Zigzag Molecules Research Articles

Synthesis, crystal structures and luminescent properties of three layered zinc complexes: Zn(1,10-phen)mI2 (m = 1, 2) and Zn2(1,10-phen)2C2O4Br2 (phen = phenanthroline)

Three 1,10-phenantroline zinc halide complexes were successfully synthesized under solvothermal method and structurally characterized by single-crystal X-ray diffraction analysis. The three title complexes Zn(1,10-phen)I2 (1), Zn(1,10-phen)2I2 (2) and Zn2(1,10-phen)2C2O4Br2 (3), crystallize in the triclinic space group P1¯(No.2) with different unit cell parameters, are isolated neutral molecules. The extra stretching force from another 1,10-phen ligand in 2 lead to the Zn−N bond lengths longer than the corresponding in 1. Meanwhile, the molecules of Zn(1,10-phen)I2 and Zn(1,10-phen)2I2 further connect each other via the π-π interactions between the adjacent phenanthrolines to form a pseudo-two-dimensional layer which parallel to b-axis. Their face-to-face distance of π-π stacking interactions between the adjoining 1,10-phen rings is 3.7264 Å and 3.4435 Å, respectively. The zinc bromide complex 3 contains C−H···O intramolecular and C−H···Br (2-D) interlayer hydrogen bonding, which contributed to the connection between the parallel zig-zag molecules. The distance of phenanthroline rings in intramolecular and interlayer is 2.6071 Å and 3.8125 Å.The luminescent emissions of free ligand 1,10-phen and its zinc halide complexes were measured in various solvents. These zinc halide complexes show the obvious luminescent phenomenon with grass-green, yellow-green and light yellow in Dimethyl sulfoxide (DMSO), respectively (the maximum emission wavelength is 530 nm, 539 nm and 496 nm). The maximum emission wavelength for 2 has a little red-shifted compared with 1. It can be concluded that the number of ligand and the electron density on coordinated Zn atoms influence the emission wavelength through charge transfer from ligand to the metal. The emission wavelengths of 3 are also slightly red-shifted compared with the free 1,10-phen ligand, which is attributed to the coordination effects of the 1,10-phen ligands to the Zn cations and [C2O4]2− group.

Anthraceno-Perylene Bisimides: The Precursor of a New Acene

A controlled synthesis strategy for a anthracene-fused perylene bisimide was developed from the cyclization of an anthracene unit pendant to a perylene diimide scaffold. The direct cyclization led to a zigzag molecule, while a Diels-Alder strategy influenced the regiochemistry of cyclization to afford the linear precursor of a new acene.

Zigzag Molecules from Pyrene-Modified Carbazole Oligomers: Synthesis, Characterization, and Application in OLEDs

A series of monodisperse, pyrene-modified oligocarbazoles were synthesized and fully characterized. Carbazoles were linked by ethynylene through the 3- and 6-positions, forming a zigzag molecular backbone and stable, size-independent absorption, and emission were observed from these oligomers in solutions because their conjugation length was confined. Oligomers with pyrene exhibited much higher fluorescence quantum yields than those of oligomers without it. Different positions of pyrene in the oligocarbazole main chain resulted in a remarkable change in absorption and emission spectra. Moreover, devices with four different architectures (types 1-4) based on these oligomers were fabricated and investigated. Pyrene-modified carbazole oligomers exhibited bifunctional properties (light-emitting and hole-transport). Moreover, these devices showed moderate performances; for example,the device based on Cz3PyCz3 presented an external quantum efficiency of 0.69% and a maximum brightness of 1782 cd/m2 at 13.5 V, which indicated these oligomers were promising optoelectric materials.

Raman scattering by zigzag fluoropolymer molecules

The Raman spectra of ultrafine powders consisting of F(CF2)nF fluoropolymer zigzag molecules treated as a one-dimensional nanocrystal are investigated. These spectra are compared with the Raman spectra of CnF2n+1Br compounds (n=6–10 and 14) and fluoroplastics. It is found that the frequencies of optical vibrations of F(CF2)nF fluoropolymer molecules are shifted by more than 10 cm−1 with respect to the relevant frequencies of C6F13Br molecules. The length of nanoparticles comprising an organofluoric ultrafine powder is estimated to be L=2–2.5 nm. This estimate is obtained from the measured frequency shifts in terms of the vibrational theory for a crystalline diatomic chain of finite length.

