Showing papers on "Hyperpolarizability published in 2021"

Structural parameter-modulated nonlinear optical amplitude of acceptor–π–D–π–donor-configured pyrene derivatives: a DFT approach

Abstract: In the present study, organic pyrene-based derivatives were selected for NLO investigation. The reference compound named methyl (E)-2-cyano-3-(5-(pyren-1-yl)thiophen-2-yl)-3-acrylate (MCPTR) was taken for the design of its derivatives, abbreviated from MCPTD1 to MCPTD8 compounds. The nonlinear optical (NLO) properties, frontier molecular orbitals (FMOs), natural bonding orbital (NBO), and UV-vis analyses of molecules (MCPTR–MCPTD8) were executed by M06 level with 6-31G(d,p) basis set. The UV-vis investigation showed that all designed compounds exhibited a redshift, and the maximum wavelength was studied in MCPTD7 (832.330 nm). The HOMO–LUMO band gaps of MCPTD1–MCPTD8 were found to be smaller as compared to those of MCPTR (3.210 eV). The global reactivity information was correlated with band gap values; MCPTD7, having a lower band gap, exhibited smaller hardness values (0.0321 Eh) with larger softness values (15.5763 Eh). The natural bond orbital analysis (NBO) helped to elucidate the hyper conjugative interactions, along with the stability and electron-transfer process. The dipole moment (μ), average polarizability 〈α〉, first hyperpolarizability (βvec) and second hyperpolarizability 〈γ〉 were computed for MCPTR–MCPTD8. Consequently, all designed compounds (MCPTD1–MCPTD8) possessed greater NLO responses than the reference compound (MCPTR). Interestingly, MCPTD7 showed a smaller energy gap and remarkable NLO response among MCPTD1–MCPTD8 compounds. The highest μtotal, 〈α〉, βvec and 〈γ〉 values for MCPTD7 were observed as 7.200, 2.40 × 10−22 esu, 2.84 × 10−27 esu and 8.6024 × 107 esu, respectively. Aptitude towards the NLO material relied upon the position of different groups, the conjugated system donor and acceptor regions. The high NLO response reveals the fact that this class of pyrene-based derivatives with a thiophene linker has remarkable contributions towards NLO technological applications.

Hydrogen-Bond-Driven Synergistically Enhanced Hyperpolarizability: Chiral Coordination Polymers with Nonpolar Structures Exhibiting Unusually Strong Second-Harmonic Generation

Abstract: Four chiral coordination polymers (CPs), M[(S,S)-C14 H14 N2 O6 ] and M[(R,R)-C14 H14 N2 O6 ] (M=Zn or Cd), have been exclusively synthesized in high yields with the aid of newly designed chiral ligand under hydrothermal condition. The CPs crystallizing in the orthorhombic nonpolar space group, C2221 , reveal three-dimensional framework structures composed of MO4 tetrahedra and the corresponding homochiral linkers. Powder second-harmonic generation (SHG) measurements indicate that the nonpolar CPs reveal very strong SHG efficiency of ca. 5-9 times that of KH2 PO4 and exhibit type-I phase-matching behavior. Density functional theory calculations suggest that the unusually large SHG efficiency found from the nonpolar CPs should be attributable to the synergistic effect of polarizable metal cations and enhanced hyperpolarizability in the donor-acceptor system originating from the hydrogen bonding in the coordinated linkers.

Tuning the Fluorescence and the Intramolecular Charge Transfer of Phenothiazine Dipolar and Quadrupolar Derivatives by Oxygen Functionalization.

Abstract: A series of new naphthalimide and phenothiazine-based push-pull systems (NPI-PTZ1-5), in which we structurally modulate the oxidation state of the sulfur atom in the thiazine ring, i.e., S(II), S(IV), and S(VI), was designed and synthesized by the Pd-catalyzed Sonogashira cross-coupling reaction. The effect of the sulfur oxidation state on the spectral, photophysical, and electrochemical properties was investigated. The steady-state absorption and emission results show that oxygen functionalization greatly improves the optical (absorption coefficient and fluorescence efficiency) and nonlinear optical (hyperpolarizability) features. The cyclic voltammetry experiments and the quantum mechanical calculations suggest that phenothiazine is a stronger electron donor unit relative to phenothiazine-5-oxide and phenothiazine-5,5-dioxide, while the naphthalimide is a strong electron acceptor in all cases. The advanced ultrafast spectroscopic measurements, transient absorption, and broadband fluorescence up conversion give insight into the mechanism of photoinduced intramolecular charge transfer. A planar intramolecular charge transfer (PICT) and highly fluorescent excited state are populated for the oxygen-functionalized molecules NPI-PTZ2,3 and NPI-PTZ5; on the other hand, a twisted intramolecular charge transfer (TICT) state is produced upon photoexcitation of the oxygen-free derivatives NPI-PTZ1 and NPI-PTZ4, with the fluorescence being thus significantly quenched. These results prove oxygen functionalization as a new effective synthetic strategy to tailor the photophysics of phenothiazine-based organic materials for different optoelectronic applications. While oxygen-functionalized compounds are highly fluorescent and promising active materials for current-to-light conversion in organic light-emitting diode devices, oxygen-free systems show very efficient photoinduced ICT and may be employed for light-to-current conversion in organic photovoltaics.

