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Stereoregular polymerization of (p-nitrophenyl)acetylene (pNPA) was performed using [Rh(norbornadiene)Cl]2 and [Rh(cyclooctadiene)Cl]2 catalysts to give poly((p-nitrophenyl)acetylene) (PpNPA), with a cis−transoid form under mild conditions. The polymer underwent isomerization from the predominant cis to trans form when compressed at 200 kg/cm2 at room temperature. The polymers, obtained before and after compression, were characterized using IR, CP MAS 13C NMR, ESR, and diffuse reflective UV methods. The data suggest that the isomerization of the resulting polymer from cis−transoid to trans−transoid form gives a conjugated trans planar zigzag structure. The trans conjugation lengths, n, in the polymer chain (CC) n after the compression were estimated as ca. 29 or 50, when polymers obtained with methanol or triethylamine as the polymerization solvents were used. The trans sequence length obtained by thermal treatment of the cis−transoid polymer was also found to have less conjugated sequences than that of the compressed polymer. It is concluded, therefore, that the compression of the predominant cis−transoid PpNPA form gives longer conjugated trans sequences compared with that of the thermal isomerization of the pristine polymer.

SynopsisThe catalytic activity of a series of [Rh L-L chel]X complexes, in which we have varied the unsaturated ligand [L-L = cis, cis-cycloocta 1,5-diene(cod) or 2,5-norbornadiene(nbd)] the nitrogen chelating ligand [chel = 2,2'-bipyridine(bipy), 2,2'-dipyridylamine(dipyam), 2,2'-bipyrazine (bipz), 4,4'-dimethyl-2,2'-bipyridine (4,4'-Mqbipy)] and the counter ion [X = PF,, ClO,, BPh,], has been examined in reactions with phyenylacetylene (PA). The catalytic behaviour of t h e [Rh(cod)Cl,],tmeda] (tmeda = N,N,N',N'tetramethylethylendiamine), [Rh(cod)Cl,],teda] (teda = triethylendiamine), of the dimer [Rh(cod)Cl],, and the use of NaOH as cocatalyst in different reaction conditions was also examined. The influence of the ligands on the catalytic activity of these Rhl complexes is discussed. 'H and 13C NMR spectra have shown that highly stereoregular polyphenylacetilene can be obtained. Conditions for homogeneous doping of PPA, to obtain materials whose conductivity varies over 10-11 magnitude orders, are proposed. The stability of the doped polymers is also discussed.

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In polymerization reactions of phenylacetylene three different types of polyphenylacetylene (PPA) were prepared by using Rh and Pt complexes as catalysts in different reaction conditions. Type I PPA is obtained with [Rh (COD) Chel] PF6 complexes (COD = cis,cis‐cycloocta 1,5‐diene; chel = 2,2′‐bipyridine, 1,10‐phenanthroline, 2,9‐dimethyl‐1,10‐phenanthroline, 5,6‐dimethyl‐1,10‐phenanthroline, 3,4,7,8‐tetramethyl‐1,10‐phenanthroline) in bulk, benzene methanol, while type II PPA is obtained with the same catalysts in p‐dioxane and type III PPA in the presence of [Pt (CCPh)2(PPh3)2] in bulk. Type I, II, and III PPA exhibit different IR and 1H‐NMR spectra, which have been compared with literature data. Correlations proposed by different Authors between spectral properties of PPA and chain structures are also discussed.

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The duration of cell proadhesive effects induced by imidazolium trans-imidazole dimethyl sulfoxide tetrachlororuthenate (NAMI-A), a compound endowed with in vivo antimetastatic properties, was tested in vitro on the human epithelial tumor cell line KB. The intensity of proadhesive effects continues to increase up to 48 to 72 h after NAMI-A withdrawal and declines only after 96 h. The proadhesive effect on cells seeded on fibronectin is greater than on plastic, since it already reaches its maximum after 24 h. This effect suggests a role for integrin activation, which is further stressed by the inhibitory activity of the disintegrin molecule echistatin. The intensity and duration of NAMI-A's proadhesive effects are correlated to cell exposure time and to the rapid release of NAMI-A metabolites in the culture medium in the first 5 min after drug withdrawal. These metabolites are probably neutral species with ruthenium-bound bioligands to allow for the rapid exchange between cells and extracellular medium. These data suggest a long-lasting effect of NAMI-A in biological systems, even at very low concentrations, and stress the low and reversible effects on kidney, where it naturally concentrates. These data on proadhesive effects are, further, relevant for in vivo antimetastatic effects, as this adhesion is associated to cell motility and invasion, which in turn are related to tumor malignancy and metastasis.