Electronic Hyperpolarizability Research Articles

Superalkali-alkaline earthide ion pairs of δ+(AM-HMHC)-AM'δ- (AM = Li, Na and K; AM' = Be, Mg and Ca) possessing large NLO responses and excellent electronic stabilities and alkalide characteristics: a DFT study.

To identify superalkali-alkaline earthide ion pairs, it's theoretically shown that, as a novel class of excess electron superalkali compounds, both chair and boat forms of (AM-HMHC)-AM' (AM = Li, Na, and K; AM' = Be, Mg, and Ca; HMHC = 1,4,7,10,13,16-hexamethyl-1,4,7,10,13,16-hexaazacyclooctadecane) are good candidates. An attractive superalkali-alkaline earthide ion pair in δ+(AM-HMHC)-AM'δ- is firstly exhibited, which possesses alkaline-earthide characteristics and nonlinear optical response superior to similar M+(calix[4]pyrrole)M'- (M = Li, Na, and K; M' = Be, Mg, and Ca) with high stability. The electronic and vibrational second order hyperpolarizabilities and the frequency-dependent first hyperpolarizabilities of δ+(AM-HMHC)-AM'δ- are presented. For each pair of (AM-HMHC)-AM', the boat conformation is preferred to its chair one in the case of Hyper-Rayleigh scattering response (βHRS). These alkaline earthides suggest prominently high βHRS up to 2.59 × 104 a.u. (boat forms of δ+(Na-HMHC)-Caδ-). We expect that this work will inspire the preparation and characterization of these new alkaline earthides as high-performance NLO materials.

Alkaline earth metal Atom-Doped Aza-Single-Strand pyridine Helix M@SP-Helix (M = Be, Mg, and Ca) as high-performance candidates for Single-Molecular redox SPDT NLO molecular switches

Redox molecular switch is undoubted to be a good choice for the requirement of terminal molecular device. By doping an alkaline earth metal atom into the aza-single-strand pyridine helical ligand to form M@SP-Helix (M = Be, Mg, and Ca), the alkaline earth metal atom not only act the role of providing two electrons but also the type of them can significantly affect the distribution region of every two electrons on SP-Helix in the in the redox process. Our results found that the electronic and vibrational static first hyperpolarizabilities as well as the frequency-dependent first hyperpolarizability exhibit high-performance single-pole double-throw (SPDT) nonlinear optics (NLO) switching effects from its oxidized state (off form) to neutral (on form) and to reduced states (on form) as obtaining four electrons by twice. Notably, the electronic first hyperpolarizability is increased approximately 1003- and 1.34 × 106-fold from 35 to 3.51 × 104 and 4.69 × 107 au for Ca@SP-Helix. Therefore, this work can provide a theoretical reference that the alkaline earth atom doping is an important method to design high-performance NLO molecular switch material.

Density functional theory investigation of the second hyperpolarizability of the phenol blue in solution

The second electronic hyperpolarizability (γ) of the phenol blue (PB) in several solvents in a wide range of dielectric constants is investigated using the Density Functional Theory. The performance of hybrid functionals, with and without long-range correction, is addressed by comparison to Hartree-Fock calculations. Among the employed exchange–correlation functionals, the LC-BLYP functional is suitable for describing the behavior of γ in solution. LC-BLYP results indicate a clear relationship between the second hyperpolarizability and the bond length alternation (BLA) coordinate for PB in solution, in agreement with experiment.

A DFT study of the chemical reactivity properties, spectroscopy and bioactivity scores of bioactive flavonols

Density function theory calculations was used to determine the molecular parameters, electronic and chemical reactivity descriptors, spectroscopy, and non-linear optical properties, electronic dipole moment, polarizability and hyperpolarizability of fifteen (15) flavonol aglycones (no sugar moiety) from plant sources to investigate their possible application as drug candidates. Geometry optimisations was carried out using the hybrid functional and basis set: M06-2X/6-31+G(d,p). Our calculations show that all the flavonols investigated are chemically reactive. Their reactivity is greatest in water hence making them suitable drug candidates since this is the ideal medium for drug delivery. The highest negative charge on the oxygen atom of the hydroxyl and high positive charge on the H atom of C5-OH are vital for antioxidant activity. The most reactive species, from reactivity descriptor calculations, is Gossypetin. All the flavonols are active as enzyme inhibitors and moderately active as G-protein-coupled receptors, ion channel modulators and protease inhibitors. The physicochemical properties show the flavonols have good bioavailability. All the compounds agree with Lipinski’s rule of 5, signifying potential use as oral active drugs.

