Synthesis, crystal structure, EPR and electrochemical studies of copper(II) dipicolinate complex with 2,2′-dipyridylamine ligand

The (2,2′-dipyridylamine)(pyridine-2,6-dicarboxylato)copper(II) trihydrate complex was synthesized and characterized by spectroscopic (IR, UV-vis, EPR), X-ray diffraction technique and electrochemical methods. The copper(II) center is surrounded by one bidentate 2,2′-dipyridylamine (dpa) and one tridentate dipicolinate (dpc) ligand, and exhibits a distorted square-pyramidal geometry. The crystal packing involves both hydrogen-bonding and π-π interactions. The solvent water molecules link monomers to one another through hydrogen-bonding interactions, forming ladder-type chains in the ab plane. π-π interactions also occur between the dpa rings of neighboring molecules and are responsible for interchain packing. Based on EPR and optical absorption studies, spin-Hamiltonian and bonding parameters have been calculated. The g-values, calculated for title complex in polycrystalline state at 298 K and in frozen DMF (110 K), indicate the presence of the unpaired electron in the d_x²-y² orbital. The evaluated metal-ligand bonding parameters showed strong in-plane σ- and π-bonding. The cyclic voltammogram of the title complex investigated in DMF (dimethylformamide) solution exhibits only metal centered electroactivity in the potential range ±1.25 V versus Ag/AgCl reference electrode.     

Phosphonobetaine/sulfur dioxide copolymer by Butler’s cyclopolymerization process

The zwitterionic monomer, ethyl 3-(N,N-diallylammonio)propanephosphonate and sulfur dioxide were cyclocopolymerized in DMSO using azobisisobutyronitrile or ammonium persulfate as initiators to afford a pH-responsive polyphosphonobetaine/SO₂ (PPB/SO₂) copolymer. The polymers, on treatment with HCl and NaOH, gave the aqueous solutions of the corresponding cationic polyphosphononic acid (CPP) and anionic polyphosphonate (APP). The solution properties of the PPB having two pH-responsive functionalities were investigated in detail by potentiometric and viscometric techniques. Basicity constants of the amine and phosphonate groups in APP were found to be “apparent” and as such follow the modified Henderson–Hasselbalch equation. The incorporation of SO₂ moiety has resulted in the decrease of basicity constant of the nitrogens in the copolymer by staggering ?2 units of log K in compare to that of the corresponding homopolymer. The basicity difference is expected to have an effect on the chelating properties of the polymers. In contrast to many polycarbo- and -sulfobetaines, the PPB was all found to be soluble in salt-free water as well as in salt (including Ca²⁺ and Li⁺)-added solutions. The PPB demonstrated ‘antipolyelectrolyte’ viscosity behavior and found to have higher viscosity values in LiCl than in NaCl or NaI.     

Benzotriazole derivatives as long wavelength photosensitizers for diaryliodonium salt initiators

Two benzotriazole derivative dyes 4,7‐bis(2,3‐dihydrothieno[3,4‐b][1,4]dioxin‐5‐yl)‐2‐dodecyl‐2H‐benzo[1,2,3]triazole, and 2‐dodecyl‐4,7‐bis(4‐hexylthiophen‐2‐yl)‐2H‐benzo[d][1,2,3]triazole are shown to work as efficient photosensitizers for a diphenyliodonium salt initiator in cationic photopolymerization of epoxide and vinyl monomers. Substituted thienyl groups are attached to benzotriazole backbone to extend conjugation and enhance electron density of the molecules. Thereby, it was possible to initiate polymerizations at room temperature using long wavelength UV and visible light. The progress of photopolymerizations was monitored using optical pyrometry. The photopolymerization of an epoxide monomer using solar irradiation was also demonstrated. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Spectrophotometric and spectrofluorimetric investigation of different equilibria of a recently synthesized Schiff base with the aid of chemometric methods

In this study ground and excited states acidic dissociation constants of a recently synthesized Schiff base was obtained in a DMF:water mixture of 30:70 (v/v) using absorption and fluorescent spectra of the Schiff base in different pH values with the aid of chemometric methods. In addition, the fluorescent of the two kinds of tautomers of this Schiff base was investigated and the rate of tautomerization was obtained using rank annihilation factor analysis (RAFA). The effect of different kinds of surfactants such as sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB) and Triton X-100 on fluorescence spectrum of the Schiff base in a DMF:water mixture of 2:98 (v/v) was investigated. CTAB increased the fluorescence intensity of the Schiff base while SDS and Triton X-100 had no significant effect on it. β-Cyclodextrin increased the fluorescence intensity of the Schiff base. Also the sensing behavior of this Schiff base toward metal ions was studied in DMF and ethanol by fluorescence spectroscopy. The Schiff base showed prominent fluorescent signal in the presence of Zn²⁺, whereas other metal ions failed to induce response and ground-state dissociation constant of the complex was determined by direct fluorimetric titration as a function of Zn²⁺ concentration.     

Bis­(acesulfamato)­tetra­aqua­cobalt(II)

The crystal structure of the first acesulfame–metal complex, namely tetra­aqua­bis­[6‐methyl‐1,2,3‐oxa­thia­zin‐4(3H)‐onato 2,2‐dioxide‐κN]­cobalt(II), [Co(C₄H₄NO₄S)₂(H₂O)₄], is re­ported. The Co^II ion resides on a twofold axis and is coordinated by four aqua ligands defining the basal plane and by two monodentate acesulfamate ligands, via their ring N atoms, in the axial positions. Two intra‐ and three intermolecular hydrogen‐bonding interactions stabilize the crystal structure and form an infinite three‐dimensional lattice.     

