Experimental and theoretical characterization of 3-amino-1-phenyl-2-buten-1-onato ligand and its copper(II) and nickel(II) complexes: synthesis, characterization, X-ray structures, DFT and TDDFT studies

This article presents a combined experimental and computational investigation of 3-amino-1-phenyl-2-buten-1-onato, APBO ligand and its copper(II) and nickel(II) complexes. APBO is an unsymmetrical, bidentate and monoanionic ligand with different coordinating atoms (N,O). A comparison among different possible conformers of the ligand has been carried out using density functional theory (DFT) method at the B3LYP/6-31+G(d,p) level. It was demonstrated that two factors control stability of the compounds as hydrogen bonding (conventional and nonconventional) and resonance effect. The effectiveness of each of these parameters on the stability of ligands is discussed. The prepared homoleptic complexes of [Ni(APBO)₂] and [Cu(APBO)₂] were characterized with IR, NMR, UV–Vis spectroscopic techniques. The X-ray crystallography of [Ni(APBO)₂] demonstrated that the bidentate APBO binds to the metal center in trans fashion and the geometry around the nickel atom is square planar. The experimental studies on the complexes were accompanied computationally by the DFT and time-dependent DFT calculations.     

Discrimination of prostate cancer cells and non-malignant cells using secondary ion mass spectrometry

This communication utilises Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) combined with multivariate analysis to obtain spectra from the surfaces of three closely related cell lines allowing their discrimination based upon mass spectral ions.     

Synthesis and characterization of graphene oxide/modified poly(<Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide) nanocomposite

In this study, the graphene oxide/poly(N-isopropylacrylamide) nanocomposite modified with 2-mercaptoethanol (GO/MPNIPAM) was synthesized in three stages. N-Isopropylacrylamide polymerization was firstly performed in the presence of azobisisobutyronitrile as an initiator, which was discovered by Homer, and 2-mercaptoethanol as a modifier. Then, the graphene oxide/modified polymer nanocomposite was synthesized by the covalent interactions between carboxylic acids of the graphene oxide and hydroxyl groups of the modified polymer during the esterification reaction. The GO/MPNIPAM nanocomposite includes some percentage of the polymer that improves solubility and stability of the GO sheets in physiological applications; due to the interaction between the MPNIPAM and the modified GO polymer, a bridge-like connection is formed between the GO sheets and the process that leads to remove a large number of hydrophilic groups on the GO nanocomposite and therefore, the GO/MPNIPAM is well dissolved in organic solvents. This property is beneficial for anti-cancer drug delivery as well as π–π interactions between the nanocomposite and aromatic drugs. The nanocomposite is not a toxic material for human body at all and has high capacity for drug delivery. Structure and morphology of the nanocomposite were studied by FTIR, SEM, XRD, UV, TGA and Raman analysis. The analysis done by X-ray diffraction pattern confirmed the presence of graphene oxide in nanocomposites and improved crystalline polymer in nanocomposites.     

Cyclic voltammetric study of the redox behavior of Fe(II)/Fe(III) systems forming during the oxidation of Fe(II) complexes with saccharin and with saccharin and 1,10-phenanthroline

The electrochemical redox behavior of Fe(II)/Fe(III) systems formed during the oxidation of complexes [Fe(C₇H₄NO₃S)₂(H₂O)₄] · 2H₂O (Fe-sac) and [Fe(C₇H₄NO₃S)₂(C₁₂H₈N₂] · 2H₂O (Fe-sac-phen) have been investigated using cyclic voltammetry in the aqueous medium. In the CVs one pair of well-defined cathodic and anodic peaks appear for the transfer of single electron in the Fe-sac complex. The peak potentials are much wider separated as compared with the free (uncoordinated) Fe(II)/Fe(III) system. The ΔE values demonstrate that the electrode process is irreversible. In the presence of secondary ligand, 1,10-phenanthroline (Fe-sac-phen complex), the redox behavior of iron complexes is quasireversible. The effect of pH on the redox behavior of iron system is studied in acetate buffer. Published in Russian in Elektrokhimiya, 2008, Vol. 44, No. 12, pp. 1504–1509. The text was submitted by author in English     

DFT Calculations and NBO Analysis of 2-Chloroethylethyldichlorosilane Unimolecular Elimination Kinetics in the Gas Phase

Ab initio molecular orbital calculations have been used to investigate the thermal decomposition kinetics of 2-chloroethylethyldichlorosilane at the B3LYP/6-311+G**,B3PW91/6-311+G**,and MPW1PW91/6-311+G** levels of theory.Among these methods,the results(activation parameters) obtained using the B3LYP/6-311+G** level are in good agreement with the available experimental data.The calculated data imply that in the unimolecular β-elimination reactions of the studied compound in the gas phase,the polarization of C(1)-Cl(3) and C(1)-H(4) bonds in the sense of C(1)δ+-Cl(3)δ-and C(1)δ+-H(4)δ-,respectively,is a determining factor in the gas phase elimination reactions 1,2 and 3.Analysis of bond order,natural bond orbital charges,bond indexes,synchro-nicity parameters,and IRC calculations suggest the elimination of 2-chloroethylethyldichlorosilane via reactions 1～3 can be described as concerted and slightly asynchronous.The transition state structures of these reactions are a four-membered cyclic structure.     

