Jan W. Zwikker

Homologous series of liquid-crystalline metal free and copper octa-n-alkoxyphthalocyanines

Abstract Two series of discotic liquid crystals, one based on metal-free and the other on copper containing phthalocyanine (Pc) as the central core and eight peripherally n-alkoxy groups (C6–C12) as substituents have been synthesized and their mesomorphic properties and structural parameters have been determined. These compounds represent a series totally devoid of polymorphism, the mesophase in all cases being Dho. In the solid state an orthorhombic two dimensional lattice with four molecules per unit cell and a presumably tilted stacking is present, while in the mesophase the planes of the molecules are on average perpendicular to the direction of the stacks. The aggregation behaviour of the C8, C10 and C12 homologues was studied as a function of solvent polarity and of concentration. The electrical properties of the copper complexes of the n-dodecoxy and n-octoxy derivatives have been determined by means of complex impedance spectroscopy and compared with those of the non-mesogenic CuPc.

Peripherally Octasubstituted Phthalocyanines with Branched Alkoxy Chains

Abstract Phthalocyanines (H2Pc) octasubstituted with branched alkoxy chains were synthesized: 2,3,9,10,16,17,23,24- octakis(3,7-dimethyloctoxy)phthalocyanine (1a) and 2,3,9,10,16,17,23,24-octakis(3,7,11-trimethyldodecoxy)phthalocyanine (1b). Their mesomorphic properties were studied by DSC, polarization microscopy and X-ray diffraction. Compound 1a, which was initially crystalline at room temperature, maintains its mesomorphic structure on cooling back to room temperature. Compound 1b is mesomorphic at room temperature. It shows a D ho→D hd transition at 34[ddot]C and a transition of unknown nature at 173[ddot]C. Both compounds display a D→I transition.

Thermal generation and (inter)conversion of (multi) cyclopenta-fused polycyclic aromatic hydrocarbons

FVT of I, 1 -dichloro- and/or 1 -chloroethenyl substituted PAHs gives access to the CP-PAHs pyracylene (l), cyclopenta(cd)pyrene (12) and benz(ghi)fluoranthene (13), cyclopent(hi)aceanthrylene (18) and cyclopent(hi)acephenanthrylene (19), and the novel cyclopenta(cd)fluoranthene (22) and isomeric cyclopent(fg)- (25a), cyclopent(ik)- (25b) and cyclopent(rnn)acepyrylene (25c), respectively. The propensity of CP-PAHs to interconvert under high temperature FVT conditions is illustrated. Possible mechanisms, such as ring-contractionhing-expansion via 1,2-H and 1,2-C shifts, are discussed.

Cyclopenta[cd]fluoranthene: Acefluoranthylene

Cyclopenta[cd]fluoranthene (1, acefluoranthylene) is obtained by Flash Vacuum Thermolysis of 3(1-chloroethenyl)fluorlanthene (4). The electronic properties (cyclic voltammetry , UV/Vis and fluorescence) of 1 are markedly affected by cyclopenta-fusion.

Synthesis of 2-acetamido-6-O-(5-acetamido-3,5-dideoxy-β-d-glycero-d-galacto-2-nonulopyranosylonic acid)-2-deoxy-d-glucose [2-acetamido-6-O-(N-acetyl-β-d-neuraminyl)-2-deoxy-d-glucose]

