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

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 (β and γ) and provide a deep understanding of the relation between the structure and NLO properties. The calculations of frequency-dependent α, β, 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 (β(-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 β 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.

Regulating Chlorine and Hydrogen Atom Transfer for Selective Photoelectrochemical C─C Coupling by Cu-coordination Effect at Semiconductor/Electrolyte Interfaces

Semiconductor-based photoelectrochemical (PEC) organic transformations usually show radical characteristics, in which the reaction selectivity is often difficult to precisely control due to the nonselectivity of radicals. Accordingly, several simple organic reactions (e.g., oxidations of alcohols, aldehydes, and other small molecules) have been widely studied, while more complicated processes like C─C coupling remain challenging. Herein, a synergistic heterogeneous/homogeneous PEC strategy is developed to achieve a controllable radical-induced C─C coupling reaction mediated by the copper-coordination effect at the semiconductor/electrolyte interfaces, which additionally exerts a significant impact on the product regioselectivity. Through experimental studies and theoretical simulations, this study reveals that the copper-chloride complex effectively regulates the formation of chloride radicals, a typical hydrogen atom transfer agent, on semiconductor surfaces and stabilizes the heterogeneous interfaces by suppressing the radical-induced surface passivation. Taking the Minisci reaction (the coupling between 2-phenylquinoline and cyclohexane) as a model, the yield of the target C─C coupling product reaches up to 90% on TiO2 photoanodes with a selectivity of 95% and long-term stability over 100 h. Moreover, such a strategy exhibits a broad scope and can be used for the functionalization of various heteroaromatic hydrocarbons.

Spectroscopic Characterization, Cyclic Voltammetry, Biological Investigations, MOE, and Gaussian Calculations of VO(II), Cu(II), and Cd(II) Heteroleptic Complexes

A novel hydrazone ligand (o-H₂BMP) N-(benzo[d]thiazol-2-yl)-3-oxo-3-(2-(1-(pyridin-2-yl)ethylidene)hydrazinyl)propanamide alongside its Cu(II), Cd(II), and VO(II) complexes were prepared and structurally characterized via various spectroscopic analyses (Fourier transform infrared spectroscopy, UV-visible spectroscopy, ¹H/¹³C NMR spectroscopy, liquid chromatography coupled to mass spectrometry, and electron paramagnetic resonance spectroscopy) as well as by elemental analysis, thermal gravimetry analysis/differential thermal analysis, and magnetic moment measurements. Powder X-ray diffraction analysis was also performed for the free ligand and its metal complexes to determine the crystallographic structures and atomic spacing. It also provided information on unit cell dimensions and the average crystallite size. Furthermore, geometric optimization and computational studies were carried out by applying Gaussian (09) software based on density-functional theory coupled with the B3LYP functional and LANL2DZ/6-31+G(d,p) mixed basis set to evaluate some distinct features such as molecular electrostatic potential, E _HOMO, and E _LUMO. Moreover, electrochemical measurements were performed for Cu(II) in the absence/presence of the chelating agent to predict the effect of complexation interaction in the solution state study. As part of the biological examination, antioxidant and antimicrobial assays were conducted for each compound individually, in addition to cytotoxicity evaluations via MTT assays for all isolated complexes compared to the corresponding metal salts. The MOE (molecular operating environment) approach was also applied to model the interface between the isolated compounds and proteins that were expressed in breast cancer at the atomic level.

Quantum computational investigation into structural, spectroscopic, topological and electronic properties of L-histidinium-L-tartrate hemihydrate: Nonlinear optical organic single crystal

For the first time, a systematic investigation of optimization in the geometrical, vibrational, natural bonding orbital (NBO), electronic, linear and nonlinear optical properties, and Hirshfeld surface analysis for the L-histidinium-l-tartrate hemihydrate (HT) crystal is reported by employing the density functional theory (DFT). The geometrical parameters and vibrational frequencies obtained from the B3LYP/6-311++G(d,p) level of theory are in good agreement with the experimental values. The presence of strong hydrogen bonding interactions in the molecule causes an intense absorption peak in the infrared spectrum below 2000 cm^-1. Quantum Theory of Atoms in Molecules (QTAIM) has been used to evaluate the topology of the electron density of a particular molecule to identify the critical points of the system using Multiwfn 3.8. These studies included ELF, LOL, and RDG studies. A time-dependent DFT approach is employed to obtain the excitation energies, oscillator strengths, and UV-Vis spectra for different solvents, such as methanol, ethanol, and water. The NBO analysis of the chosen compound, HT, is performed in terms of atom hybridization and electronic structure. The HOMO-LUMO energies and other associated electronic parameters are also computed. The nucleophilic sites are identified from MEP and Fukui functions analysis. The electrostatic potential and total density of states spectra of HT are discussed in detail. The theoretically obtained polarizability and first order hyperpolarizability values confirm that the grown material HT has NLO efficiency 15.771 times that of urea, and is proposed to be an exceptional nonlinear optical material. In addition, Hirshfeld surface analysis is performed to determine the inter-and intramolecular interactions in the title compound.

