N-Nitrosamines are a class of compounds notorious both for the potent carcinogenicity of many of its members and for their widespread occurrence throughout the human environment, from air and water to our diets and drugs. Considerable effort has been dedicated to understanding Nnitrosamines as contaminants, and methods for their prevention, remediation, and detection are ongoing challenges. Understanding the chemistry of N-nitrosamines will be key to addressing these challenges. To facilitate such understanding, we focus in this Perspective on the structure, reactivity, and synthetic applications of N-nitrosamines with an emphasis on alkyl N-nitrosamines. The role of Nnitrosamines as water contaminants and the methods for their detection are also discussed.N-Nitrosamines (or simply "nitrosamines") are a class of compounds sharing the general structure 1 (Chart 1), where
Single crystals of the new title compounds are prepared by reactions of stoichiometric amounts of the elements (1173—1273 K, 96—192 h, 70—80 wt.% yields based on Tb or Gd).
Six new uranium chalcogenides, Ba4USe6, Ba3FeUSe6, Ba3MnUSe6, Ba3MnUS6, Ba3.3Rb0.7US6, and Ba3.2K0.8US6, related to the 2H hexagonal perovskite family have been synthesized by solid-state methods at 1173 K. These isostructural compounds crystallize in the K4CdCl6 structure type in space group D3d6–R3̅c of the trigonal system with six formula units per cell. This structure type is remarkably flexible. The structures of Ba3FeUSe6, Ba3MnUSe6, and Ba3MnUS6 consist of infinite ∞1[MUQ66–] chains (M = Fe or Mn; Q = S or Se) oriented along the c axis that are separated by Ba atoms. These chains are composed of alternating M-centered octahedra and U-centered trigonal prisms sharing triangular faces; in contrast, in the structures of Ba4USe6, Ba3.3Rb0.7US6, and Ba3.2K0.8US6, there are U-centered octahedra alternating with Ba-, Rb-, or K-centered trigonal prisms. Moreover, the Ba4USe6, Ba3FeUSe6, Ba3MnUSe6, and Ba3MnUS6 compounds contain U4+, whereas Ba3.3Rb0.7US6 and Ba3.2K0.8US6 are mixed U4+/5+ compounds. Resistivity and μ-Raman spectroscopic measurements and DFT calculations provide additional insight into these interesting subtle structural variations.
Synthesis, crystal structure, optical, and electronic study of the new ternary thorium selenide Ba 3 ThSe 3 (Se 2 ) 2 Journal of Solid State Chemistry, http://dx.Abstract The compound Ba 3 ThSe 3 (Se 2 ) 2 has been synthesized by solid-state methods at 1173 K. Its crystal structure features one dimensional chains of 1 ∞ [Th(Se) 3 (Se 2 ) 2 6− ] separated by Ba 2+ cations. Each Th atom in these chains is coordinated to two Se−Se single-bonded pairs and four Se atoms to give rise to a pseudoocthedral geometry around Th. The Th−Se distances are consistent with Th 4+ and hence charge balance of Ba 3 ThSe 3 (Se 2 ) 2 is achieved as 3 × Ba 2+ , 1 × Th 4+ , 3 × Se 2− , and 2 × Se 2 2−. From optical measurements the band gap of Ba 3 ThSe 3 (Se 2 ) 2 is 1.96(2) eV.DFT calculations indicate that the compound is a semiconductor.
The three new quaternary actinide chalcogenides Ba2TiUTe7, Ba2CrUTe7, and Ba2CrThTe7 have been synthesized. From single-crystal X-ray diffraction studies these isostructural compounds are found to crystallize in a new structure type in space group D2h16–Pnma of the orthorhombic system. The structure features ∞1[MAnTe74–] strips (M = Cr or Ti; An = Th or U) that propagate in the b-direction and are separated by Ba cations. An atoms are coordinated to eight Te atoms in a bicapped trigonal-prismatic geometry while M atoms are octahedrally coordinated to six Te atoms. Sharing of the AnTe8 and MTe6 polyhedra forms ∞1[MAnTe74–] strips. The presence of the infinite linear Te–Te–Te chains in these compounds makes assignment of oxidation states arbitrary. Resistivity measurements and DFT calculations provide further insight into the properties of these compounds.
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