Hyperpolarizability Values Research Articles

Influence of End-Capped Modifications in the Nonlinear Optical Amplitude of Nonfullerene-Based Chromophores with a D-π-A Architecture: A DFT/TDDFT Study.

Nonlinear optical (NLO) materials have several uses in many fields such as solid physics, biology, medicine, nuclear physics, and material research. Therefore, a series of nonfullerene-based derivatives (CC10D1–CC10D8) with a D−π–A configuration was planned for the NLO investigation using CC10R as the reference molecule with structural alternations at acceptor moieties. Natural bonding orbital (NBO), UV–vis spectra, frontier molecular orbitals (FMOs), global reactivity parameters (GRPs), transition density matrix (TDM), and density of states (DOS) were analyzed using the M06/6-311G(d,p) functional in chloroform solvent to understand the NLO responses of CC10R and CC10D1–CC10D8. The highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) band gaps of CC10D1–CC10D6 were illustrated to be lower than that of CC10R, with the larger bathochromic shift (726.408–782.674 nm) resulting in a significant NLO response. Along with the band gap, the FMO method also identified an efficient interfacial charge transfer from D to A moieties via a π-bridge, which was further supported by the DOS and TDM map. Moreover, NBO calculations demonstrated that extended hyperconjugation and strong internal molecular interactions were important in their stabilization. The dipole moment (μ), linear polarizability ⟨α⟩, hyperpolarizability (βtotal), and second-order hyperpolarizability (γtotal.) were studied for CC10R and CC10D1–CC10D8. Among all of the derivatives, CC10D2 was proven to be the most appropriate candidate because of its suitable NLO behavior such as being well-supported by a reduced band gap (2.093 eV) and having a suitable maximum absorption wavelength (782.674 nm). Therefore, CC10D2 was reported to have a greater value of first hyperpolarizability (208 659.330 a.u.) compared with other derivatives and CC10R. For the second hyperpolarizability, a greater value was obtained for CC10R (5.855 × 107 a.u.), and its derivatives showed results comparable to that of the parent chromophore for γtotal. This theoretical framework reveals that structural customization with different acceptor units plays a significant role in obtaining attractive NLO materials for optoelectronic applications.

Investigation of Barrier Potential, Structure (Monomer & Dimer), Chemical Reactivity, NLO, MEP, and NPA Analysis of Pyrrole-2- Carboxaldehyde Using Quantum Chemical Calculations

In this work, the structural conformation of pyrrole-2-carboxaldehyde was evaluated using potential energy surface (PES) scan employing DFT computations using B3LYP method with 6-311++G(d,p) level of basis set. The molecule assumed cis form in conformational ground state being more stable than the trans by 15.21 kJ mol−1 due to the orientation of the N–C–C = O dihedral angle. Existence of hydrogen bonds due to intra- and inter-molecular interactions was envisaged. The geometrical parameters of optimized monomeric and dimeric forms have been computed. The computational structural parameters of monomer are in good agreement with its experimental counterparts. The HOMO-LUMO energies were employed for determination of chemical reactivity descriptors. The electronic properties such as frontier molecular orbitals and Global reactivity descriptors were predicted using TD-DFT method. The local reactivity descriptors such as Fukui functions were investigated to determine the electrophilic and nucleophilic attacks within the molecule. The calculated first order hyperpolarizability value exhibited its suitability for non-linear optical applications. Furthermore, the electrophilic and nucleophilic regions of the molecule were studied by molecular electrostatic potential and Fukui functions. 1H and 13C NMR chemical shifts were evaluated using GIAO method employing the same level of theory. NPA analysis and thermodynamic parameters were also calculated.

Lanthanum doped corannulenes with enhanced static and dynamic nonlinear optical properties: A first principle study

In this work, lanthanum doping on corannulene (C20H10) buckybowls has been explored for their geometrical, electronic and nonlinear optical (NLO) properties via DFT simulations. The interaction energies of −21.75 to −40.01 kcal/mol reflect that A-D complexes are thermodynamically stable. The HOMO-LUMO energy gaps of designed complexes are decreased significantly up to 48.92%. A maximum charge transfer of 1.452 |e| is observed for complex A as revealed by natural bond orbital analysis. Non-covalent interaction (NCI) and quantum theory of atoms in molecules (QTAIM) analyses have confirmed the presence of various interactions in the complexes. The complexes are transparent in UV–Visible region and absorption maxima fall near infrared region (1123–2032 nm). The highest nonlinear optical response in terms of first hyperpolarizability value of 5.08 × 104 au is observed for complex C. The hyper-Rayleigh scattering (βHRS) and frequency dependent hyperpolarizability coefficients including electro-optical Pockel's effect and second harmonic generation are also computed theoretically.

