First-order Hyperpolarizability Research Articles

Growth and physicochemical investigations on wide bandgap 2D polymeric amino acetic acid sulfato dilithium metal–organic framework

To design elevate high power lasers, enormous nonlinear efficiency with laser-induced damage thresholds (LIDTs) materials were required. The wide bandgap can significantly enhance the LIDTs of materials and the introduction of alkali cations would broaden the bandgap. Here we reported non-centrosymmetric alkali cation Li-based 2D polymeric amino acetic acid sulfato dilithium (ASDL) metal–organic framework. The single crystal XRD declared cell parameters of ASDL are good agreement with the reported value. Intermolecular interactions of ASDL molecule were investigated by Hirshfeld surface analysis. The presences of various functional groups have been confirmed by FTIR analysis. The energy values of highest occupied molecular orbital and lowest unoccupied molecular orbital are calculated. The experimental and theoretical bandgap values are 5.25 eV and 5.66 eV respectively. The dipole moment value is 32.9562 D and the first-order hyperpolarizability was 7.678 × 10−30 esu, which is ten times higher compared to the reference urea molecule. The nonlinear efficiency was 2.6 times and LIDT was six times higher than KDP. The title compound is thermally stable upto 270 °C assessed by thermogravimetric and differential thermal analysis. The mechanical stability of the crystal was analyzed using Vickers hardness test. The dielectric study was carried out to find the of charge distribution within the ASDL crystal. Some electric field and solid-state parameters are calculated. Thus, properties of ASDL crystals may applicable for high-power lasers generation.

Structural, spectral, optical, thermal and quantum chemical investigations on ethylenediammonium tetrachloro zinc crystal for optoelectronic applications

In this work a metal organic single crystal, ethylenediammonium tetrachloro zinc was investigated through combining the approach of experimental and computational method. A Well transparent non-centrosymmetric single crystal (ETZ) grown from the solvent evaporation method. The crystallinity and structural parameters are investigated by X-ray diffraction analysis. The protonation of amino groups is verified from vibrational analysis. The material holds 80% optical transparency in the entire visible region, and it has lower cut off wavelength of 233 nm. Frontier molecular orbital energies and their charge transfer mechanism are carefully investigated by frontier molecular orbital analysis. The inter and intramolecular interactions are explored through the NBO analysis. The intermolecular hydrogen bond n-σ* kinds of electronic transitions are more endowment in the ETZ molecule. The solid-state molecular packing arrangement and distinct atom to atom intermolecular interactions are briefly explained via Hirshfeld surface analysis. The SHG efficiency is 0.9 times that of standard KDP material. The dipole moment, polarizability and first-order hyperpolarizability are 17.878 D, −13.40554 × 10−24 esu and 1.719 × 10−30 esu respectively are calculated from density functional theory. The obtained results concluded that titled crystal can be a decent material for nonlinear optical applications.

Synthesis, physico-chemical studies, non-linear optical properties and DFT calculations of a new non-centrosymmetric compound: (3-ammoniumpyridinium)tetrachloridozincate (II)

A new non-linear optical inorganic–organic hybrid material [H3NCH2(C4H4NH)]ZnCl4 (3-ampH2)ZnCl4) has been synthesized and characterized by single-crystal X-ray diffraction, thermal analysis and UV–visible absorption. The compound crystallizes in the non-centrosymmetric orthorhombic space group Cmc21 allowing in principle non-linear optical properties. The structure consists of (3-ampH2)2+ cations disordered in two possible orientations stabilized through Coulombic and hydrogen-bond interactions with isolated ZnCl42− anions. Intermolecular weak π-π stacking interactions are also observed between pyridine rings. The thermal analysis indicate that (3-ampH2)ZnCl4 starts to melt at 585 K, together with the beginning of its decomposition. UV–visible measurements shows that the material is transparent in a wide range of UV–visible region with a lower cut off wavelength of 261.65 nm. The wide range of transparency in the UV–visible region and the high decomposition temperature make of (3-ampH2)ZnCl4 a good candidate for NLO application. Density functional theory (DFT) calculations indicate that the first-order hyperpolarizability βtot is about 23.38 times more than that of Potassium Dihydrogen Phosphate. (3-ampH2)ZnCl4 is a potential good NLO material.

