The effect of complex formation on the static and frequency-dependent nonlinear optical properties: A combined experimental and theoretical investigation.

A novel mixed ligand Mn(II) complex of 6-Bromopyridine-2-carboxylic acid (6Brpca) and 4,4'-dimethyl-2,2'-dipyridyl has been prepared and structurally characterized using single-crystal X-ray diffraction. The spectroscopic properties were also analyzed by using FT-IR and UV-Vis spectral techniques. The coordination complexes having transition metal ions are known to have promising optical nonlinearity behavior. Therefore, B3LYP level density functional theory was used to investigate first- and second-order hyperpolarizabilities (ß and γ) and provide a deep understanding of the relation between the structure and NLO properties. The calculations of frequency-dependent α, ß, and γ at frequencies of ω = 0.0856252 and 0.0428126 au. for 6Brpca and Dmdpy ligands as well as Mn(II) complex have been also carried out using B3LYP/LanL2DZ level. Especially second harmonic generation (SHG) first and second hyperpolarizabilities (ß(-2ω;ω,ω) and γ (-2ω;ω,ω,0)) parameters for Mn(II) complex have been calculated as 11448 × 10-30 and 680035 × 10-36 esu, respectively. It has been determined that there is a tremendous increase in ß and γ parameters when 6Brpca and Dmdpy ligands coordinate to the high spin multiplicity Mn(II) ion. Theoretical calculations revealed that the large first- and second-order hyperpolarizabilities are caused by strong intramolecular charge transfer between the transition metal and the coordinated ligands. These results indicate that the the organometallic complex under investigation is valuable candidate for optoelectronic and photonic applications.

In vitro α-glucosidase, docking and density functional theory studies on novel azide metal complexes.

Aim: The goal of this study is to synthesize new metal complexes containing N-methyl-1-(pyridin-2-yl)methanimine and azide ligands as α-glucosidase inhibitors for Type 2 diabetes. Materials & methods: The target complexes (12-16) were synthesized by reacting N-methyl-1-(pyridin-2-yl)methanimine (L1) with sodium azide in the presence of corresponding metal salts. The investigation of target protein interactions, vibrational, electronic and nonlinear optical properties for these complexes was performed by molecular docking and density functional theory studies. Results: Among these complexes, complex 13 (IC50 = 0.2802 ± 0.62 µM) containing Hg ion showed the highest α-glucosidase inhibitory property. On the other hand, significant results were detected for complexes containing Cu and Ag ions. Conclusion: Complex 13 may be an alternate anti-diabetic inhibitor according to in vitro/docking results.

[Box: see text].

Static/dynamic first and second order hyperpolarizabilities, optimized structures, IR, UV-Vis, 1H and 13C NMR spectra for effective charge transfer compounds: A DFT study.

The effective charge transfer compounds, 4-N,N-dimethylamino-4'-N'-methyl-stilbazolium m-trifluoromethylbenzene-sulfonate (DSMFS) and 4-N,N-dimethylamino-4'-N'-methyl-stilbazolium p-trifluoromethylbenzene-sulfonate (DSPFS), were simulated in terms of geometric structure, IR, UV-Vis, 1H NMR and 13C NMR spectra. UV-vis spectra for both molecules give two peaks at 290 and 436 nm assigned as n-π* and π-π* transitions. The HOMO-LUMO energy gap for DSMFS (2.8174 eV) was calculated as lower than that of DSPFS (4.6649 eV). The detailed frontier molecular orbital analysis also indicated that the intra- and inter-molecular charge transfers occur in DSMFS and DSPFS. The static and dynamic (ω = 532 and 1064 nm) nonlinear optical properties were also investigated by using B3LYP/6-311++G(d,p) level. Static first and second order hyperpolarizabilities (ß and γ) of DSMFS were obtained 1.5726 × 10-28 esu and 271.63 × 10-36 esu, and those for DSPFS were obtained as 1.5528 × 10-28 esu and 303.31 × 10-36 esu. The dynamic ß and γ were obtained as higher than the static corresponding parameters. However, the increasing wavelength in dynamic NLO calculations led to a decrease in ß and γ parameters.

First and second order hyperpolarizabilities of flavonol derivatives: A density functional theory study.