M@[12-crown-4] and M@[15-crown-5] where (M=Li, Na, and K); the very first examples of non-conventional one alkali metal-containing alkalides with remarkable static and dynamic NLO response

Excess electron compounds , such as alkalides, were shown to be promising nonlinear optical (NLO) materials with higher static and frequency-dependent nonlinearities. The intriguing alkalides are obtained after doping the alkali metals with crown ethers M@[12-crown-4] and M@[15-crown-5] (where M=Li, Na, and K). The studied complexes are thermodynamically stable and their interactions energies range from −66.51 to −3.51 kcal mol −1 . The geometric, electronic, and nonlinear optical properties are validated through density functional theory at the CAM-B3LYP/6-31+G(d,p) level of theory. The significant (negative) NBO charge present on alkali metals reveals their alkalide characteristics. Furthermore, reduced HOMO-LUMO gaps for the designed complexes show their excellent electronic and conductive properties. Being excess electron candidate the significant static first hyperpolarizability value increased up to 1.2 × 10 7 au where the β vec response recorded up to 1.1 × 10 7 au. The total hyperpolarizability nicely correlates with hyperpolarizability ( β tl ) which suggests their excellent NLO properties. Besides, the dynamic hyperpolarizability response for electro-optical pockel's effect β(-2ω;ω,0) increases up to 3.5 × 10 7 au at dispersion frequency of 1064 nm. The dynamic hyperpolarizability responses for SHG are much pronounced at the larger dispersion frequency. The dynamic second hyperpolarizability response for the dc-Kerr effect increases up to 6.4 × 10 9 au. The frequency-dependent NLO response of M@[12-crown-4] alkalides is slightly larger than those of M@[12-crown-4]. Moreover, the hyper Rayleigh scattering hyperpolarizability (β HRS ) value is calculated up to 3.4 × 10 6 au. • Single alkali metal based non-conventional alkalides are proposed as excess electron compounds. • These shows better thermodynamic stabilities and significant interactions energies for M@[15-crown-5] complexes. • The higher hyperpolarizability response for Li@[15-crown-5] rose up to 1.2 × 10 7 au. • The remarkable frequency-dependent NLO properties at ω = 1064 nm.

Quantum Mechanical Study of Three Aromatic Bioactive Fatty Alcohol Compounds with Nonlinear Optical and Potential Light Harvesting Properties

In the present work, Quantum mechanical properties of three different organic compounds [(2S)-1-(4-nitrophenyl) pyrrolidin-2-yl] methanol (NPPM), 2-(Methyl(4-nitrophenyl) nitro) ethanol (MNAE), and N, N-Bis (2-hydroxyethyl)-4-nitroaniline (HENA) were investigated by computational approach. The geometries were optimized to ground state using the density functional theory (DFT) with level B3LYP/6311-G (++d, p) basis set. The Mulliken charge distribution and molecular electrostatic potential (MEP) map of the title molecules shows the existence of huge charge distribution and the charge transfer within the molecules due to the presence of nucleophilic and electrophilic moieties. The vibrational spectra of the title molecules seem to have high intensity Raman modes. The UV–Vis spectra for the three molecules were found to indicate the presence of π-π* and n-π* electronic transitions between wavelength 300–500 nm. The computed value of first-order hyperpolarizability for the molecules were found to be higher than the reference materials. This validates the nonlinear optical responses of the title molecules. The light harvesting efficiency of the molecules were also determined. For the NPPM molecule, light harvesting efficiency of 64% was obtained. This validates the potential applications of NPPM in designing new photosensitizer solar cells.

