based calculated results infer that the designed molecule 10 show the first static hyperpolarizability is 923.93 × 10^-30 esu which is 69 times larger than that of p-nitroaniline.

A DFT analysis of electronic, reactivity, and NLO responses of a reactive orange dye: the role of Hartree-Fock exchange corrections

An experimental and theoretical study based on DFT/TD-DFT approximations is presented to understand the nature of electronic excitations, reactivity, and nonlinear optical (NLO) properties of reactive orange 16 dye (RO16), an azo chromophore widely used in textile and pharmacological industries. The results show that the solvent has a considerable influence on the electronic properties of the material. According to experimental results, the absorption spectrum is formed by four intense transitions, which have been identified as [Formula: see text] states using TD-DFT calculations. However, the TD-DFT results reveal a weak [Formula: see text] in the low-lying spectral region. Continuum models of solvation indicate that these states suffer from bathochromic (ca. 15 nm) and hypsochromic shifts (ca. 4 nm), respectively. However, the expected blue shift for the absorption [Formula: see text] is only described using long-range or dispersion-corrected DFT methods. RO16 is classified as a strong electrophilic system, with electrophilicity ω > 1.5 eV. Concerning the nucleophilicity parameter (N), from vacuum to solvent, the environment is active and changes the nucleophilic status from strong to moderate nucleophile (2.0 ≤ N ≤ 3.0 eV). The results also suggest that all electrical constants are strongly dependent on long-range and Hartree-Fock exchange contributions, and the absence of these interactions gives results far from reality. In particular, the results for the NLO response show that the chromophore presents a potential application in this field with a low refractive index and first hyperpolarizability ca. 214 times bigger than the value usually reported for urea (β = 0.34 × 10^- 30 esu), which is a standard NLO material. Concerning the solvent effects, the results indicate that the polarizability increases [Formula: see text] esu from gas to solvent while the first hyperpolarizability is calculated as [Formula: see text] esu, ca. 180%, regarding the vacuum. The results suggest RO16 is a potential compound in NLO applications. Graphical Abstract The frontier molecular orbitals, and the inverse relation between the energy-gap (E_gap) and the first hyperpolarizability (β).

Molecular modeling and nonlinear optical properties of new isostructural halogenated dihydroquinolinones

Two new isostructural halogenated dihydroquinolinones were synthesized and characterized by single crystal X-ray diffraction.

Single-Crystal Investigation, Hirshfeld Surface Analysis, and DFT Study of Third-Order NLO Properties of Unsymmetrical Acyl Thiourea Derivatives

In the current research work, unsymmetrical acyl thiourea derivatives, 4-((3-benzoylthioureido)methyl)cyclohexane-1-carboxylic acid (BTCC) and methyl 2-(3-benzoylthioureido)benzoate (MBTB), have been synthesized efficiently. The structures of these crystalline thioureas were unambiguously confirmed by single-crystal diffractional analysis. The crystallographic investigation showed that the molecular configuration of both compounds is stabilized by intramolecular N-H···O bonding. The crystal packing of BTCC is stabilized by strong N-H···O bonding and comparatively weak O-H···S, C-H···O, C-H···π, and C-O···π interactions, whereas strong N-H···O bonding and comparatively weak C-H···O, C-H···S, and C-H···π interactions are responsible for the crystal packing of MBTB. The noncovalent interactions that are responsible for the crystal packing are explored by the Hirshfeld surface analysis for both compounds. The void analysis is performed to find the quantitative strength of crystal packing in both compounds. Additionally, state-of-the-art applied quantum chemical techniques are used to further explore the structure-property relationship in the above-entitled molecules. The optimization of molecular geometries showed a reasonably good correlation with their respective experimental structures. Third-order nonlinear optical (NLO) polarizability calculations were performed to see the advanced functional application of entitled compounds as efficient NLO materials. The average static γ amplitudes are found to be 27.30 × 10^-36 and 102.91 × 10^-36 esu for the compounds BTCC and MBTB, respectively. The γ amplitude of MBTB is calculated to be 3.77 times larger, which is probably due to better charge-transfer characteristics in MBTB. The quantum chemical analysis in the form of 3-D plots was also performed for their frontier molecular orbitals and molecular electrostatic potentials for understanding charge-transfer characteristics. We believe that the current investigation will not only report the new BTCC and MBTB compounds but also evoke the interest of the materials science community in their potential use in 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.

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.