DFT study of superhalogen and superalkali doped graphitic carbon nitride and its non-linear optical properties

Abstract: DFT calculations are carried out to investigate nonlinear optical (NLO) properties of superhalogen (BCl4) and superalkali (NLi4) doped graphitic carbon nitride (GCN). It is noted that the geometries of doped GCN are sufficiently stable. The energy gap for GCN is 3.89 and it reduces to 0.53 eV in our designed molecule G4. Change in the dipole and transition dipole moment is observed along with small transition energies which are responsible for higher hyperpolarizabilities. Doped GCN has larger first and second hyperpolarizabilities which are basic requirements for NLO response. The second hyperpolarizability of GCN enhances from 1.59 × 104 to 2.53 × 108 au when doping with BCl4 and NLi4. TD-DFT calculations show the absorption maxima of doped GCN range from 700 nm to 1350 nm. EDDM analysis provides information on electronic distribution from excited to ground state. All these consequences show doped GCN can be a promising NLO material.

Synthesis of Diaminopyrimidine Sulfonate Derivatives and Exploration of Their Structural and Quantum Chemical Insights via SC-XRD and the DFT Approach.

Abstract: Two heterocyclic compounds named 2,6-diaminopyrimidin-4-ylnaphthalene-2-sulfonate (A) and 2,6-diaminopyrimidin-4-yl4-methylbenzene sulfonate (B) were synthesized. The structures of heterocyclic molecules were established by the X-ray crystallographic technique, which showed several noncovalent interactions as N···H···N, N···H···O, and C-H···O bonding and parallel offset stacking interaction. Hydrogen-bonding interactions were further explored by the Hirshfeld surface (HS) analysis. Nonlinear optical (NLO) and natural bond orbital (NBO) properties were calculated utilizing the B3LYP/6-311G(d,p) level. Frontier molecular orbitals (FMOs) and molecular electrostatic potential (MEP) were calculated utilizing the time-dependent density functional theory (TD-DFT) at the same level. The NBO analysis showed that the molecular stabilities of compounds A and B were attributed to their large stabilization energy values. The second hyperpolarizability (γtot) values for A and B were obtained as 3.7 × 104 and 2.7 × 104 au, respectively. The experimental X-ray crystallographic and theoretical structural parameters of A and B were found to be in close correspondence. Both the molecules reveal substantial NLO responses that can be significant for their utilization in advanced applications.

The synthesis, spectroscopic characterization, DFT/TD-DFT/PCM calculations of the molecular structure and NBO of the novel charge-transfer complexes of pyrazine Schiff base derivatives with aromatic nitro compounds

