Preparation of an efficient catalyst through injection of CuI on modified poly (styrene-co-maleic anhydride) and theoretical investigation of the structural and electronic properties of catalyst

A novel polymer supported [poly (styrene-co-maleic imide) (SMI)]Cu(I) nano-particles was prepared via in situ reaction of 4-amino-5-methyl-4H-1,2,4-triazole-3-thione with [poly (styrene-co-maleic anhydride)] (SMA) along with immobilization of CuI. These nano-particles were fully characterized by using scanning electron microscopy (SEM), energy dispersive spectroscopy analysis, Xray (EDAX), inductively coupled plasma (ICP) analysis, ¹H NMR and FT-IR techniques. Moreover, the structural and electronic features of metal–ligand interactions in the complex model of polymer-supported copper nanocatalyst were assessed using density functional theory calculations. The catalytic activity of these supported Cu(I) nonoparticles was examined in one of the classiest name reaction so–called “click reaction” which is coined K. B Sharpless for the regioselective synthesis of 1,2,3-triazole derivatives using a multicomponent reaction (MCR) involving benzyl halides, sodium azide and terminal alkynes in water as a green solvent. This heterogeneous catalyst showed excellent catalytic activity and was separated by simple filtration and was used at least in five consecutive runs without a significant decrease in its activity.     

Macrocyclic Cr3+, Mn2+ and Fe3+ complexes of a mimic SOD moiety: Design,structural aspects,DFT, XRD,optical properties and biological activity

A novel SOD-like macrocycle “H₂DPD” and its trivalent chromium, iron and divalent manganese complexes have been isolated and characterized using the conventional tools. The macrocycle was prepared by 2:2 condensation of P-phenylenediamine with 5,5-dimethyl1,3-cyclohexanedione. IR and electronic spectral data suggested that H₂DPD coordinates to the metal ion as N₄ tetradentate donor with two Cl⁻ occupying the remaining two sites of the distorted octahedron. XRD spectrum of Cr³⁺ complex indicated that the complex crystallizes in a face-centered monoclinic structure with lattice parameters: a = 10.9380 Å; b = 12.4870 Å; c = 12.4600 Å, α = γ = 90° and β = 111.430 with space group P 1 21/c 1 (14). The energy gap (E_HOMO-E_LUMO), molecular electrostatic potential map (EPM) of title compounds, bond length, bond angle, as well as global and local reactivity were estimated using DFT method. The E_g values obtained from electronic spectra of Cr³⁺, Mn²⁺ and Fe³⁺ complexes were found to be 1.284, 1.220 and 1.138 eV, respectively which are in accordance with those evaluated by DFT revealing semiconductor nature. Also, the thermal degradation of all title compounds was carried out and the kinetic parameters were evaluated using Coats-Redfern and Horowitz-Metzger equations. Moreover, the compounds have screened for antibacterial as well as superoxide mimic activities. Cr³⁺ complex exhibited the most significant potent activity against all bacterial strains. With respect to SOD-like activity, the macrocycle showed the most remarkable SOD-like activity comparable to the standard drug, ascorbic acid.     

A theoretical study on the pure and doped ZnO nanoclusters as effective nanobiosensors for 5-fluorouracil anticancer drug adsorption

The electronic sensitivity and effectiveness of the pristine, Fe,- Mg-, Al- and Ga-doped ZnO nanoclusters interacted with 5-fluorouracil (5-FU) anticancer drug are theoretically investigated in the gas phase using the B3LYP/wB97XD density functional theory calculations with LANL2DZ basis set. It is concluded that 5-FU adsorption on the doped nanoclusters has relatively higher adsorption energy as compared with the pristine zinc oxide. A number of thermodynamic parameters, such as band gap energy (E_g), adsorption energy (E_ad), molecular electrostatic potential, global hardness (η) and density of electronic states, are attained and compared. Also, calculated geometrical parameters and electronic properties for the studied systems indicate that Mg- and Ga-doped Zn₁₂O₁₂ present higher sensitivity to 5-FU compared with the pristine nanocluster. Theoretical results reveal that adsorption of 5-FU on the doped nanoclusters is influenced by the electronic conductance of the nanocluster. Therefore, Mg- and Ga-doped ZnO can be considered as promising nanobiosensors for detection of 5-FU in medicine.     

