1-Eth-oxy-3-[4-(eth-oxy-carbon-yl)phen-yl]-3-hy-droxy-1-oxopropan-2-aminium chloride.

The title compound, CHNO ·Cl, was prepared as a racemate of ,- and ,-enanti-omers by reduction of the corresponding hy-droxy-imino-ketone. In the crystal, layers are formed hydrogen bridges of four ammonium groups to chloride ions; these lamellae are connected inter-digitated benzoic ester groups.

(10)-4,5,6,7,8,9-Cyclo-deca-[][1,2,3]selena-diazole.

The title compound, CHNSe, was prepared from a semicarbazone and selenium dioxide. The planes of the heterocycle and the double bond are almost mutually orthogonal and the hexa-methyl-ene tether is nearly strain-free.

3a,4,5,8,9,9a-Cyclo-octa-[][1,3]dioxole-2-thione.

The thio-nocarbonate of -cyclo-octenediol, CHOS, crystallizes with a 9/1 disorder in the position of the and -enanti-omers. As a result of -annulation, both rings adopt a twist conformation.

Redetermined structure of methyl 3-{4,4-di-fluoro-2-[2-(methoxy-car-bon-yl)-ethyl]-1,3,5,7-tetra-methyl-4-bora-3a,4a-di-aza--in-da-cen-6-yl}pro-pion-ate.

In the title compound, CHBFNO, a highly fluorescent boron-dipyrromethene dye, the methyl-propionate moieties have different conformations. In the crystal, weak C-H⋯F and C-H⋯O inter-actions link the mol-ecules. Some optical properties are presented.

5-[(4-Methyl-phen-yl)sulfon-yl]-1-phenyl-thio-pyrano[4,3-]indole-3(5)-thione di-chloro-methane monosolvate.

Rhodium-catalyzed [2+2+2] cyclo-addition of carbon di-sulfide to ,-dialkynyl-tosyl-anilines gives two isomeric indolo-thio-pyran-thio-nes, a violet and a red isomer. This is the first crystal structure of a red isomer, which crystallizes with one solvent mol-ecule of di-chloro-methane in the asymmetric unit, CHNOS·CHCl. In the extended structure, centrosymmetric pairs of the planar annulated system are arranged in strands and solvent mol-ecules fill the space between the strands.

2,5-Bis[5-(3,5-dido-decyl-oxyphen-yl)-1,3,4-oxa-diazol-2-yl]-3,6-di-methyl-pyrazine.

The nearly planar mol-ecule of the title compound, CHNO, is centrosymmetric with two all- chains, the other two chains have an unit starting with the oxygen atoms. The chains are inter-digitated in the packing.

()-4,5-Di-bromo-3,3,6,6-tetra-methyl-2,3,6,7-tetra-hydro-thiepine-1,1-dione.

The crystal of the title compound, CHBrOS, is formed from layers built from centrosymmetric pairs of mol-ecules. The mol-ecule adopts a twist conformation with the carbon atoms next to sulfur above or below the mean plane.

13,13'-Bi(dibenzo[,]fluorenyl-idene).

The asymmetric unit of the title compound, CH, contains two almost identical mol-ecules. The mol-ecules have approximate symmetry. They show a largely twisted double bond, the mol-ecular halves enclosing dihedral angles of 62.

Diethyl [(2,5-di-iodo-4-methyl-phen-yl)meth-yl]phospho-nate.

The title compound, CHIOP, was prepared in three steps from -xylene. Heterodimers between nearly identical mol-ecules are connected three hydrogen bonds from benzylic and ester methyl-ene groups to phospho-nate. The dimers form chains along the -axis direction, stabilized by C-H⋯O bridges.

[2,5-Bis(di-propyl-amino)-4-(hy-droxy-meth-yl)phen-yl]methanol.

The centrosymmetric title compound, CHNO, was prepared in five steps from diethyl succinate. The di-propyl-amino groups are almost orthogonal to the central phenyl-enedi-methanol ring [dihedral angle = 87.62 (9)°].

-11-Selena-12,13-di-aza-bicyclo-[10.3.0]penta-deca-10a(13a),12-dien-1-ol.

The title compound, CHNOSe, crystallizes in strands of enanti-omeric mol-ecules connected O-H⋯N hydrogen bonds. There are only slight deviations from an ideal conformation in the deca-methyl-ene chain, indicating just a little strain.

5,12-Diselena-3,4,13,14-tetra-aza-tri-cyclo[9.3.0.0]tetra-deca-3,13-diene.

The title compound, CHNSe, crystallizes in a non-symmetrical conformation with a dihedral angle between the heterocycles of 45.0 (3)° and a nearly strain-free tetra-methyl-ene tether. The crystal studied was non-merohedrally twinned with a fractional contribution of 0.

Impact of Substitution Pattern and Chain Length on the Thermotropic Properties of Alkoxy-Substituted Triphenyl-Tristriazolotriazines.

Tristriazolotriazines (TTTs) with a threefold alkoxyphenyl substitution were prepared and studied by DSC, polarized optical microscopy (POM) and X-ray scattering. Six pentyloxy chains are sufficient to induce liquid-crystalline behavior in these star-shaped compounds. Thermotropic properties of TTTs with varying substitution patterns and a periphery of linear chains of different lengths, branching in the chain and swallow-tails, are compared.

-(,)-4-Bromo-10,10-dimethyl-9,11-dioxabi-cyclo-[6.3.0]undec-4-ene.

In the title compound, a cyclo-octene ring in a twist-boat conformation and a dioxolane ring with a distorted envelope conformation are annulated in a configuration. Alternating strands of single enanti-omers build up the crystal. Within the strands, the mol-ecules are connected by weak C-H⋯O hydrogen bonds.