Density Functional Theory Studies of Structural Nonlinear Optic and Electronic Properties of Chalcone (E)-3-(Furan-2-Yl)-1-Phenylprop-2-en-1-one Molecule

In this study, the geometry optimization of Chalcone (E)-3-(Furan-2-yl)-1-Phenylprop-2-en-1-one molecule was performed at Density Functional Theory (DFT) with Becke-3-Lee-Yang-Parr (B3LYP) the hybrid functional using the 6-311++G(d,p) basis set in the gas phase. The highest occupied molecular orbital (HOMO) energy, the lowest unoccupied molecular orbital (LUMO) energy, the polarizability (α), and hyperpolarizability (β) values of title molecule were calculated DFT/B3LYP/6-311++G(d,p) method in the ground sate. The 1H and 13C NMR spectroscopy values of the molecule were calculated at DFT/B3LYP method using dıfferent basis sets such as 6-31G, 6-31+G, 6-31G(d) and 6-311+(2d,p) and the calculated 1H and 13C NMR values were compared with the experimental values in the literature. The equilibrium state (ground state) dipole moment values of the molecule were calculated as 3.33 Debye by B3LYP/6-311++ G(d,p) method. The electronic energy, dipole moment, polarizability and hyperpolarizability of the title molecule are analyzed and reported. The calculated geometric parameters (bond lengths and bond-dihedral angles) of the molecule were compared with the experimental values in the literature and they were found to be in good agreement The approximate geometry of the molecules in three dimensions was drawn in the GaussView 5.0 molecular imaging program, and all theoretical calculations were used with the Gaussian 09W package program.

Electronic second hyperpolarizability of alkaline earth metal chains end capped with −NH2 and –CN

A comparative study of the electronic structure and second hyperpolarizability has been performed by considering alkaline earth metal-bridged chains (Ben, Mgn, Can) end capped with NH2 and CN groups. For the sake of comparison of the calculated second hyperpolarizability, analogous molecular species H2N−(CC)n−CN has also been included in the present investigation. Since the metal-metal interactions are weaker, the dispersion corrected DFT methods are employed to calculate the stability of the investigated species. Similar to the conventional donor-π-acceptor system, the longitudinal component of first- and second-hyperpolarizabilities of Mg and Ca chains increases on increasing the chain length. The highest γzzzz value of Mg and Ca chains (n ​= ​7) are found to be in the order 107 au and 108 au, respectively. Both transition moment and transition energy associated with the crucial electronic transition play a significant role in the variation of second hyperpolarizability.

Vibrational and nonlinear optical properties of amine-capped push-pull polyynes by infrared and Raman spectroscopy

The vibrational properties of a series of push-pull polyynes have been studied by infrared and Raman spectroscopy. The simultaneous activation of a strong infrared and Raman mode, i.e. the collective vibration of CC bonds of the sp carbon chain, highlights the effectiveness of a polyyne bridge in promoting charge transfer between the electron donor (D) and acceptor (A) ends, thus suggesting that ad-hoc functionalized polyynes are worth being explored as building blocks of organic materials with attractive first-order optical nonlinearity. The optical, electronic, and vibrational properties of these molecules have been investigated with the support of density functional theory calculations, as well as the electronic and vibrational first hyperpolarizabilities ($\beta$). The mid-low region of the IR spectra (800-1600 cm$^{-1}$) has been analyzed in detail, searching for marker bands of the specific terminations of the different sp carbon chains thus achieving a complete vibrational characterization of sp hybridized push-pull systems.

Analyzing integrated π…π, C[sbnd]H…π and hydrogen bonding interactions in N, N-Dimethyl-4-aminopyridinium benzilate

Studying the non-covalent interactions is the central core of research for the researchers in supramolecular chemistry. In such a way, a proton transfer molecular salt, N,N-Dimethyl-4-aminopyridinium benzilate (DAPB) has been synthesized and the crystal has been grown by solvent evaporation technique. With the help of Single crystal X-ray diffraction, the supramolecular architecture of the synthesized salt has been investigated and found to be molecule is stabilized by strong NH…O and OH…O hydrogen bonds in addition to other non-covalent interactions such as CH…O, CH…π and π…π interactions. The dark spots on the Hirshfeld surfaces and the proportions on the fingerprints support the nature of various interactions found in the three-dimensional structure. The higher proportion of C…H/H…C contacts pictures out the influence of CH…π stacking interactions over the hydrogen bonding interactions. Theoretical electronic spectral analysis, ESP, NBO and hyperpolarizability analyses were calculated to understand the microscopic properties of the molecule. The presence of inter and intramolecular interactions observed for DAPB are responsible for the increased second hyperpolarisabilities at 1064 nm. Thus, the non-covalent interactions greatly influence the microscopic properties of DAPB.

