The preferred U-conformation of m-quinquephenyl. An X-ray crystal structure determination and molecular mechanics study

Synthesis of Polyphenylene Molecular Wires by Surface‐Confined Polymerization

“…They are flanked by discrete circular satellites that occupy H4 substrate lattice sites, and by analogy with 1,4‐diiodobenzene results we infer these are iodine atoms. Figure 5 shows an overlaid scale model of a PMP oligomer; its vertex‐vertex periodicity (7.37 Å from single‐crystal X‐ray analysis for m ‐quinquephenyl24) matches the structures observed in our experiment (7.1 Å). Chains with more than 30 repeated m ‐phenylene units were observed.…”

Oligomeric Pseudorotaxanes Adopting Infinite‐Chain Lattice Superstructures

“…The adoption of polymeric lattices by oligomers in previous work can be ascribed [15] to the heterogeneous nature of the oligomeric chains and consequent disorder in the crystal, [16] whereas in the present study we show that polymeric lattices can be preferred even for rigorously pure, homogeneous oligomers. It would appear that the critical chain length for the formation of the polymer lattice in the crystal occurs between 3 NPE and 5 NPE.…”

The structure of poly(m-phenylene): a prediction from single-crystal X-ray studies of m-deciphenyl and m-undeciphenyl

“…Below a certain chain-length however the concentration of chain-ends must be high enough to destabilise the polymer-type lattice since rn-quinquephenyl does not adopt this structure. 4 It has not escaped our notice that the structure we have identified immediately suggests a possible structure for poly(m-phenylene) itself. We have compared the X-ray powder pattern predicted from the structure of m-deciphenyl with an experimental pattern obtained for a sample of poly(rn-phenylene) prepared by nickel-catalysed coupling of pure rn-dichlorobenzene .g…”

“…These angles may be compared with the values of 36,31, -32, and 36" found in rn-quinquephenyl which , because of its torsional signreversal, does not achieve a helical conformation. 4 Although the crystal structure of rn-deciphenyl is perhaps not obviously compatible with that of a monodisperse ten-ring oligomer, it can be shown to arise from longitudinal disorder associated with the presence of orthogonally arranged twofold axes normal to the chain direction. This form of crystallograpic disorder results in a structure with well-defined (though partial-mass) atomic positions since, with the exception of hydrogen atoms at the oligomer chain-ends, individual atoms are either superposed by symmetry or are absent.$ The existence of a polymer lattice with dominant generalised disorder is consistent with our observation that the eleven-ring oligomer, rn-undeciphenyl, crystallises in the same space group as its ten-ring homologue, with identical (to within 30) unit cell dimensions.…”

“…3 Very recently however, a U-shaped conformation identified for rn-quinquephenyl in the solid state led the authors of that study to speculate on possible helical conformations for higher rn-phenylene oligomers. 4 and indeed that of poly(rn-phenylene) itself still remained unknown. As part of a continuing programme of single-crystal X-ray studies of aromatic oligomers aimed at the prediction and analysis of high-performance polymer structures , 6 we have now investigated the crystal structures of rn-deciphenyl and rn-undeciphenyl as potential models for poly(rn-phenylene).…”