The effect of pressure-induced conformational changes on the longitudinal acoustic mode in perfluoro-n-alkanes

An investigation of the longitudinal acoustic mode (LAM) in a series perfluoro-n-alkanes under pressure has been carried out using Raman spectroscopy in conjunction with a diamond anvil cell. Perfluoro-n-alkanes are shown to undergo a phase transition from a helical to a planar zigzag structure at 5 kbar. This conformational change with pressure results in an abrupt increase in the LAM frequency. Since the chain axis elastic modulus of a planar zigzag molecule is larger than that of a helical one, such a conformational change leads to stiffening of the backbone giving rise to the observed change in the LAM frequency.

Molecular resolution analysis of .alpha.-FeOOH-dispersed activated carbon fibers

The irregularity of the micropore walls of {alpha}-FeOOH-dispersed activated carbon fibers ({alpha}-FeOOH-ACF) was examined by the adsorption of planar, spherical, and zigzag molecules at 303 K and powder x-ray diffraction at room temperature. {alpha}-FeOOH-ACF gave more diffuse x-ray diffraction patterns with high background than the original ACF, indicating that the surface of {alpha}-FeOOH-ACF has a more amorphous structure than that of the original ACF. {alpha}-FeOOH can adsorb more planar molecules and fewer zigzag molecules than the original ACF. The relationships between the logarithm of the monolayer capacity from the BET plot and the logarithm of molecular area determined from both molecular weight and liquid density at 303 K were linear, indicative of fractal pore walls. The surface fractal dimension, D{sub 8}, of the micropore wall was determined from the linear plots; the dispersion of ultrafine {alpha}-FeOOH increased the D{sub 8} value. The relationships between the logarithm of the micropore volume from the DR plots and the logarithm of molecular volume were linear; the apparent exponents determined from the plots are greater than the D{sub 8} values, suggested slightly heterogeneous micropore size distribution.

Structural studies of polyethers. IX. Planar zigzag modification of poly(ethylene oxide)

AbstractA new crystal modification was found in poly(ethylene oxide) stretched about two‐fold after necking at room temperature. An x‐ray diffraction analysis indicated that the planar zigzag molecule passes through a triclinic unit cell with parameters α = 4.71 Å, b = 4.44 Å, c (fiber axis) = 7.12 Å, α = 62.8°, β = 93.2°, and γ = 111.4°. The space group is P1−Ci1. Packing of the molecule is very similar to that of monoclinic polyethylene.

The Bent Excited State of Acetylene

THE band systems of C2H2 and C2D2 at 2400–2100 A. have been studied in absorption, and the vibrational and resolved rotational structures fully analysed. It emerges that, in its excited state, acetylene is a plane centrosymmetric zig-zag (like ethylene from which two trans-related hydrogen atoms have been removed). It is therefore an asymmetric top. Its dimensions in the lowest vibrational level of that state are CC = 1.383 A., CH = 1.08 A., ∠CCH = 120.2°. The frequency of the CC stretching vibration is 1,385 cm.−1 in C2H2 and 1,300 cm.−1 in C2D2, the derived mean force-constant being F = 7.2 × 105 dyne/cm.; while the vibration which together opens the angles has the frequency 1,049 cm.−1 in C2H2 and 835 cm.−1 in C2D2, the corresponding mean bending-force-constant being δ = 8.5 × 10−12 dyne.-cm./radian. The electronic wave function has the two-fold axis and plane, but not the centre of symmetry of the zig-zag molecule. The lowest vibrational level of this bent excited state lies at 42,209 cm.−1 in C2H2 and at 42,280 cm.−1 in C2D2, above that of the linear normal state, the difference of 71 cm.−1 arising from differences in zero-point vibrational energy. In the transition from the normal to the excited state, the electrons oscillate perpendicularly to the plane of the bent molecule. The resultant electron-spin remains zero. The transition probability, expressed as an oscillator strength, is 8 × 10−5. All this follows from the analysis of the spectra.