Parent Monomer Research Articles

Synthesis of linked berberine dimers and their remarkably enhanced DNA-binding affinities

This communication describes the facile synthesis of five novel berberine dimers and their strong affinities toward double-stranded DNA. These berberine dimers were synthesized in 37–84% yields from the reaction of berberrubine with dihaloalkanes of varying lengths, and fully characterized by HRMS and 1H NMR. Compared with the monomeric parent berberine, these dimers showed greatly enhanced binding affinities up to approximately 100-fold, with two double helical oligodeoxynucleotides, d(AAGAATTCTT)2 and d(TAAGAATTCTTA)2, which was investigated by means of fluorescence spectrometry.

Exploring the localized-to-delocalized boundary in mixed-valence systems using infrared spectroelectrochemistry.

Infrared spectroelectrochemistry has been used to explore the vibrational properties of a pyrazine-bridged osmium-polypyridine dimer as a function of its formally metal-centered oxidation states (i.e., Os(II)Os(II), Os(II)Os(III), and Os(III)Os(III)). The infrared spectrum of the "mixed-valent" species is particularly interesting and exhibits features consistent with both electronic localization and delocalization on the vibrational time scale, as revealed by the presence of both (i) a highly active totally symmetric mode from the bridging pyrazine ligand (nu(8a)), and (ii) total coalescence of at least four modes from peripheral bipyridine ligands. The nature and origin of the observed peaks were confirmed by analysis of the shifts in vibrational frequencies accompanying deuteration of pyrazine and also by comparison of the data for the dimeric complexes with those for the parent monomers.

Diastereoselective assembling of 21-C-alkylated nickel(II) complexes of inverted porphyrin on a platinum(II) template.

Reaction of 21-C-methyl and 21-C-benzyl nickel(II) complexes of inverted meso-tetratolylporphyrin with platinum(II) dichloride or its bis(benzonitrile) complex yields a chloroplatinum(II) species containing two nickel(II) carbaporphyrinoids in a cis arrangement. One of the carbaporphyrinoids coordinates to the platinum ion with the external nitrogen while the other is bound with the external nitrogen and one ortho-carbon of the adjacent meso-aryl ring. The reaction is highly chemoselective. (1)H and (13)C NMR experiments in solution show the diastereoselectivity of the reaction. Single-crystal X-ray data confirm the presence of the diastereomer with opposite configurations of the Ni(II)-coordinated carbons in the subunits of the dimer. Cyclovoltammetric measurements reveal an anodic shift of the nickel(II) oxidation potentials of dimers with respect to those of the parent monomers and two different reduction couples. Reaction of unsubstituted inverted porphyrin with Pt(PhCN)(2)Cl(2) in chlorobenzene yields a monomeric platinum(II) complex of inverted porphyrin. This complex displays a markedly upfield (195)Pt NMR shift compared to tetraphenylporphyrinatoplatinum(II). Under strongly basic conditions deprotonation of the external nitrogen of inverted porphyrin and both electrochemical and chemical oxidation of platinum(II) center are observed.

Visualization of monomer and polymer inside porous stones by using X-ray tomography

Estimate of sorption of liquid materials inside porous stones is an important parameter in industrial material testing and cultural heritage conservation. In the latter case, a suitable polymer can be used for both consolidation and conservation, it being applied either in the final form or as its parent monomer, which is subsequently allowed to polymerize in situ by the classical method or by frontal polymerization. However, the sorption of such materials through the stone is often difficult because of their viscosity and/or stone porosity. For this reason, the amount of monomer (or polymer) is a parameter of great interest in order to determine the extent of protection reachable by the treatment. In this paper a new methodology based on X-ray tomography is presented. The methodology makes use of a contrast agent added to the monomer that does not interact with its propagation inside the stone and allows to increase the absorption coefficient and so to observe the monomer inside the sample, which is finally frontally polymerized.

