Volume 80, Issue 8

The equilibrium structure ( r e ) of gaseous 1,4-bis(trimethylsilyl)-1,3-butadiyne (СН 3 ) 3 SiCCCCSi(СН 3 ) 3 ( 1 ) has been determined by a synchronous GED/MS experiment. The electronic structures of 1 , as well as of (СН 3 ) 2 CCCCCC(СН 3 ) 2 ( 2 ) and PhCCCCPh ( 3 ), which differ in the nature of the terminal groups, are described using the NBO and QTAIM methods. Based on the lengths, orders and ellipticity parameters of the bonds, the linear СССС fragment in 1 was described as a polyyne, in 2 as a cumulene, and in the planar compound 3 with π-conjugated Ph groups as a polyyne with a small ellipticity of the С≡С bonds. The molecular and electronic structures of the molecular ions [ 1 ] + , [ 2 ] + , [ 3 ] + and other ions recorded in the EI mass spectrum of 1 were calculated at the B3LYP/cc-pVTZ level of theory. A comparison of the structural parameters of 1 , 2 and 3 and the corresponding ions indicates the possibility of modifying the nature of a linear carbon chain both by ionization and by changing the terminal substituents.

A cobalt(II) coordination polymer, formulated as [Co(bpbe) 2 (terephthalate)(H 2 O) 2 ] n (where bpbe = bis(1-(pyridin-3-ylmethyl)-benzimidazol-2-ylmethyl)ether), has been synthesized and characterized by elemental analysis, IR and UV/Vis spectroscopy and single-crystal X-ray diffraction. The structural analysis shows that the compound has a chain structure. The electrocatalytic activity towards hydrogen evolution reaction (HER) and ascorbic acid sensing were investigated by fabricating glassy carbon electrodes (Co/GCE) containg the new polymer. The results of HER measurements showed that the overpotential ( η 10 298K ) and Tafel slope ( b 298K ) were −700 mV and 151.5 mV·dec −1 for Co/GCE, but −941 mV and 277.9 mV dec −1 for bare/GCE. The η 10 298K and b 298K of Co/GCE were significantly positive shifted and significantly reduced compared with bare/GCE, indicating that Co/GCE has a good electrocatalytic HER activity. In addition, the recognition performance of Co/GCE for ascorbic acid was studied by chronoamperometry. The results show that Co/GCE has specific recognition performance for ascorbic acid. The detection limit is 0.3 μ m in the response range of 0.5 μ m –4 m m . The new electrode has long-term stability and good selectivity. This work provides a meaningful reference for the application of non-noble transition metal coordination polymers in electrocatalysis.

CeNiZn and α -CePdZn (both ZrNiAl type, hexagonal space group P 6‾2 m ) form a complete range of solid solutions CeNi 1– x Pd x Zn. Samples were synthesized with steps of x = 0.1 or 0.05 from the pure elements by induction-melting. The structure of CeNi 0.59(1) Pd 0.41 Zn was refined from single crystal X-ray diffractometer data: a = 727.61(8), c = 396.75(4) pm, w R 2 = 0.0301, 297 F 2 values and 17 variables. Both the 1 a and 2 d transition metal sites show Ni/Pd mixing. The cell volume decreases from α -CePdZn to CeNiZn in a discontinuous manner. This is directly related to a change in the cerium magnetic ground state. The properties change from Curie-Weiss paramagnetic α -CePdZn to homogeneous mixed valence in CeNiZn. The magnetic susceptibility data of the intermediate-valence representatives could be fitted with the Sales-Wohlleben interconfiguration-fluctuation model.

