The preparation of [1,2,4]triazolo[1,5-a]pyrimidines catalyzed by Schiff base zinc(ii) complex supported on magnetite nanoparticles under mild conditions.

Nano-[CuFe2O4@SiO2/propyl-1-(O-vanillinaldimine)][ZnCl2] was prepared by placing a Schiff base zinc(ii) complex on a magnetite core and fully characterized by various analyses such as FT-IR, FE-SEM, EDAX, SEM-coupled EDX, TGA, VSM and TEM. The complexes supported on silica-coated magnetite copper ferrite nanoparticles were used as a reusable catalyst for the synthesis of 5-methyl-N,7-diphenyl-4,7-dihydro-[1,2,4]triazolo[1,5-a] pyrimidine-6-carboxamides resulting in 40% to 96% yield in the reactions of various aldehydes, acetoacetanilide, and 3-amino-1,2,4-triazole at 60 °C under solvent-free conditions. The zinc complex can change its structure from tetrahedral to square planar and catalyze the reaction. Some products containing the benzyloxy moiety are new and have been reported for the first time.

TiO2/porous carbon as a new nanocomposite and catalyst for the preparation of 4H-pyrimido[2,1-b]benzimidazoles.

A nano TiO2/porous carbon nanocomposite (TiO2/PCN) was designed by the pyrolysis of peanut shells as bio waste with nano titanium dioxide. In the presented nanocomposite, titanium dioxide is properly placed in the positions and pores of the porous carbon, so that it acts as an optimal catalyst in the nanocomposite structure. The structure of TiO2/PCN was studied by various analyses such as Fourier transform infrared spectroscopy (FT-IR), energy-dispersive X-ray Spectroscopy (EDX), scanning electron microscopy (SEM), SEM coupled EDX (SEM mapping), transmission electron microscopy (TEM), X-ray fluorescence (XRF) and BET. TiO2/PCN was successfully tested as a nano catalyst for the preparation of some 4H-pyrimido[2,1-b]benzimidazoles in high yields (90-97%) and short reaction times (45-80 min).

Template synthesis, DNA binding, antimicrobial activity, Hirshfeld surface analysis, and 1D helical supramolecular structure of a novel binuclear copper(ii) Schiff base complex.

A new binuclear copper(ii) Schiff base complex [Cu2 L2 - (NO3)2]·2CH3OH (1) [L = 2,6-bis((E)-(p-tolylimino)methyl)-4-methoxyphenol] was synthesized using a template method in which the tridentate N2O Schiff base ligand was derived from [1 + 2] condensation of 2,6-diformyl-4-methoxyphenol and p-methyl aniline in the presence of copper(ii) ions as the template agent. The X-ray diffraction analyses revealed that this complex crystallizes in the monoclinic system with space group P21/n. The most remarkable structural feature of 1 is that it contains two types of 1D right-handed helical chains. The molecules are linked by intermolecular hydrogen bonds and π⋯π interactions, then a 3D supramolecular network was constructed. Moreover, the intermolecular interactions on the crystal packing of 1 have been further studied using Hirshfeld surface analysis and corresponding 2D fingerprint plots. Binding interaction of this complex with calf thymus DNA (CT-DNA) has been investigated using absorption and emission studies, viscosity experiments and circular dichroism studies. Complex 1 shows significant binding to the DNA. The results of fluorescence spectroscopy and UV absorption spectroscopy, CD spectroscopy and viscosity indicated that this complex interacted with CT-DNA in a groove binding mode where the binding constant was 1.3 ± 0.2 × 104 L mol-1. Our fluorimeteric study showed that the reaction between 1 and CT-DNA was exothermic (ΔH = 59.6 kJ mol-1; ΔS = 268.79 J mol-1 K-1). Antibacterial activities of the complex were screened by the disc diffusion method against three Gram-positive bacteria (Staphylococcus aureus ATCC 25923, Enterococcus faecalis ATCC 23212 and S. epidermidis ATCC 34384), and three Gram-negative bacteria (Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853 and Klebsiella pneumonia ATCC 70063). The results indicated that this complex demonstrated acceptable antibacterial activities.

The electronic mechanism ruling the dihydrogen bonds and halogen bonds in weakly bound systems of H3SiH···HOX and H 3SiH···XOH (X = F, Cl, and Br).