The electrochemical formation and properties of bilayers composed of polypyrrole and C60Pd films

Bilayers composed of the redox-active polymers, polypyrrole (a p-doped system) and C60Pd (an n-doped system), were prepared by sequential electropolymerization of parent monomers. The C60Pd film was formed under cathodic polarization in the potential range for reduction of palladium(II) acetate and C60. Polypyrrole was obtained by electro-oxidation of parent monomer. The electrochemical properties of the electrode/polypyrrole/C60Pd and electrode/C60Pd/polypyrrole bilayers, which are redox active over an unusually broad potential range, have been analyzed by cyclic voltammetry, and the morphology of these films has been investigated by scanning electron microscopy. In the case of the electrode/polypyrrole/C60Pd bilayer, the high permeability of C60Pd film for the supporting electrolyte ions allows the oxidation of the polypyrrole inner layer. A strong solvent effect was observed for the voltammetric response of inner polypyrrole layer. The charging processes of outer C60Pd layer do not significantly depend on the solvent. In the case of the electrode/C60Pd/polypyrrole bilayer, the outer polypyrrole layer inhibits the reduction of the inner C60Pd layer. The low permeability of this polypyrrole film for supporting electrolyte cations is responsible for such a behavior.

Biocompatibility of Hydroxylated Metabolites of BISGMA and BFDGE

Unpolymerized dental monomers can leach out into the oral biophase and are bioavailable for metabolism. We hypothesize that metabolites would be less toxic than parent monomers. We first identified the formation of metabolites from bisphenol F diglycidyl ether (BFDGE) and Bisphenol A glycidyl methacrylate (BISGMA) after their exposure to liver S9 fractions. Then, the metabolites and parent compounds were subjected to in vitro cytotoxicity, mutagenicity, and estrogenicity studies. Bisphenol A bis(2,3-dihydroxypropyl) ether and bisphenol F bis(2,3-dihydroxypropyl) ether were the hydroxylated metabolites of BISGMA and BFDGE, respectively. Cytotoxicity against L929 cells showed that the metabolites were significantly (p < 0.05) less cytotoxic than the parent monomers. Only BFDGE was mutagenic in the Ames assay with strain TA100 of Salmonella typhimurium. Parent and metabolite compounds did not stimulate estrogen-dependent MCF-7 cell proliferation above solvent controls. These results indicated that the hydroxylated metabolites were non-mutagenic, non-estrogenic, and less cytotoxic than their parent monomers.

The stabilization of monomeric parent compounds of phosphanyl- and arsanylboranes.

The structures of the parent compounds of phosphanyl- and arsanylboranes, H(2)BPH(2) and H(2)BAsH(2), were calculated by DFT-B3LYP methods. Such compounds have not previously been obtained preparatively. By applying the concept of Lewis acid/base stabilisation, [(CO)(5)W(H(2)EBH(2).NMe(3))] (E=P (3), As (4)) derivatives have been synthesised by the metathesis reactions between Li[(CO)(5)WEH(2)] and ClH(2)BNMe(3) (E=P, As). Comprehensive thermodynamic studies on these systems verify the high stability of the Lewis acid/base stabilised complexes. Unexpected based on the thermodynamic calculations, UV radiation of the phosphanylborane 3 leads to the dinuclear phosphanido-bridged complex [(CO)(8)W(2)(mu-PHBH(2).NMe(3))(2)] (5) by H(2) and CO elimination.

Kinetics and mechanism of the first aquation stage for the [Cr(pic)3]0 and [Cr(pic)2(OH)]20 complexes in HClO4 solutions

Aquation of [Cr(pic)3]0 and [Cr(pic)2(OH)]20 in aqueous HClO4 solutions leads to formation of the common product – [Cr(pic)2(H2O)2]+. The first, reversible stage, the ring opening via Cr—N bond breaking in [Cr(pic)3]0 is followed by the second, rate-determining step – one-end bonded pic ligand liberation. In the case of the [Cr(pic)2(OH)]20 complex, the first faster stage produces the singly bridged dimer, which undergoes cleavage into the parent monomers in the second, much slower step. The subsequent aquation of [Cr(pic)2(H2O)2]+ is extremely slow and leads to [Cr(pic)(H2O)4]2+ formation, which practically does not undergo further ligand substitution under the conditions applied. Kinetics of the first aquation stage for [Cr(pic)3]0 and of the second step for [Cr(pic)2(OH)]20 were studied spectrophotometrically in the 0.1–1.0 M HClO4 range at I = 1.0 M. The observed pseudo-first order rate constant for [Cr(pic)3]0 decreases with [H+] increase according to the rate law: kobs = k1 + k−1Q1/[H+], where k1 and k−1 are the rate constants of the forward and the reverse processes in the unprotonated substrate and Q1 is the protonation constant of the pyridine nitrogen atom. In the case of the [Cr(pic)2(OH)]20 complex, the rate for the singly bridged dimer cleavage does not depend on [H+]. The activation parameters for the chelate-ring opening in [Cr(pic)3]0 and for the singly bridged dimer cleavage have been determined and discussed. Some kinetic data of the slow, second aquation stage for the [Cr(pic)3]0 complex and of the fast, first aquation stage for the doubly bridged dimer have been studied; for both reactions the rate increases linearly with the increase in [H+].

