Crystal structure of poly(p‐phenylene) prepared by organometallic technique

Abstract

The two‐dimensional crystal structure of poly(p‐phenylene) is investigated by linkedatom Rietveld analysis of the x‐ray diffraction powder profile. Two molecular chains are packed in a rectangular pgg unit cell (a = 0.779 nm; b = 0.551 nm) with a paracrystalline shift distortion along the chain axis. The molecular conformation is not rigidly planar; rotations between adjacent phenyl‐ring planes in a molecule alternate with an angle of about 20°. The setting angle between the mean molecular plane and the a axis is 55.5°.

First-principles calculation of the conformation and electronic structure of polyparaphenylene

“…1. According to HF calculations 26,28 as well as x-ray reflection experiments 13,14,16 the difference between the bond lengths l 1 and l 2 within a ring is about 0.02 Å which is much smaller than the difference between either in-ring bond length l 1 or l 2 and the inter-ring bond length d. For computational convenience then, we have only considered a single bond length l within the ring, which largely reduces the computational effort. The geometry parameters l, d, h, and together with the torsional angle ␣ are optimized and listed in Table I, together with other reported theoretical and experimental results.…”

“…To investigate these effects, we have carried out several sets of calculations separately varying the interring carbon-carbon bond distance d, the ring carbon-carbon bond distance l 2 , and the phenyl ring bond angle with all other internal coordinates kept fixed. The equilibrium parameters in these calculations were taken to be averaged values of the experimental data, 13,14,16 i.e., l 1 ϭ1.38 Å, l 2 ϭ1.40 Å, dϭ1.48 Å, and ϭ118.04°. Note that, as for the fixed internal coordinates, the experimental value of the torsion angle for the stable configuration ͑22.7°͒ was chosen.…”

“…Baudour et al [13][14][15] found an angle of 13°for pterphenyl, for p-quaterphenyl a mean torsional angle of 17.1°b etween the external ͑the first or the fourth͒ and the adjacent internal ͑the second or the third͒ phenyl rings, and a mean angle of 22.7°between the two internal rings. Sasaki 16 measured a torsional angle of almost 20°for p-quaterphenyl and Baker et al 17 obtained values between 20°and 30°. All of these measurements indicated that the oligomers crystallize in an alternately tilted structure: i.e., a structure in which all the odd numbered rings and all the even numbered rings are located in two planes tilted with respect to each other by the torsional angle.…”

Synthesis and solvatochromism of soluble polyethers containing isolated emissivep-aryl vinylene derivatives

“…Longer side groups on P2 lead to a more nonplanar conformation of the conjugated units and reduce their effective conjugation length. 16 This phenomenon is obviously more enhanced in solution compared to the film-state where interchain packing and aggregation are dominant.…”

Thiophene–phenylene/naphthalene‐based step‐ladder copolymers

“…The relatively small distortion is similar to the situation in unsubstituted oligo(para-phenylene)s (distortion angle: $19 ). 30 In contrast, a higher distortion Figure 3. Absorption and PL emission spectra of the copolymers SL1 and SL4 in dilute toluene solution at room temperature (A, 293 K), at low temperature (B, 77 K), and as thin films (C).…”