In this study, seventeen flavonol derivatives (1-17) were evaluated with regard to their first- and second-order hyperpolarizability parameters. For this purpose, the molecular geometries of 1-17 were optimized by using B3LYP/6-311++G(d,p) level. Spectroscopic characterizations for 1-17 were executed through the calculations of IR, UV-vis, 1H NMR and 13C NMR spectra. The quantum chemical parameters such as electronegativity, chemical hardness, chemical potential and electrophilicity indexes were obtained by using the frontier molecular orbital (FMO) energies. The potential energy distribution (PED) analysis was used to provide a detailed assignment of vibrational bands. Important contributions to electronic absorption bands from FMOs were also evaluated. The distribution of FMOs to the whole molecule was investigated to determine the nature of electronic charge transfers in 1-17. The static and dynamic first- and second-order hyperpolarizability parameters for 1-17 were calculated by using B3LYP/6-311++G(d,p) level. The static ß and γ were calculated at the ranges of 9.8279-0.0303 × 10-29 esu and 80.200-268.40 × 10-36 esu. The dynamic ß and γ (ω = 532 nm) were also obtained in the field of 1.0440-71.786 × 10-29 esu and 306.20-3607.00 × 10-36 esu. This wide range of ß and γ values indicate that flavonol derivatives with rational substitution may be promising candidates for first- and second-order NLO applications.

Concentration effects on optical properties, DFT, crystal characterization and α-glucosidase activity studies: Novel Zn(II) complex.

A novel Zn(II) complex of 6-ClpicH and picH was synthesized and its structure was determined by XRD technique. The detailed experimental optical susceptibility and band gap, refractive index, linear polarizability, optical and electrical conductivity parameters in various concentrations were investigated by means of the UV-Vis spectroscopic data. The optical band gap, refractive index (n), linear optical susceptibility (χ(1)), third-order nonlinear optical susceptibility (χ(3)), second- and third-order nonlinear optical (ß and γ) parameters were examined by using DFT/M06-L and ωB97XD/6-311++G(d,p) levels. The IC50 value of Zn(II) complex against α-glucosidase was also obtained at 0.44 mM. The experimental band gap of the Zn(II) complex at 13, 33, 44 and 94 µM concentrations in ethanol were found to be 4.38, 4.37, 4.35 and 4.28 eV, respectively. The third-order NLO susceptibility χ(3) parameter at 94 µM concentration corresponding to the photon energies of 4.6 and 5.7 eV in the UV-Vis region were observed at 206.6 × 10-13 and 294.3 × 10-13 esu, respectively. Besides, the theoretical χ(3) values were obtained at 50.58 × 10-13 and 20.37 × 10-13 esu by using M06-L level. These results indicate that Zn(II) complex could be an effective third-order NLO candidate material. In brief, the detailed theoretical and experimental structural, spectral and optical properties of the Zn(II) complex were presented comparatively.

Novel metal complexes containing 6-methylpyridine-2-carboxylic acid as potent α-glucosidase inhibitor: synthesis, crystal structures, DFT calculations, and molecular docking.

The World Health Organization (WHO) report shows that diabetes mellitus (DM) will be one of the ten deadly diseases in the near future. The best way to prevent DM is to decrease blood glucose levels and keep under control; therefore, it is important to design and synthesize the effective inhibitors that can be used in the treatment of DM disease. In this respect, a series of ten metal complexes containing 6-methylpyridine-2-carboxylic acid {[Cr(6-mpa)2(H2O)2]·H2O·NO3, (1), [Mn(6-mpa)2(H2O)2], (2), [Ni(6-mpa)2(H2O)2]·2H2O, (3), [Hg(6-mpa)2(H2O)], (4), [Cu(6-mpa)2(Py)], (5), [Cu(6-mpa)2(H2O)]·H2O, (6), [Zn(6-mpa)2(H2O)]·H2O, (7), [Fe(6-mpa)3], (8), [Cd(6-mpa)2(H2O)2]·2H2O, (9), and [Co(6-mpa)2(H2O)2]·2H2O, (10)} were synthesized as α-glucosidase inhibitors. We found that the IC50 values of the synthesized complexes ranged from 0.247 ± 0.10 to > 600 µM against α-glucosidase. The spectral analyses for these complexes characterized by XRD and LC-MS/MS were also carried out by FT-IR and UV-Vis spectra. Additionally, the DFT/HSEh1PBE/6-311G(d,p)/LanL2DZ level was applied to obtain optimal molecular geometries and spectral behaviors as well as significant contributions to the electronic transitions for the complexes. The molecular docking study was also performed to display interactions between the target protein (the template structure Saccharomyces cerevisiae isomaltase) and the synthesized complexes (1-10).

A novel series of mixed-ligand M(II) complexes containing 2,2'-bipyridyl as potent α-glucosidase inhibitor: synthesis, crystal structure, DFT calculations, and molecular docking.

