Mixed Basis Set Research Articles

Zn2+-Schiff’s Base Complex as an “On–Off-On” Molecular Switch and a Fluorescence Probe for Cu2+ and Ag+ Ions

The present study presents a thorough theoretical analysis of the electronic structure and conformational preference of Schiff's base ligand N,N-bis(2-hydroxybenzilidene)-2,4,6-trimethyl benzene-1,3-diamine (H2L) and its metal complexes with Zn2+, Cu2+ and Ag+ ions. This study aims to investigate the behavior of H2L and the binuclear Zn2+ complex (1) as fluorescent probes for the detection of metal ions (Zn2+, Cu2+ and Ag+) using density functional theory (DFT) and time-dependent density functional theory (TDDFT). The six conformers of the H2L ligand were optimized using the B3LYP/6-311 + + G** level of theory, while the L-2-metal complexes were optimized by applying the B3LYP functional with the LANL2DZ/6-311 + + G** mixed basis set. The gas-phase and solvated Enol-cis isomer (E-cis) was found to be the most stable species. The absorption spectra of the E-cis isomer and its metal complexes were simulated using B3LYP, CAM-B3LYP, M06-2X and ωB97X functionals with a 6-311 + + G** basis set for C, O, N and H atoms and a LANL2DZ basis set for the metal ions (Zn2+, Cu2+ and Ag+). The computational results of the B3LYP functional were in excellent agreement with the experimental results. Hence, it was adopted for performing the emission calculations. The results indicated that metal complex (1) can act as a fluorescent chemosensor for the detection of Ag+ and Cu2+ ions through the mechanism of intermolecular charge transfer (ICT) and as a molecular switch "On-Off-On" via the replacement of Cu2+ by Ag+ ions, as proved experimentally.

Silver cluster doped graphyne (GY) with outstanding non-linear optical properties.

This research study addresses the computational simulations of optical and nonlinear optical (NLO) characteristics of silver (Ag) cluster doped graphyne (GY) complexes. By precisely following DFT and TD-DFT hypothetical computations, in-depth characterization of GY@Agcenter, GY@Agside, GY@2Agperpendicular, GY@2Agabove, and GY@3Agcenter is accomplished using CAM-B3LYP/LANL2DZ while the CAM-B3LYP/mixed basis set is used for study of 2GY@Agcenter, 2GY@Agside, 2GY@2Agperpendicular, 2GY@2Agabove, and 2GY@3Agcenter. The effects of various graphyne surface based complexes on hyperpolarizabilities, frontier molecular orbitals (FMOs), density of states (DOS), absorption maximum (λmax), binding energy (Eb), dipole moment (μ), electron density distribution map (EDDM), transition density matrix (TDM), electrostatic potential (ESP), vertical ionization energy (EVI) and electrical conductivity (σ) have been investigated. Infrared (IR), non-covalent interaction (NCI) analysis accompanied by isosurface are performed to study the vibrational frequencies and type of interaction. Doping strategies in all complexes impressively reformed charge transfer characteristics such as narrowing band gap (Eg) in the range of 2.58–4.73 eV and enhanced λmax lying in the range of 368–536 nm as compared to pure GY with 5.78 eV Eg and 265 nm λmax for (GY@Agcenter–GY@3Agcenter). In the case of (2GY@Agcenter–2GY@3Agcenter), when compared to 2GY with 5.58 eV Eg and 275 nm absorption, maximum doping techniques have more effectively modified λmax in the region of 400–548 nm and Eg, which is in the order of 2.55–4.62 eV. GY@3Agcenter and 2GY@3Agcenter reflected a noteworthy increment in linear polarizability αO (436.90 au) and (586 au) and the first hyperpolarizability βO (5048.77 au) and (17 270 au) because of their lowest excitation energy (ΔE) when studied in comparison with GY (αO = 281.54 and βO = 0.21 au) and 2GY surface (αO = 416 and βO = 0.06 au). Focusing on harmony between the tiny Ag clusters and graphyne surface as well as their influences on NLO properties, graphyne doping using its two-unit cells (2GY) is found to be expedient for the development of future nanoscale devices.