-12-Selena-13,14-di-aza-tri-cyclo-[9.3.0.0]tetra-deca-11,13-diene.

The centrosymmetric crystal structure of the title compound, CHNSe, is built up from alternating strands of ()- and ()-enanti-omers. These strands, which propagate along the axis direction, are composed of homochiral mol-ecules related to each other by twofold screw axes. The shape of the mol-ecule is an almost planar unit around the selena-diazole ring with a hexa-methyl-ene chain as an arched handle.

Methyl 3,3,6,6-tetra-methyl-1,8-dioxo-4,5,7,9-tetra-hydro-2-xanthene-9-carboxyl-ate.

The title mol-ecule, CHO, is built by annulation of a half-chair cyclo-hexenone and a twist-cyclo-hexenone to a flat 4--pyrane boat. In the crystal, mol-ecules are connected van der Waals inter-actions and C-H⋯O hydrogen bonds.

2,5-Bis[()-2-phenyl-ethen-yl]-3,6-bis-(pyridin-2-yl)pyrazine.

The mol-ecule of the title compound, CHN, exhibits inversion symmetry adopting the shape of a St Andrew's Cross. It shows dihedral angles between adjacent aryl units of around 50° whereas torsion angles of 10° are found along the aryl-ene vinyl-ene path.

The head-to-head photodimer of indeno-indene.

Irradiation of 1-(1-benzo-cyclo-butenyl-idene)benzo-cyclo-butene gives indeno-indene and its head-to-head photodimer nona-cyclo-[9.7.7.

Synthesis, Thermal, and Optical Properties of Tris(5-aryl-1,3,4-oxadiazol-2-yl)-1,3,5-triazines, New Star-Shaped Fluorescent Discotic Liquid Crystals.

The synthesis of tris(aryloxadiazolyl)triazines (TOTs), C -symmetrical star-shaped mesogenes with a 1,3,5-triazine center, 5-phenyl-1,3,4-oxadiazole arms, and various peripheral alkoxy side chains is reported. Threefold Huisgen reaction on a central triazine tricarboxylic acid and suitable aryltetrazoles yields the title compounds. Selected analogues with a benzene center are included in this study and allow for an evaluation of the impact of the central unit on the physical properties.

Time-Resolved Photochemistry of Stiffened Stilbenes.

Broadband transient absorption spectroscopy is used to study the photoisomerization of stiffened stilbenes in solution, specifically E/ Z mixtures of bis(benzocyclobutylidene) (t4, c4) and ( E)-1-(2,2-dimethyltetralinylidene)-2-2-dimethyltetraline (t6). Upon excitation to S, all evolve to perpendicular molecular conformation P, followed by decay to S, while the spectra and the kinetic behavior crucially depend on the size of the stiffening ring. In 4, contrary to all previously studied stilbenes, the trans and cis absorption and excited-state spectra are nearly indistinguishable, while the corresponding isomerization times are comparable: τ = 166 ps for t4 and τ = 64 ps for c4 in n-hexane, as opposed to 114 and 45 ps in acetonitrile, respectively.

Tetrakis(oxadiazolylphenyl)pyrazines: New St. Andrew's Cross-Shaped Liquid Crystals.

π-Conjugated molecules with the shape of St. Andrew's cross have been synthesized via fourfold Huisgen reaction. Four 2,5-diaryl-1,3,4-oxadiazol arms are attached to a central pyrazine nucleus.

Isomerisation of Liquid-Crystalline Tristriazolotriazines.

Star-shaped discotic liquid crystals with columnar superstructures constitute a highly interesting class of organic materials. Phenyl-substituted tris[1,2,4]triazolo-[1,3,5]triazine, prepared by a Huisgen reaction of phenyltetrazole and cyanuric chloride, represents an excellent core for discotic liquid crystals (DLCs). The thermal stability is not perfect, at temperatures above the clearing point, a successive threefold isomerization leads to a highly planar, C -symmetrical isomer, which mainly differs in the orientation of the aryl substituents to the centre of the molecule.

Light-Induced Alkylation of (Hetero)aromatic Nitriles in a Transition-Metal-Free C-C-Bond Metathesis.

A light-induced C-C-σ-bond metathesis was achieved through transition-metal-free activation of an unstrained C(sp)-C(sp)-σ-bond in 1-benzyl-1,2,3,4-tetrahydroisoquinolines. A photoredox-mediated single-electron oxidation of these precursor amines yield radical cations which undergo a homolytic cleavage of a C(sp)-C(sp)-σ-bond rather than the well-known α-C-H-scission. The resulting carbon-centered radicals are used in the ipso-substitution of (hetero)aromatic nitriles proceeding through another single-electron transfer-mediated C-C-bond cleavage and formation.

Crystal structure of 11-[4-(hex-yloxy)phen-yl]-1,2,4-triazolo[4,3-a][1,10]phenanthroline.

The title compound, C25H24N4O, was prepared from 2-chloro-phenanthroline and hexyl-oxyphenyl-tetra-zole. The main difference between the two independent mol-ecules (A and B) in the asymmetric unit is the orientation of the all-anti-configured hex-yloxy chain: in A the C-O-C-C torsion angle is 175.9 (2)° whereas it is -88.

3-(4-Hexyl-oxyphen-yl)-1,2,4-triazolo[3,4-b]benzo-thia-zole.

The title compound, C20H21N3OS, was prepared by Huisgen reaction of 5-(4-hexyl-oxyphen-yl)tetra-zole and chloro-benzo-thia-zole. The essentially planar benzo-thia-zolotriazole framework [maximum deviation from the mean plane of 0.077 (1) Å for the bridgehead N atom] and the phenyl ring form a dihedral angle of 53.