Synthesis,structural, spectroscopic,and thermal studies of some transition-metal complexes of a ligand containing the amino mercapto triazole moiety

A new series of transition-metal complexes of Schiff base ligand containing the amino mercapto triazole moiety ( HL ) was prepared. The Schiff base and its metal complexes were elucidated by different spectroscopic techniques (infrared [IR], ¹H nuclear magnetic resonance, UV–Visible, mass, and electron spin resonance [ESR]), and magnetic moment and thermal studies. Quantum chemical calculations have been carried out to study the structure of the ligand and some of its complexes. The IR spectra showed that the ligand is chelated with the metal ion in a neutral, tridentate, and bidentate manner using NOS and NO donors in complexes 1 – 6 , 10–12 , and 7 and 8 , respectively, whereas it behaves in a monobasic tridentate fashion using NOS donor sites in copper(II) nitrate complex ( 9 ). The magnetic moment and electronic spectra data revealed octahedral and square pyramidal geometries for complexes 2 , 11 , 12 , and 5 – 8 and 10 , respectively. However, the other complexes were found to have tetrahedral ( 4 ), trigonal bipyramidal ( 1 and 3 ), and square planar ( 9 ) structures. Thermal studies revealed that the chelates with different crystallized solvents undergo different types of interactions and the decomposition pathway ended with the formation of metal oxygen (MO) and metal sulfur (MS) as final products. The ESR spectrum of copper(II) complex 10 is axial in nature with hyperfine splitting with ²B_1g as a ground state. By contrast, complexes 7 and 8 undergo distortion around the Cu(II) center, affording rhombic ESR spectra. The HL ligand and some of its complexes were screened against two bacterial species. Data showed that complex 12 demonstrated a better antibacterial activity than HL ligand and other chelates.     

Biological assays and theoretical density functional theory calculations of Rh(I), Ir(III), and Ru(II) complexes of chiral phosphinite ligand

Four metal complexes, IL-OPPh₂-Ru-p-cymene (3) , IL-OPPh₂-Ru-benzene (4) , IL-OPPh₂-Ir-Cp* (5) , IL-OPPh₂-Rh-COD (6) , have been evaluated for in vitro antioxidant activity such as 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and reducing power activity. Maximum scavenging activity (71.43%) was obtained with IL-OPPh₂-Ru-p-cymene, whereas IL-OPPh₂-Rh-COD showed the highest reducing power ability. The complexes were also studied for their antimicrobial activity against three Gram-positive and three Gram-negative bacteria. In addition, DNA binding of the complexes was evaluated using calf thymus DNA. Both Ru(II) complexes exhibited good DNA-binding activity while the other complexes did not have any activity. Furthermore, ab initio quantum calculations of four complexes were also carried out using density functional theory to better understand their chemical behaviors.     

Efficient structural modification of electron-withdrawing substituents on Pt(II) complexes for red emitters: A theoretical study

In this study, the electronic structures and optical properties of a cyclometalated Pt(II) complex (M1) and a series of derivatives (M1–F, M1–CF₃, and M1–CN) with electron-withdrawing substituents (–F, –CF₃, and –CN) at the carbazole moiety were theoretically investigated by density functional theory and time-dependent density functional theory. The calculation results reveal that these Pt complexes display deep red phosphorescence emission above Λ = 640 nm. When the ³MLCT/π → π* to triplet metal-centered ³MC/d–d state decay mechanism is taken into consideration, the nonradiative decay rate constant (k_nr) decreased in the order M1 > M1–CF₃ > M1–F > M1–CN. The <T₁|H_SOC|S_m> and kr values of M1-F are similar with those of M1, however the Knr rate ofM1-F is larger than that of M1. M1–F is expected to have improved quantum yields. Moreover, through the analyses of the HOMO/LUMO level and triplet energy, it is found that the introduction of –F and –CN substituents in M1 results in efficient energy transfer from the host material 4,4′-N,N′-dicarbazole-biphenyl to these complexes. In view of the electroluminescent applications in organic light-emitting diodes, M1–F can serve as efficient deep-red guest materials with improved electron injection and transport ability.     

Synthesis,spectral, DFT calculations and biological studies of solvatochromic copper(II)-ONS hydrazone derived from 2-aminochromone-3-carboxaldehyde

