Vol 59, No 5 (2018)

Various structural possibilities for small gallium-indium Ga_mIn_n–m (n = 4, 6, 8 and m < n) clusters are investigated using the density functional theory (DFT) method at the B3LYP/TZP level. The optimized structures tend to prefer compact structures, wherein the trigonal prism and rhombic prism configurations are favoured for n = 6 and 8, respectively. The bonding energy per atom is calculated according to the cluster size. The HOMO-LUMO gaps, ionization potentials, electron affinities, and chemical hardness (η) are also computed for the most stable isomers of each cluster and used to predict their relative stabilities. The obtained results indicate that the Ga-rich clusters are more stable than the In-rich ones with the same total number of atoms. The Ga–Ga bond is stronger than the Ga–In bond and the latter is stronger than the In–In one. Therefore, the Ga₇In cluster is relatively the most stable structure. The relative reactivity of Ga_mIn_n–m (n = 4, 6, 8 and m < n) clusters could be predicted based on the chemical hardness. The computed large HOMO-LUMO gap energies could be used as an index of the kinetic stability for the studied clusters.

In this study, FT-IR and FT-Raman spectra of 3-methyl picolinic acid (MPA) are recorded in the ranges 4000–450 cm^–1 and 4000–50 cm^–1, respectively. The optimized geometry is obtained by scaled quantum mechanical calculations using density functional theory employing the B3LYP functional with the 6–311++G(d,p) basis set. Vibrational assignments are suggested for all the fundamental vibrations unambiguously, using the potential energy distribution obtained in the computations. The rms error between the observed and calculated frequencies is found to be 8.48 cm^–1. The dipole moment, polarizability, and hyperpolarizability values are computed to study the NLO behavior of the molecule. The NBO analysis is made to study the stability of the molecule arising from hyperconjugative interactions and charge delocalization.

This study investigates the interaction between C²⁰ and the cis-PtCl₂(NH₃)₂ complex using MPW1PW91 quantum chemical calculations in gas and solution phases. Two interaction modes between C²⁰ and the cis-PtCl₂(NH₃)₂ complex are considered: I-isomer (η₂-C²⁰) and II-isomer (η₁-C²⁰). It also determines the effects of the solvent polarity on the dipole moment, electronic spatial extent (ESE), structural parameters, and frontier orbital energies of two possible isomers of the C²⁰…cis-PtCl₂(NH₃)₂ complex. The bonding interaction between C²⁰ and the cis-PtCl₂(NH₃)₂ complex was examined through energy decomposition analysis (EDA). The metal–ligand bonds are evaluated using the percentage composition of the specific groups of frontier orbitals. The quantum theory of atoms in molecules (QTAIM) analysis is applied to assess the Pt–C bonds within the complex. Finally, the Pt–C spin-spin coupling constants are calculated using the gauge independent atomic orbital (GIAO) method.

The present study illustrates the stability of [CpFe(CO)₂(NCS)] and [CpFe(CO)₂(SCN)] linkage isomers by the use of MPW1PW91 quantum method in the gas and solution phases. Our results reveal that the [CpFe(CO)₂(NCS)] isomer is more stable than the [CpFe(CO)₂(SCN)] isomer. Based on the polarizable continuum model, the effect of the solvent polarity on the stability, structural parameters, frontier orbital energies, and vibrational modes of carbonyl ligands (ν_CO) of these linkage complexes is explored. The molecular orbital analysis suggests that the major contributions to HOMO and LUMO arise from the ambidentate ligand and Fe in two isomers, respectively. In addition, the bonding interaction between the CpFe(CO)₂ fragment and the ambidentate ligand is studied by means of the energy decomposition analysis. The back-bonding effect in Fe–CO bonds is revealed in the calculation of the quadrupole polarization of the carbon atom by the QTAIM analysis. The character of Fe–N and Fe–S bonds in these complexes is analyzed by the natural bond orbital analysis.

A detailed spectroscopic investigation along with quantum chemical studies on 3a,8a-dihydroxy-2-thioxo- 1,3,3a,8a-tetrahydroindeno[1,2-d]imidazol-8(2H)-one (dihydroxy-thioxo-tetrahydroindeno-imidazole) is carried out and shows the antimicrobial activity. The density functional method at the B3LYP/6-311++G(d,p) level is used to obtain the equilibrium geometries of the title compound. We have performed the vibrational analysis of the title compound at their equilibrium geometries and established the complete assignment of significant vibrational modes. The calculated vibrational frequencies are shown to be in perfect agreement with the experimentally observed FT-IR spectra of the molecule under study. The electronic properties of the molecule are discussed with the help of the descriptors such as HOMO-LUMO and MEPS, and several electronic and thermodynamic parameters are calculated which are closely related to the chemical reactivity and reaction paths. In addition, the molecular docking and NBO analyses are also carried out to get a better insight of the molecule.