Evaluation of the Electrophilicites and Band Gaps of Conductive Polymers: A New Model

It is shown that the obtained hardness and electrophilicity values of the short length oligomers for a heterocyclic conductive polymer from density functional theory method are quadraticly correlated to those obtained from semiempirical method. Therefore these quantities for all oligomers (up to 15 repeating units) are predicted using the obtained quadratic relations. Both of these predicted quantities for different oligomers are fitted to a new exponential model (Y = Y_∞ e^d/n) to estimate the electronic properties for the considered conjugated polymers. The calculated band gaps from this model show better agreement with the reported experimental data than those predicted by the previous models. Because of a wide range of variations, the electrophilicity could be a better index for investigating the doping effect in polymers than the hardness.

     

Merging tribenzotriquinacene with hexa-peri-hexabenzocoronene: a cycloheptatriene unit generated by Scholl reaction

The single-wing extension of the bowl-shaped tribenzotriquinacene (TBTQ) framework with polycondensed aromatic hydrocarbon units has been reported. In the course of a Scholl reaction, one of the three-dimensional bays of the TBTQ core has been bridged by a PAH unit to generate a seven-membered ring within the merged TBTQ-(hexa-peri-hexabenzocoronene) scaffold.     

A Theoretical Study of NBO,NICS, and 14N NQR Parameters of Adenine Tautomers in the Gas Phase via DFT

The natural bond orbital (NBO) analysis, nucleus independent chemical shift (NICS), and ¹⁴N NQR parameters of the most stable tautomers of adenine in the gas phase were predicted using density functional theory method. The NBO analysis revealed that the resonance interaction between lone pair of the nitrogen atom and empty non‐Lewis NBO increases with increasing the p character of the nitrogen lone pair. The present investigation indicated the π clouds in both the considered heterocyclic rings containing six electrons, and these tautomers has the aromatic character. The NICS study utilizing the gauge‐invariant atomic orbital method showed that there are diatropic currents in the heterocyclic rings of the tautomers, so we determined the order of overall aromaticity of these tautomers. The results of NQR parameter calculations showed three parameters are effective on nuclear quadrupole coupling constant; the p character value of lone pair electrons of nitrogens, and the related occupancies and whenever, the lone pair electrons of nitrogens participate in the formation of chemical bond and/or π system of the ring, the q_zz and consequently its χ decreases.     

On a graph of ideals

We associate a graph Γ₊(R) to a ring R whose vertices are nonzero proper right ideals of R and two vertices I and J are adjacent if I+J=R. Then we try to translate properties of this graph into algebraic properties of R and vice versa. For example, we characterize rings R for which Γ₊(R) respectively is connected, complete, planar, complemented or a forest. Also we find the dominating number of Γ₊(R).     

Effect of non-aqueous solvents on stoichiometry and selectivity of complexes formed between 4′-nitrobenzo-15-crown-5 with Fe3+, Y3+, Cd2+, Sn4+, Ce3+ and Au3+ metal cations

The complexation processes between Fe³⁺, Y³⁺, Cd²⁺, Sn⁴⁺, Ce³⁺ and Au³⁺ metal cations with macrocyclic ligand, 4′-nitrobenzo-15-crown-5 (4′NB15C5), were studied in acetonitrile (AN), methanol (MeOH) and nitromethane (NM) solvents at different temperatures using conductometric method. The conductance data show that the stoichiometry of the complexes formed between this macrocyclic ligand and Cd²⁺, Au³⁺ cations is 1: 1 (ML), but in the case of Fe³⁺, Y³⁺ and Ce³⁺ metal cations, 2: 1 (M₂: L) and 2: 2 [M₂: L₂] complexes are formed in nitromethane solutions. The results show, that the selectivity of 4’NB15C5 for the studied metal cations in methanol solutions at 15°C is: Sn⁴⁺ > Cd²⁺ > Y³⁺ > Fe³⁺ ∼ Ce³⁺ > Au³⁺, but in the case of acetonitrile, the stability order was found to be: Y³⁺ > Au³⁺ > Fe³⁺ > Cd²⁺. The values of stability constants of the 1: 1 [M: L] complexes were determined from conductometric data using a GENPLOT computer program. The values of thermodynamic parameter (ΔH _c ^o and ΔH _c ^o) for formation of the complexes were obtained from temperature dependence of the stability constants, using the van’t Hoff plots. The results show that the values of standard enthalpy (ΔH _c ^o) and standard entropy (ΔH _c ^o) change with the nature of the non aqueous solvents.