A Ruthenium(II) Nitrosyl Complex of N-Dehydroacetic Acid-Sulfadiazine: Synthesis, DFT Studies and in silico ADME Properties

A sulpha drug-derived Schiff base ligand N-dehydroacetic acid-sulfadiazine was synthesized by treatment of dehydroacetic acid and sulfadiazine. A mononuclear Ru(II) nitrosyl complex of the Schiff base ligand cis-[RuCl2(NO)(PPh3)(dha-sdz)] was synthesized. The complex was characterized by spectral (IR, 1H NMR and UV/visible) techniques and physico-chemical studies. A cyclic voltammetric technique observed the electrochemistry of the complex compound. Therefore, the Gaussian 09 programme has been used to optimized molecular structure, electronic surface analysis, NLO properties through DFT approaches via mixed basis set at B3LYP/LANL2DZ level of theory. The 1H NMR spectrum of complex compound was computed with the GIAO method and correlated to experimental chemical shift. The TD-DFT based electronic absorption spectrum was computed using the PCM model. Additionally, the synthesized compound was predicting its in silico ADME properties, showing good physico-chemical and bioactivity. Finally, the in vitro antioxidant activity of the studied compound was monitored via two radical scavenging inhibitors.

Colorimetric detection of Pb2+ ions using curcumin silver nanoparticles

The silver nanoparticles (AgNPs) complexed with curcumin (CUR) extracted from turmeric (TMR) were synthesized and applied for a simple and rapid colorimetric technique for Pb2+ detection. The results reveal that our low-cost and rapid AgNPs-CUR sensor is highly selective for Pb2+ ions with the detection limit of 13.6 µM (2.8 mg.L−1) and can be applied for real water samples. Not only the observed absorption spectrum and the solution color can reveal the contamination of Pb2+ in the sample, but also an orange floccules precipitate can be clearly observed by naked-eye within 20 min. In addition, the results obtained from DFT calculation agree well with the experiments. Density functional theory (DFT), at the M06 level with mixed basis set of 6-31G(d) and def2-tzvp, was applied to propose the binding mechanism of AgNPs with CUR and AgNPs-CUR with Pb2+. Calculated binding energies of the compound of AgNPs with CUR and the AgNPs-CUR with Pb2+ are −145.8 and −361.4 kcal mol−1, respectively, indicating that the AgNPs-CUR is strongly interact with Pb2+ ions through formation of highly stable Pb2+AgNPs-CUR complexes indicating the stable aggregative phenomena which agrees well with FTIR spectrum.

Radical Mechanism of Ir III /Ni II -Metallaphotoredox-Catalyzed C(sp 3 )–H Functionalization Triggered by Proton-Coupled Electron Transfer: Theoretical Insight

Photoredox catalysis can be induced to activate organic substrates or to modulate the oxidation state of transition-metal catalysts via unique single-electron transfer processes, so as to achieve c...

Probing Basis Set Requirements for Calculating Core Ionization and Core Excitation Spectra Using Correlated Wave Function Methods.

We investigate the basis set requirements for the accurate calculation of core excitations and core ionizations using correlated wave functions of coupled cluster type and linear response methods for describing the excitation. When a core excitation is described as an energy difference calculated using density functional theory, the basis set can be tailored to provide a balanced description of the reference- and excited-hole states. When the core excitation process is described by coupled cluster linear response methods, however, the basis set requirements are somewhat different. A systematic study of the sensitivity of the result to the basis set parameters suggests that a relatively large set of s- and p-type basis functions in combination with a careful selection of valence and core polarization functions is required. Based on these results, we propose a hierarchical sequence of basis sets, denoted ccX-nZ (n = D, T, Q, 5) for the atoms B-Ne, which are suitable for the calculation of core excitations by the correlated wave function linear response and equation-of-motion methods. The ccX-nZ series provides lower basis set errors for a given cardinal number or number of basis functions than other existing basis sets. For large systems, the ccX-nZ basis sets can be combined with the standard basis sets by placing the ccX-nZ only on the atoms where core excitations are of interest, but the accuracy of such mixed basis sets appears to be system-dependent.