Syntheses, crystal structures, optical properties, antibacterial activity and DFT calculations of two substituted benzyl triphenylphosphinium picrates

Two new organic hybrid materials, namely, 4-chlorobenzyl triphenylphosphinium picrate and 4-iodobenzyl triphenylphosphinium picrate [4ClBzTPP][PIC](1) and [4IBzTPP][PIC](2), have been grown by slow evaporation solution growth technique and characterized by elemental analysis, spectroscopy, thermal analysis, powder and single crystal XRD. Two new picrates crystallize in triclinic space group P−1 and consist of a pair of [4ClBzTPP]+/[4IBzTPP]+ cations and picrate anions. The one-dimensional anionic chain are constructed by the non-bonded O···O and N···O interactions. Experimental vibrational bands (IR and Raman) have been discussed and assigned. The HOMO-LUMO energy gap explains the charge transfer interactions in the molecules. TG-TDA technique reveals that two materials were stable up to 215 °C and 253 °C, respectively. Excited by 250 nm ultraviolet light, two materials emit main luminescent emissions bands at about 374 nm and 524 nm in solid state at room temperature. In addition, two picrates show good antibacterial activities against Escherichia coli and Staphylococcus aureus. The results of DFT calculations based on the structures of 1 and 2 indicate that the first hyperpolarizability value (βtot) of two crystals are 5.8 and 32.3 times that of KDP, respectively, which show good nonlinear optical properties.

Multi-State Second-Order Nonlinear Optical Switches Incorporating One to Three Benzazolo-Oxazolidine Units: A Quantum Chemistry Investigation.

This contribution employs quantum chemistry methods to describe the variations of the second nonlinear optical responses of molecular switches based on benzazolo-oxazolidine (BOX) units, connected by π-linkers, along their successive opening/closing. Under the fully closed forms, all of them display negligible first hyperpolarizability (β) values. When one BOX is opened, which is sketched as C→O, a push–pull π-conjugated segment is formed, having the potential to enhance β and to set the depolarization ratio (DR) to its one-dimensional-like value (DR = 5). This is observed when only one BOX is open, either for the monoBOX species (C→O) or for the diBOX (CC→CO) and triBOX (CCC→CCO) compounds, i.e., when the remaining BOXs stay closed. The next BOX openings have much different effects. For the diBOXs, the second opening (CO→OO) is associated with a decrease of β, and this decrease is tuned by controlling the conformation of the π-linker, i.e., the centrosymmetry of the whole compound because β vanishes in centrosymmetric compounds. For the triBOXs, the second opening gives rise to a Λ-shape compound, with a negligible change of β, but a decrease of the DR whereas, along the third opening, β remains similar and the DR decreases to the typical value of octupolar systems (DR = 1.5).

Ferrocene appended 1,8-naphthalimide chromophores: Synthesis, theoretical, the effect of phenyl substitution on aggregation-induced enhanced emission and second-order nonlinear optical studies

A new ferrocene appended linear donor-π-acceptor (D-π-A) type 1,8-naphthalimide chromophores [FcPhNap-n-butyl (1) and Fc(Ph)2Nap-n-butyl (2)] have been synthesized and characterized using various analytical and spectroscopic techniques. The chromophores 1 and 2 show the one-electron transfer process, which was examined through cyclic voltammetric (CV) method. The solvatochromic studies show red shift by increasing the solvent polarity from non-polar to polar for both the chromophores 1 and 2, due to the better stabilization of the more polarized excited state than the ground state in the polar solvent. The fluorescence studies show low fluorescence emission, which was enhanced by aggregation in THF/water mixture when the water ratio is increased upto 60%, due to the restricted intramolecular rotation (RIR) process in the aggregated state. Also, the quantum yield increases 3.4 (1) and 6.8 (2) times in the aggregation induced enhanced emission (AIEE) state than THF solution for both the chromophores [THF/AIEE = 0.05/0.17 for 1 and 0.03/0.22 for 2]. The second-order non-linear optical properties of the chromophores 1 and 2 were studied using Kurtz and Perry powder technique, chromophore 2 shows 1.2 times higher SHG efficiency than 1, owing to the presence of additional phenyl group in 2, which further supports the effective charge transfer process from donor to acceptor. Furthermore, optical and non-linear optical properties of chromophores 1 and 2 were analyzed by DFT/TD-DFT calculations using different functionals (B3LYP, long-range corrected CAM-B3LYP and LC-BLYP) with 6–31+G** level of theory. The B3LYP functional shows higher hyperpolarizability values [β0 = 109.2 × 10-30 esu (1), 299.7 × 10-30 esu (2)], due to the overestimation of the dipole moment, polarizability and hyperpolarizabilities between the donor–π–acceptor systems in B3LYP-hybrid functional, which leads to incorrect long-range charge transfer.