DFT studies of nanomaterials designed by the functionalization of modified carboxylated carbon nanotubes with biguanide derivatives for nanomedical, nonlinear and electronic applications

Density functional theory calculations were carried out to study nanomaterials obtained by the functionalization of biguanide derivatives (metformin, buformin) at the tube end cap of modified carboxylated carbon nanotubes. Reaction and solvation energies, nonlinear and electronic properties, and quantum molecular descriptors were investigated. Our results reveal that the syntheses of these nanomaterials are possible. The solvation energies show that their dissolution in water is thermodynamically favorable. These nanomaterials are soft and strongly reactive and electrophile. The results found for the static first-order hyperpolarizabilities and the energy gaps suggest that they can be exploited for nonlinear and electronic applications.

Quantum chemical calculations, structural, spectral and nonlinear optical investigations of a novel crystal N,N ′-diphenylguanidinium 3,5-dichlorobenzoate

A proton transfer crystal, N,N′ -diphenylguanidinium 3,5-dichlorobenzoate (DPGCB), was synthesized, and single crystals were grown using the slow evaporation solution method. The crystal structure was confirmed via single crystal X-ray diffraction at 25 °C, and results show that the crystal structure was stabilized through NH…O, CH…O, and CH…Cl hydrogen bonding interactions. Hirshfeld surface analysis reveals that the van der Waals H…H (32.3%) contacts play a significant role in crystal packing. Optimized geometry demonstrates the formation of R22 (6) graph set involving NH…O hydrogen bond. Natural bond orbital (NBO) and Mulliken charge analyses also support the existence of NH…O hydrogen bonding interactions. Molecular electrostatic potential analysis proves the proton transfer mechanism in the formation of DPGCB. The UV–visible absorption spectrum proves that the absorption at 209 nm is mainly due to the π→π* transition. The time-dependent density functional theory (TD-DFT) analysis of DPGCB reveals that the electronic transition at 247 nm in acetone phase originated from the contribution of π→π* transition bands. DFT predicts that the highest unoccupied molecular orbital–lowest unoccupied molecular orbital(HOMO–LUMO) energy gap is 4.70 eV. The compound is stable up to 200 °C. It is found that the value of the first-order hyperpolarizability of DPGCB is 25times greater than that of urea. The Z-scan study shows that the third-order susceptibility of DPGCB is 1.80 × 10−6 esu, which is attributable to the strong electron cloud delocalization between two ionic moieties through hydrogen bonding association.

Non-linear optical response of meso substituted dipyrromethene boron difluoride dyes: Synthesis, photophysical, DFT and Z scan study

2-(Naphthalen-2-yl)benzo[d]thiazole meso fused dipyrromethene boron difluoride dyes are synthesised and their linear and non-linear optical properties are studied. The third order nonlinear susceptibility (χ3) value obtained from the Z-scan experiment is 11.21 × 10−13 and 13.30 × 10−13 esu. The global hybrid (B3LYP and BHHLYP) and range-separated hybrid (CAM-B3LYP) functional with the basis set 6-311++G(d,p) performed better in computing the linear and non-linear optical properties. The computed β0 value (56.36 × 10−30 esu and 48.64 × 10−30 esu for Kr-OH-BDY and Kr-OMe-BDY respectively) of both the dyes are superior to that of urea (βo = 0.371 × 10−30 esu). Thermal and reorientational study display the dominating electronic contribution to the linear polarizability (α) whereas for first-order hyperpolarizability (β), pure vibrational contributions found to be more operative in both the dyes. The geometries of the dyes were optimized by using B3LYP/6-311++ G(d,p) level of theory.

