8,9-dioxa-6-methylbicyclo(5.2.0)nona-2,4-diene: a 1,2-dioxetane formed by (2+2)-cycloaddition of singlet oxygen to 7-methyl-1,3,5-cycloheptatriene.

Photosensitized oxygenation of 7-methyl-1,3,5-cycloheptatriene affords the title compound in ca. 15% yield, which represents the first 1,2-dioxetane derived from a cyclic conjugated polyene; its characterization, chemiluminescence, and mechanistic aspects are reported.     

Mixed-ligand Copper(II) Complexes: Investigation of their Spectroscopic, Catalysis, Antimicrobial and Potentiometric Properties

Schiff base ligands HL¹–HL⁶ have been prepared from the reaction of 2,6-diformyl-4-t-butylphenol and 2,6-di-formyl-4-methylphenol with various aromatic amines in ethanolic solution. The Schiff base ligands 2,2′-dipyridine (dp) mixed-ligand Cu^II complexes have been obtained. Mixed-ligand Cu^II complexes containing the dp ligand have ionic nature and they conduct the electricity in solution media. The complexes have been obtained in two different forms: one of them is [Cu₂(Lⁿ)Cl₃] (n: 1, 2, 3, 4, 5 and 6) and other complexes have the general formula [Cu₂(Lⁿ)(dp)₂]3Cl. Ligands and their complexes have been characterized by elemental analyses, FT-IR, electronic spectra, molar conductance, ¹H(¹³C)-n.m.r. and mass spectral data. Their stoichiometric protonation constants have been determined potentiometrically in dioxan using a combined pH electrode at 25 °C, under a nitrogen atmosphere. For the calculation of the protonation constants, PKAS computer programme has been used. The effects of the substituents on the protonation constants and the additivities of these effects are discussed. The antimicrobial activity studies of the ligands and their complexes have been studied against the Bacillus megaterium, Micrococcus luteus, Corynebavterium xenosis, Enterococcuc faecalis, bacteria and Saccoramyces cerevisia, yeast. The catalytic properties of the complexes have been studied on the ascorbic acid, catechol and 2,6-di-t-butylphenol substrates. Thermal behaviour of the complexes has been studied by thermal techniques.     

Chemistry of dioxine-annelated cycloheptatriene endoperoxides and their conversion into tropolone derivatives: an unusual non-benzenoid singlet oxygen source

The chemistry of two bicyclic endoperoxides, obtained by photooxygenation of 2,3-dihydro-7H-cyclohepta[1,4]dioxine and 2,3-dihydro-7H-cyclohepta[b][1,4]dioxin-7-one was investigated with the aim of synthesizing the respective tropolone derivatives. The reaction of these endoperoxides with base, thiourea and their thermolysis provided the desired tropolone derivatives in high yield. On the other hand, the thermolysis of the endoperoxide derived from 2,3-dihydro-7H-cyclohepta[b][1,4]dioxin-7-one underwent an unprecedented route and formed parent molecule and singlet oxygen instead of the expected troponoids. The formation mechanisms of all products are discussed.     

Synthesis,Characterization and Stability Constants of Polynuclear Metal Complexes

Unsymmetric tridentate ligands, 4-methyl-2,6-di(4-methyliminomethyl)phenol (HL¹), 4-(t-butyl)-2,6-di(4-methylphenyliminomethyl)phenol (HL²), 2,6-di(4-bromophenyliminomethyl)-4-methylphenol (HL³), 2,6-di(4-bromophenyliminomethyl)-4-(t-butyl)phenol (HL⁴), 2,6-di(4-hydroxyphenyliminomethyl)-4-methylphenol (HL⁵) and 4-(t-butyl)-2,6-di(4-hydroxyphenyliminomethyl)phenol (HL⁶), and their binuclear Cu^II, Co^II and Ni^II complexes were synthesized and characterized by elemental analysis, FT-IR, u.v.-vis spectrometry magnetic moments, ¹H(¹³C)-n.m.r. and mass spectral data. Also, the electrical conductivities of the complexes have been measured using 10-³ M solutions in MeCN. The complexes are weak electrolytes. In the electronic spectra of the complexes of the HL¹-HL⁶ ligands, the 480-410 nm band has been determined as the charge-transfer band. While the HL⁵ and HL⁶ ligands have five potential donor atoms, other ligands have only three. Protonation constants of the ligands have been studied in dioxan-water mixtures. In addition, the antimicrobial properties of the ligands and their metal complexes have been studied:Bacillus megaterium, Micrococcus luteus, Corynebavterium xenosis, Enterococcus faecalis, bacteria and Saccoramyces cerevisia, yeast. The keto-enol tautomeric equilibria of the ligands have been investigated in polar and non-polar solvents.     