High third-order nonlinear optical susceptibility in new fluorinated poly(p-phenylenevinylene) copolymers measured with the Z-scan technique

The third-order nonlinear optical properties of a series of copoly(2, 3, 5, 6-tetrafluoro-1, 4-phenylenevinylene-2, 5-dioctyloxy-1, 4-phenylenevinylene) that contain variable ratios of two differently substituted monomers have been studied in chloroform solutions at l=1064 nm by the picosecond Z-scan technique. Nonlinear refractive index n(2) of the samples investigated has been found to be negative, and a strong dependence of its magnitude on the copolymer's composition has been observed. The highest third-order nonlinear optical susceptibility, |x((3))|=(6 +/- 2)x 10(-10) esu, was measured for a copolymer obtained by reaction of equimolar quantitites of the parent monomers.

Effects of phosphine ligand chelation on the reactivity of monomeric parent amido ruthenium complexes: synthesis and reactivity of such a complex bearing monodentate ligands.

The parent amido complex cis-(PMe(3))(4)Ru(H)(NH(2)) (2) has been prepared via the deprotonation of [cis-(PMe(3))(4)Ru(H)(NH(3))(+)][BPh(4)(-)]. The amido complex is a somewhat weaker base than the DMPE analogue trans-(DMPE)(2)Ru(H)(NH(2)) but is still basic enough to quantitatively deprotonate fluorene and reversibly deprotonate 1,3-cyclohexadiene and toluene. Complex 2 exhibits very labile phosphine ligands, two of which can be replaced by DMPE to yield the mixed complex cis-(PMe(3))(2)(DMPE)Ru(H)(NH(2)). Because of the ligand lability, 2 also undergoes hydrogenolysis and rapid exchange with labeled NH(3). The amide complex reacts with alkyl halides to yield E2 and S(N)2 products, along with ruthenium hydrido halide complexes including the ruthenium fluoride cis-(PMe(3))(4)Ru(H)(F). Ruthenium hydrido ammonia halide ion pair intermediates [cis-(PMe(3))(4)Ru(H)(NH(3))(+)][X(-)] are observed in some deprotonation and E2 reactions, and measurement of the equilibrium constants for NH(3) displacement from these complexes suggests that they benefit from significant hydrogen bonding between X(-) and NH(3) groups. Cumulenes also react with complex 2 to afford the products of insertion into an NH bond. The rates of neither these NH insertion reactions nor the reversible deprotonation reactions show any dependence on the concentration of PMe(3) present, suggesting that these reactions take place directly at the NH(2) group and do not involve precoordination of substrate to the metal center.

In-Vitro Stability, Metabolism, and Transport of Dental Monomers Made from Bisphenol A and Bisphenol F

The stability and bioavailability of the biomaterial monomers, bisglycidyl methacrylate (BISGMA), bisphenol F diglycidyl ether (BFDGE), and bisphenol A dimethacrylate (BPADM) were investigated using in-vitro techniques. A reverse-phase high-pressure liquid chromatographic/mass spectrometric (HPLC/MS) system was developed to quantitate each monomer and its primary metabolite. Each monomer (10 x 10 -6 M) was incubated at 37 °C under various conditions. Aliquots (N = 3) were removed at various time intervals and quantitated from a standard curve. The in-vitro transport of each parent monomer and its tetrahydroxy metabolite was measured in a Caco-2 system. BISGMA and BPADM were stable in aqueous solution at pH 1. However, BFDGE, was unstable. Plasma esterase of the rat rapidly hydrolyzed the ester compounds, but human esterase did not have a hydrolytic effect on BISGMA or BPADM. BFDGE disappeared in both rat and human plasma, but no tetrahydroxy metabolite was observed. All three parent compounds were unstable in human- and rat-hepatic fractions producing either tetrahydroxy metabolites or bisphenol A (BPA). The tetrahydroxy metabolites, however, were relatively stable under identical conditions, but BPA disappeared when incubated in hepatic-microsomal fractions. While BPADM metabolism produced BPA, an estrogen disrupter, BISGMA and BFDGE did not appear to produce BPA. These results suggest that the potential toxicity of leached dental monomers is more likely to be a result of the metabolite rather than the parent monomer. From Caco-2 transport studies, BFDGE and its tetrahydroxy metabolite both crossed the Caco-2 membrane at a low rate of transport in 2 h (approximately 3 and 5.2%, respectively). The BISGMA metabolite crossed at approximately 8%, indicative of a moderate rate of transport, and BPA crossed at approximately 10% in 1 h (high rate of transport). The transport of BPADM and BISGMA was unable to be determined due to nonspecific absorption to the acrylic vertical transport well. The transport of BFDGE tetrahydroxy metabolite is of particular interest as BFDGE is likely to be chemically hydrolyzed in stomach acid. It is well known that epoxies react with acids resulting in ring opening, so it is not surprising that BFDGE decomposes at pH 1. As a result, it is necessary to identify the decomposition (hydrolysis) products and test their bioavailability.