Structural and Vibrational Investigation of Benzil-(1,2-Diphenylethane-1,2-Dione): Experimental and Theoretical Studies

Single crystals of benzil commonly known as 1,2-diphenylethane-1,2-dione are grown by the slow evaporation method at room temperature. Gaussian 09 program is applied for theoretical calculations with B3LYP/6-311++G(d,p) basis set. The structure is optimized, and the energy, structural parameters, vibrational frequencies, IR, and Raman intensities are determined. Complete natural bonding orbital (NBO) analysis is carried out to analyze the intramolecular electronic interactions and their stabilization energies. From the second-order perturbation theory analysis of the benzil molecule, it is observed that there exists a hyperconjugative intramolecular stabilization energy between 17.45 and 22.76 KJmol-1. HOMO-LUMO analysis has been performed to identify the charges transferred within the molecule. The energy gap is calculated to be 2.919 eV and thus establishes the soft nature of the molecule. The molecular electrostatic potential (MEP) of the grown crystal was analyzed using the B3LYP method with 6-311++G(d,p) basis set. First-order hyperpolarizability calculations reveal the nonlinear optical microscopic behavior of the benzil molecule with nonzero values. The total value of the first-order hyperpolarizability (βtot) is of the order of41.5246×10−31 esu, which is found to be 11.135 times that of urea. Hence, benzil can be referred to as a good material for nonlinear optical applications.

Synthesis, Crystal structure, photoluminescence properties and quantum mechanics studies of two schiff bases of 2-amino-p-cresol

The compounds, (E)-2-((2,5-dimethoxybenzilidene) amino)-4-methylphenol (DMB–APC) and 2-((E)-((E)-3-(4-methoxyphenyl)allylidene)amino)-4-methylphenol (TPPC) were synthesized and characterized using FTIR, 1H and 13C NMR, MS and single crystal X-ray crystallographic techniques. The molecular geometry and vibrational frequencies of the compounds in the ground state were calculated using the density functional theory in conjunction with Becke 3-Lee–Yang Parr functional and 6–31 G (d,p) basis set. The electronic structure calculation (energy gap) and molecular electrostatic potential map of the compounds were performed at the B3LYP level of theory and the 6 -31 G (d,p) basis set.. The nonlinear optical properties [dipole moment(μ), average polarizability(α), anisotropy of polarizability (Δα) and first hyperpolarizability(β)] of the compounds were determined from fluorescence spectra and quantum mechanical calculation. The excitation spectra of the compounds showed bands in the UV region of 306, 345 nm for DMB–APC and 311, 410 nm for TPPC, while the emission spectra of the compounds showed bands in the visible region centred at 462, 486 nm for DMB–APC and 492, 533 nm for TPPC. The energy gap of the first electron excitation from HOMO to LUMO are 3.89 and 3.69 eV, while the first hyperpolarizability is 100.55 and 154.22 eV for DMB–APC and TPPC respectively. The calculated parameters of the compound are in good agreement with the experimental data. Based on the emission bands, low energy gap, and the high first hyperpolarizability values, DMB –APC and TPPC show promise for the development of non-linear optical materials.

Synthesis of second order nonlinear optical multichromophore based on double-donors with enhanced electro-optic coefficients and thermal stability

Our work was related to the systhesis of several nonlinear optical dendrimers L1-L3 with identical Bis(N,N-diethyl)aniline-derived donor bridge and phenyl-trifluoromethyl-tricyanofuran acceptor. The dendritic structure of multichromophores can effectively reduce the electrostatic interaction between chromophores. And the strong acceptor result in large first-order hyperpolarizability of the chromophores. Multichromophores L2-L3 showed very high poling efficiencies due to large steric hindrance and first-order hyperpolarizability value of chromophores. A large poling efficiency (2.10 ± 0.08 nm2/V2) and r33 (205 p.m./V) have been achieved for neat chromophore L3 thin films at 1310 nm. Besides, the glass transition temperature (Tg) of L2 and L3 has greatly improved to 125 °C and 133 °C, respectively. All of these provided an new insights into molecular design of chromophore with enchanced poling efficiency and high thermal stability.

