Transient excited-state absorption and gain spectroscopy of a two-photon absorbing probe with efficient superfluorescent properties

The synthesis, linear photophysical properties, two-photon absorption (2PA), excited-state transient absorption, and gain spectroscopy of a new fluorene derivative tert-butyl 4,4'-(4,4' (1E,1'E)-2,2'-(9,9-bis(2- (2-ethoxyethoxy)ethyl)-9H-fluorene-2,7-diyl)bis(ethene-2,1-diyl)bis(4,1 phenylene)]dipiperazine-1-carboxylate (1) are reported. The steady-state linear absorption and fluorescence spectra, along with excitation anisotropy, fluorescence lifetimes, and photochemical stability of 1 were investigated in a number of organic solvents at room temperature. The 2PA spectra of 1 with a maximum cross-section of ~ 300 GM were obtained with a 1 kHz femtosecond laser system using open-aperture Z-scan and two-photon-induced fluorescence methods. The transient excited-state absorption (ESA) and gain kinetics of 1 were investigated by a femtosecond pump-probe methodology. Fast relaxation processes (~1-2 ps) in the gain and ESA spectra of 1 were revealed in ACN solution, attributable to symmetry-breaking effects in the first excited state. Efficient superfluorescence properties of 1 were observed in a nonpolar solvent under femtosecond excitation. One- and two-photon fluorescence microscopy imaging of HCT 116 cells incubated with probe 1 was accomplished, suggesting the potential of this new probe in two-photon fluorescence microscopy bioimaging.     

Hankel operators in Schatten ideals

We study membership to Schatten ideals S _E , associated with a monotone Riesz–Fischer space E, for the Hankel operators H _f defined on the Hardy space H ²(∂D). The conditions are expressed in terms of regularity of its symbol: we prove that H _f ∈S _E if and only if f∈B _E , the Besov space associated with a monotone Riesz–Fischer space E(dλ) over the measure space (D,dλ) and the main tool is the interpolation of operators. Received: December 17, 1999; in final form: September 25, 2000?Published online: July 13, 2001     

The Vapor-Liquid Polycondensation of Cyclohexylphosphoric Dichloride with Hydroquinone

The vapor-liquid polycondensation of cyclohexylphosphoric dichloride with hydroquinone was investigated. The influence of the temperature, reaction time, base concentration, and molar ratio of reagents on the yield, inherent viscosity, and molecular weight of the obtained polymer was studied. Second order, central, composite, rotatable experimental design was used in order to carry out this work and to mark limits of the experimental field for optimal yields and high inherent viscosities.     

Photometrische Bestimmung von Kohlenmonoxyd in der Luft

Zusammenfassung Es wird ein photometrisches Verfahren der CO-Bestimmung beschrieben, das auf der Absorption des Gases in einer alkalischen Lösung der Silberverbindung der p-Sulfamidbenzoesäure beruht. Die Silberverbindung wird zu metallischem Silber reduziert, das in kolloider Verteilung bleibt. Die Extinktion dieses Silbersols wird gemessen. Sie ist unter den Bedingungen der Arbeitsvorschrift im Bereich von 0,001–0,5% CO der Konzentration des Kohlenmonoxyds proportional. Bei Wellenlängen unterhalb 500 m nimmt die Extinktion stark zu. Die Messungen werden deshalb zweckmäßig im kurzwelligen Licht durchgeführt. Mit Zeiss-Filter S 42 wird z. B. nahezu die doppelte Meßempfindlichkeit erreicht wie mit Filter S 50. Die Durchführung der CO-Bestimmung wird genau beschrieben.     

1,3-Dipolar cycloaddition reaction of bipyridinium ylides with the propynamido-β-cyclodextrin. A regiospecific synthesis of a new class of fluorescent β-cyclodextrins

The 1,3-dipolar cycloaddition reaction of bipyridinium ylides with the electron deficient propynamido-β-cyclodextrin was studied. This reaction resulted in the regiospecific formation of a new class of fluorescent β-cyclodextrins. The new fluorophore systems were characterized spectroscopically by their absorption and emission maxima and their quantum yields.     