ICMMS-2: Metal−organic Frameworks for Hydrogen Storage: Theoretical Prospective

The adsorption of H2 in dehydrated and hydrated Materials of Institute Lavoisier (MIL-101) was investigated theoretically. The effect of terminal water molecules on adsorption as one of the more vital MIL-n trivalent chromium-based porous carboxylates in metal-organic frameworks application in the renewable energy field was also theoretically studied. The MIL-101 structures were optimized for geometry and energy minimization was performed. The calculations were carried out using density functional theory approach with B3LYP functional and mixed basis set of Lanl2DZ and 6-31G(d, p) for Cr and light atoms (C, H, O, F), respectively, as implemented in the Gaussian 09 program package. The spin and atomic charges distribution on the Cr metal atoms, adsorbate, and water molecules are calculated using natural bond orbital (NBO). The density of states (DOS) for the clusters was obtained using Gaussian smearing of Kohn–Sham orbital energies. The natural bond orbital (NBO) for molecular orbital analysis and atomic charge calculations were utilized. For the dehydrated MIL-101, more adsorbate molecules were found near the exposed Cr2 sites than the fluorine saturated Cr1 sites. Furthermore, terminal water molecules in the hydrated MIL-101 made more interaction sites and enhanced adsorption.

Design, structural investigations and antimicrobial activity of pyrazole nucleating copper and zinc complexes

The present study accounts for the construction of two novel complexes by the interaction of pyrazole nucleating ligand with Cu(II) (1) and Zn(II) (2) ions in 1:1 equivalent ratio, and their structural investigation by elemental analyses, FT-IR, NMR and thermal studies. Complex 1, additionally characterized by single crystal X-ray crystallography, reveals the coordination of the pyrazole nucleating ligand to the metal ions by the imine nitrogen, carbonyl oxygen and phenolic oxygen of the ligand and chloride ion. Furthermore, the coordination environment of the central atom adopts slightly distorted square-planar geometry with sum of interbond angles equal to 701.49°. The analysis of CN bond lengths shows that the double bond is localised within imine moiety and respective bonds shows considerable degree of delocalisation within pyrazole ring. The mixed basis set 6-311G(d) and LANL2DZ with B3LYP functional is applied for DFT calculation to determine the bonding insights into the structure of the complex. Natural Population Analysis (NPA) is also carried out to define the nature of the charge on copper atom in complex 1. In addition, Hirshfeld surface analysis is also carried out to know the various intermolecular interactions. The ligand and its complexes were evaluated against Pseudomonas aeruginosa, Escherichia coli, Shigella sonnei, Bacillus subtilis, Aspergillus niger, Aspergillus flavus, Fusarium oxysporum, Penicillium notatum microbial species, and showed significant effects on the tested microbes.

Ground and Excited State Electronic Structures of d8-Squared Planar Platinum(II) and Gold(III) Complexes Bearing Cyclometallated 2,6-Diphenylpyridine and Pyrene-Derived N-Heterocyclic Carbene

Electronic structures of four pyrene-derived N-heterocyclic carbene complexes of platinum(II) and gold(III) bearing cyclometallated 2,6-diphenylpyridine have been investigated theoretically. The structures of all complexes in gas phase have been first optimized. Different functionals and basis sets have been tested to find the best theoretical method. The results show that B3PW91 (LANL2DZ/6-31G*) combination give the best description of the molecules as compared with experimentally determined structural features. Using the calculation data from that best functional and mixed basis set combination, frontier molecular orbitals of the complexes have been examined. To gain understanding on the nature of electronic transitions in the UV-vis absorption spectra of the compounds, TD-DFT calculations have been carried out. A details analysis of the vertical excitation reveals that the nature of all the vertical electronic transitions in the complexes. Notably, the lowest energy transitions are πcb + dPt → $$\pi _{{{\text{cb}}}}^{{\text{*}}}$$ (for Pt1 and Pt2) and πCNC → dAu + $$\pi _{{{\text{CNC}}}}^{{\text{*}}}$$ (for Au1 and Au2) charge transfer in nature. A sharp contrast in lowest energy triplet excited state for d8‑squared planar Au1 and Pt1 has been demonstrated. While no contribution from gold(III) d orbital to the SOMO and SOMO – 1 orbital of Au1, there is significant contribution of platinum(II) dyz orbital in the SOMO – 1 orbital of Pt1, suggesting possible interaction of this singly occupied orbital with radical of π-symmetry substrates.

