Synthesis of aminobismethylenephosphonic acids on a platform of <Emphasis Type="Italic">p-tert</Emphasis>-Butylthiacalix[4]arene in 1,3-<Emphasis Type="Italic">alternate</Emphasis> configuration

Aminobismethylenephosphonic acids on a platform of p-tert-butylthiacalix[4]arene were obtained by reacting macrocyclic amines with phosphorous acid and formaldehyde under acid catalysis. Free phenol hydroxy groups on the lower rim of p-tert-butylthiacalix[4]arene were found to inhibit the interaction with the amino moieties of the macrocycle. In the case of amino derivatives of thiacalix[4]arene containing no hydroxy groups the reaction led to the formation of target compounds in good yields.     

Thermal study of CVD metal–organic precursors

Journal of Thermal Analysis and Calorimetry - The pressure of the saturated and unsaturated vapors of Zr(thd)4 and Y(thd)3 (thd = 2,2,6,6-tetramethyl-3,5-heptanedionate) has been...     

Molecular structure and retention behaviour of some polycyclic aromatic and perhydroaromatic hydrocarbons on graphitized carbon black

Summary On efficient glass capillary columns packed with graphitized thermal carbon black (GTCB) the stereoisomers of aromatic and saturated tricyclic hydrocarbons are completely separated and identified. The Henry's adsorption constants of the individual isomers were determined from mixtures at different temperatures. Five isomers of perhydroanthracene, five isomers of perhydrofluorene, two isomers of perhydrophenalene, four isomers of perhydroacenaphthene, as well as phenalene, dihydrophenalene, acenaphthene and acenaphthylene were investigated. The increase of the hydrogenization degree of unsaturated tricyclic hydrocarbons reduces the retention. Among the saturated tricyclic isomers the retention becomes shorter with the larger bending of the molecules, i.e. from the molecule having more equatorial bonds to the molecules having more axial connections. The experimentally determined Henry's constants were qualitatively compared with the structure of the separated molecules.     

Dissymmetrization in X-irradiated RbTiOPO4 crystal

Electron paramagnetic resonance has been used to study the hole and electron paramagnetic centers formed in X-irradiated RbTiOPO₄, the crystals of the KTP family. X-irradiation of RbTiOPO₄ crystals at 77 K produced an oxygen hole center and four different trivalent titanium electron centers I₁, II, III and IV. Theg-tensors, their principal values and axes for the defects were calculated and compared with those for KTiOPO₄ centers. X-irradiation at 300 K produced another two oxygen hole centers and three electron centers I₁, I₂ and II. EPR spectra of the center II revealed dissymmetrization, i.e., irregular distribution of growth defects, between the physically equivalent sites lowering the point group symmetry of the local environment of paramagnetic centers Ti³⁺.