Computational quantum chemistry methods are used to study simultaneous cation-π and π–π stacking interactions with a graphene sheet and on the inner and outer faces of some bent graphenes as curved surfaces of carbon nanohorns (CNHs). Structural parameters and energy data of ternary benzene–graphene–Na⁺ and benzene-bent graphene–Na⁺ complexes are studied. Also, effects of charge transfer and aromaticity are estimated to determine how changes in the structure influences the above interactions. The results indicate that the graphene curvature leads to structural changes affecting simultaneous interactions of the Na+ cation and benzene with bent graphenes. Also, the results show that although π–π stacking is a weak interaction, it can manipulate the order of binding energies in complexes involving both mentioned interactions and affect drug delivery abilities of these systems.

A new third order nonlinear optical single crystal of 2-phenylbenzimidazolium-p-toulenesulphonate is grown by the solvent evaporation technique using methanol as a solvent. The single crystal X-ray diffraction analysis reveals that crystals belong to the triclinic system. A nuclear magnetic resonance and Fourier transform infrared spectroscopic study confirms the formation and vibrational analysis for the compound. UV-visible absorption studies are also carried out for the crystal. Nonlinear refractive index, absorption coefficient, and third order nonlinear optical susceptibility of the crystals are evaluated by Z-Scan studies.

The title compound (disodium dipotassium copper(II) tris-[molybdate (VI)]) is prepared by form melt and characterized by single crystal X-ray diffraction and UV-vis spectroscopy. It crystallizes in the triclinic space group P-1 with a = 7.4946(8) Å, b = 9.3428(9) Å, c = 9.3619(9) Å, α = 92.591(7)°, β = 105.247(9)°, γ = 105.496(9)°, V = 604.7 ų, and Z = 2. Its structure is isotypic with that of Na₄Mn(MoO₄)₃. It is formed by Cu₂O₁₀ distorted bi-octahedral dimers linked by two bridging bidentate Mo₂O₄ tetrahedra and, additionally, two monodentate Mo₁O₄ tetrahedra to form Cu₂Mo₄O₂₀ units. These units are linked by the insertion of Mo₃O₄ tetrahedra to build infinite ribbons disposed along the c axis. All of these ribbons form a one-dimensional framework. Both K1 and K3 cations are located in the inversion center, and all the other atoms are at general positions. The structure model is supported by the bond valence sum (BVS) and charge distribution CHARDI methods. The Cu²⁺ cations adopt the [4+2] CuO₆ Jahn-Teller distortion giving rise to an intense d–d transition in the UV-vis absorption spectra.

The present paper reports static dielectric constants, densities, viscosities, and refractive indices of the binary mixtures of ethanol with DMSO measured at 303 K, 308 K, 313 K. These measured parameters are used to obtain the derived properties, such as the Bruggeman factor, the molar polarization, the excess molar volume, the excess viscosity, the excess static dielectric constant, and the excess molar polarization. The variation in magnitudes of these quantities with composition and temperature is used to discuss the type, strength, and nature of binary interactions. The excess parameters are fitted to the Redlich Kister (R-K) fit equation. The evaluated values of the excess dielectric constant and the excess molar polarization infer that deviations of their mixture values occur from the mole-fraction mixture law. The results confirm that there are dipole-dipole interactions between unlike molecules of ethanol+DMSO mixtures and that 1:1 complexes are formed. The excess static dielectric constant indicates that there is a decrease in the total number of parallel aligned effective dipoles that contribute to the mixture dielectric polarization. It is observed that the excess molar volume becomes more and more positive with the corresponding increase in the temperature. This observation certainly leads to the inference that the intermolecular interaction strength decreases with the temperature.

Two new complexes [{Zn(L¹)(μ-OAc)Zn(CH₃CHOHCH₃)}₂] and [Ni(L₂)(H₂O)(CH₃OH)] with asymmetric Salamo-type ligands (H₃L¹ and H₂L²) are synthesized and structurally characterized. In the Zn(II) and Ni(II) complexes, the terminal and central Zn(II) atoms are found to have slightly distorted square pyramidal and trigonal bipyramidal symmetries respectively, while the Ni(II) atom is hexa-coordinated and has a slightly distorted octahedral symmetry. Interestingly, a self-assembling continual zigzag 1D chain is formed by intermolecular hydrogen bonds in the Ni(II) complex. Furthermore, the Zn(II) and Ni(II) complexes in the ethanol solution show intense photoluminescence.