Ab initio potential energy surface and microwave spectra for Kr-NCCN complex

Ab initio potential energy surface of Kr-NCCN complex has been investigated using the coupled-cluster singles and doubles with noniterative inclusion of connected triples [CCSD(T)], which including two mixed basis sets, aug-cc-pvDz for the C and N atoms, and aug-cc-pvDz-pp for the Kr atom, containing the midbond function of 3s3p2d1f1g. The potential energy surface of Kr-NCCN complex has a T-shaped global minimum locating at R = 6.96 a0, θ = 90° with the energy of −281.677 cm−1, the two equivalent local minima with the energy of −123.513 cm−1 locating at the linear geometry for R = 10.70 a0, and two saddle points between the global and the two local minima are located at R = 10.61 a0, θ = 10.1° and 169.9° with V = −123.304 cm−1, respectively. The bound state energies up to J = 9 for Kr-NCCN are calculated based on the potential energy surface by solving the Schrödinger equation, and the microwave transition frequencies are also investigated. Finally, the calculated spectroscopic constants are obtained based on the calculated rotational energy levels. These results could provide a theoretical basis for the experimental spectra research of Kr-NCCN complex.

Transition metals induce control of enhanced NLO properties of functionalized organometallic complexes under laser modulations

The molecular engineering of organometallic complexes has recently attracted renewed interest on account of their potential technological applications for optoelectronics in general and optical data storage. The transition metal which induces control of enhanced nonlinear optical properties of functionalized organometallic complexes versus not only the intensity but also the polarization of the incident laser beam is original and important for all optical switching. This makes organometallic complexes valuable and suitable candidates for nonlinear optical applications. In the present work, we report the synthesis and full characterization of four organometallic complexes consisting of N, N-dibutylamine and azobenzene fragments but differ by auxiliary alkynyl ligands or metal cations. Thus, a ferrocenyl derivative 1 and three ruthenium complexes 2–4 have been prepared. The nonlinear optical properties of the four new azo-based ruthenium and iron organometallic complexes in the solid state, using polymethylmethacrylate as matrix, have been thoroughly studied. This concept is extended to computing the HOMO and LUMO energy levels of the considered complexes, dipole moment, first and second order hyperpolarizabilities using the 6–31 + G(d,p) + LANL2DZ mixed basis set. The second and third nonlinear optical properties of the resulting polymer composites were obtained by measuring SHG and THG response by means of the Maker fringe technique using a laser generating at 1,064 nm with a 30 ps pulse duration. The values of the second and third order NLO susceptibilities of the four organometallic complexes were found to be higher than the common references used. Theoretical calculation shows that the large first and second order hyperpolarizablities are caused by strong intramolecular charge transfer between the transition metal parts and the ligands though a conjugated transmitter. These results indicate that the present organometallic complexes are valuable candidates for optoelectronic and photonic applications.

A theoretical study of the structural and electronic properties of some titanocenes using DFT, TD-DFT, and QTAIM

Titanocenes are gradually proven to possess good anticancer activity. In this paper, we present a theoretical study of some properties of six promising anticancer titanocenes synthesized by the Tacke research group. The structural and electronic properties of the complexes have been investigated herein using the density functional theory (DFT) and the time-dependent DFT (TD-DFT) associated with a mixed basis sets comprising the 6-31 + G(d,p) basis set for C, H, and O atoms and the 6-31G(d) basis sets for the Ti4+ and Cl− ions. According to the results from topological analysis, even though there are strong Ti–C interactions in all complexes studied, the cyclopentadienyl derivatives are not covalently linked to the central Ti4+ ion through all of their carbon atoms. In addition, the Ti–Cl is the strongest metal-ligand bond. From the analyses of electronic spectra, it turns out that the complexes studied strongly absorb in the UV region of the electromagnetic spectrum and that the transitions are mainly LMCT, LLCT, and ILCT character. Our results are undoubtedly vital for further studies on the structure-activity relationship and mechanisms of interaction between the investigated titanocenes and DNA.

B3LYP, M06 and B3PW91 DFT assignment of nd8 metal-bis-(N-heterocyclic carbene) complexes.

