New laser crystals of complex oxides doped with ions of d elements with variable valence and different structural localization. Review

Ions of d elements in complex oxides with olivine and phenakite structures exhibit diverse structural localization and may incorporate into crystals in various oxidation states. The complexity of the structure of these materials requires a complex approach in investigation of their spectroscopic characteristics with regard to the type of optical center and the growth conditions. The method of estimation of the distribution of an activator ion over crystallographically non-equivalent cationic positions on the basis of the symmetry analysis of the structure of these positions with regard to the spatial distribution of the activator-ion electron density is described. The results of experimental studies of the spectroscopic characteristics of vanadium and chromium ions in the crystals with the olivine (Mg₂SiO₄, Ca₂GeO₄, and CaMgSiO₄) and phenakite (LiGaSiO₄, LiAlGeO₄, and Zn₂SiO₄) structures performed by us (some experimental data are reported for the first time) are analyzed with regard to the growth conditions. Data in the literature are also analyzed. In order to estimate the structural and valence states of the d ions, a number of other experimental techniques were used, and the experimental data were compared with the calculated energy-level diagrams for activator ions in centers of various types. This approach made it possible to adequately describe the possibilities of complex oxides Mg₂SiO₄, Ca₂GeO₄, CaMgSiO₄, LiGaSiO₄, LiAlGeO₄, and Zn₂SiO₄ doped with d ions, regarded as new laser media.     

Synthesis of cyclic sulfonamides by reaction of <Emphasis Type="Italic">N</Emphasis>-sulfinyl-3-(trifluoromethyl)aniline with norbornenes

N-Sulfinyl-3-(trifluoromethyl)aniline reacted with bicyclo[2.2.1]hept-2-ene and bicyclo[2.2.1]-hepta-2,5-diene to give the corresponding Diels?Alder adducts which were oxidized to 8-trifluoromethyl-2,3,4,4a,6,10b-hexahydro-5λ⁶-1,4-methanodibenzo[c,e][1,2]thiazine-5,5(1H)-diones. The cycloaddition occurred predominantly with participation of the S=N–C¹=C⁶ fragment of N-sulfinyl-3-(trifluoromethyl)aniline and exclusively at the endo side of bicyclo[2.2.1]heptenes.     

Synthesis and structure of novel substituted <Emphasis Type="Italic">N</Emphasis>-sulfinylanilines

N-Sulfinylanilines derived from 4-bromoaniline, 3-nitroaniline, and 4,4′-di(ethane-1,2-diyl)dianiline were synthesized. X-ray diffraction analysis of 4-bromo-N-sulfinylaniline, 3-nitro-N-sulfinylaniline, and 4,4′-(ethane-1,2-diyl)di-N-sulfinylaniline was performed. The sulfinyl function in the planar conformation of the Ar-NSO fragment was found to have Z configuration. The nature of intra- and intermolecular structure-forming interactions was established.     

Synthesis of benzothiazine sulfonamides via heteroatomic Diels–Alder reaction of <Emphasis Type="Italic">para</Emphasis>-fluoro-<Emphasis Type="Italic">N</Emphasis>-sulfinylaniline with bicyclo[2.2.1]heptenes

Reaction of 4-fluoro-N-sulfinylaniline with norbornene and norbornadiene has afforded the Diels–Alder adducts of benzothiazine structure that have been oxidized into the corresponding benzothiazine sulfonamides. Structure of the obtained compounds and stereochemistry of the diene addition and epoxidation of norbornene olefin bonds have established by means of X-ray diffraction method.     

Electrons of <Emphasis Type="Italic">l</Emphasis> shells of free atoms as a regular system of points on a sphere: III. Factors of self-organization of electrons in the periodic table

The factors determining the self-organization of the electron system of an atom at different levels of the periodic table are considered. Specifically, these factors are the isotropy and three-dimensional nature of space and the indistinguishability of electrons. The concept of a simplex is used, whose vertices correspond to a regular system of particles (minimum in number for a given space) in the state of the global minimum of the system’s potential. These factors implement the principle of simplicity (small number of particles) and hierarchy in the periodic table of elements. The global minimum of the potential of s, p, d, and f shells is reached in odd-dimensional spaces. In a three-dimensional space, such a minimum is reached for d and f shells, in contrast to s and p shells, through shell mixing.     

Identification of the valency of chromium ions in single crystals of alkali-metal and ammonium phosphates from optical spectra

Presented at the All-Union Seminar on the Optics of Anisotropic Media, April 9–13, 1990, Zvenigorod.