Diabetes mellitus (DM) is a common degenerative disease and characterized by high blood glucose levels. Since the effective antidiabetic treatments attempt to decrease blood glucose levels, keeping glucose under control is very important. Recent studies have demonstrated that α-glucosidase inhibitor improves postprandial hyperglycemia and then reduces the risk of developing type 2 diabetes in patients. Therefore, the design and synthesis of high affinity glucosidase inhibitors are of great importance. In this regard, novel series of mixed-ligand M(II) complexes containing 2,2'-bipyridyl {[Hg(6-mpa)2(bpy)(OAc)]·2H2O, (1), [Co(6-mpa)2(bpy)2], (2), [Cu(6-mpa)(bpy)(NO3)]·3H2O, (3), [Mn(6-mpa)(bpy)(H2O)2], (4), [Ni(6-mpa)(bpy)(H2O)2]·H2O, (5), [Fe(6-mpa)(bpy)(H2O)2]·2H2O, (6), [Fe(3-mpa)(bpy)(H2O)2]·H2O, (7)} were synthesized as potential α-glucosidase inhibitors. Their effects on α-glucosidase activity were evaluated. All synthesized complexes displayed α-glucosidase inhibitory activity with IC50 values ranging from 0.184 ± 0.015 to > 600 µM. The experimental spectral analyses were carried out using FT-IR and UV-Vis spectroscopic techniques for these complexes characterized by XRD and LC-MS/MS. Moreover, the calculations at density functional theory approximation were used to obtain optimal molecular geometries, vibrational wavenumbers, electronic spectral behaviors, and major contributions to the electronic transitions for the complexes 1-7. Finally, to display interactions between the synthesized complexes and target protein (the template structure Saccharomyces cerevisiae isomaltase), the molecular docking study was carried out.

Synthesis, antioxidant activity and SAR study of novel spiro-isatin-based Schiff bases.

A new series of 21 Schiff bases of spiro-isatin was synthesized, and their DPPH, CUPRAC and ABTS cation radical scavenging abilities were investigated for antioxidant activity. The results showed that all the synthesized compounds exhibited antioxidant activity for each assay. 5̍-(2,3-Dihydroxybenzylideneamino)spiro[[1,3] dioxolane-2,3̍-indoline]-2̍-on (5c) (IC50 = 4.49 µM, for DPPH; IC50 = 0.39 µM, for ABTS.+; and A0.50 = 0.42 µM, for CUPRAC) showed significantly better ABTS, CUPRAC and DPPH radical scavenging ability than quercetin (IC50 = 8.69 µM, for DPPH; IC50 = 15.49 µM, for ABTS.+; and A0.50 = 18.47 µM, for CUPRAC), which is used as a standard. SAR study showed that the synthesized compounds had higher ABTS.+ activity than DPPH and CUPRAC activities. Moreover, the compounds (5c and 5d), containing two hydroxyl groups, exhibited the highest antioxidant activities for all assays. Quantum chemical calculations were also carried out to support SAR results.

Copper(II) complex with 6-methylpyridine-2-carboxyclic acid: Experimental and computational study on the XRD, FT-IR and UV-Vis spectra, refractive index, band gap and NLO parameters.

Crystal structure of the synthesized copper(II) complex with 6-methylpyridine-2-carboxylic acid, [Cu(6-Mepic)2·H2O]·H2O, was determined by XRD, FT-IR and UV-Vis spectroscopic techniques. Furthermore, the geometry optimization, harmonic vibration frequencies for the Cu(II) complex were carried out by using Density Functional Theory calculations with HSEh1PBE/6-311G(d,p)/LanL2DZ level. Electronic absorption wavelengths were obtained by using TD-DFT/HSEh1PBE/6-311G(d,p)/LanL2DZ level with CPCM model and major contributions were determined via Swizard/Chemissian program. Additionally, the refractive index, linear optical (LO) and non-nonlinear optical (NLO) parameters of the Cu(II) complex were calculated at HSEh1PBE/6-311G(d,p) level. The experimental and computed small energy gap shows the charge transfer in the Cu(II) complex. Finally, the hyperconjugative interactions and intramolecular charge transfer (ICT) were studied by performing of natural bond orbital (NBO) analysis.

Synthesis, structural and spectroscopic evaluations and nonlinear optical properties of 3,5-bis(4-methoxyphenyl)-4,5-dihydro-1H-pyrazole-1-carbothioic O-acid.