New ONS hydrazone ligand, 2-[(2-aminochromon-3-yl)methylidene]-N-phenylhydrazinecarbothioamide, HL , was synthesized and reacted with different salts of Cu (II) ion (OAc⁻, NO₃⁻, SO₄²⁻ and Cl⁻) in absence and presence of secondary ligands (L′); 8-hydroxyquinoline, 1,10-phenanthroline or SCN⁻; to form binary and ternary Cu(II)-chelates. The ligand and its Cu(II)-complexes were fully characterized by analytical, spectral, thermal, conductivity and magnetic susceptibility measurements. The metal chelates showed octahedral, square planar and /or distorted tetraherdal arrangements. Coats–Redfern equations used to calculate the kinetic parameters of the thermal decomposition stages (E_a, A, ΔH, ΔS and ΔG). The compounds exhibit luminescence property; promising interesting potential applications as photoactive materials. Lippert–Mataga, Bakhshiev, Kawski–Chamma–Viallet and microscopic solvent polarity parameter and E_T^N correlation methods were applied on the solvatochromic shifts of emission spectra to evaluate the ground (μ_g) and excited (μ_e) states dipole moments. Excited state dipole moment is larger than the ground state which may be attributed to π-π* transition. The coordinating anions play an important role on the position and intensity of emission band. The ligand and its metal complexes showed antimicrobial activity towards Gram–positive bacteria, Gram–negative bacteria, yeast and fungus. The molecular structural parameters of HL and its Cu(II)- complexes have been calculated on the basis of DFT engaged in the Gaussian 09 program at the B3LYP/6-31G(d,p) level; the theoretical data are correlated with the experimental data.     

Novel halogenated cyclopentasilylene-2,4-dienes via DFT

In view of immense importance of silylenes and the fact that their properties undergo significant changes on substitution with halogens, here, we have used B3LYP/6-311++G** level of theory to access the effects of 1–4 halogens (X = F, Cl, Br, and I) on four unprecedented sets of cyclopentasilylene-2,4-dienes; with the following formulas: SiC₄H₃X ( 1 _X ), SiC₄H₂X₂ ( 2 _X ), SiC₄HX₃ ( 3 _X ), and SiC₄X₄ ( 4 _X ). In going down from F to I, the singlet (s)-triplet (t) energy gap (ΔE_s-t, a possible indication of stability), and band gap (ΔE_H-L) decrease while nucleophilicity (N), chemical potential (μ), and proton affinity (PA) increase. The overall order of N, μ, and PA for each X is 2 _X > 1 _X > 3 _X > 4 _X . Precedence of 2 _X over 1 _X is attributed to the symmetric cross conjugation in the former. The highest and lowest N are shown by 2 _I and 4 _F . The trend of divalent angle () for each X is 4 _X > 1 _X > 3 _X > 2 _X . The results show that in going from electron withdrawing groups (EWGs) to electron donating groups (EDGs), the ΔE_s-t and ΔE_H-L decrease while N, μ, and PA increase. Also, rather high N of our scrutinized silylenes may suggest new promising ligands in organometallic chemistry.     

New monodentate and bidentate silylene ligands by DFT

Considering the importance of silylene ligands in transition metal-mediated catalytic reactions, we have scrutinized eight novel monodentate ( 1 – 4 ) and bidentate ( 1 ^′ - 4 ^′ ) derivatives of 2,5-diX-cyclopentasilylene-2,4-dienes (X = NH₂, OH, PH₂, and SH), at M06/6-311++G** level of theory. To probe the complexation ability of our scrutinized silylene ligands with Rh atom ( 1 _Rh - 4 _Rh and 1 ^′ _Rh - 4 ^′ _Rh , respectively), thermodynamic and structural parameters such as complexation energy (ΔE_Com), singlet-triplet energy gap (ΔE_s-t), bond length, along with NBO and atoms in molecules analyses are provided. In going from less electron donating groups (EDGs) to more EDGs (NH₂ > OH > PH₂ > SH), the σ -donor strength and ligand flexibility increase. Structures 1 and 1 ^′ turn out as the most nucleophilic species for showing the highest nucleophilicity (N = 5.47 and 5.40 eV, respectively). Furthermore, they exhibit the highest proton affinity values (PA = 271.46 and 271.23 kcal/mol, respectively). The results indicate that bidentate coordination mode of silylene leads to a stronger Si-Rh complex. The overall orders of σ -donation ability for monodentate and bidentate silylene ligands are 1 > 2 > 3 > 4 and 1 ^′ > 2 ^′ > 3 ^′ > 4 ^′ , respectively.     

Structure and bonding of lanthanide dinitrogen complexes,Ln(N2)1-8

Lanthanide dinitrogen complexes, Ln(N₂) _x (x = 1-8), were investigated by Density Functional Theory computations using the B3LYP exchange-correlation functional in conjunction with quasirelativistic pseudopotentials for Ln. After a recent study on the lanthanum complexes (A. Kovács, Structural Chemistry 2018 , 29, 1825), the present study aimed to probe the changes upon variously filled 4f subshells of Ln on the structures, stabilities, and bonding properties in related complexes of Nd, Ho, and Lu. The bonding properties were assessed on the basis of natural atomic charges, Ln valence orbital populations, and analysis of bonding molecular orbitals.