Synthesis, structural characterization and Hirshfeld surface analysis of 4-hydroxyanilinium picrate hydrate

Abstract Structure characterization of single crystals of 4-hydroxyanilinium picrate hydrate (HAPH) by single-crystal X-ray diffraction (XRD) analysis shows that the compound C12H12N4O9 crystallizes in monoclinic space group P21/c. The band gap energy is estimated and photoluminescence studies exhibit fluorescent emission. High value of first-order molecular hyperpolarizability (β) estimated by theoretical calculation reveals good nonlinear optical (NLO) character of the material and the behaviour is rationalized. Intra- and intermolecular interactions are quantified by Hirshfeld surface analysis derived from single crystal XRD data.

Influence of thiophene spacer and auxiliary acceptor on the optical properties of 4-(Diethylamino)-2-hydroxybenzaldehyde based D-π-A-π-D Colorants with N-alkyl donors: Experimental, DFT and Z-scan study

We report here design and synthesis of four new D-π-A-π-D type dyes (4 and 5) with triphenylamine/N-ethyl carbazole as fixed rotor/donor and N, N-diethyl amine as a secondary donor having dicyanovinylene as a common acceptor. The Influence of π-linker (thiophene) along with an auxillary cyano group on the nonlinear and linear optical properties is investigated. Molecules with thiophene spacer (4b and 5b) exhibit progressive variation in their absorption and emission profiles reflecting the effect of π-linker, compared to those devoid of thiophene spacer (4a and 5a). The dyes display solvent dependent emission [e.g. 4b (toluene = 689 nm) and 5b (DMSO = 795 nm)] suggesting a more polarized photo-excited state arising as a result of enhanced intramolecular charge transfer in the excited state. The solvatochromic nature is supportive of a general solvent effect, which is confirmed by solvent polarity plots (Weller’s and Rettig’s plot). The trends in the optical properties were also validated by time dependent density functional theory computations which further reveals charge transfer (from secondary donor to acceptor) for the long wavelength absorption. Dye with the highest charge transfer dipole moment relatively has the maximum two-photon absorption cross-section area (4b = 246–399 GM) which was established using theoretical two-level model. Non-linear optical properties were investigated using solvatochromic two-level model and computationally using global and range separated hybrid functionals. The dyes show high first-order hyperpolarizability (β0) in the range of 191–1162 × 10−30 e.s.u. and second-order hyperpolarizability (γ0) in the range of 491–6,704 × 10−36 e.s.u. Z-scan results show 4a (3.79 × 10−13 e.s.u.) possesses a higher value of third order nonlinear susceptibility in DMSO. Thus, the dyes can be considered as promising candidates for NLO application in material science.

Generic Classification Scheme for Second-Order Dipolar Nonlinear Optical Organometallic Complexes That Exhibit Second Harmonic Generation.

The molecular design rules of organic nonlinear optical (NLO) materials are well established, especially those pertaining to the first-order molecular hyperpolarizability, β, which governs second-harmonic generation (SHG): a phenomenon that is responsible for the frequency doubling processes in many optical applications. The availability of these rational guidelines has propelled the development of new organic SHG chromophores. Conversely, the development of organometallic SHG-active complexes has not been steered so clearly. Many reports on individual series of complexes suggest a singular correlation between their structure and SHG properties. Several reviews have catalogued such results, but these have only distinguished compounds by chemical type, while their SHG properties are described one-by-one for each chemical. We herein propose a generic classification scheme that can systematically rationalize dipolar SHG properties for all organometallic complexes. This classification method stands to provide the holistic information that is needed to generate a rational set of guidelines for the systematic molecular design of dipolar SHG-active organometallic chromophores. Our scheme shows that only a simple set of molecular design rules is required to relate the chemical structure of an organometallic complex to its second-order dipolar SHG properties. This is despite the fact that these molecular design rules are rooted in a complicated panoply of ligand- and crystal-field theory, resonance structures, intramolecular charge transfer considerations, metal oxidation states, and metal coordination attributes. While the roots of these rules can be derived at the individual chemical level, their derivation via our workflow of simple decision-making processes which connect these rules within a simple classification scheme, stands to facilitate a rational molecular design approach toward the materials discovery of organometallic complexes for SHG applications.