Nonlinear optical properties and optimization strategies of D-π-A type phenylamine derivatives in the near-infrared region

Modifying simple molecular structures to significantly improve nonlinear optical (NLO) performance is a primary prerequisite for scientific research. Based on the four phenylamine derivatives reported in previous studies, we designed four organic nonlinear molecules by changing the acceptor group and π-linker. (Time-dependent) density functional theory (DFT/TD-DFT) was performed on molecular geometry optimization, the contribution of π electrons to the bond order, linear and two-photon absorption (TPA) spectra, the intra-molecular charge transfer matrix (CTM), and NLO coefficients. These aspects were considered to analyze in detail how the structural modification of acceptors and π-linkers affects NLO characteristics. The three modification methods were: adding a carbonyl group at the junction of the π-linker and the acceptor group, adding a carbonyl group and a nitrogen atom to the acceptor group, and replacing the quinolinone with a pyrenyl group as the π-linker. The latter two methods can significantly reduce the excitation energy and enhance the intensity of intra-molecular charge transfer during the two-photon transition. The maximum TPA cross-sections and wavelengths of the designed molecules are DPPM (84722.6 GM, 815.7 nm) and DDPM (21600.6 GM, 781.3 nm). These two molecules have large TPA cross-sections in the near-infrared region, which renders them as possible NLO materials with broad application prospects.

Co(II), Ni(II), and Zn(II) complexes based on new hybrid imine-pyrazole ligands: structural, spectroscopic, and electronic properties

The present work reports the theoretical investigation of Co(II), Ni(II), and Zn(II) complexes containing Schiff bases (used as ligands) derived from the reaction of 2-hydroxy-1-naphthaldehyde with N-(2-aminoethyl) pyrazoles. The spectral analyses were carried out using infrared, Raman, and UV-Vis spectroscopy. Vibrational analyses were performed in order to investigate the mechanisms involving metal-ligand and intra-ligand vibrations and indicated the possibility of charge transfer related to the transitions n[Formula: see text]* and [Formula: see text]*. Structure optimizations and normal coordinate force field calculations were performed via the density functional theory (DFT) method at the HSE06/6-311G(d,p)/LanL2DZ level. A thorough analysis was also conducted regarding the nonlinear optical (NLO) properties and the natural bond orbital (NBO) of the complexes. The results show that these complexes have prospective application as materials for NLO. Furthermore, the NBO analysis confirms the coordination between the lone pair (LP) electrons of the donor atoms (O and N) and the metal acceptors. Finally, studies were conducted regarding the electronic properties of the complexes; among the properties investigated included the frontier molecular orbitals (FMO) and the molecular electrostatic potential (MEP), allowing to determine the energy gap and charge distribution.

Synthesis, characterization, antioxidant, antileishmanial, anticancer, DNA and theoretical SARS-CoV-2 interaction studies of copper(II) carboxylate complexes

Copper(II) carboxylate complexes [Cu2(OOCR)4L2] (1) and [Cu2(OOCR`)4OCO(R`)CuL2]n (2), where L = 2-methyl pyridine, R = 2-chlorophenyl acetate and R` = 2-fluorophenyl acetate were synthesized and characterized by FT-IR spectroscopy and single crystal X-ray analysis. Complex 1 exhibits the typical paddlewheel array of a dinuclear copper(II) complex with carboxylate ligands. In complex 2, this scaffold is further extended into a polymeric arrangement based on alternate paddlewheel and square planar moieties with distinct coordination spheres. The complexes showed better 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl radical scavenging activities and have been found to be more potent antileishmanial agents than their corresponding free ligand acid species. UV-Vis absorption titrations revealed good DNA binding abilities {Kb = 9.8 × 104 M-1 (1) and 9.9 × 104 M-1 (2)} implying partial intercalation of the complexes into DNA base pairs along with groove binding. The complexes displayed in vitro cytotoxic activity against malignant glioma U-87 (MG U87) cell lines. Computational docking studies further support complex-DNA binding by intercalation. Molecular docking investigations revealed probable interactions of the complexes with spike protein, the nucleocapsid protein of SARS-CoV-2 and with the angiotensin converting enzyme of human cells.