Thermal behavior of Co<Subscript>x</Subscript>Fe<Subscript>3−x</Subscript>O<Subscript>4</Subscript>/SiO<Subscript>2</Subscript> nanocomposites obtained by a modified sol–gel method

The thermal behavior of Co_xFe_3?xO₄/SiO₂ nanocomposites obtained by direct synthesis starting from nonahydrate ferric nitrate and hexahydrate cobalt nitrate in different ratios with and without the addition of 1,4-butanediol was studied. For the synthesis of Co_xFe_3?xO₄ (x = 0.5–2.5) dispersed in the silica matrix a wide Co/Fe molar ratio was used. The decomposition processes, formation of crystalline phases, gases evolvement and mass changes during gels annealing at different temperatures were assessed by thermal analysis. The absence of succinate precursor and a low mass loss were observed in the case of the gel obtained in the absence of 1,4-butanediol. In case of gels obtained using a stoichiometric ratio of Co/Fe, no clear delimitation between Co and Fe succinates was observed, while for samples with a Fe or Co excess, the formation of the two succinates was observed. The evolution of the crystalline phase after annealing (673, 973 and 1273 K) investigated by X-ray diffraction analysis and Fourier transformed infrared spectrometry revealed that in samples with Fe excess, stoichiometric Fe/Co ratio or low Co excess, the cobalt ferrite (CoFe₂O₄) was obtained as a single phase, while in samples with higher cobalt excess, olivine (Co₂SiO₄) as a main phase, cobalt oxide and CoFe₂O₄ as secondary phases were obtained after annealing at 1273 K. The SEM images confirmed the nanoparticles embedding in the silica matrix, while the TEM and X-ray diffraction data showed that the obtained nanoparticles’ size was below 10 nm in most samples.     

Oligonuclear 3d-4f complexes as tectons in designing supramolecular solid-state architectures: impact of the nature of linkers on the structural diversity

Heteronuclear cationic complexes, [LCuLn]3+ and [(LCu)2Ln]3+, were employed as nodes in designing high-nuclearity complexes and coordination polymers with a rich variety of network topologies (L is the dianion of the Schiff base resulting from the 2:1 condensation of 3-methoxysalycilaldehyde with 1,3-propanediamine). Two families of linkers have been chosen: the first consists of exo-dentate ligands bearing nitrogen-donor atoms (bipyridine (bipy), dicyanamido (dca)), whereas the second consists of exo-dentate ligands with oxygen-donor atoms (anions derived from the acetylenedicarboxylic (H2acdca), fumaric (H2fum), trimesic (H3trim), and oxalic (H2ox) acids). The ligands belonging to the first family prefer copper(II) ions, whereas the ligands from the second family interact preferentially with oxophilic rare-earth cations. The following complexes have been obtained and crystallographically characterized: [LCu(II)(OH2)Gd(III)(NO3)3] (1), [{LCu(II)Gd(III)(NO3)3}2(mu-4,4'-bipy)] (2), 1infinity[LCu(II)Gd(III)(acdca)(1.5)(H2O)2].13H2O (3), 2infinity[LCu(II)Gd(III)(fum)(1.5)(H2O)2].4H2O.C2H5OH (4), 1infinity[LCu(II)Sm(III)(H2O)(Hfum)(fum)] (5), 1infinity[LCu(II)Er(III)(H2O)2(fum)]NO3.3H2O (6), 2infinity[LCu(II)Sm(III)(fum)(1.5)(H2O)2].4H2O.C2H5OH (7), [{(LCu(II))2Sm(III)}2fum2](OH)2 (8), 1infinity[LCu(II)Gd(III)(trim)(H2O)2].H2O (9), 2infinity[{(LCu(II))2Pr(III)}(C2O4)(0.5)(dca)]dca.2H2O (10), [LCu(II)Gd(III)(ox)(H2O)3][Cr(III)(2,2'-bipy)(ox)2].9H2O (11), and [LCuGd(H2O)4{Cr(CN)6}].3H2O (12). Compound 1 is representative of the whole family of binuclear Cu(II)-Ln(III) complexes which have been used as precursors in constructing heteropolymetallic complexes. The rich variety of the resulting structures is due to several factors: 1) the nature of the donor atoms of the linkers, 2) the preference of the copper(II) ion for nitrogen atoms, 3) the oxophilicity of the lanthanides, 4) the degree of deprotonation of the polycarboxylic acids, 5) the various connectivity modes exhibited by the carboxylato groups, and 6) the stoichiometry of the final products, that is, the Cu(II)/Ln(III)/linker molar ratio. A unique cluster formed by 24 water molecules was found in crystal 11. In compounds 2, 3, 4, 9, and 11 the Cu(II)-Gd(III) exchange interaction was found to be ferromagnetic, with J values in the range of 3.53-8.96 cm(-1). Compound 12 represents a new example of a polynuclear complex containing three different paramagnetic ions. The intranode Cu(II)-Gd(III) ferromagnetic interaction is overwhelmed by the antiferromagnetic interactions occurring between the cyanobridged Gd(III) and Cr(III) ions.     