Novel nonlinear optical chromophores based on coumarin: Synthesis and properties studies

Novel nonlinear optical chromophores JC-TCF and JC-FTCF using tetramethyljulolidine-based coumarin as the electron-donor and tricyanofuran derivatives as the electron acceptors were designed, synthesized and investigated. The obtained chromophores own good solubility in common solvents, and good compatibility with host polymers. The chromophores also have good thermal stability, and the decomposition temperature exceed 200 °C. The UV–vis spectra indicated that JC-TCF and JC-FTCF possess good intramolecular charge transfer ability. Density functional theory (DFT) was used to study the energy gap and first-order hyperpolarizability(β). After contact poling, the guest-host polymer films of polymethyl methacrylate containing 20% wt JC-TCF and 20% wt JC-FTCF exhibited the highest electro-optic coefficient (r33) up to 40 p.m./V and 76 p.m./V respectively, and the results indicated the chromophores’ microscopic β value could be effectively translated to macroscopic EO activity, and the tetramethyljulolidine-based coumarin could be an useful candidate in the development of NLO materials.

Growth, structural, optical, thermal, laser damage threshold and theoretical investigations of organic nonlinear optical 2-aminopyridinium 4-nitrophenolate 4-nitrophenol (2AP4N) single crystal

The good quality organic 2-aminopyridinium 4-nitrophenolate 4-nitrophenol (2AP4N) single crystals with the dimension of 30 × 5 × 5 mm3 have been grown by slow evaporation solution technique (SEST) at ambient temperature within the period of 30 days using methanol as solvent. Initially, the structure of grown 2AP4N single crystal was confirmed by the single crystal X-ray diffraction (SXRD). Intermolecular interactions of 2AP4N molecule were analyzed by Hirshfeld surface analysis. The grown crystal was studied by powder X-ray diffraction (PXRD) measurement, it has sharp peaks which indicates good crystallinity. The presence of various functional groups have been confirmed by FTIR and FT-Raman spectra analysis. The optical quality (transparency) of the grown crystal was studied by UV–Vis NIR spectral analysis and it has good optical transparency in the visible and near IR regions with the cut-off wavelength of 470 nm. The energy values of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) have been calculated. The density of states (DOS) spectra was used to study the bonding, anti-bonding and non-bonding interactions. The Mulliken charge distribution was used to confirm the sign and magnitude of charge of each atom. The distribution of charge and its related properties were analyzed by the molecular electrostatic potential (MEP). The natural bonding orbital (NBO) theory was used to analyse the inter-intra molecular interactions of 2AP4N. First-order hyperpolarizability (βtotal) of 2AP4N molecule was found to be 1.071−29 esu, which is 28.6 times that of urea. Photoluminescence measurement reveals that the 2AP4N crystal has very high emission at 500 nm. The thermal stability of grown crystal was found to be 90 °C. The dislocation density was analyzed and it was confirmed to possess less defects. The laser damage threshold (LDT) energy has been measured by using Nd: YAG laser (532 nm). The efficiency of second harmonic generation (SHG) of grown 2AP4N was evaluated by Kurtz-Perry powder technique. The SHG efficiency of 2AP4N was found to be 4.5 times that of standard KDP material. The high SHG values of 2AP4N crystals may be more favorable for nonlinear optical (NLO) device applications.

