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The combination of Heck–Cassar–Sonogashira–Hagihara reaction, column chromatography, leading to the synthesis of luminophoric dialdehydes 5, and the subsequent Horner–Wadsworth–Emmons polycondensation reactions of 5 and the bisphosphonates 3 enables the synthesis of a new type of defect-free π-conjugated polymers with well defined general structure –(Ar–C≡C–Ar–C≡C–Ar–CH=CH–Ar–CH=CH–)[sub n], 7. The chemical structure was confirmed by NMR, infrared and UV/Vis spectroscopy. High molecular weight (M[sub w] up to 500 000 g/mol), thermostable, soluble and transparent film forming materials were obtained. The new compounds show thermotropic and lyotropic mesomorphic behavior on polarized optical microscopy. The incorporation of triple bonds into the PPV backbone increases the oxidation and the reduction potentials, thus making these polymers potentially good electron transporting materials if used in light-emissive-diodes devices. The polymers are photoconductive and show very good photoluminescent properties in solution as well as in solid state. Identical absorption (λ[sub max,abs] = 445 nm) and emission (λ[sub max,em] = 490 nm) behaviors were observed for all polymers in solution (CHCl[sub 3]), resulting to a fluorescence quantum yield of 70%, but the photophysical behavior in solid state was side groups-dependent. The orange-coloured polymer 7ac (R[sup 2] = (CH[sub 2])[sub 7]CH[sub 3]; λ[sub max,abs] = 465 nm; λ[sub max,em] = 602 nm) is characterized with a very large Stokes shift (137 nm) and lower fluorescence quantum yield (19%), whereas the yellow-coloured polymers 7aa, 7bb and 7ab, consisting of side groups equal or longer than O(CH[sub 2])[sub 11]CH[sub 3](λ[sub max,abs] = 480 nm, λ[sub max,em] = 508 nm) were characterized with smaller Stokes shift (around 30 nm) and comparatively higher fluorescence quantum yields (34 to 44%); as a result of hindered interchain π -π interactions, and consequently limited formation of excimer complexes, which are regarded as an important deactivation channel of the excitons. [ABSTRACT FROM AUTHOR]

Abstract--An improved and simplified synthetic method for 4-bromo-2,2'-bipyridine (5) has opened a way to the synthesis of the model compounds 8a, b of polymer 9. 8a, b confirmed the effective conjugation segment of polymer 9 to consist of an alternation of three aryl and two ethynyl units (Ar--C Is equivalent to C--Ar--C Is equivalent to C--Ar) due to the zig-zag structure of the polymer. It was found to be the smallest conjugated unit necessary to obtain excellent fluorescence. [ABSTRACT FROM AUTHOR]

Novel 2,2′-bipyridine-based conjugated polymers of formula 2 have been synthesized by Pd-catalyzed cross-coupling reactions between 4,4′-dibromo-2,2′-bipyridine (3) and substituted phenyldiacetylenes (4). The zig-zag arrangement of the 2,2′-bipyridine units implies a helical conformation of 2. The solubility of 2 requires at least a dodecyl side-chain. 2 is thermostable up to 400°C. The polymers have a high fluorescence quantum yield in solution (60%). [ABSTRACT FROM AUTHOR]