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 (β 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.

Solvent effects on the electronic and optical properties of Ni(II), Zn(II), and Fe(II) complexes of a Schiff base derived from 5-bromo-2-hydroxybenzaldehyde

In this article, the electronic, optical, and charge transfer properties of a Schiff base ligand prepared using 5-bromo-2-hydroxybenzaldehyde and ethyl 6-acetyl-2-amino-4,5,6,7-tetrahydrothieno[2,3- c]pyridine-3-carboxylate (C19H19BrN2O4S) and its Fe(II) (C19H30BrN2O10SClFe), Ni(II) (C19H28BrN2O9SClNi), and Zn(II) (C19H28BrN2O9SClZn) complexes are described based on different solvents environments and supported by theoretical calculations. Theoretical calculations are carried out using density functional theory (DFT/UB3LYP/LANL2DZ). The optical densities, optical band gaps, and refractive indices of the ligand and its Fe(II), Ni(II), and Zn(II) complexes in different solvent environments are obtained. The reorganization energies are calculated to determine the charge transfer rate of the studied compounds using both experimental and theoretical data. These experimental and theoretical results show that the ligand and its metal complexes can be used for optoelectronic applications and charge transfer materials in organic light-emitting diode applications.

The crystal structure of catena-poly[(μ2-4,4′-dipyridine-κ2N,N′)-bis(3,5,6-trichloropyridine-2-oxyacetato-κO)-bis(ethanol-κO)nickel(II)], C28H26Cl6N4NiO8

C28H26Cl6N4NiO8, monoclinic, I2/a (no. 15), a = 15.7577(10) Å, b = 12.6174(7) Å, c = 16.7333(10) Å, β = 99.609(6)Å, V = 3280.3(3) Å3, Z = 4, Rgt(F) = 0.0674, wRref(F2) = 0.1665, T = 291.2(3) K.

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).

Crystal structure of aqua-bis(5-bromo-6-methyl-picolinato-κ2 N,O)zinc(II) dihydrate, C14H16Br2N2O7Zn

C14H16Br2N2O7Zn, orthorhombic, Pna21 (no. 33), a = 15.4300(3) Å, b = 10.6264(2) Å, c = 11.4638(2) Å, V = 1879.66(6) Å3, Z = 4, R gt(F) = 0.0328, wR ref(F 2) = 0.0709, T = 293 K.

A mononuclear cobalt(II) salophen-type complex: Synthesis, theoretical and experimental electronic absorption and infrared spectra, crystal structure, and predicting of second- and third-order nonlinear optical properties

A tetradentate Schiff base ligand, (4-nitro-N,N'-o-phenylene-bis(5-methoxysalicylideneimine)) (H₂L), and its cobalt(II) complex (CoL•DMF) were synthesized. Elemental analysis, and FT-IR and ¹H NMR spectra were used to confirm the molecular structure of H₂L ligand. In addition, elemental analysis, molar conductance measurement, infrared and electronic absorption spectroscopies as well as single crystal X-ray diffraction were employed to distinguish the molecular structure of the complex that has a slightly distorted square-planar geometry around the cobalt(II) ion. The geometries of H₂L and CoL were optimized by means of the DFT/(U)PBE0/Def2-TZVP level of theory. Good agreement of the optimized geometric parameters of the complex with the corresponding experimental ones and successfully reproduction of the FT-IR spectra of the ligand and complex validated the applied method. Based on the optimized structure of CoL, its electronic absorption spectrum was reproduced by using time-dependent density functional theory (TDDFT) at the same level. Its analysis was carried out to assign the observed electronic transitions and determine their characters. The computed nonlinear optical (NLO) parameters (β, γ and < γ > values) of H₂L and CoL by using TDDFT at the same level combined with the sum-over-states (SOS) method are considerable larger values than reference compound i.e. urea. The ligand and the complex in the absence of nitro and methoxy moieties referred to as H₂L' and CoL' respectively were optimized to elucidate the effect of these moieties on hyperpolarizabilities values.