Molecular Structure, Spectral, Electronic and Thermodynamic, First‐Order Hyperpolarizability, NBO and Molecular Docking Studies of Novel Acenaphthylene Pyrrolidine Derivative

AbstractThe compound 3′‐(1‐benzyl‐5‐methyl‐1H‐1,2,3‐triazole‐4‐carbonyl)‐1′‐methyl‐4′‐(3‐nitrophenyl)‐2H‐spiro[acenaphthylene‐1,2′‐pyrrolidin]‐2‐one [BTNANP] was synthesized and characterized by (FT‐IR/FT‐Raman), NMR (1H and 13C), UV‐Visible, Fluorescence and XRD studies. The molecular geometry was optimized using density functional theory (DFT/B3LYP) method with 6–311G (d,p) basis set in the ground state and compared with the experimental data. The entire vibrational assignments of wave numbers were made on the basis of potential energy distribution (PED) by VEDA 4 programme. Stability of the molecule arising from hyper conjugative interactions, charge delocalization has been analysed using the Natural Bond Orbital (NBO) analysis. It was also confirmed by the assignments of UV‐Vis spectrum. The fluorescence spectrum confirms that the title compound is a red‐light emitting material. In addition, NLO, MEP, Mulliken atomic charges, thermodynamic properties, HOMO and LUMO energy gap were theoretically predicted. The global chemical reactivity descriptors were calculated for BTNANP and used to predict their relative stability and reactivity. The antimicrobial activity of the compound was also tested against the selected bacterial and fungal pathogens. The molecular docking studies concede that the title compound may exhibit inhibition activity against topoisomerase II and lanosterol 14 α‐demethylase.

Chromophores with side isolate groups and applications in improving the poling efficiency of second non-linear optical (NLO) materials

In this paper, alkyl groups with different lengths are introduced to the two-dimensional spindle-type chromophores as the steric isolators to improve the poling efficiency and long term stability of the poled polymers for second-order nonlinear optical materials. The structure and thermal properties of alkyl functionalized chromophores are characterized by the 1H NMR, FT-IR, UV–Vis, DSC, TGA et al. The chromophores with different alkyl groups present extremely similar maximum absorbance wavelength (480 nm), which means they have very similar first-order hyperpolarizability. Guest-host polymer doped with chromophores has been prepared. Those materials display different glass transition temperatures and good thermal stability. According to the electro-optic coefficients studies and poling efficiency results, chromophores with longer alkyl side chain groups exhibit better poling efficiency and larger electro-optic coefficients. Especially for the chromophores with octyl group, the poling efficiency increases up to 3 times compared to the reference chromophore 2-(3-{2,5-Phenylmethanol-4-[4-(dimethylamino)styryl]-styryl-5,5-dimethylcyclohex-2-enylidene)malononitrile (STC), while the corresponding electro-optic coefficient of the poled polymers increases up to 4 times, indicating a significant effect of the isolate groups on improving the poling efficiency.

Experimental and theoretical insights on the dimeric cation molecule L-alanine L-alaninium chloride for nonlinear optical applications

Single crystal of L-alanine L-alaninium chloride was grown by the slow evaporation solution growth method from double distilled water as a solvent at room temperature. The crystal belongs to monoclinic system with P21 space group. The crystallinity of the material was confirmed through powder X-ray diffraction analysis. The optical excellency of the material was examined through UV–Vis–NIR studies. The melting point of the crystal is ascertained to be 202 °C and the SHG activity of the crystal was studied by Kurtz-Perry powder technique. Hirshfeld surface analysis predicts that H‧‧‧H and O‧‧‧H/H‧‧‧O interactions are predominated over the crystal packing. Theoretical studies such as geometry optimization, TD-DFT, frontier molecular orbital analysis and first-order hyperpolarizability calculations are accomplished by B3LYP (DFT) functional and 6-31G(d,p) as a basis set. The high values of melting point and first-order hyperpolarizability propose that the title crystal is a remarkable material for optoelectronic applications.