A cavity-forming mutation in insulin induces segmental unfolding of a surrounding alpha-helix.

To investigate the cooperativity of insulin's structure, a cavity-forming substitution was introduced within the hydrophobic core of an engineered monomer. The substitution, Ile(A2)-->Ala in the A1-A8 alpha-helix, does not impair disulfide pairing between chains. In accord with past studies of cavity-forming mutations in globular proteins, a decrement was observed in thermodynamic stability (DeltaDeltaG(u) 0.4-1.2 kcal/mole). Unexpectedly, CD studies indicate an attenuated alpha-helix content, which is assigned by NMR spectroscopy to selective destabilization of the A1-A8 segment. The analog's solution structure is otherwise similar to that of native insulin, including the B chain's supersecondary structure and a major portion of the hydrophobic core. Our results show that (1) a cavity-forming mutation in a globular protein can lead to segmental unfolding, (2) tertiary packing of Ile(A2), a residue of low helical propensity, stabilizes the A1-A8 alpha-helix, and (3) folding of this segment is not required for native disulfide pairing or overall structure. We discuss these results in relation to a hierarchical pathway of protein folding and misfolding. The Ala(A2) analog's low biological activity (0.5% relative to the parent monomer) highlights the importance of the A1-A8 alpha-helix in receptor recognition.

Molecular pathology of dityrosine cross-links in proteins: structural and functional analysis of four proteins.

The dityrosine bond (DT) is an oxidative covalent cross-link between two tyrosines. DT cross-linking is increasingly identified as a marker of oxidative stress, aging and disease, and has been detected in diverse pathologies. While DT cross- linked proteins have been documented, the consequences of the DT link on the structure and function of the so modified proteins are yet to be understood. With this in view, we have studied the properties of intermolecular DT-dimers of four proteins of diverse functions, namely the enzyme ribonuclease A, the signal protein calmodulin, and the eye lens proteins alpha- and gamma B-crystallins. We find that DT is formed through radical reactions and type I photosensitization (including .OH, O2- and OONO-), but not by 1O2 and NO, (which modify his, trp and met more readily). Tyr residues on the surface of the protein make DT bonds (intra- and intermolecular) most readily and preferentially. The conformation of each of these DT-dimers, monitored by spectroscopy, is seen not to be significantly altered in comparison to that of the parent monomer, but the structural stability of the DT cross-linked molecule is lower than that of the parent native monomer. The DT-dimer is denatured at a lower temperature, and at lower concentrations of urea or guanidinium chloride. The effect of DT-cross-linking on the biological activities of these proteins was next studied. The enzymatic activity of the DT-dimer of ribonuclease A is not lost but lowered. DT-dimerization of lens alpha-crystallin did not significantly affect the chaperone-like ability; it inhibits the self-aggregation and precipitation of target proteins just as well as the parent, unmodified alpha-crystallin does. DT-dimerization of gamma B-crystallin is however seen to lead to more ready aggregation and precipitation, a point of interest in cataract. In the case of calmodulin, we could generate both intermolecular and intramolecular DT cross-linking, and study both the DT-dimer and DT-monomer. The DT-dimer binds smooth muscle light chain kinase and also Ca2+, but less efficiently and over a broad concentration range than the native monomer. The intramolecular DT-monomer is weaker in all these respects, presumably since it is structurally more constrained. These results suggest that DT cross-linking of globular proteins weakens their structural stability and compromises (though does not abolish) their biological activity, both of which are pathologically relevant. The intramolecular DT cross-link would appear to lead to more severe structural and functional consequences.

