Synthese und Molekülstruktur neuer Ringsysteme aus 1,1,3,3-Tetrachlor-1,3-diphosphapropan

Synthesis and Molecular Structure of new Ring Systems from 1,1,3,3-Tetrachloro-1,3-diphosphapropane 1,1,3,3-Tetrachloro-1,3-diphosphapropane 1 reacts in two different ways to form new heterocycles. Partial oxidation of 1 with tetrachloroorthobenzoquinone furnishes the methylene-bridged λ³P, λ⁵P species 3 . Subsequent reactions with di- and triethylamine lead to the condensed ring system 6 with the P?C bonds connected to a central four-membered ring. Compound 6 displays crystallographic inversion symmetry, a short transannular P? P distance and an extremely distorted tetrahedral coordination geometry at the four-membered ring phosphorus atoms. 1 reacts with 7 to give the heterocycle 8 with a central eight-membered ring involving four phosphorus atoms. The eight – membered ring shows a ?bent”? crown conformation, the condensed five – membered rings display envelope conformation.     

Ternäre Lithium-Selten-Erd-Nitrate mit einsamen Nitrationen: Li3[M(NO3)5](NO3) (M = Gd?Lu,Y). Die Kristallstruktur von Li3Er(NO3)6

Ternary Lithium Rare Earth Nitrates with Lonesome Nitrate Ions: Li₃[M(NO₃)₅](NO₃) (M = Gd? Lu, Y). The Crystal Structure of Li₃Er(NO₃)₆ Single crystals of the ternary nitrate Li₃Er(NO₃)₆ are obtained from a solution of “Er(NO₃)₃” in the melt of LiNO₃. In Li₃Er(NO₃)₆ (monoclinic, P2₁/n, Z = 4; a = 776.0(1); b = 748.86(8); c = 2 396(1) pm; β = 90.76(3)°; R1 = 0.0490; wR2 = 0.0792), Er³⁺ is surrounded by five bidentate nitrate ligands yielding the anionic units [Er(NO₃)₅]^2?. These are arranged in the direction of the 2₁ screw axis. Two lonesome NO₃^? ions are in the middle of such a “helix” and are connected by Li⁺ with the anions [Er(NO₃)₅]^2?. The helices are moved against each other by about half of the lattice constant a and are connected by further Li⁺ ions.     

Fragmentation of 1-aryl-5-(2-dialkylaminovinyl)-1H-tetrazoles upon electron impact

The mass spectrometric behaviour of 1-aryl-5-(2-dialkylaminovinyI)-lH-tetrazoles was studied, especially 1-phenyl-5-(2-dimethylaminovinyl)-l H-tetrazole as a typical example of D- and ¹⁵N-labelled derivatives revealed a rearrangement via a carbodiimide-like intermediate ion.     

[Rb2(H2O)2][Re3(μ-Cl)3Br7(H2O)2]2 · H2O,ein gemischtes Halogenid-Hydrat mit anionischen Dimeren {[Re3(μ-Cl)3Br7(H2O)2]2 · H2O}2−

[Rb₂(H₂O)₂][Re₃(μ-Cl)₃Br₇(H₂O)₂]₂ · H₂O, a Mixed Halide-Hydrate with the Anionic Dimer {[Re₃(μ-Cl)₃Br₇(H₂O)₂]₂ · H₂O}^2? [Rb₂(H₂O)₂][Re₃(μ-Cl)₃Br₇(H₂O)₂]₂ · H₂O crystallizes as dark redbrown single crystals from an hydrobromic-acid solution of ReCl₃ and RbBr at 0°C. An important feature of the crystal structure (monoclinic, C2/c; a = 1494.61(8); b = 835.71(4); c = 3079.96(19) pm; β = 97.801(4)°; V_m = 573.9(4) cm³mol^?1; R = 0.060; R_w = 0.038) is the connection of two anions [Re₃(μ-Cl)₃Br₇(H₂O)₂]^? via a water molecule to dimers, {[Re₃(μ-Cl)₃Br₇(H₂O)₂]₂ · H₂O}^2?. These dimeric units are contained in slabs that are stacked in the [001] direction and held together by Rb⁺ cations and crystal water.     