In this study, we report a combined experimental and theoretical study on 3,5-bis(4-methoxyphenyl)-4,5-dihydro-1H-pyrazole-1-carbothioic O-acid (C18H18N2O3S) molecule. The compound crystallizes in the trigonal space group R-3 with a=b=27.7151(12) Å, c=12.4866(6) Å, α=ß=90.0°, γ=120.0° and Z=18. The crystal packing is stabilized by O-H⋯O and O-H⋯S intermolecular hydrogen bonds. These hydrogen bond interactions are also proved by NBO analysis. A detailed spectroscopic investigation is performed by the application of FT-IR and FT-NMR in addition to the theoretical approaches. Small energy gap between the frontier molecular orbitals is responsible for the nonlinear optical activity of the title molecule.

The effects of electronegative substituent atoms on structural, vibrational, electronic and NLO properties of some 4-nitrostilbene derivates.

Organic compounds which have one or more aromatic systems in conjugated positions show charge transfer interactions which are responsible for the non-linear properties of the compounds. A conjugated π electron system enables a pathway for the entire length of conjugation under the perturbation of an external electric field. When electron donating and withdrawing moieties are located at terminal position of conjugated backbone, nonlinear optical (NLO) properties have been increased significantly which involve the correlated and high delocalized π electron states. Recently synthesized organic complexes, 1-(4-fluorostyryl)-4-nitrostilbene (1), 4-Chloro 4-nitrostilbene (2), 4-Bromo 4-nitrostilbene (3) and 4-Iodo 4-nitrostilbene (4), were simulated using density functional theory (DFT). Based on the optimized geometries, spectroscopic and NLO properties of these complexes were discussed as compared with each other.

Conformational, spectroscopic and nonlinear optical properties of biologically active N,N-dimethyltryptamine molecule: a theoretical study.

The effective psychoactive properties of N,N-dimethyltryptamine (DMT) known as the near-death molecule have encouraged the imagination of many research disciplines for several decades. Although there is no theoretical study, a number of paper composed by experimental techniques have been reported for DMT molecule. In this study, the molecular modeling of DMT was carried out using B3LYP and HSEh1PBE levels of density functional theory (DFT). Our calculations showed that the energy gap between HOMO and LUMO is low, demonstrating that DMT is a biologically active molecule. Large hyperconjugation interaction energies imply that molecular charge transfer occurs in DMT. Moreover, NLO analysis indicates that DMT can be used an effective NLO material.

Effects of donor-acceptor groups on the structural and electronic properties of 4-(methoxymethyl)-6-methyl-5-nitro-2-oxo-1,2-dihydropyridine-3-carbonitrile.

Quantum chemical calculations on the geometric parameters, harmonic vibrational wavenumbers and 1H and 13C nuclear magnetic resonance (NMR) chemical shifts values of 4-(methoxymethyl)-6-methyl-5-nitro-2-oxo-1,2-dihydropyridine-3-carbonitrile [C9H9N3O4] molecule in ground state were performed using the ab initio HF and density functional theory (DFT/B3LYP) methods with 6-311++G(d,p) basis set. The results of optimized molecular structure were presented and compared with X-ray diffraction results. The theoretical vibrational frequencies and 1H and 13C NMR chemical shifts values were compared with experimental values of the investigated molecule. The observed and calculated values were found to be in good agreement. Since the title compound contains different electron-donor and -acceptor groups as well as lone pair electrons, and multiple bonds, the effects of these groups on the structural and electronic properties are found out. In addition, conformational, natural bond orbital (NBO), nonlinear optical (NLO) analysis, frontier molecular orbital energies, molecular surfaces, Mulliken charges and atomic polar tensor based charges were investigated using HF and DFT methods.

Quantum chemical calculations on the geometrical, conformational, spectroscopic and nonlinear optical parameters of 5-(2-Chloroethyl)-2,4-dichloro-6-methylpyrimidine.

The optimized geometry, (1)H and (13)C NMR chemical shifts, conformational and natural bond orbital (NBO) analyses, thermodynamic parameters, molecular surfaces, Mulliken, NBO and APT charges for 5-(2-Chloroethyl)-2,4-dichloro-6-methylpyrimidine [C7H7Cl3N2] were investigated by the ab initio HF and density functional theory (DFT/B3LYP) methods with 6-311++G(d,p) basis set. The calculated structural parameters (bond lengths, bond angles and dihedral angles) and (1)H and (13)C NMR chemical shifts values are compared with experimental values of the investigated compound. The observed and the calculated values are found to be in good agreement. The energies of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) were calculated, and the obtained energies displayed that charge transfer occurs in 5-(2-Chloroethyl)-2,4-dichloro-6-methylpyrimidine compound. In addition, the linear polarizability (α) and the first order hyperpolarizability (ß) values of the investigated compound have been computed by using HF and DFT methods.