Abstract: The novel charge-transfer (CT) solid complexes of pyrazine Schiff bases, derived from 2-aminopyrazine and substituted benzaldehydes (N-benzylidenepyrazin-2-amine, (NBPA)) and N-(((4-dimethylamino)benzylidene)pyrazin-2-amine) (NDMABPA) with some aromatic nitro compounds have been synthesized and characterized experimentally using ultraviolet-visible (UV-Vis) absorption, infrared spectra and proton nuclear magnetic resonance (1HNMR) spectroscopy. Complexes were formed in a molar ratio of 1 : 1 with good indications for the existence of charge-transfer in its molecular structure. Theoretical studies were done on donors and acceptors, elucidating their structures and active sites where the charge-transfer occurs. The experimental work was done in ethanol. Solution characterizations included the determination of the molecular structure of formed CT complexes, verifying the 1 : 1 (donor:acceptor) ratio in ethanol. The quantum mechanical calculations of geometries and energies were attained using the density functional theory with Becke's three parameter exchange functional method. The Lee–Yang–Parr correlation functional approach (B3LYP/DFT) combined with the 6-31G(d,p) basis set has been consecutively carried out in solution using ethanol as a solvent to compliment measured results, and to justify CT within donors and acceptors. The optimized energy, complexation energy, geometrical parameters, natural atomic charges, as well as the 3D-plots of the molecular electrostatic potential maps (MEP) were computed and elucidated. They agreed with the experimental results, wherein complex stabilities are attributed to the occurence of charge-transfer. The electronic spectra were computed and executed using time dependent-density functional theory (TD-DFT) via the addition of polarizable continuum solvation method PCM, PCM-TD-DFT. The allowed singlet transitions are positioned, and their highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) involvement is represented. The descriptions of frontier HOMO and LUMO molecular orbitals attributed to the first four singlet transitions, are shown. For all formed solid complexes, the main relationship between donor and acceptor molecules is through the π–π* interaction. A secondary n–π* transition was noticed in some complexes. The vibrational wavenumbers were also determined using B3LYP/6-31G(d,p), and the results match with the experiment. The small energy gap between HOMO and LUMO energies indicate that CT occurs within donors and acceptors. The hyperconjugative interactions, molecular stability, bond strength and intramolecular CT have been investigated applying natural bond orbital (NBO) analysis. The mean polarizability, total static dipole moment, anisotropy of polarizability, and mean first-order hyperpolarizability have also been attained. The obtained values show that CT complexes are accomplished candidates to non-linear optical (NLO) materials.

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

Abstract: 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 0.875 eV, 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 × 10−12 esu, 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.

Remarkable static and dynamic NLO response of alkali and superalkali doped macrocyclic [hexa-]thiophene complexes; a DFT approach

Abstract: In this study, the nonlinear optical (NLO) response of alkali metal atom (Li, Na and K) and their corresponding superalkali (Li3O, Na3O and K3O) doped six membered cyclic thiophene (6CT) has been explored. The optimized geometries of complexes; Li@6CT, Na@6CT, K@6CT, Li3O@6CT, Na3O@6CT and K3O@6CT depict that the superalkalis and alkali metals interact through the active cavity of 6CT. Interaction energies reveal that superalkalis have higher interaction with 6CT than alkali metals. The nonlinear optical (NLO) response of the reported complexes is estimated via both static and dynamic hyperpolarizabilities which are further rationalized by the HOMO–LUMO gap, natural bond orbital (NBO) charge transfer, dipole moment, polarizabilities and βvec. A remarkably high NLO response is computed for Na3O@6CT among all of the complexes. The static hyperpolarizability of the Na3O@6CT complex is 5 × 104 au along with the highest βvec value (2.5 × 104 au). High charge transfer (1.53e−) and small EH–L gap (2.96 eV) is responsible for such a large NLO response. For dynamic NLO responses, electro-optic Pockel's effect (EOPE) and second-harmonic generation (SHG) are explored. A very large quadratic nonlinear optical response (3.8 × 10−12 au) is observed for the Na3O@6CT complex. Moreover, the absorption spectrum of the Na3O@6CT complex shows ultra-high transparency in the ultraviolet and visible regions unlike any other of its counterparts.

Surface functionalization of twisted graphene C32H15 and C104H52 derivatives with alkalis and superalkalis for NLO response; a DFT study.

Abstract: Herein, we present the detailed comparative study on geometric, electronic, optical and non-linear optical response of alkalis and superalkalis doped twisted graphene. The results illustrate that alkali metals and superalkalis interact with the central ring of the twisted graphene through non-covalent interactions which demonstrate the stability of the resultant complexes. NBO charges indicate the transfer of electrons from dopant (alkali metal atoms and superalkalis) towards twisted graphene sheet. Superalkalis doped twisted graphene complexes exhibit higher first hyperpolarizability values compared to alkali metals analogues. Among superalkalis doped complexes, K3O@C104H52 shows the highest βo value of 1.68 × 105 au. In frequency dependent first hyperpolarizability analysis, strong second harmonic generation (SHG) response of K3O@C32H15 complex is observed at both selected resonance frequency values (532 nm and1064 nm) whereas EOPE value of K3O@C32H15 complex shows higher induced response at 1064 nm wavelength. The static hyperpolarizability (βo) further increases under the influence of applied electric field. Among all complexes, Li3O@C32H15 graphene complex has the highest βo value (1.40 × 105 au) under applied electric field along x axis when sheet is in y-z plane. This analysis will be an important guideline for future studies on twisted graphene based NLO materials.

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

Abstract: 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 (βo) 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 (Ei) 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.

