Synthesis of Poly[p-(7-phenylene-7-(2′,5′-dihexyl-4-biphenylene))norbornane]: The First Soluble Polymer with Alternating Conjugation and Homoconjugation

Abstract

composition of donor : acceptor = 1 : 0.4, its upper bands are not half-filled. Whereas all other k-type superconductors have the composition of donor : acceptor = 2 : 1 and therefore, half-filled upper bands. The deviation from halffilling makes the on-site Coulomb repulsion comparatively unimportant; this stabilizes the metal state, but is disadvantageous with respect to superconductivity. [15] The same situation has been found in (EOET±TTP) 3 AsF 6 , [5b] and (CH± TTP)(I 3 ) 0.31 . [5c] In summary, we have found a k-type organic metal based on a newly prepared TTP derivative CPEO±TTP. To our knowledge, there is no report on metallic k-type salt base on ethylenedioxy-substituted TTF. [16] In contrast, CPEO± and EOET±TTP afford k-type salts retaining metallic conductivity down to low temperature. Therefore, combination of TTP framework and ethylenedioxy substituent would be suitable for exploring new k-type metals. The preparation of radical-cation salts based on the other ethylenedioxy substituted TTPs is actively in progress. Experimental CPEO±TTP: Red microcrystals; m.p. = 246±247 C (decompose.); 1 H NMR (270 MHz, CS 2 -[ 2 H 6 ]benzene) d 4.17 (s, 4H), 2.49±2.56 (m, 4H), 2.35± 2.45 (m, 2H); I.R. (KBr) u (cm ±1 ) 1653, 1452, 1168. (CPEO±TTP)(SbF 6 ) 0.4 : C 15 F 2.4 H 10 O 2 S 8 Sb 0.4 , M = 573.02, monoclinic, space group C2/c, a = 45.144(3), b = 7.984(4), c = 10.999(5) . b = 99.72 (2), V = 3907(2) 3 , Z = 8, D c = 2.235 g/cm 3 , Mo Ka radiation, l = 0.71069 , m = 23.06 cm ±1 , F(000) = 2576.00. The data were collected on a Rigaku AFC7R diffractometer equipped with graphite monochromated Mo Ka radiation using the o±2y scan technique to a maximum 2y of 55. The structure was solved by direct methods and refined by full-matrix least squares analysis (anisotropic for non-hydrogen atoms) to R = 0.065, R w = 0.070 for 1359 observed (I ³ 3s (I)) reflections from 4816 unique data. All calculations were performed using the teXsan crystallographic software package of Molecular Structure Corporation. Atomic coordinates, bond distances and angles, and thermal parameters have been deposited at the Cambridge Crystallographic Data Center.

Synthesis and characterization of new copolymers based on fluorenylidene-linked conjugated oligo(p-phenylene)s

“…Our interpretation is that the biphenylfluorene unit participates to some degree in the conjugation of p-electrons along the polymer backbone. Similarly as described by A. G. Martínez et al, [27] homoconjugation (a through-space p-orbital overlap) could exist between both phenylene rings of the biphenylfluorene unit, as revealed by a characteristic absorption band at 228 nm. This phenomenon results in a bathochromic shift of absorption in the copolymers as well as in the model compounds.…”

“…As a non-p-conjugated unit, the bridging carbon atom of norbornane was used. [27,36] Using the Pd-catalyzed Suzuki polycondensation method, which allows coupling of benzene derivatives bearing both bromo and boronic acid (or their ester) substituents, we synthesized soluble fluorene derivatives of poly(p-phenylene) and some model compounds. [37 -41] Tetrakis(triphenylphosphine)palladium(0) was used as the catalyst precursor.…”

Electron Delocalization in Homoconjugated 7,7‐Diarylnorbornane Systems: A Computational and Experimental Study

“…The synthesis of compounds 6 – 9 ,25, 26 12 – 13 ,27 and 14 – 15 28 was carried out according to the general procedure described in Scheme , which has been previously reported by our research group. For the preparation of the reference compounds 17 – 19 we used a synthetic route described in the literature for DPM derivatives,29 also depicted in Scheme .…”

Homoconjugation in poly(phenylene methylene)s: A case study of non-π-conjugated polymers with unexpected fluorescent properties

“…Previously it has been proposed that π‐orbitals of aromatic groups separated by a methylene group (or other groups with comparable geometry) can overlap – a phenomenon which is rarely considered – and hence establish a conjugation over two CC single bonds. This phenomenon is termed homoconjugation .…”