Quantum chemical characterization of N-(2-hydroxybenzylidene)acetohydrazide (HBAH): a detailed vibrational and NLO analysis.

The molecular modeling of N-(2-hydroxybenzylidene)acetohydrazide (HBAH) was carried out using B3LYP, CAMB3LYP and PBE1PBE levels of density functional theory (DFT). The molecular structure of HBAH was solved by means of IR, NMR and UV-vis spectroscopies. In order to find the stable conformers, conformational analysis was performed based on B3LYP level. A detailed vibrational analysis was made on the basis of potential energy distribution (PED). HOMO and LUMO energies were calculated, and the obtained energies displayed that charge transfer occurs in HBAH. NLO analysis indicated that HBAH can be used as an effective NLO material. NBO analysis also proved that charge transfer, conjugative interactions and intramolecular hydrogen bonding interactions occur through HBAH. Additionally, major contributions from molecular orbitals to the electronic transitions were investigated theoretically.

An experimental and theoretical study on the novel (Z)-1-((naphthalen-2-ylamino)methylene)naphthalen-2(1H)-one crystal.

A novel compound has been synthesized, and its structure has been characterized by IR, UV-vis, NMR and X-ray single-crystal determination techniques. The title compound crystallizes in the orthorhombic space group P212121 with a=6.2120(4)Å, b=10.8242(7)Å, c=22.3857(15)Å and Z=4. The crystal structure has intramolecular N-H···O hydrogen bond and C-H···Cg interaction. These hydrogen bonds and interactions are effective in crystal packing. The optimum molecular geometry, conformational analysis, normal mode wavenumbers, infrared and Raman intensities, corresponding vibrational assignments, chemical shift assignments, and thermo-dynamical parameters have been investigated with the help of Density Functional Theory (DFT). Detailed vibrational assignments have been made on the basis of potential energy distribution (PED). In order to understand the electronic transitions of the compound, time dependent DFT (TD-DFT) calculations were performed in gas phase. Also, the dipole moment, linear polarizabilities, anisotropy and first hyperpolarizabilities values have been computed.

The synthesis, characterization and theoretical study on nicotinic acid [1-(2,3-dihydroxyphenyl)methylidene]hydrazide.

In this study, we reported a combined experimental and theoretical study on nicotinic acid [1-(2,3-dihydroxyphenyl)methylidene]hydrazide (C13H11N3O3) molecule. The title compound was prepared and characterized by 1H and 13C FT-NMR, FT-IR and single-crystal X-ray diffraction. The compound crystallizes in the monoclinic space group P21/c with a=6.2681(3) Å, b=16.5309(7) Å, c=12.4197(6) Å, α=90°, ß=111.603(4)°, γ=90° and Z=4. In addition, the molecular geometry, vibrational frequencies, gauge including atomic orbital (GIAO), continuous set of gauge transformations (CSGT), individual gauges for atoms in molecules (IGAIM) 1H and 13C NMR chemical shift values, natural bond orbital (NBO), nonlinear optical (NLO) and HOMO-LUMO analyses, molecular electrostatic potentials (MEPs) and thermodynamic properties of the title compound in the ground state were investigated by using Hartree-Fock (HF) and density functional theory (DFT/B3LYP) methods with 6-311++G(d,p). Besides, the hardness and electronegativity parameters were obtained from HOMO and LUMO energies. Obtained results indicate that there is a good agreement between the experimental and theoretical data.

1-Pentamethylbenzyl-3-(n)buthylbenzimidazolesilver(I)bromide complex: synthesis, characterization and DFT calculations.

A novel NHC complex of silver(I) ion, 1-pentamethylbenzyl-3-(n)buthylbenzimidazolesilver(I)bromide, was prepared and fully characterized by single crystal X-ray structure determination. FT-IR, NMR and UV-vis spectroscopies were employed to investigate the electronic transition behaviors of the complex. Additionally, the molecular geometry, vibrational frequencies, gauge including atomic orbital (GIAO) (1)H and (13)C chemical shift and electronic transition values of silver(I) complex were calculated by using density functional theory levels (B3LYP and PBE1PBE) with LANL2DZ basis set. Also, the vibrational frequencies were supported on the basis of the potential energy distribution (PED) analysis calculated for PBE1PBE level. We were also investigated total static dipole moment (µ), the mean polarizability (〈α〉), the anisotropy of the polarizability (Δα), the mean first-order hyperpolarizability (〈ß〉) of the title complex. Natural bond orbital (NBO) analysis was performed to determine the presence of hyperconjugative interactions, and charge distributions.