Alina T. Dubis

Preparation and characterization of composites that contain small carbon nano-onions and conducting polyaniline

Small multilayer fullerenes, also known as carbon nano-onions (CNOs; 5-6 nm in diameter, 6-8 shells), show higher reactivity than other larger carbon nanostructures. Here we report the first example of an in situ polymerization of aniline on phenyleneamine-terminated CNO surfaces. The green, protonated, conducting emeraldine polyaniline (PANI) was directly synthesized on the surface of the CNO. The functionalized and soluble CNO/PANI composites were characterized by TEM, SEM, DSC, Raman, and infrared spectroscopy. The electrochemical properties of the conducting CNO/PANI films were also investigated. In comparison with pristine CNOs, functionalized carbon nanostructures show dramatically improved solubility in protic solvents, thus enabling their easy processing for coatings, nanocomposites, and biomedical applications.

Small noncytotoxic carbon nano-onions: First covalent functionalization with biomolecules

Small carbon nano-onions (CNOs, 6-8 shells) were prepared in high yield and functionalized with carboxylic groups by chemical oxidation. After functionalization these nanostructures were soluble in aqueous solutions. 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2 tetrazolium (MTS) tests showed excellent cytocompatibility of all CNOs analyzed at 30 and 300 microg mL(-1), so these carbon nanostructures can be safely used for biological applications. The first covalent functionalization of oxidized CNOs (ox-CNOs) with biomolecules, by using biotin-avidin interactions is reported here. Multilayers were prepared on a gold surface by layer-by-layer assembly and the process was monitored by surface plasmon resonance (SPR) spectroscopy and atomic force microscopy (AFM). Covalent binding of molecules to the short amine-terminated organosulfur monolayers was assessed by Fourier transform infrared spectroscopy using total attenuated reflactance mode (FT-IR/HATR).

Infrared spectroscopic and theoretical ab initio studies on conformational isomers of methyl pyrrole-2-carboxylate

Abstract The structure of methyl pyrrole-2-carboxylate has been studied on the basis of both IR spectra and ab initio RHF calculations (6-31G ∗∗ and 6-311++G ∗∗ basis sets). The calculations on two conformations of molecular structure have been carried out. IR spectra show that the concentration of one of the conformers in CCl 4 solution is higher; the theoretical studies show that such conformer is more stable than the second one.

Feeding-deterrent activity of α-asarone isomers against some stored Coleoptera

All isomers of α-asarone [(E)-4-prop-1-enyl-1,2,5-trimethoxybenzene] were tested for their feeding deterrent activity against adults of Sitophilus granarius and Tribolium confusum and larvae of Trogoderma granarium and Tribolium confusum. (E)-2-prop-1-enyl-1,3,5-trimethoxybenzene exhibited the strongest deterrent activity against all the species tested. The total coefficients of deterrency for this compound were 140.6 and 169.7 for Tribolium confusum adults and larvae, respectively, and 144.9 and 104.6 for larvae of Trogoderma granarium and adults of Sitophilus granarius, respectively. © 2000 Society of Chemical Industry

Spectroscopic and theoretical studies on the monomeric and dimeric forms of methyl pyrrole-2-carboxylate

The infrared spectra of a very dilute solution and a KBr pellet of methyl pyrrole-2-carboxylate (MPC) are compared with the theoretical spectra of monomeric and dimeric forms of MPC obtained at the RHF/6-311+G* level of theory, showing that dimers connected through N–H⋯O interactions are dominant in the solid state. Ab initio calculations are used for the analysis of geometries of both monomeric and dimeric forms of MPC. The H-bond energy for MPC dimer is calculated and the basis set superposition error (BSSE) is corrected by the counterpoise method of Boys and Bernardi. The Bader theory is also used to analyse N–H⋯O interactions within the MPC dimer. The experimental IR spectra, results of ab initio calculations and the analysis of topological parameters obtained from the Bader theory show that H-bonds of MPC dimer are of medium strength. The N–H⋯O interactions of MPC are also compared with a sample of other conventional and unconventional H-bonds and a measure of the H-bond strength introduced recently is applied in this study.

Electrochemical properties of oxidized carbon nano-onions: DRIFTS-FTIR and raman spectroscopic analyses.