Electronic structure and first hyperpolarizability of triple helicene compounds

Density functional theory (DFT) investigations on the reported triple helicene and four new substituted compounds are employed to aid in the design of nonlinear optical (NLO) materials with large first hyperpolarizability βHRS. The influences of different substituents were analyzed in terms of geometric and optoelectronic parameters such as energy gap, UV–vis absorption spectra, and electronic absorption energies. The investigation shows that the combination insertion of the donor unit and acceptor unit, especially the combination introduction of NH2 units at the R1 and R2 positions and NO2 units at the R3 and R4 positions, effectively reduces the band gap, makes the FMOs obvious spatial charge separation, broadens the absorption spectrum and produces a larger red shift, and obtains a larger βHRS value. Considering their strong NLO response, the studied compounds have the probability to be candidates used as excellent second-order NLO materials.

Applicability of DFT functionals for evaluating the first hyperpolarizability of phenol blue in solution.

The first electronic hyperpolarizability (β) of phenol blue (PB) in several solvents in a wide range of dielectric constants is investigated using the density functional theory (DFT). The reliability of various exchange-correlation functionals is assessed by a comparison to reference Møller-Plesset second-order perturbation theory (MP2) calculations. The equilibrium geometry of PB in each solvent is obtained by using the average solvent electrostatic configuration/free energy gradient method, which performs optimizations on the free energy hyper-surface by employing iteratively the sequential quantum mechanics/molecular mechanics methodology. The dependence of β on the bond length alternation (BLA) coordinate is rationalized by means of the two-level model. Within the employed exchange-correlation functionals, the LC-BLYP functional shows the best performance for describing the static and dynamic MP2 results of β, which increases as the BLA diminishes, reaching a maximum in an intermediate value of BLA. The results also illustrate the role played by the difference between the ground- and excited-state dipole moments (Δμ) in determining the hyperpolarizability behavior in solution. Particularly, in the aqueous solution case, Δμ goes to around zero when BLA is near zero, leading to an abrupt decline in the β value. The DFT results of this study, therefore, indicate a clear relationship between the first hyperpolarizability and the BLA coordinate for the PB in solution, in agreement with experiment.

Push–pull effect to improve the electronic and optical properties of [7] circulene

AbstractIn the present research, an electron donor‐acceptor (push‐pull) compound based on [7] circulene was studied using density functional theory (DFT) methods. The electron donor and acceptor units were attached to [7] circulene to improve optical properties. It was demonstrated that the band gap of [7]circulene molecule was lowered in electron donor and acceptor groups' presence, also the CN‐CIR7‐NHLi and CF3‐CIR7‐NHLi molecules have the lowest values of the band gap. It was observed that the optical properties of [7]circulene molecule was improved in the presence of electron donor and acceptor units. Between these units, the ‐CN and ‐CF3 as electron acceptors and ‐NHLi substituents as electron donor groups have higher enhancements on optical properties of circulene which is corresponding to the results obtained for energy gap values. The electric dipole moment (𝜇D) and the charge transfer, the electronic properties, polarizability (α), and first hyperpolarizability (β) values of the investigated molecules have been also computed. The results of this research may be useful in designing new materials applicable as improved photosensitizer and photodynamic therapy. All calculations and analyses are carried out by using DFT and dependent time DFT (TD‐DFT) with the B3LYP/6–311G (d,p) model in the Gaussian 09 software packages.

Nonlinear Optical Study in a Set of Dibenzylideneacetone Derivatives with Potential for Optical Frequency Conversion

The search for advanced optical materials, in particular, materials with nonlinear optical responses, has, in the last years, experienced substantial growth due to their vast applications in the photonics field. One of those applications is ultra-fast optical frequency conversion, in the optics communications field. Organic compounds have emerged as promising candidates for raw materials to develop nonlinear optical devices, such as optical converters, due to their intrinsic ultra-fast electronic responses. Also, the easy tailoring of organic molecular structures makes organic materials much more appealing than the inorganic ones. In this work, we have performed a linear and nonlinear optical characterization of a set of dibenzylideneacetone derivatives. The nonlinear optical responses investigated correspond to second- and third-order nonlinear processes, namely, first electronic molecular hyperpolarizability and two-photon absorption cross-section, respectively. The value of the first electronic molecular hyperpolarizability, up to 52 cm4·statvolt−1, could be considered a robust value when compared to the short-sized π-electron backbone length of the studied compounds. Such results suggest that these compounds exhibit the potential to be used as optical frequency converters. Quantum chemical calculations were used to predict the theoretical value of the first molecular hyperpolarizability, as well as to simulate the one- and two-photon absorption spectra for all compounds.