The dihydrogen bond complexes (H3SiH∙∙∙HOX) and halogen bond complexes (H3SiH∙∙∙XOH) formed between SiH4 and hypohalous acids HOX (X = F, Cl, and Br) have been studied at the MP2/6-311++G(2d,2p) computational level. The analyses of structure and infrared vibration frequencies have revealed tendencies in the red shifts and blue shifts of the stretch frequencies of the Si-H, H-O, and O-X bonds. Besides the computation of the interaction energies, punctual atomic charges and charge transference amounts were determined at light of the Natural Bond Orbital (NBO) approach, by which the quantifications of the s- and p-characters of hydrogen, oxygen, and silicon also were useful to unveil the frequency shifts aforementioned. With the purpose to elucidate the donor/acceptor interface along the charge transfer mechanism between the dihydrogen bonds and halogen bonds, the application of the hierarchical cluster analysis (HCA) and principal component analysis (PCA) chemometric techniques were useful in this regard. Moreover, the interaction strengths of the H3SiH∙∙∙HOX and H3SiH∙∙∙XOH complexes was computed through a model that embodies the frequency shifts and topological parameters derived from quantum theory of atoms in molecules (QTAIM).

A computational study of hydrogen bonds in intermolecular systems of high complexity: arachno-pentaborane(11)···Y with Y = O2 and N 2.

The interactions of arachno-B(5)H(11) with N(2) and O(2) were theoretically studied. In the B(5)H(11)···N(2) and B(5)H(11)···O(2) complexes, the terminal hydrogens of B(5)H(11) work as electron donors whereas the bridge ones as electron acceptors. The optimized structures and the corresponding harmonic vibration spectra were investigated through the MP2/aug-cc-pVDZ level of theory. In order to characterize the hydrogen bonds, the topological calculations inherent to the QTAIM protocol and MEP analysis were carried out. The NBO analyses were useful in the interpretation of the red-shifts and blue-shifts on the stretch frequencies of the proton donors, of course in agreement with the Bent rule for the chemical bonding as well as by the conceptions of hyperconjugation or hybridization.

Ultra-sensitive quantification of copper in food and water samples by electrochemical adsorptive stripping voltammetry.

A new electrochemical adsorptive stripping voltammetry method was developed for the determination of trace amounts of copper in food and water samples. The study of electrochemical behavior of Cu ion indicated that Cu(II) and Schiff base formed a complex in H3BO4-NaOH buffer solution (pH = 7.25). An accumulation potential of -100 mV (vs Ag/AgCl) was applied while the solution was stirred for 60 s. The response curve was recorded by scanning the potential, and the peak current of -0.31 V (vs Ag/AgCl) was recorded. The peak current and concentration of copper accorded with linear relationship in the range of 0.04-120 ng mL(-1). The relative standard deviation (for 12 ng mL(-1) of copper) was 1.73%, and the detection limit was 0.007 ng mL(-1). The possible interference of some common ions was studied. The proposed method was applied to the determination of copper in water, rice, wheat, tea, milk, and tomato with satisfactory results.

[µ-N,N'-Bis(2-amino-eth-yl)ethane-1,2-diamine-κ(4)N(1),N(1'):N(2),N(2')]bis-{[N,N'-bis-(2-amino-eth-yl)ethane-1,2-diamine-κ(4)N,N',N'',N''']cadmium} tetra-kis-(perchlorate).

The centrosymmetric dinuclear cadmium title complex, [Cd(2)(C(6)H(18)N(4))(3)](ClO(4))(4), was obtained by the reaction of N,N'-bis-(2-amino-eth-yl)ethane-1,2-diamine (trien) with Cd(NO(3))(2)·4H(2)O and sodium perchlorate in methanol. The Cd(II) cation is coordinated by four N atoms of a non-bridging trien ligand and by two N atoms of a bridging trien ligand in a slightly distorted octa-hedral coordination geometry. The bridging ligand shares another two N atoms with a neighboring symmetry-equivalent Cd(II) cation. The structure displays C-H⋯O and N-H⋯O hydrogen bonding. The perchlorate anion is disordered over two sets of sites in a 0.854 (7): 0.146 (7) ratio.

Bis[N-(3-amino-prop-yl)propane-1,3-di-amine-κN,N',N'']cadmium nitrate perchlorate.

The title complex, [Cd(C(6)H(17)N(3))(2)](ClO(4))(NO(3)), was synthesized by the reaction of Cd(NO(3))(2)·4H(2)O, bis-(3-amino-prop-yl)-amine and sodium perchlorate in methanol. The asymmetric unit of the title complex consists of one Cd(2+) cation, two tridentate bis-(3-amino-prop-yl)amine ligands, one nitrate anion and one perchlorate anion. The Cd(2+) cation is coordinated by six N atoms of the bis-(3-amino-prop-yl)amine ligands in a slightly distorted octa-hedral coordination geometry. In the crystal, mol-ecules are held together by an intricate network of N-H⋯O inter-actions. One of the two amine ligands was found to be disordered over two sets of sites, with a ratio of 0.802 (3):0.198 (3), similarly to the nitrate anion, with a ratio of 0.762 (10):0.238 (10).