Photoinduced enhancement of luminescence from (dibenzoylmethanato)boron difluoride in polymethyl methacrylate

The photochemical behavior of (dibenzoylmethanato)boron difluoride in the polymethyl methacrylate matrix was studied. Photoinduced luminescence enhancement was observed, and a mechanism of the process related to the aggregation of high-polarity luminophore molecules under irradiation was suggested.     

Structure and luminescence properties of antimony(III) complex compounds

The influence of the structure of the anion sublattice on the spectral luminescence properties is investigated using the example of antimony(III) complex compounds with outer-sphere organic cations. It is established that the factors favorable for the enhancement of the luminescence of antimony(III) ions are the island structure of the anion sublattice with minimum distortions of the antimony(III) coordination polyhedron and closely spaced energy levels of the outer-sphere organic cation and the antimony(III) ion.     

X-ray single crystal study of reversible thermochromism and the pecularities of atomic thermal motion in n,n-diphenylguanidinium(1+) hexabromotellurate (IV)

Peculiarities of the atomic structure of N,N-diphenylguanidium (1+) hexabromotellurate (IV), (C₁₃H₁₄N₃)₂[TeBr₆], which has reversible thermochromic properties, have been studied by X-ray single crystal method at different temperatures. It has been revealed that temperature-dependent distortions of the geometry of the thermochrom compound are not expressed anyhow substantially; therefore, the temperature behavior of thermal parameters of Br atoms was studied in detail. For the first time the interrelation between the thermochromic properties of the complex and peculiarities of atomic thermal vibrations has been disclosed: abnormally great increase in the deflection angle of the axis σ₃ of the ellipsoid of thermal vibrations of apical bromine atoms from Te-Br bond direction under the temperature reduction reflects the decrease of vibronic interaction between the ground and the first excited state of Te(IV) (the display of Jahn-Teller dynamic effect of the second order) and, correspondingly, results in asymmetry lessening of the band A in the absorption spectrum and causes the change in compound color determined by it. There has been revealed the presence of C-H…Br hydrogen bond via hydrogen atoms of phenyl rings of diphenylguanidium. Basing on the analysis of atomic thermal parameters, it has been established that the apical atom Br(4) having the shortest distance in the octahedron is linked with the central atom relatively weaker than other atoms.     

Electronic structure and luminescent properties of antimony(III) complex compounds with nitrogen containing outer-sphere organic cations

X-Ray photoelectron (XPS) and luminescent spectroscopy have been used to investigate complex compounds of antimony(III) halides with nitrogen containing organic bases. Inequality of bonds of amine and imine groups was found by XPS to disappear when complexes of antimony(III) with N,N′-diphenylguanidine (Dphg) were formed. The appearance of N1s symmetric line when transiting from Dphg to the cation N,N′-diphenylguanidine ( Dphg⁺) in complex compounds of antimony(III) testifies to this. The study performed demonstrates that electron density increment on the antimony(III) central atom (complexing agent) results in the bathochromic shift ³P₁ → ¹ S ₀ of the luminescence band of antimony(III) ion.     

Crystal Structure and Luminescence of the [Eu(Phen)2(NO3)3] Complex. The Role of the Ion-Coactivator

The [Eu(Phen)₂(NO₃)₃] complex was synthesized via reaction of europium nitrate with 1,10-phenanthroline (Phen) and studied by X-ray diffraction analysis. The crystals are monoclinic: a= 11.168(1), b= 17.976(2), c= 13.053(1) Å, = 100.577(2)°, space group C2/c, Z= 4, (calcd) = 1.801 g/cm³. The central europium atom coordinates (on a two-fold axis) six oxygen atoms of three nitrate groups with distances of 2.499(2), 2.502(2), and 2.542(2) Å and four nitrogen atoms of two phenanthroline molecules with distances of 2.542(2) and 2.593(2) Å. The influence of ion-coactivators on the luminescence of Eu³⁺in the [Eu _x M_{1 - x} (Phen)₂(NO₃)₃] complexes (M = Y, La, Nd, and Lu) is discussed.     

Fluorescent and photochemical properties of TbIII complexes with acrylic acid-based macromolecular ligands

The fluorescent and photochemical properties of Tb^III complexes with macromolecular ligands based on acrylic acid were studied. The photochemical behavior of the macromolecular Th^II complexes with acrylic acid-alkyl methacrylate copolymers differs considerably from those of Tb^III complexes with polyacrylic acid and of low-molecular-weight analogs; in the former case, the intensity of Tb³⁺ photoluminescence noticeably increases during photolysis rather than decreases. It was found that the increase in the length of the alkyl group in the alkyl methacrylate favors the enhancement of the luminescence during the photolysis. The higher efficiency of the enhancement of the Eu³⁺ fluorescence during the photolysis of similar complexes of Eu³⁺ compared to the complexers of Tb³⁺ is due to the nature of the electrodipole hypersensitive⁵D₀–⁷F₂ transition in Eu³⁺.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 2007–2010, August, 1996.     

Reversible luminescence thermochromism of dibenzoyl(methanato)boron difluoride

Reversible luminescence thermochromism of dibenzoyl(methanato)boron difluoride was found. A substantial hypsochromic shift of the luminescence band maximum (60 nm) with a temperature decrease from 300 to 77 K was observed, and the luminescence color changed from green to blue. A considerable decrease (by 0.386 Å) in the unit cell parameters along the c axis was detected by X-ray diffractometry when the temperature of the crystal decreased from 293 to 123 K. Shortening of the distances between the planes of adjacent molecules (stacking factor) weakens the interaction between the dimers and enhances the monomeric and excimeric luminescence. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 1032–1034, April, 2005.     

Photolysis of light-transforming polymeric materials based on europium(III) nitrate with 1,10-phenanthroline and quinaldic acid

Light-transforming polymeric materials based on two luminophor dopants (europium(III) nitrate with 1,10-phenanthroline and quinaldic acid characterized by intense luminescence in the spectral range of 400–650 nm) have been fabricated. It has been established that the photoresistance of polymeric materials based on the fabricated composites is higher than that of the polymeric material activated with europium(III) nitrate with 1,10-phenanthroline. It has been also established that luminescence and photochemical characteristics of polymeric composites are determined by the dopant molar ratio: the maximum luminescence intensity and photoresistance characterize the polymeric material containing europium(III) nitrate with 1,10-phenathroline and quinaldic acid at a molar ratio of 1: 2.     

The effect of solvation on spectral-luminescence properties of 2,2-difluoro-4-methylnaphto-[2,1-<Emphasis Type="Italic">е</Emphasis>]-1,3,2-dioxaborine

The processes of formation and dissociation of aggregates and formation of solvates of 2,2-difluoro- 4-methylnaphto-[2,1-е]-1,3,2-dioxaborine (1) with the chloroform molecule have been investigated by the methods of stationary and time-resolved spectroscopy. It has been revealed that, in the case of solutions in chloroform, a slow (within 1 h) dissociation of aggregates under the effect of solvent molecules takes place. It has been demonstrated that using chloroform as a solvent allows varying the content of luminophor aggregates in the polymeric composite and, thus, controlling the material spectral-luminescence properties.