The electrochemical reactions of carboxylic and lactone groups on carbon nano-onions (CNOs) in aqueous solutions result in non-Kolbe products: alcohols, ketones, ethers and epoxides. The anodic/cathodic conversion of ox-CNOs was assessed by Boehm titrations and by Raman and DRIFTS-FTIR (diffuse reflectance infrared Fourier transform spectroscopy). The electrochemical properties of oxidized carbon nano-onions were investigated by cyclic voltammetry in aqueous solutions. The ox-CNOs are electrochemically active as a result of the reduction of the oxygen-containing groups.

Spectroscopic and theoretical studies on some new pyrrol-2-yl-chloromethyl ketones

A novel series of pyrrole-2-yl chloromethyl ketones were synthesized and studied by FT-IR, 1H, 13C NMR spectroscopy and DFT calculations at the B3LYP/6-311++G(d,p) level of approximation. Two stable conformations were detected in solution: s-cis and s-trans forms where the CO group is located on the same side or the opposite side of N–H group, respectively. The conformational stability of these molecules is governed mainly by intermolecular hydrogen bonding interactions. The strength of hydrogen bonds was evaluated on the basis of 1H chemical shift and infrared red shift ΔνN–H of the stretching vibration of N–H proton donating bonds. The quantum theory of ‘atoms in molecules’ as well as the natural bond orbital method were applied to characterize hydrogen bonding interactions.

Conformational Preferences of 2-Acylpyrroles in Light of FT-IR and DFT Studies

Conformations of alpha-substituted pyrroles have been effectively studied using spectroscopic methods assisted by theoretical calculations developed in the recent decade. The question of how to effectively study the conformation of 2-acylpyrrole no longer remains unanswered. The detailed spectroscopic studies conducted in the last decade and interpreted on the basis of theoretical calculations provide a satisfactory answer to that question. Based on the Density Functional Theory (DFT) calculations of conformational properties of 2-acylpyrroles, for which two stable rotameric forms were predicted, syn and anti-conformers have been studied either by experimental or theoretical methods. The family of 2-acylpyrroles have both a proton donor N-H group and a proton acceptor C=O group. This structure favors the formation of doubly hydrogen-bonded cyclic dimers connected by two N-H...O=C bonds. The tendency to form cyclic dimers stabilizes the syn-conformation. Due to these properties 2-acylpyrroles can be used as structural models for the conformational analysis of peptides. This review summarizes recent investigations of conformations of 2-acylpyrroles, with a particular emphasis on the hydrogen bonds forming within these systems. The influence of 2-substitution on different aspects of stability of these molecular systems and the usefulness of infrared spectroscopy supported by theoretical calculations in H-bonds and conformational studies are discussed. Among the molecular properties hydrogen bond energy, structural characteristics such as C=O bond length of dimers and unique spectral features of 2-acylpyrroles that can be used to predict and investigate the conformation and structure of proteins are considered.

New insights into the electrodeposition and redox properties of [M(Bipyridyl)3](ClO4)3 (M=Co and Fe) films in media of low dielectric constant

Abstract The process of solid phase formation on the electrode surface during the electrochemical oxidation of [M II (bpy) 3 ] 2+ (M=Co and Fe) has been investigated by dc and pulse voltammetry, chronoamperometry, infrared spectroscopy and scanning electrochemical microscopy. The efficiency of film deposition and the properties of the solid layer depend on the supporting electrolyte and the solvent used. Films formed in mixtures of acetonitrile and low dielectric constant solvents (toluene, benzene, dichloromethane) are electrochemically inactive over a large potential range. The solid phase grown on the electrode surface proceeds according to a progressive nucleation mechanism following by 3-dimensional grown of the microcrystals. These films are directly reduced in the potential range of the first reduction step of respective [M II (bpy) 3 ] 2+ complexes. Films of perchlorate salts of Co(III) and Fe(III) bipyridyl complexes formed in other low dielectric constant media (dichloromethane, 1,2-dichloroethane, toluene+dimethylformamide, toluene+acetone, toluene+butyronitrile, etc.) are reversibly reduced at potentials close to about 0 V. Films formed in the presence of acetonitrile exhibit different morphology and crystallographic structure than films obtained by electrolysis in acetonitrile-free solutions. Acetonitrile-induced structural changes in the films are probably responsible for the formation of electrochemically inactive phases.

1H and13C NMR spectral analysis of (E)-asarone and its isomers

1H and 13C NMR data for six [(E)‐1‐propenyl]trimethoxybenzene isomers are reported. Spectral assignments were made on the basis of chemical shifts, 1H,1H coupling constants and two‐dimensional heteronuclear 1H,13C correlation techniques (HETCOR, COLOC). Copyright