On the Riesz difference sequence space

In the present paper, we define the difference sequence space r ^q (p, Δ), which is defined as follows:

Segmental dynamics of poly(methyl acrylate)-d3 adsorbed on anopore: a deuterium NMR study

The segmental dynamics of poly(methyl acrylate-d3) (PMA-d3) adsorbed in the pores of anopore membranes has been investigated using deuterium NMR over the temperature range 25-80 degrees C. The onset of the NMR glass-transition temperature (Tg) for the adsorbed samples was approximately 15 degrees C higher than that for the bulk sample. The adsorbed polymer contained segments with restricted mobility (glassy), even at the highest temperatures studied, at which the bulk polymer showed only mobile segments. The spectra from samples with different adsorbed amounts of PMA-d3, between 1.1 and 4.2 mg/m2, were similar in their temperature-dependent mobilities. Neither was there much difference in the spectra of PMA-d3 on anopore samples with pore sizes of 0.2 and 0.02 microm. However, for a solvent-washed sample with an adsorbed amount of 0.7 mg/m2, additional restriction in PMA-d3 mobility was observed.     

Morphology of large ZSM-5 crystals unraveled by fluorescence microscopy

Understanding the internal structure of ZSM-5 crystallites is essential for improving catalyst performance. In this work, a combination of fluorescence microscopy, AFM, SEM, and optical observations is employed to study intergrowth phenomena and pore accessibility in a set of five ZSM-5 samples with different crystal morphologies. An amine-functionalized perylene dye is used to probe acid sites on the external crystal surface, while DAMPI (4-(4-diethylaminostyryl)- N-methylpyridinium iodide) is used to map access to the straight channels in MFI from the outer surface. The use of these dyes is validated by studying the well-understood rounded-boat type ZSM-5 crystals. Next coffin-shaped ZSM-5 crystals are considered; we critically evaluate the seemingly conflicting 2-component and 3-component models that have been proposed to account for the hourglass structure in these crystals. The data prove that observation of an hourglass structure is essentially unrelated to a 90 degree rotation of the pyramidal crystal components under the (010) face. Hence, in perfectly formed coffin-shaped crystals, the straight channels can be accessed from (010). However, in other crystal batches, sections with a 90 degrees rotation can be found; they are indeed located inside the crystal sections under (010) but often only partially occupy these pyramidal components. In such a case, both straight and sinusoidal pores surface at the hexagonal face. The results largely support the 3-component model, but with the added notion that 90 degree rotated sections (as proposed in the 2-component model) are most likely to be formed inside the defect-rich, pyramidal crystal sections under the (010) faces.     

Synthesis of a dipyrromethane functionalized monomer and optoelectrochromic properties of its polymer

A dipyrromethane functionalized monomer; 5-(4-tert-butylphenyl)dipyrromethane (BPDP) was synthesized. The structure of the monomer was characterized by nuclear magnetic resonance (¹H NMR and ¹³C NMR) and Fourier transform infrared (FTIR) spectroscopies. Electrochemical polymerization of BPDP was performed in acetonitrile (AN)/LiClO₄. The resulting conducting polymer was characterized by FTIR spectroscopy and electrical conductivity measurements. Spectroelectrochemical behavior and switching ability of P(BPDP) film were investigated by UV-Vis spectroscopy. P(BPDP) revealed color changes between yellow and blue in the reduced and oxidized states, respectively. In order to investigate electrochromic properties and stability of the P(BPDP) in electrochromic device (ECDs) application, dual type polymer ECD based on P(BPDP) and poly(ethylene dioxythiophene) (PEDOT) were constructed. Spectroelectrochemistry, switching ability and stability of the devices were investigated by UV-Vis spectroscopy and cyclic voltammetry.     

FT-Raman, FT-IR and NMR spectra, vibrational assignments and density functional studies of 1,3-bis(benzimidazol-2-yl)-2-thiapropane ligand and its Zn(II) halide complexes

1,3-bis(benzimidazol-2-yl)-2-thiapropane (L) ligand and its zinc halide ZnX₂ (X = Cl, Br, I) complexes have been synthesized. The compounds were characterized using the elemental analysis, molar conductivity, FT-Raman, FT-IR (mid i.r., far i.r.), ¹H and ¹³C NMR spectra, and quantum chemical calculations performed with Gaussian 03 package program set. The optimized geometries and vibrational frequencies of the ligand and [Zn(L)Cl₂] complex were calculated using the DFT/B3LYP method with a 6–31g(d) basis set. The geometry optimization of [Zn(L)Cl₂] yields a slightly distorted tetrahedral environment around Zn ion, while the molecule clearly reveals the Cs symmetry. The molar conductivity data reveals that the complexes are neutral. The ligand is bidentate, via two of the imine nitrogen atoms in the bis-imidazole ring units, and together with the monodentate coordination of the two halides to the metal centre.     

Self-organized coherence in fiber laser arrays

We report the production of stable, coherent, and same-phase states in arrays of fiber lasers. Provided that proper interactions between the lasers are present, arrays will spontaneously self-organize into stable coherent same-phase states. There is no need for active control. Power scaling, power spectra, spatial interference fringes, and temporal data all support this conclusion.