Synthesis,spectroscopy, electrochemistry and in situ spectroelectrochemistry of partly halogenated coumarin phthalonitrile and corresponding metal-free,cobalt and zinc phthalocyanines

In this study, the preparation of novel 7-hydroxy-3-(2-chloro-4-fluorophenyl)coumarin (1), the ligand, 7-(3,4-dicyanophenoxy)-3-(2-chloro-4-fluorophenyl)coumarin (2), metal-free phthalocyanine 3 and metallophthalocyanine complexes 4 and 5 (MPcs, M = Co, Zn), β-substituted with 7-oxo-3-(2-chloro-4-fluorophenyl)coumarin functional group was achieved. By the reaction of 7-hydroxy-3-(2-chloro-4-fluorophenyl)coumarin (1) with 1,2-dicyano-4-nitrobenzen in dry DMF as the solvent in the presence of K₂CO₃ as the base, the 7-(3,4-dicyanophenoxy)-3-(2-chloro-4-fluorophenyl)coumarin (2) was synthesized. Compound 2 reacted with Co(CH₃COO)₂·4H₂O in 2-N,N-dimethylaminoethanol to furnish a novel coumarin containing cobalt(II) phthalocyanine 4. The cyclotetramerization of 2 with Zn(CH₃COO)₂·2H₂O in 2-N,N-dimethylaminoethanol gave the novel coumarin containing Zn(II)phthalocyanine 5; while tetramerization without any metal salts in 2-N,N-dimethylaminoethanol gave the metal-free phthalocyanine 3. The structures of obtained compounds were confirmed by elemental analysis, UV–Vis, IR, MALDI-TOF mass and ¹H NMR spectra. The cyclic and differential pulse voltammetry, and in situ spectroelectrochemistry of 7-oxo-3-(2-chloro-4-fuorophenyl)coumarin substituted phthalocyanines 3, 4 and 5 allowed us to identify metal- and phthalocyanine ring-based redox processes of the complexes.     

Oblique interaction of electrostatic nonlinear structures in relativistically degenerate dense magnetoplasmas

We have investigated the interaction of obliquely propagating ion acoustic solitary waves in a magnetoplasma with relativistically degenerate electrons. Using the quantum hydrodynamics model and by employing the extended Poincaré–Lighthill–Kuo technique, we have derived a set of Korteweg de Vries equations for two solitons. We have observed that the system under consideration allows the formation of only compressive solitons and their velocities remain in the sub-acoustic limit. Furthermore, phase shifts of solitons as a result of their interaction have been calculated. The phase shifts have been observed to be dependent on the obliqueness and the physical parameters of plasma. It has also been noticed that phase shifts remain negative for the whole range of parameters generally found in white dwarf stars. We have observed that the phase shifts enhance with the enhancement in number density, however, the converse happens when the magnetic field is enhanced. It has also been observed that the phase shift is slightly greater for the solitons that are less oblique as compared to their more oblique counterparts. Furthermore, we have estimated the spatial scales of interaction of solitons using the parameters found in white dwarf stars.     

Deposition of silica thin films formed by sol–gel method

Deposition of silica thin films on silicon wafer was investigated by in situ mass measurements with a microbalance configured for dip coating. Mass change was recorded with respect to deposition time when the substrate was fully immersed in the silica sol. Mass gain during deposition was higher than predicted from monolayer coverage of silica nano particles. This implied that deposition was facilitated by gelling of the nanoparticles on the substrate. The rate of deposition was enhanced by increasing the particle concentration in the sol and by decreasing the particle size from 12 to 5 nm. Increasing the salt concentration of the silica sol at constant pH enhanced the deposition of the silica particles. Reducing the pH of the sol from 10 to 6 decreased the deposition rate due to aggregation of the primary silica particles.     

Synthesis of room-temperature ionic liquids with the weakly coordinating [Al(ORF)4]- anion (RF=C(H)(CF3)2) and the determination of their principal physical properties

A large series of ionic liquids (ILs) based on the weakly coordinating alkoxyaluminate [Al(hfip)(4)](-) (hfip: hexafluoroisopropoxy) with classical as well as functionalized cations were prepared, and their principal physical properties determined. Melting points are between 0 ([C(4)MMIM][Al(hfip)(4)]) and 69 °C ([C(3)MPip][Al(hfip)(4)]); three qualify as room-temperature ILs (RTILs). Crystal structures for six ILs were determined; their structural parameters and anion-cation contacts are compared here with known ILs, with a special focus on their influence on physical properties. Moreover, the biodegradability of the compounds was investigated by using the closed-bottle and the manometric respirometry test. Temperature-dependent viscosities and conductivities were measured between 0 and 80 °C, and described by either the Vogel-Fulcher-Tammann (VFT) or the Arrhenius equations. Moreover, conductivities and viscosities were investigated in the context of the molecular volume, V(m). Physical property-V(m) correlations were carried out for various temperatures, and the temperature dependence of the molecular volume was analyzed by using crystal structure data and DFT calculations. The IL ionicity was investigated by Walden plots; according to this analysis, [Al(hfip)(4)](-) ILs may be classified as "very good to good ILs"; while [C(2)MIM][Al(hfip)(4)] is a better IL than [C(2)MIM][NTf(2)]. The dielectric constants of ten [Al(hfip)(4)](-) ILs were determined, and are unexpectedly high (ε(r)=11.5 to 16.8). This could be rationalized by considering additional calculated dipole moments of the structures frozen in the solid state by DFT. The determination of hydrogen gas solubility in [Al(hfip)(4)](-) RTILs by high-pressure NMR spectroscopy revealed very high hydrogen solubilities at 25 °C and 1 atm. These results indicate the significant potential of this class of ILs in manifold applications.