Abstract Silver triflate-promoted condensation of methyl 5-acetamido-4,7,8,9-tetra- O -acetyl-2-chloro-2,3,5-trideoxy-β- d - glycero - d - galacto -2-nonulopyranosonate (9) with benzyl-2-acetamido-2-deoxy-3,4- O -(1,1,3,3-tetraisopropyldisiloxane-1,3-diyl)-α- d -glucopyranoside, followed by removal of the 1,1,3,3-tetraisopropyldisiloxane-1,3-diyl group and subsequent acetylation, afforded a 4:1 mixture of benzyl 2-acetamido-3,4-di- O -acetyl-2-deoxy-6- O -(methyl 5-acetamido-4,7,8,9-tetra- O -acetyl-3,5-dideoxy-β- d - glycero - d - galacto -2-nonulopyranosylonate)-α- d -glucopyranoside (13) and the (2→6)-α-linked isomer. After selective crystallisation, 13 was obtained in 46% yield based on the precursor of 9 , methyl 5-acetamido-2,4,7,8,9-penta- O -acetyl-3,5-dideoxy- d - glycero - d - galacto -2-nonulopyranosonate (8) . An additional product of the condensation reaction was methyl 5-acetamido-4,7,8,9-tetra- O -acetyl-2,6-anhydro-3,5-dideoxy- d - glycero - d - galacto -non-2-enopyranosonate, which was obtained in 40% yield based on 8 . O -Deacetylation of 13 and subsequent saponification gave benzyl 2-acetamido-2-deoxy-6- O -(potassium 5-acetamido-3,5-dideoxy-β- d - glycero - d - galacto -2-nonulopyranosylonate)-α- d -glucopyranosi de (16) . Catalytic hydrogenolysis of 16 yielded the title product as its potassium salt.

A novel enantiopure proline-based organonickel(III) halide monocation with a pentadentate C, N2, O2-bonded bis(ortho-chelating) aryldiamine ligand☆

Abstract An attempt was made to use the enantiopure arylnickel(II) complex [Ni(L ★ − N , C , N )Br], 1 , (L ★ is the monoani ligand, 2,6-bis[(2-( S )-2-isopropoxycarbonyl-1-pyrrolidinyl)methyl)phenyl) as a catalyst for the Kharasch addition reaction of CCl 4 to alkenes which led instead to a new ionic arylnickel(III) complex [Ni(L ★ )Cl] 2 [NiCl 4 ] (=[ 2-Cl ] 2 [NiCl 4 ]. An X-ray diffracti study of this complex revealed the presence of two identical monocations [ 2-Cl ] + that have octahedrally coordinated Ni(III) centres and a single dianionic NiCl 4 2− unit. The octahedral ligand sphere of cation [ 2-Cl ] + is best described as tetragonally compressed, with the meridional coordination comprising N 2 , O 2 donative bonding from the two N atoms of the pyrollidine groups and two carbonyl O atoms of the ester groups of L ★ , the mutually trans apical sites are occupied by a Cl atom and the C atom of the NiC aryl bond; i.e. the monoanionic organic ligand L ★ binds as a monoanionic C, N 2 , O 2 pentadentate system. Spectroscopic data for [ 2-Cl ] + are presented and compared with those for the square-planar arylnickel(II) complex 1 , in which the oxygen donor atoms of the ester groups of L ★ are not coordinated and the ligand thus acts as a C, N 2 terdentate system.

Poly(iminomethylenes). 9. Induction of screw sense in the nickel(II)-catalyzed polymerization of chiral isocyanides

Abstract A rule is presented which predicts the screw sense of the polymers obtained in a nickel(II)catalyzed reaction from chiral isocyanides of the type R1R2R3CNC. It is based on the steric effects and on the ligand properties of R1, R2 and R3. The optical rotation data on ten chiral isocyanides and their polymers verify this rule. The results suggest that the asymmetric induction of screw sense is controlled kinetically at the catalyst center. A thermodynamically controlled process appears to be less likely.

Reduction of Acetylenic Compounds to (E)-Olefins by Alkali Metals – An Investigation of the Scope

Efficient procedures have been developed for the stereospecific reduction by alkali metals of disubstituted acetylenes with long carbon chains. Acetylenes containing two or more (isolated) triple bonds are reduced considerably more easily than are monoynes.

The crystal structure of 2-methoxy-1,4-benzoquinone: molecular recognition involving intermolecular dipole–dipole- and C–H ⋯ O hydrogen bond interactions

In its crystal structure 2-methoxy-1,4-benzoquinone 2 is networked into a planar hexagonal pattern by intermolecular dipole–dipole- and extensive C–H ⋯ O hydrogen bond interactions leading to a graphite-like layer packing motif.

Poly(iminomethylenes). 8. Circular insertion mechanism of nickel(II)-catalyzed polymerization of isocyanides

Abstract A merry-go-round sequence of ligand/insertions is proposed for the polymerization of isocyanides by nickel(II). The mechanism agrees with kinetic results as well as with data on the reactivity of coordinated isocyanides and on substitution at nickel(II).