First row transition metals decorated boron phosphide nanoclusters as nonlinear optical materials with high thermodynamic stability and enhanced electronic properties; A detailed quantum chemical study

Abstract: Electronic as well as nonlinear optical properties (first hyperpolarizabilities) of boron phosphide nanoclusters doped with first row transition metals (Sc–Zn) are explored using density functional theory (DFT) calculations. Four different doping sites (b64, b66, r4, and r6) of the B12P12 nanocluster are considered for doping of the transition metals. Computational results revealed that these transition metals doped boron phosphide complexes are highly stable, and their HOMO–LUMO energy gaps are considerably reduced as compared to the pristine B12P12 nanocage. The highest interaction energy (−74.42 kcal mol−1) is observed for Ni@r4-B12P12 complex. The lowest HOMO–LUMO energy gap (1.44 eV) is computed for Sc@b64-B12P12 complex. Moreover, adsorption of the first row transition metals (Sc–Zn) on the surface of B12P12 nanocluster significantly enhanced the nonlinear optical response of the resultant complexes. The highest static first hyperpolarizability value (4.4 × 104 au) is computed for Sc@r4-B12P12 complex. Moreover, frequency dependent hyperpolarizability calculations are also performed to evaluate the practicality of the transition metal doped boron phosphide (M@B12P12) complexes. The highest electro-optical Pockels effect (EOPE) value of 4.4 × 105 au is computed for Sc@r4-B12P12 complex while Sc@r6-B12P12 gives the highest second harmonic generation (SHG) value of 1.1 × 105 au. This study will be advantageous for providing guidance in further designing of new high-performance nonlinear optical (NLO) materials.

Endohedral metallofullerene electrides of Ca12O12 with remarkable nonlinear optical response

Abstract: Herein, the structural, electronic, thermodynamic, linear and nonlinear optical properties of inorganic electrides, generated by alkali metal doping in group II–VI Ca12O12 fullerene, are studied. Endohedral doping of alkali metal leads to the formation of electrides whereas no such phenomenon is seen for exohedral doping. The electride nature of the endohedral fullerenes is confirmed through the analysis of frontier molecular orbitals. The results show that doping of alkali metal atoms leads to a reduction of the HOMO–LUMO gap and increase of the dipole moment, polarizability and hyperpolarizability of nanocages. Doping causes shifting of electrons from alkali metal atoms towards the Ca12O12 nanocage, which serve as excess electrons. Furthermore, the participation of excess electrons for enhancing the NLO response of these nanocages has been confirmed through the calculation of hyperpolarizability (βo). For exploring the controlling factors of hyperpolarizability, a two level model has been employed and the direct relation of hyperpolarizability with Δμ & fo, while an inverse relation of hyperpolarizability with ΔE has been studied. The electrides possess remarkable nonlinear response where the highest hyperpolarizability can reach up to 1.0 × 106 a.u. for endo-K@Ca12O12. This electride has the lowest ΔE of 0.63 eV among all compounds studied here. These intriguing results will be expedient for promoting the potential applications of the Ca12O12-based nano systems in high-performance nonlinear optical (NLO) materials.

DFT studies of single and multiple alkali metals doped C24 fullerene for electronics and nonlinear optical applications.

Abstract: The geometric, electronic and nonlinear properties of exohedral and endohedral single and multiple alkali metal (Li, Na and K) atom doped C24 fullerene are studied. First, the most stable orientations at the most stable spin state are evaluated. Complexes with odd metal atoms are stable at doublet spin state and complexes with even number of metal atoms are stable at singlet spin state. Thermodynamic analysis shows that Li4C24 among all complexes with highest thermodynamic stability has interaction energy of −190.78 kcal mol−1. The energy gaps (GH-L) are fairly reduced in single and multi-doped cages, and the lowest energy gap is observed for K4C24 complex. NBO analysis is performed to validate the charge transfer from alkali metal toward C24. The largest amount of charge (0.95 |e|) transfer is monitored in exohedral K2C24 complex where the highest charge transfer is for potassium (K) metal. Total density of states (TDOS) spectra of doped complexes justify the involvement of alkali metals and nanocage in new HOMO formation for the excess electrons. First hyperpolarizability is descriptor of NLO properties of single and multi-doped complexes are calculated. It is observed that doping of alkali metal atoms (Li, Na and K) greatly enhances the first hyperpolarizability. Among all the complexes of C24, Na3C24 shows the highest hyperpolarizability value of 2.74 × 105 au. The results of this study are a guideline for the computational designing of highly efficient and thermodynamically stable complexes for the optical and optoelectronic technologies.

