Designer dendrimers: branched oligosulfonimides with controllable molecular architectures

The synthesis of "designer" dendrimers and dendrons with sulfonimide units at every branching point is reported. The synthesis is based on a series of (regio)selective functionalization reactions of amines and sulfonamides allowing precise control of the dendrimers' shape, the number of branches in each generation, and their peripheral decoration with functional groups. In principle, structurally different branches can be incorporated at any position within the dendrimer structure at will. Structurally perfect symmetrical and two-faced "Janus"-type dendrimers, as well as dendrimers and dendrons with intended interstices were synthesized on a preparative scale and fully characterized. Oligosulfonimide dendrons of various generations bearing an aryl bromide functional group at their focal points were attached to a p-phenylene core with the aid of Suzuki cross-coupling reactions resulting in dendrimers with photoactive terphenyl cores. The structure and the high purity of all dendritic sulfonimides were confirmed by means of (1)H and (13)C NMR, electrospray ionization mass spectrometry (ESI-MS), and elemental analysis. The utility of MALDI-TOF mass spectrometry for the analytical characterization of these dendrimers was evaluated in comparison to electrospray ionization. Two model branched oligosulfonimides were characterized in the solid state by single-crystal X-ray analysis. Reaction selectivities and conformation of sulfonimide branching points were rationalized by DFT calculations.     

Crystal structure of lanthanum potassium octacyanomolybdate(IV) nonahydrate

The crystal structure of KLaMo(CN)₈ · 9H₂O was determined from X-ray diffraction data. The crystals are monoclinic, space group P2₁/c, a = 8.7451(4), b = 25.2761(13), c = 10.6744(5) Å, β = 117.059(3)°, V = 2101.22(17) ų, Z = 4, ρ(calcd) = 2.037 g/cm³, R = 0.0242, wR ₂ = 0.0500 for 5656 independent reflections. The coordination polyhedra of the Mo, La, and K atoms are the tetragonal antiprism [Mo(CN)₈], the monocapped tetragonal antiprism [La(NC)₄(OH₂)₅], and the strongly distorted monocapped trigonal prism [K(NC)₃(OH₂)₄], respectively. The La and K atoms are N-linked by seven bridging cyano groups to form double layers with two sandwiched uncoordinated water molecules and the sandwiched terminal CN group. The complex can be formulated as “[K(H₂O)₂][La(H₂O)₅][Mo(CN)₈]” _n · 2nH₂O.     

Molecular and crystal structure of derivatives of higher internal perfluoroalkenes

Institute of Heteroorganic Compounds, Academy of Sciences of the USSR. Translated from Zhurnal Strukturnoi Khimii, Vol. 30, No. 2, pp. 199–203, March–April, 1989.     

Effects of electron transitions on the susceptibility of Cd3Mg

The monotone susceptibility component has been examined at 4.2–420 K for Cd_1–xMg_x ordering single crystals for 0.18 < x < 0.33. The temperature and concentration curves for the susceptibility components show features related to structural and electronic topological transitions. The susceptibility anomalies at the electron-transition points are correlated with the boundaries to the existence of the allotropic forms.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, No. 4, pp. 23–28, April, 1988.I am indebted to N. V. Kornienko for assistance in distilling the magnesium, to L. E. Usenko for analyzing the alloys, to M. A. Obolenskii for providing facilities for measuring the susceptibility, and to I. V. Svechkarev for critical comments on the results.     

Mechanoactivation of solid-phase iodochlorination of olefins with potassium dichloroiodate(I)

Mechanoactivation of iodochlorination of olefins with a new reagent, potassium dichloroiodate(I), was studied.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2357–2358, September, 1996.     

Deposition and Etching of Thin Films by Means of Beam Plasma Discharge with Tube-Like Electron Beam

The efficiency of energy dissipation caused by the mechanism of turbulent plasma heating from a tube-like electron beam in a electronegative gas is measured calorimetrically. Amorphous Si-layers are deposited from a SiH₄/Ar discharge both on conducting and nonconducting substrates and are analyzed by means of Auger-spectrometry. The velocity and specific energy of etching of SiO₂-layers in a CF₄-plasma are determined. Measured etching velocities of tungsten surfaces biased differently against the space potential provide information on the mechanism of plasma etching in a SF₆-plasma. Simultaneously performed Langmuir-probe measurements permit predictions to be made on the properties of the etching plasma.