DFT study of superhalogen-doped borophene with enhanced nonlinear optical properties

The concern of the present study is to investigate the nonlinear optical properties of superhalogen-doped borophene owing to its broad applications. The first principle study of the material for its nonlinear optical properties elaborated its use for electrical and optical applications. The superhalogen-based borophene in lithium ion-based batteries and medical appliances have made it one of the most potential materials for optoelectronics. First, hyperpolarizability (β_o) of pure and doped B₃₆ is computed, and the difference between their values was examined. The vertical ionization energy (VIE) was calculated for pure and doped systems. The interaction energy (E_i) for all combinations was computed. It would be expected to be one of the best materials to have high capacity and resistance. For all the calculations and to calculate the highest occupied molecular orbital and lowest unoccupied molecular orbital energy gap, the density functional theory (DFT) method was used. It is predicted that these combinations are more beneficial and can display better nonlinear optical (NLO) properties in electronic devices. Superhalogen-doped BF₄ borophene-36 ground state optimized geometry, frontier molecular orbitals HOMO and LUMO, maximum absorption (λ_max), density of states (DOS) analysis, and electrostatic potential diagram (MEP) are displayed here_.

A novel photochemical sensor based on quinoline-functionalized phenazine derivatives for multiple substrate detection

A novel photochemical sensor based on quinoline-functionalized phenazine derivatives for highly sensitive detection of multiple substrates (l-Arg, CO₂, and pH) was designed and synthesized.

Static- and frequency-dependent NLO properties of dithienothiophene and thienothiophene bridges — A computational investigation

We have explored detailed linear and nonlinear optical properties of push-pull systems bearing thienothiophene and dithienothiophene spacers. By using density functional theory (DFT), frequency-dependent strategies were applied to examine the polarizability ([Formula: see text] and hyperpolarizability ([Formula: see text] and [Formula: see text]. The set of global and range-separated hybrid functionals with different Hartree–Fock (HF) exchange percentage at two basis sets cc-pVDZ and cc-pVTZ were used to evaluate the nonlinear optical (NLO) properties. The observed trends in the absorption maxima supported by perturbation potential analysis; as the absorption maxima increases, the respective amplitude potential decreases. For the investigated compounds, [Formula: see text]-conjugation along with the type of substituted acceptor plays a crucial role in the enhancement of NLO properties. The presence of acceptor group and length of conjugation increase between the D and A group; the first- and second-order intrinsic hyperpolarizability increases, leads to enhanced first- as well as second-order hyperpolarizability. Bond length alternation (BLA)/bond order alteration (BOA) exploration suggested that compounds attain cyanine limit. The trends in NLO properties for investigated compounds are supported by chemical reactivity descriptors, hardness and hyperhardness analysis. The polarizability is linearly correlated with the hyperpolarizability parameters ([Formula: see text] and [Formula: see text] and shows a good regression coefficient by figures of merit analysis.

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).

Benchmark study of the linear and nonlinear optical polarizabilities in proto-type NLO molecule of para-nitroaniline

In the present investigation, for the first time, we have performed a thorough study about different functionals and basis sets for linear and nonlinear optical (NLO) properties of para-nitroaniline ([Formula: see text]-NA), which is considered as proto-type NLO molecule, among organic NLO materials. There is a dire need of such data base for [Formula: see text]-NA because many investigators are using such values of [Formula: see text]-NA for comparative analysis. A range of different functionals including HF, BLYP, PW91, PBE, B3LYP, M06, M06-2X, PBE0, BHandHLYP, CAM-B3LYP, LC-BLYP, and B3LYP-D3 are applied in conjugation with several commonly basis sets such as 6-31G*, 6-311G*, 6-311G**, 6-311+G**, cc-pVDZ, and cc-pVTZ. A variety of functional and basis sets combinations are calculated and graphically compared with each other. The calculated total dipole moment for the [Formula: see text]-NA is found to be 6.79[Formula: see text]D which is quite closer to experimentally determined value. The lowest calculated value for linear isotropic polarizability at HF/6-31G* level of theory is [Formula: see text] esu while higher values observed with remaining all methods especially 14% polarizability increases in presence of basis set with diffuse functions and similar trend of variation is also observed in linear anisotropic polarizability. Similarly, the calculated value of frequency dependent second-order polarizability is found to be [Formula: see text] esu at PBE0/6-311+G** level of theory which is quite closer to experimental value of [Formula: see text] esu. A comparison between the calculated and experimental results shows good agreement among geometries, dipole moments and NLO polarizabilities for [Formula: see text]-NA. Moreover, the frontier molecular orbital (FMO) and electron density difference map (EDDM) analysis along with density of state (DOS) plots are also presented to get more physical intuitions into the structure–property relationship and electronic communications between terminal accepter and donor groups through [Formula: see text]-conjugation. The present investigation provides benchmark data including various commonly used functionals and basis sets for the calculation of NLO properties of [Formula: see text]-NA. Thus, the present investigation will put straight several future studies when it comes to comparative NLO study of organic materials.