This paper is focused on the examination of the bonding properties of a series of [M(NHC)2X2] (M = nd8 transition metal; X = Cl, Br and I) complexes in normal, abnormal and mixed C∩C coordination modes. Structures have been optimised in gas phase using B3LYP, M06 and P3BW91 functionals. Two basis sets have been used: the LanL2DZ and a mixed basis set (LanL2DZ for nd8 transition metals as well as halogen atoms and 6-311+G(d,p) for other atoms). Results obtained indicate that the B3PW91 bond distances are closer to experimental data. The complexation energies obtained for each binding mode increase in the order: Ni2+ < Pd2+ < Pt2+, independently of the halogen atom adopted. From the Quantum Theory of Atoms in Molecule (QTAIM) approach, the instability has been found to follow this trend: M - X < M - C. The analysis of metal-ligand interactions using the natural bond orbital (NBO) revealed that the strongest metal-ligand interactions are observed in the normal binding mode. The NCH → MX2 donation terms were found to be interestingly predominant compared with back donation ones in the complexes studied, except in Pt chloride ones. The contribution of electrostatic interaction energy between the above fragments (∆Eelstat term) is in the range 57.48-63.95% traducing the fact that the interactions are mostly electrostatic. Graphical abstract.

Distribution of oscillator strengths and correlated electron dynamics in artificial atoms

The electronic structure of the quasi-two-dimensional disk-like artificial atom involving holes inside has been studied by the full configuration interaction (FCI) wave function employing mixed basis sets consisting of standard atomic orbitals and anisotropic Gaussian-type functions. The one-particle confinement potential for electrons has been modeled by a sum of an anisotropic harmonic-oscillator potential and attractive Coulomb potentials, the latter being responsible for the hole positive charges. The oscillator strengths from the ground state to a number of low-lying excited states have been calculated by the FCI energies and wave functions for different strength of the harmonic confinement ω. The results for two electrons with a hole at the center, namely, the He-like system, have shown accumulation of the oscillator strengths distributed among different dipole-allowed transitions in the excitation into the center-of-mass modes or the plasmon modes for increasing confinement strength ω. The system of two electrons with two impurity holes, namely, the H2-like system, has been also studied, which has shown a far more complicated trend of the oscillator strengths with respect to ω owing to the additional degree of freedom of the internuclear distance r. The observed trend has been rationalized on the basis of the nodal patterns in the molecular orbitals and in the electron density distributions.

Mixed Ramp-Gaussian Basis Sets for Core-Dependent Properties: STO-RG and STO-R2G for Li-Ne

The traditional Gaussian basis sets used in modern quantum chemistry lack an electron-nuclear cusp, and hence struggle to accurately describe core electron properties. A recently introduced novel type of basis set, mixed ramp-Gaussians, introduce a new primitive function called a ramp function which addresses this issue. This paper introduces three new mixed ramp-Gaussian basis sets - STO-R, STO-RG and STO-R2G, made from a linear combination of ramp and Gaussian primitive functions - which are derived from the single-core-zeta Slater basis sets for the elements Li to Ne. This derivation is done in an analogous fashion to the famous STO-$n$G basis sets. The STO-RG basis functions are found to outperform the STO-3G basis functions and STO-R2G outperforms STO-6G, both in terms of wavefunction fit and other key quantities such as the one-electron energy and the electron-nuclear cusp. The second part of this paper performs preparatory investigations into how standard all-Gaussian basis sets can be converted to ramp-Gaussian basis sets through modifying the core basis functions. Using a test case of the 6-31G basis set for carbon, we determined that the second Gaussian primitive is less important when fitting a ramp-Gaussian core basis function directly to an all-Gaussian core basis function than when fitting to a Slater basis function. Further, we identified the basis sets that are single-core-zeta and thus should be most straightforward to convert to mixed ramp-Gaussian basis sets in the future.

Dispersion-Corrected Density Functional Theory Study of the Noncovalent Complexes Formed with Imidazo[1,2-a]pyrazines Adsorbed onto Silver Clusters.