Influence of Peripheral Modification of Electron Acceptors in Nonfullerene (O-IDTBR1)-Based Derivatives on Nonlinear Optical Response: DFT/TDDFT Study.

Fullerene-based organic compounds have been reported as useful materials with some limitations; nonetheless, fullerene-free compounds are primarily considered to be the most substantial materials for the development of modern technology. Therefore, in this study, a series of compounds (NFBC2–NFBC7) having an A-π-D architecture were designed for the first time from a synthesized nonfullerene (O-IDTBR) compound by changing different acceptor groups. The synthesized nonfullerene (O-IDTBR1) compound and its designed derivatives were optimized with frequency analyses at the M06/6-311G(d,p) level. These optimized structures were further characterized by different quantum chemical approaches. The study required that the designed compounds possess a low energy gap in comparison to that of O-IDTBR1 (2.385 eV). Moreover, density of state (DOS) calculations supported the FMO analysis and displayed charge transfers from the HOMO to the LUMO in an effective manner. The λmax values of the investigated chromophores were observed to be greater than that of the reference compound. Amazingly, the highest amplitude of linear polarizability ⟨α⟩ and first (βtot) and second hyperpolarizability values were achieved by NFBC6 at 1956.433, 2155888.013, and 7.868 × 108 au, respectively, among all other derivatives. Effective NLO findings revealed that nonfullerene-based derivatives may contribute significantly to NLO technology.

Synthesis, solvatochromism and DFT study of pyridine substituted benzanthrone with ICT characteristics

We have explored the relation between the substituent and optical nonlinearity of pyridinepiperazine substituted benzanthrone dye. We report the synthesis of 3-(4-(pyridine-2-yl)piperazin-1-yl)-7H-benzo[de]anthracen-7-one (Pyridine-PBA). The molecular structure of the title dye was further confirmed by using FT-IR, 1H NMR, 13C NMR, and X-ray crystallographic techniques. The 3-substituted benzanthrone dye was examined for solvent dependent photophysical properties. The polarity plots indicate that hydrogen bonding interactions are influential in most of the solvents. Further analysis of Stokes’ shift data with multi parameter solvent polarity scale signifies that with an increase in solvent hydrogen bond donor ability a bathochromic shift is observed resulting in an increment in the dipole moment of the Pyridine-PBA dye on excitation. Computational results indicate that the electron excitation has some charge transfer characteristics. Furthermore, the calculated first static hyperpolarizability (β) and second hyperpolarizability (γ) values using range separated DFT methods fare better than the estimates for urea.

Synthesis of Crystalline Fluoro-Functionalized Imines, Single Crystal Investigation, Hirshfeld Surface Analysis, and Theoretical Exploration.

This investigation is focused on the synthesis of two halo-functionalized crystalline Schiff base (imine) compounds: (E)-2-methoxy-6-(((3-(trifluoromethyl)phenyl)imino)methyl)phenol (MFIP) and (E)-1-(((2-fluorophenyl)imino)methyl)naphthalen-2-ol (FPIN) by the condensation reaction of substituted benzaldehydes and substituted aniline. The crystal structures of MFIP and FPIN were determined unambiguously by single-crystal X-ray diffraction (SC-XRD) studies. Intermolecular interactions and the role of fluorine atoms in the stabilization of the crystal packing are explored for both compounds using Hirshfeld surface analysis. Accompanied with experimental studies, quantum chemical calculations were also performed for comprehensive structure elucidation at the M06/6-311G(d,p) level of theory. A comparison of experimental and density functional theory results for geometrical parameters exhibited excellent agreement. Interestingly, Frontier molecular orbitals and natural bond orbital (NBO) findings revealed that intramolecular charge transfer and hyper-conjugation interactions had played a significant role to stabilize the molecules. Both compounds exhibited a relatively larger value of hardness with a smaller global softness, which, as proposed by the SC-XRD and NBO study, shows a higher stability. Nonlinear optical (NLO) findings showed that FPIN manifested a larger value of linear polarizability (<a> = 293.06 a.u.) and second-order hyperpolarizability (<γ> = 3.31 × 105 a.u.) than MFIP (<a> = 252.42 and <γ> = 2.08 × 105 a.u.) due to an extended conjugation. The above-mentioned findings of the entitled compounds may play a crucial role in NLO applications.