Localization and Locality for Resistance Forms

For a resistance form ${(X, \mathcal{D}(\varepsilon),\varepsilon)}For a resistance form (X, D(e),e){(X, \mathcal{D}(\varepsilon),\varepsilon)} and a point x₀ ? X{x_0 \in X} as boundary, on the space X₀:=X \{x₀}{X_0:=X {\setminus}\{x_0\}} we consider the Dirichlet space D_x0:={f ? D(e) | f(x₀)=0}{\mathcal{D}_{x_0}:=\{f\in\mathcal{D}(\varepsilon)\, |\, f(x_0)=0\}} and we develop a good potential theory. For any finely open subset D of X ₀ we consider a localized resistance form (D_{X0 \ D},e_D{\mathcal{D}_{X_0 {\setminus} D},\varepsilon_{D}}) where D_{X0 \ D}:={f ? D_x0 | f=0{\mathcal{D}_{X_0 {\setminus} D}:=\{f\in\mathcal{D}_{x_0}\, |\, f=0} on X₀ \ D}, e_D(f,g):=e(f,g){X_0 {\setminus} D\},\, \varepsilon_D(f,g):=\varepsilon(f,g)} for all f,g ? D_{X0 \ D}{f,g\in\mathcal{D}_{X_0 {\setminus} D}}. The main result is the equivalence between the local property of the resistance form and the sheaf property for the excessive elements on finely open sets.     

Cobalt-containing silicotungstate sandwich dimer [{Co3(B-beta-SiW9O33(OH))(B-beta-SiW8O29(OH)2)}2]22-

The 6-cobalt-substituted [{Co3(B-beta-SiW9O33(OH))(B-beta-SiW8O29(OH)2)}2]22- has been characterized by IR and UV-vis spectroscopy, elemental analysis, magnetic studies, electrochemistry, and gel filtration chromatography. A single-crystal X-ray analysis was carried out on K10Na12[{Co3(B-beta-SiW9O33(OH))(B-beta-SiW8O29(OH)2)}2].49H2O (KNa-1), which crystallizes in the monoclinic system, space group P2(1)/n, with a=19.9466(8) A, b=24.6607(10) A, c=34.0978(13) A, beta=102.175(1) degrees, and Z=2. Polyanion 1 represents a novel class of asymmetric sandwich-type polyanions. It contains three cobalt ions, which are encapsulated between an unprecedented (B-beta-SiW9O34) fragment and a (B-beta-SiW8O31) unit. Polyanion 1 is composed of two sandwich species via two Co-O-W bridges in the solid state and almost certainly in solution as well based on gel filtration chromatography. UV-visible spectroscopy and cyclic voltammetry also confirmed its stability. Two well-separated groups of waves appeared in the voltammetric pattern: the wave observed in the negative potential range versus a saturated calomel electrode features the redox processes of WVI centers; the two reversible redox couples observed in the positive potential domain are attributed to the redox processes of Co2+ centers and indicated that the two types of Co2+ centers in the structure are oxidized in separate waves. Such reversibility of Co2+ centers within multi-Co-substituted polyoxometalates is uncommon. The magnetic properties of KNa-1 are also discussed. The ferromagnetic ground state has been studied by magnetic susceptibility and magnetization measurements and fitted according to an anisotropic exchange model.     

A Multiplicity Result for an Elliptic Anisotropic Differential Inclusion Involving Variable Exponents

In this paper we are concerned with the study of a class of quasilinear elliptic differential inclusions involving the anisotropic $\overrightarrow {p}(\cdot)$ -Laplace operator, on a bounded open subset of ${\mathbb R}^n$ which has a smooth boundary. The abstract framework required to study this kind of differential inclusions lies at the interface of three important branches in analysis: nonsmooth analysis, the variable exponent Lebesgue–Sobolev spaces theory and the anisotropic Sobolev spaces theory. Using the concept of nonsmooth critical point we are able to prove that our problem admits at least two non-trivial weak solutions.