New end-on azido-bridged dinuclear copper(II) complex [Cu₂L₂(μ_1,1-N₃)₂] (I) (HL = 2-[(3-amino-2,2-dimethylpropylimino)-methyl]-4-bromophenol) is synthesized and characterized by the elemental analysis and FT-IR spectroscopy. The crystal structure of I is determined by X-ray diffraction. The crystal of I is monoclinic, space group P2_1/c, a = 10.7926(4) Å, b = 12.4222(4) Å, c = 11.0894(4) Å, β = 100.085(2)°, V = 1463.76(9) ų, Z = 2. The crystal structure shows that the structure contains [Cu₂L₂(μ_1,1-N₃)₂] units joined together by intermolecular H-bonding interactions to form a 2D rectangular grid.

Mononuclear cis,cis,trans-[Ru(CO)₂Cl₂(Pz*H)₂] (1) and dinuclear [Ru²(DMSO)₃Cl₂(Pz*H)× (μ-H)(μ-Pz*)(μ-DMSO)] (2) complexes (DMSO = dimethylsulfoxide and Pz* = 3,5-dimethylpyrazolate) are obtained by the reaction of KTp* in methanol (KTp* = potassium tris(3,5-dimethylpyrazolyl)borate) with [Ru(CO)₃Cl₂]₂ and cis-[RuCl₂(DMSO)₄] precursors, respectively. These complexes are obtained from the degradation of the scorpionate KTp* ligand and characterized by IR, ¹H NMR, and X-ray crystallography.

A novel nitrogen-rich ionic salt of bis(aminoguanidium) bis(5-nitroimino-1,2,4-triazolate-3-yl) methane ((AG)₂BNTM) is synthesized for the first time and its crystal structure is then determined by X-ray diffraction. Along with the crystal structures and the optimization of geometric structures, we employ the Hirshfeld surface analysis to analyze the types of interactions and relative energetic contributions of the weak intermolecular-interaction. Thermal stability was studied by the DSC-TGA technique.

The structure of the 4-[(4-ethyl-5-phenyl-4H-1,2,4-triazol-3-yl)sulfanyl]phthalonitrile titled molecule is determined by means of X-ray diffraction. The title compound has weak inter- and intramolecular C–H…N-type hydrogen bonds. Furthermore, there is a π–π interaction between triazole and phenyl rings.

Herein we report the synthesis and magnetic properties of a new one-dimensional Co(II) chain compound with the formula [Co(tricH₄)Cl] (tricH₅ = N-[tris(hydroxymethyl)methyl]glycine). In this structure, the cobalt ion has a slightly distorted octahedral coordination environment. TricH₄ is a pentadentate ligand using one nitrogen and four oxygen atoms to coordinate to the Co(II) ions. The three hydroxyl groups are all not detprotonated and the carboxylate moiety of the tricH₄ lignd is a bridge leading to a 1D chain. The crystal structure is stabilized by the intrachain and interchain hydrogen bonding. Magnetic susceptibility measurements exhibit only weak ferromagnetic exchange interactions found within the chain complex due to the carboxylate bridges.

In this work, the biosensor behavior of the DA-DA dinucleotide (DA2N) in the presence of DL-lysine (DLL) and three different single carbon nanotubes (SWNT), i.e., (5-5), (6-6), and (7-7), is studied by molecular dynamics (MD) simulation and density functional theory (DFT) approaches. The MD simulation of the system of DA2N with DLL and various nanotubes was performed. The obtained results for the RMSD values reveal that the simulated systems are in the equilibrium. The single point energy calculations of the DA2N structure in various simulations are performed. The HOMO-LUMO gap and their corresponding orbitals are obtained for DA2N. The results indicate that the adenine ring is responsible for the charge transfer in DA2N. The calculated Fukui indices show that the nitrogen atom of the five-membered adenine ring plays a more active role in the DA2N reactivity.

In an attempt to understand the antibacterial, antioxidant, and anticancer properties of phthalocyanines containing azo dye, new metallophthalocyanines (M: Mn, Co, Zn) substituted with guaiacol azo dyes are described. The high DPPH scavenging and ferrous ion chelating activity are obtained from almost all compounds. All compounds exhibit a poor antibacterial activity against the studied bacteria. Cytotoxicity, apoptotic and necrotic effects are examined on human breast cancer cells (MCF-7) and fibroblast cells. It is determined that methoxy groups at newly synthesized compounds increase the antioxidant property but decrease other antibacterial and anticancer properties.