The 1:1 adduct of 2,5-dihydroxy-1,4-benzoquinone with 4,4′-bipyridine

2,5-Di­hydroxy-1,4-benzo­quinone (DHBQ) and 4,4′-bi­pyridine (BPY) crystallize in a 1:1 ratio as a neutral molecular adduct, C₆H₄O₄·C₁₀H₈N₂, in space group C2/c, with half of each mol­ecule in the asymmetric unit. The mol­ecules are linked by a strong O—H⃛N hydrogen bond [O⃛N 2.6323 (15) Å] and a weak C—H⃛O hydrogen bond [C⃛O 3.2082 (17) Å] to form infinite stacks of parallel one-dimensional hydrogen-bonded ribbons. The two rings of the bi­pyridine are twisted at 28.3° with respect to each other, and the benzo­quinone ring is inclined at an angle of 18.3° with respect to the plane of the neighbouring pyridine ring. The 4,4′-bi­pyridine mol­ecule lies on a twofold axis and the benzo­quinone mol­ecule lies across an inversion centre.     

Raman spectra of molecular crystals. Carbon disulphide

Raman and far-infrared spectra of polycrytalline CS₂ samples at 79 and 18°K are reported, with assignments of molecular and lattice modes. Observed frequencies are compared with those from lattice dynamics calculations based on atom-atom interactions.     

复合材料应力分析的非均匀等参单元

本文提出了非均匀有限元概念,推导了非均匀等参单元刚度矩阵公式.作为应用实例,用轴对称非均匀元素计算了复合材料绳索端头的应力分布.     

Uranium(VI) sulfilimine complexes: a new class of nitrogen analogues of the uranyl ion

The compound tetraphenylphosphonium tetrachlorooxo-S,S-diphenylsulfiliminatouranium, [Ph4P][UOCl4(NSPh2)], has been prepared in high yield from [Ph4P][UOCl5] and [Ph2S=NSiMe3]. An X-ray structure of this compound shows that the uranium atom has a pseudooctahedral geometry with oxygen and nitrogen atoms in trans positions. The structure of the analogous phosphoriminato complex [Ph4P][UOCl4(NPPh3)] has been determined for comparison. Derivatization of the sulfide group shows that only a limited range of functionalization confers stability toward reduction. The emission spectrum of the first electronic excited state reveals a greatly reduced energy compared with that of the uranyl ion. This red shift in the transition is consistent with the weakening of the U-N bond relative to the U-O bond.     

Cancellation in Skew Lattices

Distributive lattices are well known to be precisely those lattices that possess cancellation: x úy = x úzx \lor y = x \lor z and x ùy = x ùzx \land y = x \land z imply y = z. Cancellation, in turn, occurs whenever a lattice has neither of the five-element lattices M ₃ or N ₅ as sublattices. In this paper we examine cancellation in skew lattices, where the involved objects are in many ways lattice-like, but the operations ù\land and ú\lor no longer need be commutative. In particular, we find necessary and sufficient conditions involving the nonoccurrence of potential sub-objects similar to M ₃ or N ₅ that ensure that a skew lattice is left cancellative (satisfying the above implication) right cancellative (x úz = y úzx \lor z = y \lor z and x ùz = y ùzx \land z = y \land z imply x = y) or just cancellative (satisfying both implications). We also present systems of identities showing that left [right or fully] cancellative skew lattices form varieties. Finally, we give some positive characterizations of cancellation.     

eHydrogenation: Hydrogen-free Electrochemical Hydrogenation

Hydrogenation reactions are staple transformations commonly used across scientific fields to synthesise pharmaceuticals, natural products, and various functional materials. However, the vast majority of these reactions require the use of a toxic and costly catalyst leading to unpractical, hazardous and often functionally limited conditions. Herein, we report a new, general, practical, efficient, mild and high-yielding hydrogen-free electrochemical method for the reduction of alkene, alkyne, nitro and azido groups. Finally, this method has been applied to deuterium labelling.