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

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

Aggregation induced emission (AIE)-active ferrocene conjugated linear π−extended multi donor−π−acceptor (D-D′-π-A) chromophores: Synthesis, structural, theoretical, linear and nonlinear optical studies

A new series of ferrocene (D) and methoxyphenyl (D′) conjugated D-D′-π-A push-pull chromophores [Fc-(RPh)C=CH–CH=CN-R’{R, R’ = H, CN (1), OCH3, CN (2), H, C6H4NO2 (3), OCH3, C6H4NO2 (4)}] were synthesized and spectroscopically characterized. The structure of the chromophore 3 was confirmed by single crystal X-ray diffraction studies, and it was crystallized in triclinic crystal system with P-1 centrosymmetric space group. In the crystal packing, several non-covalent interactions (H-bonding and C–H·····π) were observed. The thermal behaviour of the chromophores 3 and 4 has been investigated using thermogravimetric analysis and was found to be stable up to 230 °C. The solvatochromic studies of the chromophores 1–4 showed a positive solvatochromism with red-shift from non-polar to polar solvents due to the high dipolar excited state in the presence of strong electron-donor and acceptor moieties. The electrochemical performance of the chromophores revealed the one-electron transfer from the ferrocene to ferrocenium ion Fe2+⇌Fe3+. The chromophores 1–4 exhibited low fluorescence intensity and quantum yield as a consequence of the quenching nature of ferrocene, it was further enhanced through the aggregation-induced emission (AIE) process in THF/H2O mixtures by the restriction of intramolecular rotation (RIR), and the chromophores 1–4 showed 2 times higher quantum yield in the aggregated state. The second-order nonlinear optical response was attained by Kurtz-Perry powder technique. The second harmonic generation (SHG) efficiencies of the chromophore 4 was close to the standard KDP, owing to the presence of multi-donor [Ferrocene (D) and methoxyphenyl (D′)] and acceptor groups with extended π-conjugation. In addition, the mesomeric effect (+M) of the methoxy group makes an effective charge transfer process. The optical and nonlinear optical properties of the chromophores were further analyzed by density functional theory (DFT) with different functionals (B3LYP, CAM-B3LYP and LC-BLYP). The hyperpolarizability values were underestimates in the B3LYP-hybrid functional because of the corrected long-range charge transfer between donor and acceptor in the D-π-A systems. The frontier molecular orbital (FMO) level helps for better understanding the charge transfer, nonlinear optical (NLO) properties, and the calculated HOMO-LUMO energy levels were in good agreement with the experimental results.

Synthesis, linear and non-linear optical properties of “push-pull” chromophores based on 9,9-dimethyl-9H-fluoren-2-amine

Photophysical properties including the first hyperpolarizability of a series of chromophores (SP1-SP5) possessing “push-pull” type conjugation were investigated to evaluate the proficiency as non-linear optically active materials. The compounds are based on the 9,9-dimethyl-9H-fluoren-2-amine platform, which acts as a donor unit and different types of acceptors have been incorporated to design SP1-SP5. The first hyperpolarizability (βHRS) value was in the range of 102 × 10−30 esu to 174 × 10−30 esu, and the trends in the experimental βHRS have been rationalized in terms of the difference in the dipole moment (Δμge) of the ground and excited state, oscillator strength of the contributing absorption bands and the band gaps. The intrinsic efficiency of the non-linear response of these dipolar compounds possessing a single major dipolar hyperpolarizability tensor component βzzz was also determined from the intrinsic hyperpolarizability, a real figure of merit of the non-linear optical response. Comparison of the experimental off-resonant first hyperpolarizability, βHRS, as well as the intrinsic hyperpolarizability of this set of D-π-A chromophores, lacking linear conjugation, revealed advantage over the already reported counterparts based on benzothiazole platform.