Imidazo[1,2-a]pyrazines are cyclic amidine-type compounds composed of α-amino acid residues. A full structural identification of these molecules constitutes an analytical challenge, especially when imidazo[1,2-a]pyrazines are obtained from physical processes (e.g., sublimation and pyrolysis of amino acids). A valuable source of molecular information can be obtained from absorption spectroscopies and related techniques encompassing the use of metallic substrates. The aim of this study is to provide new knowledge and insights into the noncovalent intermolecular interactions between imidazo[1,2-a]pyrazines and two Agn (n = 4 and 20) clusters using density functional theory (DFT) methods. Semiempirical DFT dispersion (DFT-D) corrections were addressed using Grimme’s dispersion (GD2) and Austin–Petersson–Frisch (APF) functionals in conjunction with the 6-31+G(d,p) + LANL2DZ mixed basis set. These DFT-D methods describe strong interactions; besides, in all cases, the APF dispersion (APF-D) energies of interaction appear to be consistently overestimated. In comparison with B3LYP calculations, the mean values for the difference in the energies of interaction calculated are 2.25 (GD2) and 6.24 (APF-D) kcal mol–1 for Ag4–molecules, and 2.30 (GD2) and 8.53 (APF-D) kcal mol–1 for Ag20–molecules. The effect of applying GD2 and APF-D corrections to the noncovalent complexes is nuanced in the intermolecular distances calculated, mainly in the Ag···N(amidine) bonding, which appears to play the most important role for the adsorptive process. Selective enhancement and considerable red shifts for Raman vibrations suggest strong interactions, whereas a charge redistribution involving the metallic substrate and the absorbate leads to a significant rearrangement of frontier molecular orbitals mainly in the Ag20–molecule complexes. Finally, time-dependent DFT calculations were carried out to access the orbital contributions to each of the transitions observed in the absorption spectrum. The corresponding UV–vis spectra involve transitions in the visible region at around 400 and 550 nm for the Ag4–molecule and the Ag20–molecule complexes, respectively.

Rose bengal- Pioglitazone drug reaction novel products. Structures – biological activity and cytotoxicity relationship and evaluation with theoretical calculations.

The PIOG-RBeng reaction novel products were characterized by thermal in comparison with spectroscopic data using FT-IR, 1H-NMR, and then confirmed by XRD measurements and Theoretical computational calculations. The software of Gaussian 09W package had been used for computations. The geometries of Rose bengal (RBeng), Pioglitazone (PIOG) drug and their reaction products were optimized using B3LYP method and (DFT)/GENECP level was obtained by using Def2TZVP basis set. The basis set 6-311++G (d, p) had been used for remainder atoms. The mixed basis set was used due to its flexibility. HOMO and LUMO energy values, chemical hardness and electronegativity had been calculated for compounds. NBO calculations were made for measurement qualitatively the intra-molecular delocalization in systems under investigation on the same level using (NBO 3.1) program implanted in Gaussian 09W.The theoretical calculations involved estimation of global reactivity descriptors, local descriptors and molecular electrostatic potential (MEP) maps. TD-DFT approximation was used to calculate the FT-IR and 1HNMR spectra of the studied compounds; which actually compared with practical data. Successful correlation between experimental and theoretical calculations had been made to confirm structures of studied compounds. The X-ray diffraction (XRD) was used to study the crystallographic structures of compounds under investigation. The practical results are also correlated to theoretical calculations of electronegativity (X), polarizability, HOMO and LUMO values of PIOG and PIOG-RBeng reaction products. The vibrational frequencies were evaluated in comparison with the corresponding normal modes at the optimized geometry. The investigated compounds are highly effective against Hepatocellular carcinoma, Breast carcinoma and Colon carcinoma cells. It is concluded that; cancer cells over expression promotes tumorigenic functions; can be suppressed by reaction products inhibitors.

Solvent-free mechanochemical synthesis, hirshfeld surface analysis, crystal structure, spectroscopic characterization and NBO analysis of Bis(ammonium) Bis((4-methoxyphenyl) phosphonodithioato)-nickel (II) dihydrate with DFT studies

Abstract The green chemistry route for synthesis of dithiophosphonate nickel complex of the type, [Ni{S2P(O) (4-C6H4–OMe)}2]·2NH4·2H2O was reported1 and the structure confirmed by single crystal XRD. This work deals with FT-IR, and NMR spectral, NBO and Hirshfeld surface studies on bis(ammonium) bis((4-methoxyphenyl) phosphonodithioato)-nickel dihydrate. The molecular structure, vibrational frequencies and intensity of the vibrational bands were interpreted with the aid of structure optimizations and geometrical parameter calculations based on density functional theory (DFT) method via mixed basis set at B3LYP/GENECP level of theory. The 13C and 1H Nuclear Magnetic Resonance (NMR) of the complex were computed by gauge independent atomic orbital (GIAO) method and compared with experimental chemical shift. The reported experimental and calculated results were correlated and was further expressed with correlation plots and correlation coefficient. Matching consistency resulted between computed data on optimized geometric parameters, vibrational frequencies and NMR chemical shifts and their corresponding experimental data. Computed Natural Bond Orbital (NBO) analysis explore the interactions as well as charge transfers among different orbitals and lone pairs happening within the compound. Hirshfeld surface analyses further establish and quantify intermolecular interactions of [Ni{S2P(O)·(4-C6H4–OMe)}2]·2NH4·2H2O.