Synthesis of Novel Chromophore Based on Tricyanocyclopentenone Acceptor and Its NLO Property

Novel organic second Nonlinear optical (NLO) chromophore GZP-T based on tricyanocyclopentenone electronic acceptor group were designed and synthesized in this paper. The structure of chromophore GZP-T is characterized by mass spectrum and nuclear magnetic resonance spectroscopy. And chromophore FTC based on traditional tricyanofuran electronic acceptor was also prepared as the contrast. Their delocalized energy levels were estimated by UV–VIS spectra. Their thermal properties were studied by thermogravimetric analysis (TGA). Obviously, chromophore GZP-T showed lower delocalized energy levels and higher thermal decomposition temperature (just about 290 °C). The poled films showed the largest second-order nonlinear optical coefficients of 103.1 and 68.6 pm/V, respectively, for chromophore GZP-T and FTC. These advantages of chromophore GZP-T are attributed to the improvement of first-order hyperpolarizability and the attenuatation of intermolecular dipole interaction by the introduction of tricyanocyclopentenone electronic acceptor. And in another word, tricyanocyclopentenone electronic acceptor may be a promising way to drastically change the nonlinear optical features of the titled compounds and show a direction of designing new electron acceptor in the field of nonlinear optical materials.

Design and Synthesis of Coumarin-Imidazole Hybrid Chromophores: Solvatochromism, Acidochromism and Nonlinear Optical Properties.

A set of linear and asymmetric coumarin-imidazole hybrid compounds having a N,N-diethylamine at 7-position and imidazole at 3-position on the coumarin were synthesized. Insertion of thiophene π-spacer between coumarin and imidazole moieties (5b, 5d) leads to redshifted absorption and emission compared to 5a and 5c. All the compounds show a noticeable response to trifluoroacetic acid with a redshifted absorption and an increase in emission intensity by twofold. The ratio of ground and excited state acidity constant was calculated using Förster energy cycle, and the ratios were found to be 0.25, 0.96, 0.52 and 1.87, respectively, for 5a-5d. Due to the thiophene π-spacer, elongation of π-conjugation in 5b and 5d leads to high values of polarizability (α), first-order hyperpolarizability (β) and second-order hyperpolarizability (γ). Compound 5b exhibits a high value (895 GM) of two-photon absorption cross section (σ2PA), measured using two-level model.

Crystal growth, physical properties, and theoretical investigation on organic acentric single crystal towards efficient second-order NLO applications: Triphenylguanidine

A novel organic nonlinear optical crystal Triphenylguanidine (TPG) was grown by the solvent evaporation method. Single-crystal X-ray diffraction (XRD) studies showed that the TPG compound crystallizes in orthorhombic crystal system with Pna21 space group and the corresponding lattice planes of reflections were indexed using powder XRD studies. Fourier transform infrared and Fourier transform Raman studies revealed the presence of various functional groups in the TPG crystal. The molecular structure of TPG was also confirmed using the NMR studies. UV–Vis studies validate the aptness of TPG crystal towards nonlinear optical applications. TPG crystal shows blue emission from photoluminescence studies. The mechanical stability of the grown crystal was identified using Vickers microhardness studies. Dielectric studies were carried out as a function of frequency at room temperature. Powder SHG effective nonlinearity of TPG crystal is about 2.3 times that of standard KDP. The thermal stability of TPG crystal was investigated by the TG-DTA studies. Using Gaussian 03 program the HOMO–LUMO energy gap and first-order hyperpolarizability value for TPG molecule were calculated. The calculated first-order hyperpolarizability value of TPG molecule is 17 times that of urea.

Zintl superalkalis as building blocks of supersalts.