DFT study of the influence of boron/nitrogen substitution on the electronic and nonlinear optical properties of the benzene-substituted graphdiyne fragment

A series of B/N-substituted benzene-substituted graphdiyne fragments (1) were studied in detail by density functional theory to evaluate their electronic structures and nonlinear optical (NLO) properties. Substituting a B (N) atom for a C atom introduces extra holes (electrons) in the electronic structure of the compound. The introduction of the N atom can effectively narrow the large energy gap of the 1, but the value for the B-substituted system does not change significantly. Such compounds show superior NLO response with respect to pristine 1, and the static first hyperpolarizability (β0) values of most of N-substituted compounds are larger than the corresponding B-substituted compounds. Moreover, the result of static β0 of the system can be deeply understood by the distribution of first hyperpolarizability density. These fascinating findings can provide valuable insights for the development of potential high-performance NLO nanomaterials.

Highly accurate DFT investigation for triggering the ultra-strong static and dynamic nonlinear optical properties of superalkali doped aminated graphdiyne (NH2-GDY) donor-π-acceptor (D-π-A) quantum dots

Keeping in mind the desirability of novel two-dimensional materials with an ultra-high nonlinear optical (NLO) response for the fabrication of optoelectronic devices, we have investigated nine complexes by doping superalkalis (M2X; M = Li, Na, K and X = F, Cl, Br) onto the novel aminated graphdiyne (NH2-GDY) quantum dots. The geometric, electronic and NLO responses (static and dynamic) of the M2X doped aminated graphdiyne (M2X@NH2-GDY) complexes have been systematically investigated using density functional theory (DFT) computations. All the superalkalis are preferably oriented on the triangular large porous site of NH2-GDY containing extensive delocalized π-conjugated electrons and interact via an intermolecular π-electron donor–acceptor (D-π-A) process. The lithium and potassium-containing superalkali doped complexes exhibit high structural stability due to their large interaction energies. The change in the electronic properties of the M2X doped NH2-GDY quantum dots is investigated by analyzing the NBO charge transfer, vertical ionization energies (VIEs), HOMO-LUMO energy gaps and density of states spectra. TD-DFT calculations show ultra-high transparency of these complexes in the ultraviolet region. The strong NLO characteristics of the designed complexes are demonstrated by their high static and dynamic hyperpolarizability values. Among all the nine complexes, the K2F@NH2-GDY, K2Cl@NH2-GDY and K2Br@NH2-GDY complexes possess exceptionally high βo values: 1.16 × 104, 1.06 × 104 and 1.02 × 104 au, respectively, owing to the large atomic radius and high atomic number of the potassium metal atoms. The frequency-dependent NLO responses, Electro-Optical Pockels Effects (EOPE) and Second Harmonic Generation (SHG) are analyzed to investigate the dynamic NLO response. It is revealed that the K2X@NH2-GDY complexes also exhibit exceptionally high dynamic NLO responses (107 or 108 au) at 1064 nm wavelength. Our present research not only highlights the significance of superalkali doping on aminated graphdiyne quantum dots but also indicates that the K2X@NH2-GDY complexes are potentially important for next-generation optoelectronic devices.

Superalkali (Li2F, Li3F) doped Al12N12 electrides with enhanced static, dynamic nonlinear optical responses and refractive indices

In the present work, superalkalis (Li2F and Li3F) doped Al12N12 nanocages have been designed and investigated theoretically to elucidate the correlations between geometric, electronic and nonlinear optical properties. All complexes (A-E) are stable inorganic electrides as indicated by their interaction energies (−52.97 to −87.58 kcal/mol). The decrease in HOMO-LUMO energy gaps (5.44–5.87 eV) has caused a remarkable increase in the nonlinear optical response of A-E complexes. The maximum values of first hyperpolarizability (1.20 × 104 a.u.) and second hyperpolarizability (1.65 × 107 a.u.) have been achieved for complex A. The highest dynamic hyperpolarizability coefficients including second harmonic generation (9.08 × 105 a.u.) and electro-optic Pockel's effect (9.56 × 105 a.u.) are obtained for complex A at 532 nm. The electric field-induced second harmonic generation (up to 3.52 × 108 a.u.) and dc-Kerr effect (up to 8.13 ×108 a.u.) along with a large quadratic nonlinear refractive index (up to 5.41 × 10−11 a.u.) of the designed electrides reflected their large NLO response.