Novel cyclic and linearizing cyclic Pd(II) nanohoop-based cordination complexes achieving nonlinear optical activity transparency trade-off optimization

In this work, we systematically designed and comparatively analyzed the geometric structures, electronic absorption spectra, polarizabilities, first hyperpolarizability (βtot) and dynamic hyper-Rayleigh scattering response of circular Pd(II)-nanohoop complexes with 2,2′-bipyridine-embedded CPPs ligand and curved complexes decorated with alkyl tether accompanied by linear counterparts via quantum chemical calculations. Correlating results demonstrated that in comparison to conventional linear species, nanohoop ligand coordinated with metal Pd(II) can achieve remarkably improved quadratic nonlinear optical (NLO) coefficient, whereas are not accompanied by a certain degree of bathochromic shift in the absorption band. This phenomenon effectively overcomes the trade-off between good transparency and high second-order NLO response. Intriguingly, alkyl tether modified curved complexes own the largest quadratic NLO responses in our case, even the conjugation is broken by alkyl chain modified. Noteworthily, further extending phenylene backbone will not yield any positive effect on the enhancement of their βtot values for circular and linear systems once the number of phenylene reaches a certain degree, suggesting that size-dependent effect can be deemed to an effective approach to obtain the desired NLO response. Additionally, the polarizable environment has a significant influence on second-order NLO behavior, especially an accelerated trend changing from gas phase to solid phase. Overall, we hope these results can enrich the cognition into the NLO structure-function correlations based on metal nanohoop complexes and provide new avenue toward coping with trade-off between good transparency and high NLO performance.

Electronic and vibrational hyperpolarizabilities of alkali‐ and alkaline‐earth‐doped boron nitride nanotubes

AbstractThis work reports the results of the vibrational corrections and frequency dependence to the first hyperpolarizabilities of the alkali‐ and alkaline‐earth‐doped boron nitride nanotubes. The electronic contributions were computed by means of the density functional theory with the M06‐2X functional, and the vibrational corrections were calculated using the perturbation theoretical method and the field‐induced coordinates methodology. The results for the electronic contribution show that such materials exhibit large first hyperpolarizabilities and electride characteristic. We also show that the distribution of the excess electron, which originates from the doping atoms, plays an important role in the large electronic hyperpolarizabilities (βel). Moreover, our findings strongly indicate that the effect of vibrations on the hyperpolarizabilities can be quite important and can even be much larger than the electronic counterpart.

Chalcone-based molecules: Experimental and theoretical studies on the two-photon absorption and molecular first hyperpolarizability.

Five chalcone-based molecules denominated by C-3 ((E)-1-(4-methoxyphenyl)-3-phenylprop-2-en-1-one), C-4 ((E)-1,3-bis(4-methoxyphenyl)prop-2-en-1-one), C-5 ((E)-1-(benzo[d][1,3]dioxol-5-yl)-3-(4-methoxyphenyl)prop-2-en-1-one), C-6 ((E)-3-(naphthalen-1-yl)-1-phenylprop-2-en-1-one) and C-7 ((E)-1-(4-methoxyphenyl)-3-(naphthalen-1-yl)prop-2-en-1-one) were synthesized by Claisen-Schmidt reaction in solution of NaOH in water/ethanol 2:1. The aldehydes used were benzaldehyde, anisaldehyde, and β-naphthaldehyde, while the used ketones were acetophenone, p-methoxyacetophenone, and 3,4-methylenedioxyacetophenone. Z-scan and hyper-Rayleigh scattering techniques were used to study the nonlinear optical properties of these compounds in dichloromethane medium. By using Z-scan technique with femtosecond pulses, two-photon absorption cross-sections (σTPA) were determined, while the first molecular electronic hyperpolarizabilities (βHRS) were evaluated by the hyper-Rayleigh scattering technique, with picosecond pulses. From the recorded two-photon absorption spectra, it was identified that compound C-7 presented the highest σTPA, regarding the HOMO-LUMO transition, with a value of 40 GM, while C-6 achieved the lowest value for the same transition with 13 GM. Concerning the values of the first molecular hyperpolarizability, compound C-4 presented the highest value, 38 × 10-30 cm4 statvolt-1, while C-3 presented the lowest βHRS value of about 16 × 10-30 cm4 statvolt-1. Time-dependent density functional theory calculations were used to simulate the one- and two-photon absorption spectra, as well to predict the theoretical value of βHRS in dichloromethane and vacuum medium.