Alkali metal cations and halogen anions are common components of ionic salts. Recently, a new class of salts termed supersalts was reported, each of which contains a superalkali and a superhalogen that mimic an alkali metal cation and a halogen anion, respectively. Using three different functionals, namely B3LYP, wB97X, and M06-2X, we theoretically investigated a new subset of supersalts composed of Zintl-based superalkalis and inorganic superhalogens via computational modeling. The calculated dipole moment and first-order hyperpolarizability values for these supersalts indicate that they present nonlinear optical (NLO) behavior. The supersalts of Zintl superalkalis (Ca2P7, Sr2P7, Ba2P7) and superhalogens (BF4, BeF3, NO3) studied here were found to be stable. Graphical Abstract Using the first-principles calculation, a new class of supersalts by using Zintl-based superalkalis and inorganic superhalogens has been designed.

Synthesis, characterization, NLO properties, antimicrobial, CT-DNA binding and DFT modeling of Ni(II), Pd(II), Pt(II), Mo(IV) and Ru(I) complexes with NOS Schiff base

Thermal reaction of Ni(NO3)2.6H2O, PdCl2, PtCl2, Mo(CO)6 and Ru3(CO)12 with the prepared Schiff base ligand N-(2-hydroxy-1-naphthylidene)-2-aminothiophenol (H2L) resulted in the formation of the five complexes; [Ni(HL)2], 1; [Pt(H2L)Cl2], 2; [Pd2(HL)2Cl2], 3; [Mo(O2)(H2L)], 4; and [Ru(CO)3(HL)], 5. The studied compounds were characterized using different spectroscopic techniques (IR, 1H NMR, mass) elemental analyses, magnetic measurement, molar conductance, and thermal analysis. The kinetic and thermodynamic parameters of the complexes were computed. The geometry of studied 1:1 Pt(II)-, Pd(II)- Mo(IV)- and Ru(I)- complexes and 1:2 Ni(II)- complex were investigated at the B3LYP/GENECP level of theory. The geometries of the studied complexes are non-planner as indicated from the dihedral angles between central metal ion and coordinated atoms of the ligand. DFT calculations have been also carried out to calculate the global properties; hardness (η), global softness (S) and electronegativity (χ). The mean first-order hyperpolarizability (<β>) was calculated and compared with Urea as a reference material. The results of the mean first-order hyperpolarizability (<β>) showed that the ligand and the studied complexes are excellent candidates to NLO materials. Also, the interaction of the reported compounds with calf thymus DNA (CT-DNA) by different techniques revealed that the complexes could bind to CT-DNA by intercalative mode. The binding of the reported complexes to calf thymus DNA has been investigated using fluorescence and UV–Vis absorption spectra. The results indicated a much lower binding affinity of the ligand than that of the complexes. Biological activities of the compounds have been studied.

Molecular dynamics simulations for optical Kerr effect of TIP4P/2005 water in liquid and supercooled states

The optical Kerr effect (OKE) spectroscopy measured with heterodyne detection (HD) is a useful tool to provide information regarding intermolecular vibrations and structural relaxations in liquid water. Recently, the measurements of the OKE spectroscopy have been extended to the supercooled regime of water. Though the measured results can be well described by using a phenomenological model, the time-resolved OKE spectroscopy of liquid and supercooled water still need a comprehensive understanding. In this paper, we investigated the OKE nuclear response functions of this peculiar liquid and their reduced spectral densities by performing molecular dynamics simulations with the TIP4P/2005 water model. The collective polarizability of water was computed via a dipolar induction scheme, which involves the intrinsic polarizability and the first-order hyperpolarizability tensor of water molecule. Our simulation results were qualitatively consistent with the HD-OKE experimental observations for displaying that the polarizability anisotropy relaxation of supercooled water in the high-density liquid phase was fragile-like by following a stretching exponential decay with an exponent βs insensitive to temperature and the temperature dependence of the relaxation time exhibited a power-law divergence at a singular temperature Ts with a critical exponent γs. Indicated by our quantitative results, Ts was predominately determined by the structural arrest, but βs and γs were not only related to the structural relaxation but also influenced by the collective polarizability of the liquid. For all investigations, the effects due to the first-order hyperpolarizability tensor were examined.