The high-temperature modification of ZrCr 6 P 4 was synthesized in a tin-flux reaction of the components with the starting composition (atomic ratio) Zr:Cr:P:Sn = 1:3.37:2.34:40 in an evacuated silica tube. After a pre-reaction at T = 770 K the ampoule was heated to 1,270 K and crystals were grown with a cooling rate of 50 K h −1 to room temperature. β -ZrCr 6 P 4 is isotypic with β -UCr 6 P 4 . Its structure was refined from single crystal X-ray diffractometer data: orthorhombic space group Pmmn , a = 344.10(5), b = 699.00(11), c = 1,188.8(3) pm, w R 2 = 0.0421, 432 F 2 values, 40 variables. The chromium and phosphorus atoms in β -ZrCr 6 P 4 build a covalently bonded [Cr 6 P 4 ] network in which the zirconium atoms fill distorted hexagonal prismatic voids. The three crystallographically independent phosphorus atoms exhibit trigonal prismatic metal coordination, and these prisms are condensed to a propeller-like motif. The relationship between the α -ZrCr 6 P 4 and β -ZrCr 6 P 4 structures is readily evident from their chromium substructures which show different connectivity patterns of the same monomeric building unit, however, with slightly differing ranges for the Cr–Cr distances (272–278 pm in α -ZrCr 6 P 4 and 257–287 pm in β -ZrCr 6 P 4 ).

The series of intermetallic compounds RE 4 Pd 11 Al 8 ( RE = Y, Sm, Gd–Lu) was synthesized from the elements by arc-melting, followed by a two-step annealing process in order to increase phase purity. Sm 4 Pd 11 Al 8 and Yb 4 Pd 11 Al 8 were prepared by induction-melting of the elements in sealed niobium ampoules. The polycrystalline samples were characterized through their X-ray powder patterns. The structures of Y 4 Pd 11.06 Al 7.94 , Sm 4 Pd 11.39 Al 7.61 , Dy 4 Pd 11.44 Al 7.56 and Yb 4 Pd 11.19 Al 7.81 were refined from single crystal X-ray diffractometer data. The four structure refinements revealed small degrees of Pd/Al mixing. The aluminides RE 4 Pd 11 Al 8 crystallize with a new structure type, orthorhombic space group Pmmn . The structures contain four crystallographically independent rare earth sites with coordination numbers ranging from 14 to 18. These four polyhedra types are condensed via common edges and faces. The palladium and aluminum atoms form a complex [Pd 11 Al 8 ] substructure with large ranges of Pd–Al (244–279 pm), Pd–Pd (280–319 pm) and Al–Al (265–328 pm) distances. The striking structural unit within the [Pd 11 Al 8 ] substructure is a butterfly-type Al 4 cluster with 264.9–279.3 pm Al–Al, comparable to the Si 4 butterfly in the Zintl phase Ba 3 Si 4 . This Al 4 cluster is coordinated solely by palladium atoms. Temperature-dependent magnetic susceptibility data of RE 4 Pd 11 Al 8 with RE = Tb–Tm show Curie-Weiss behavior. The magnetic ordering temperatures are 28.4(5) K for RE = Tb, 21.6(5) K for RE = Dy, 6.0(5) K for RE = Ho and 3.9(5) K for RE = Er. Tm 4 Pd 11 Al 8 shows no magnetic order down to 2.2 K.

Thiocyameluric acid C 6 N 7 S 3 H 3 was reacted with various aqueous solutions of metal hydroxides and other metal salts, as well as ammonia. Crystalline products were obtained from reaction mixtures containing main group metal hydroxides. Only in the case of strontium hydroxide single crystals of Sr[HC 6 N 7 S 3 ]·6H 2 O suitable for an X-ray structure analysis were formed. Similar to other cyamelurates containing anions like [C 6 N 7 O 3 ] 3– , [HC 6 N 7 O 3 ] 2– or [H 2 C 6 N 7 O 3 ] – , or analogous melonates [C 6 N 7 (NCN) 3 ] 3– , the anion [HC 6 N 7 S 3 ] 2– in the title salt is completely planar. The hydrogen atom is located at a terminal N atom, which indicates that mono- and di-hydrogen thiocyamelurates and thiocyameluric acid preferably occur as thioketone tautomeric isomers, and are not encountered in the thiol form, at least in the solid state. Since all water molecules coordinate the strontium atoms and the anions do not act as ligands the salt may be described as [Sr(H 2 O) 6 ][HC 6 N 7 S 3 ].

The approach to derive the Goldschmidt tolerance factor (GTF) for perovskite structures has been generalized and reformulated in terms of the geometry of regular polyhedra. The polyhedral approach was shown to be applicable for deriving the conceptual and functional GTF analogs for the non-perovskite structures containing at least two different and reasonably regular coordination polyhedra with the same or nearly the same edge lengths.