Bis(4-dialkylaminophenyl)heteroarylamino donor chromophores exhibiting exceptional hyperpolarizabilities

Abstract: Organic electro-optic (EO) materials incorporated into silicon-organic hybrid and plasmonic-organic hybrid devices have enabled new records in EO modulation performance. We report a new series of nonlinear optical chromophores engineered by theory-guided design, utilizing bis(4-dialkylaminophenyl)heteroarylamino donor moieties to greatly enhance molecular hyperpolarizabilities. Hyperpolarizabilities predicted using density functional theory were validated by hyper-Rayleigh scattering measurements, showing strong prediction/experiment agreement and >2-fold advancement in static hyperpolarizability over the best prior chromophores. Electric field poled thin films of these chromophores showed significantly enhanced EO coefficients (r33) and poling efficiencies (r33/Ep) at low chromophore concentrations compared with state-of-the-art chromophores such as JRD1. The highest performing blend, containing just 10 wt% of the novel chromophore BTP7, showed a 12-fold enhancement in poling efficiency per unit concentration vs.JRD1. Our results suggest that further improvement in chromophore hyperpolarizability is feasible without unacceptable tradeoffs with optical loss or stability.

Computational Study of Structural, Molecular Orbitals, Optical and Thermodynamic Parameters of Thiophene Sulfonamide Derivatives

Abstract: Thiophene and sulfonamide derivatives serve as biologically active compounds, used for the manufacture of large numbers of new drugs. In this study, 11 selected derivatives of thiophene sulfonamide were computed for their geometric parameters, such as hyperpolarizability, chemical hardness (ƞ), electronic chemical potential (μ), electrophilicity index (ω), ionization potential (I), and electron affinity (A). In addition, FT-IR and UV-Vis spectra were also simulated through theoretical calculations. The geometrical parameters and vibrational frequencies with assignments of the vibrational spectra strongly resemble the experimentally calculated values. Besides, the frontier molecular orbitals were also determined for various intramolecular interactions that are responsible for the stability of the compounds. The isodensity surfaces of the frontier molecular orbitals (FMOs) are the same pattern in most of the compounds, but in some compounds are disturbed due to the presence of highly electronegative hetero-atoms. In this series of compounds, 3 shows the highest HOMO–LUMO energy gap and lowest hyperpolarizability, which leads to the most stable compound and less response to nonlinear optical (NLO), while 7 shows the lowest HOMO–LUMO energy gap and highest hyperpolarizability, which leads to a less stable compound and a high NLO response. All compounds have their extended three-dimensional p-electronic delocalization which plays an important role in studying NLO responses.

Oxacarbon superalkali C3X3Y3 (X = O, S and Y = Li, Na, K) clusters as excess electron compounds for remarkable static and dynamic NLO response.

Abstract: An intriguing class of excess electron oxacarbon superalkali clusters is explored for nonlinear optical response through density functional theory (DFT) methods at CAM-B3LYP/6–311++G(d,p). These superalkali clusters shows noticeable binding energies per atom (Eb) which reveals their thermodynamic stabilities (−86.45 ∼ −119.44 kcal mol−1). The obtained significant VIPs values also suggest the electronic stability of these clusters. The VIP values range from 2.06 eV to 3.42 eV. These clusters show remarkable electronic properties and their HOMO-LUMO gaps (EH-L) are significantly reduced. The lowest H-L gap of 0.96 eV is obtained for C3O3K3 while the highest H-L gap of 2.07 eV is calculated for C3S3Li3. The obtained PDOS spectra further provide evidence for the superior electronic properties of these clusters. The clusters show excellent nonlinear optical properties as revealed from remarkable values (1.6 × 106 au) of static first hyperpolarizability. The controlling factors for hyperpolarizability are also explored by using conventional two-level model. The calculated values of βo are correlated nicely with βtl. The crucial excitation energy is the key factor in controlling the first hyperpolarizability. In these excess electron clusters, the second hyperpolarizability (γo) response increases up to 4.3 × 109 au. Moreover, the calculated scattering hyperpolarizability (βHRS) values are quite significant in these clusters and the highest value of 1.3 × 106 au is calculated for C3S3K3. Additionally, these clusters also possess larger dynamic nonlinearities. The dynamic second hyperpolarizability with dc-Kerr effect increases up to 1.0 × 1011 au. The remarkable values for refractive index (n2) also suggest the excellent nonlinearity of these superalkali clusters.