Synthesis, structural characterization, thermal behaviour and antimicrobial activity of copper, cadmium and zinc chelates of traizole-thiole ligand in comparison with theoretical molecular orbital calculations

This research involved structural and molecular behaviour of the ligand HL, 4-amino-5-(2,2-dichloro-1-methylcyclopropyl)-4H-1,2,4-triazole-3-thiol toward the transition metal ions namely Cu (II), Cd(II) and Zn (II) had been studied using elemental analyses, magnetic, electronic, FT- IR, 1H-NMR, XRD and Thermal analyses (TGA and DTA). The interpretation of practical data obtained had been evaluated and confirmed by theoretical molecular modelling. The computations had been done by software of Gaussian 09W package. The geometries of traizole-thiole ligand and its metal chelates were fully optimized using density functional theory B3LYP method. There are no symmetry constrains had been applied during geometry optimization. (DFT)/GENECP level by implementing Def2TZVP basis set was used for Cu, Cd and Zn-atoms; and basis set 6-311++G (d, p) was used for other atoms. The mixed basis set had been selected due to its flexibility. HOMO and LUMO energy values for chelates, chemical hardness and electronegativity had been calculated. NBO calculations had been done at the same level using (NBO 3.1) program involved in the software of Gaussian 09W for measuring the intra-molecular delocalization in systems under investigation qualitatively. TD-DFT approximation at the same level of theory was used to calculate the electronic absorption spectra of the studied chelates. Their structures were confirmed via correlation between experimental and theoretical calculations. The ligand and its metal chelates biological activities had been tested against Gram-positive (Staphylococcus aureus ATTC 12600), Gram-negative (Escherichia coli ATTC 11775 and) bacteria, two fungus (Aspergillus flavus and Candida albicans).. These biological activities are tested and give the order Zn-HL˃ Cd-HL˃ Cu-HL ˃˃ HL as a general trend in relation to transition metal cation present in chelate entity. This trend is also correlated to theoretical calculations of chelates electronegativity (X), polarizability and HOMO and LUMO values. Also this trend is correlated to theoretical calculations of energy gap values eV (Zn- HL = 5.19, Cd-HL = 4.32 and Cu-HL = 2.08) and in reverse order to electronegativity (X) values. The variation of electronegativity (X) values is supported by electrostatic potential, for any two molecules, where electron will be partially transferred from one of low X to that of high X. The results show that the order of decreasing X (increasing CT within the molecules) is: Cu-HL > Cd-HL > Zn-HL >> HL. Some of them have the order of magnitude effect like standard Amoxicillin.

Hirshfeld surface analysis and DFT studies on molecular structure, vibrational spectra, NMR chemical shifts and NBO analysis of Bis(2-hydroxyethyl(phenyl)carbamodithioate) nickel (II)

The ‘Bis(2-hydroxyethyl(phenyl)carbamodithioate) nickel (II)’ compound, C18H20N2NiO2S4 was synthesized and verified by single crystal X-ray diffraction. The molecule was characterized by FT-IR and NMR spectroscopies and computed in ground state by Density Functional Theory (DFT/B3LYP) via mixed basis set at unrestricted B3LYP/GENECP level of theory with 6–311++G (d, p), for C, N, H, O, S and landl2dz for Ni. The optimized geometric parameters, vibrational frequencies and NMR chemical shifts showed good consistency with the experimental data. The correlation plots for the experimental versus theoretical values establish correlation coefficient of close to 1, hence optimal agreement in the experimental and the theoretical data. Hirshfeld surface analyses (dnorm surfaces and two-dimensional fingerprint plots) for C18H20N2NiO2S4 are presented and discussed. Natural Bond Orbital (NBO)analysis was also calculated to explore the interactions and charge transfers among different orbitals and lone pairs taking place within the titled compound.