Synthese,Struktur und einige Reaktionen [N-(N′,N′,N″,N″-tetramethyl)-guanidinyl]-substituierter Phosphorylverbindungen

Synthesis, Structure, and some Reactions of N-(N′,N′,N″,N″-tetramethyl)guanidinyl-substituted Phosphoryl Compounds The tetramethylguanidinyl-substituted phosphoryl compounds 1 – 10 were prepared in the reaction of the appropriate chlorophosphoryl compounds with either N′,N′,N″,N″-tetramethylguanidine (HTMG) or N-trimethylsilyl-(N′,N′,N″,N″-tetramethyl)guanidine (TMSTMG). With methyl iodide 1 reacted with N-alkylation to give the ammonium salt 11. 1 reacted with BF₃ · Et₂O at both imino nitrogen atoms with formation of the bis-BF₃-adduct 12 . The X-ray structure determination of phenylphosphonic acid-bis(N′,N′,N″,N″-tetramethylguanidinide) 3 shows shortened PN-bonds and widened PNC-angles, consistent with the partial double bond character of the PN-bond.     

Solvent intercalation in cobalt dimethylglyoximato complexes: A miniature host-guest system

When crystallized from appropriate solvents, the complex aqua-bis(dimethylglyoximato)nitrocobalt (III) may incorporate solvent molecules, thus forming a variety of mixed crystals. In the resulting host-guest crystals, the space groupP2_l/m and the packing motif of the pure host compound are retained. Lattice constantsa andb remain essentially unaltered upon intercalation, whereasc and the monoclinic angle depend largely on the clathrated guest. Space filling and intermolecular contacts are discussed.Dedicated to Professor Peter Paetzold at the occasion of his 60th birthday. A preliminary account of this work has been given at the Spring Meeting of the British Crystallographic Association, Newcastle upon Tyne, 1994.     

Biocatalytic reversible control of the stiffness of DNA-modified responsive hydrogels: applications in shape-memory,self-healing and autonomous controlled release of insulin

The enzymes glucose oxidase (GOx), acetylcholine esterase (AchE) and urease that drive biocatalytic transformations to alter pH, are integrated into pH-responsive DNA-based hydrogels. A two-enzyme-loaded hydrogel composed of GOx/urease or AchE/urease and a three-enzyme-loaded hydrogel composed of GOx/AchE/urease are presented. The biocatalytic transformations within the hydrogels lead to the dictated reconfiguration of nucleic acid bridges and the switchable control over the stiffness of the respective hydrogels. The switchable stiffness features are used to develop biocatalytically guided shape-memory and self-healing matrices. In addition, loading of GOx/insulin in a pH-responsive DNA-based hydrogel yields a glucose-triggered matrix for the controlled release of insulin, acting as an artificial pancreas. The release of insulin is controlled by the concentrations of glucose, hence, the biocatalytic insulin-loaded hydrogel provides an interesting sense-and-treat carrier for controlling diabetes.

Biocatalytic control over the stiffness of pH-responsive hydrogels is applied to develop shape-memory, self-healing and controlled release matrices.     

1H-CRAMPS Solid-State NMR and X-Ray Crystal Studies of Inclusion Complexes Formed from 3,3′-bis(9-Hydroxy-9-fluorenyl)-2,2′-binaphthyl Hosts with Acetone

The crystal structures of inclusion compounds of 3,3-bis(9-hydroxy-9-fluorenyl)-2,2-binaphthyl host (1) and its chloro (2) or bromo (3) derivatives substituted in 2,7-positions of the fluorene units with acetone guests (1A–3A) were determined by X-ray studies as well as by ¹H-CRAMPS solid-state NMR. Using this NMR technique allows identification of differently bound guest molecules due to their different chemical shifts caused by the influence of the ring current effects of the host aryl units.     

Helical unwinding in polymer-dispersed ferroelectric liquid crystals

We demonstrate that ferroelectric liquid crystals dispersed in a polymer matrix can form uniaxially aligned elliptical droplets. The alignment is controlled by mechanical shear during the polymerization of a UV-curable adhesive. The possibility of prealignment makes polymer-dispersed ferroelectric liquid crystals suitable for application in flexible electro-optical displays. In contrast to surface stabilized ferroelectric liquid crystal displays, the electro-optical effect in our system is due to the deformed-helix ferroelectric (DHF) effect.