Impact of deuteration on the ultrafast nonlinear optical response of toluene and nitrobenzene.

Nonlinear pulse propagation inside highly nonlinear media requires accurate knowledge on the temporal response function of the materials used particular in the case of liquids. Here we study the impact of deuteration on the ultrafast dynamics of toluene and nitrobenzene via all optical Kerr gating, showing substantially different electronic and molecular contributions, which was quantified by fitting a multichannel decay model to the data points. Specifically we found that deuteration imposes the time-integrated nonlinearities to reduce particular for toluene which could be caused by both reduced electronic hyperpolarizabilities as well as weaker intermolecular interactions. The results achieved reveal that deuterated organic solvents represent promising materials for infrared photonics since they offer extended infrared transmission compared to their non-deuterated counterparts while maintained strong nonlinear responses.

Theoretical exploration of second-order nonlinear optical properties of mono- and bimetallic Pt(II) dithienylcyclopentene complexes: Ligands and photoisomerization effect

On the basis of great diverse applications of nonlinear optical (NLO) materials, organometallic complexes have attracted considerable attention. In this paper, we present a detailed investigation on a series of Pt(II) dithienylcyclopentene(DTE)-based complexes via density functional theory method with the aim of evaluating their structures, electronic absorption spectra and first hyperpolarizabilities. The calculations demonstrate that the first hyperpolarizabilities can be enhanced by the introduction of quinolone into the complexes because of the enlarged spatial separation of electron density. However, Pt(II) complexes containing perfluorocyclopentene ring exhibit decreasing NLO response attributed to lower amount of charge transferred and short effective CT distance. The static first hyperpolarizabilities (βtot) of monometallic Pt(II) complexes are larger than those of bimetallic Pt(II) complexes due to correlative mixed charge-transfer patterns. More importantly, the closed-ring (1c) complex comprising DTE unit exhibits the largest βtot value approaching 144 × 10−30 esu, with the contrast over five times compared to corresponding open-ring due to the better π-conjugated delocalization and smaller HOMO and LUMO energy gap. In general, we envision our work will be beneficial for further rational design of DTE-containing Pt(II) complexes as high performance NLO materials.

Optical and nonlinear optical properties of Ln(Tp)2, where Ln = La,…,Lu and Tp = tris(pyrazolyl)borate: a DFT+TD-DFT study

DFT calculations of electronic, structural, thermodynamic properties, magnetic moment, static and dynamic polarizability and hyperpolarizability of Ln(Tp)2 (Ln = rare earths, Tp = ring-unsubstituted tris(pyrazolyl)borate) complexes.

First molecular electronic hyperpolarizability of series of π-conjugated oxazole dyes in solution: an experimental and theoretical study.

In this work, we report the experimental and theoretical first molecular electronic hyperpolarizability (βHRS) of eleven π-conjugated oxazoles compounds in toluene medium. The Hyper-Rayleigh Scattering (HRS) technique allowed the determination of the experimental dynamic βHRS values, by exciting the compounds with a picosecond pulse trains from a Q-switched and mode-locked Nd:YAG laser tuned at 1064 nm. Theoretical predictions based on time-dependent density functional theory level using the Gaussian 09 program package were performed with three different functionals (B3LYP, CAM-B3LYP, and M06-2X), to calculate both static and dynamic theoretical βHRS values. Good accordance was found between the experimental and theoretical values, in particular for the CAM-B3LYP and M06-2X functionals.

Electronic and Vibrational Hyperpolarizabilities of Lithium Substituted (Aza)benzenes and (Aza)naphthalenes

In this article we report results for the electronic and vibrational hyperpolarizabilities of ten molecules: Li@benzene, Li@pyridine, Li@pyrimidine, and Li@pyrazine; Li@naphthalene, Li@quinoline, Li@isoquinoline, Li@cinnolin, Li@quinazoline, and Li@quinoxaline. An electron correlation study shows that second-order many-body perturbation theory and density functional theory with CAM-B3LYP and M05-2X functionals give results for the electronic hyperpolarizabilities in good agreement with coupled cluster with single and doubles reference values. Static and dynamic vibrational corrections were computed through the perturbation theoretical method of Bishop and Kirtman and using a variational approach. In general, we obtained notable discrepancies between the results obtained by the two methods for the pure vibrational corrections because of the deficiency of the perturbation method to properly treat low-frequency normal modes present in the investigated systems. However, both methods give results similar to the zero-point vibrational average corrections.