Optically Active Polyaniline Derivatives Prepared by Electron Acceptor in Organic System: Chiroptical Properties

A novel synthetic process was developed to yield optically active polyaniline derivatives (PANIs) prepared by electron acceptor, 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ), using either (+)- or (−)-camphorsulfonic acid (CSA) as the chiral inductor in organic media. Either thin films of PANIs/(+)-CSA and PANIs/(−)-CSA or their solutions exhibit mirror-imaged circular dichroism (CD) spectra in the visible region, indicating diastereoselection in the electron-transfer polymerization in the presence of chiral inductor. The films were confirmed to remain their chiral configuration during reversible dedoping/redoping cycles in solid state. Unique chiroptical properties of PANIs/(+)- or (−)-CSA dissolved in m-cresol indicate that there exists a solvent effect on the PANIs' chain conformations and subsequent chiroptical properties, and the solvent effect is strongly dependent upon the structure of parent monomer and nature of various organic solvents. The PANIs' chain conformation in m-cresol solution forms durin...

Polymerization of isomeric N-(4-substituted benzylidene)-4-ethynylanilines and 4-substituted N-(4-ethynylbenzylidene)anilines by transition metal catalysts: preparation and characterization of new substituted polyacetylenes with aromatic Schiff base type pendant groups

N-(4-substituted benzylidene)-4-ethynylanilines R–C6H4–CHN–C6H4–CCH, where R=Me, t-Bu, F, Br, CN, NO2, Me2N and –CC–SiMe3 and isomeric 4-substituted N-(4-ethynylbenzylidene)anilines R–C6H4–NCH–C6H4–CCH, where R=Me, t-Bu, F, Br, I, CN, NO2 and –CC–SiMe3 were polymerized using (i) [Rh(cod)OCH3]2 [(cod)=η4-cyclooctadiene] in THF, (ii) Mo(CHCPhMe2) (N–C6H3–iPr2-2,6)[O–CMe(CF3)2]2 in aromatics, (iii) PdCl2 in DMF. All catalysts tested exhibited high tolerability towards –CH=N– group (confirmed also by the in situ 1H NMR study) providing polyacetylenes with aromatic Schiff base type pendant groups. Positive correlation between acidity of ethynyl group and monomer polymerizability was found for Rh catalyst. Depending on catalyst, molecular weight of polymers decreases in the series: Rh (Mw=45 000–300 000)>Mo (Mw=13 000–40 000)>Pd (Mw about 5000). The main chain cis double bond content and the microstructure uniformity of polymer were found to decrease in the same order. In THF, all polymers prepared exhibited fluorescence (λmax=500–550nm) considerably red-shifted in comparison with their parent monomers.

Full-Electrochemical Preparation of Conducting/Insulating Binary Polymer Films

Binary polymer films consisting of an insulating polymer and a conducting polymer have been successfully prepared by sequential electropolymerization of the parent monomers. The insulating polymer (polyacrylonitrile or polyethylacrylate) is formed under cathodic polarization in a potential range where the growing chains are chemically grafted onto the nickel or carbon electrode. The conducting polymer (polybithiophene or polypyrrole) is formed by electrooxidation of the parent monomer. The electrochemical reactions and the electrochemical properties of the films have been analyzed by cyclic voltammetry and chronoamperometry. The influence of the main experimental parameters on the composition and morphology of the films has been investigated by X-ray photoelectron spectroscopy and atomic force microscopy. This approach strongly improves the adhesion of the conducting polymer as a result of its combination with the grafted polyacrylonitrile. This combination of insulating and conducting polymers is a way t...

Positioning of the Carboxamide Side Chain in 11-Oxo-11H-indeno[1,2-b]quinolinecarboxamide Anticancer Agents: Effects on Cytotoxicity

A series of 11-oxo-11H-indeno[1,2-b]quinolines bearing a carboxamide-linked cationic side chain at various positions on the chromophore was studied to determine structure–activity relationships between cytotoxicity and the position of the side chain. The compounds were prepared by Pfitzinger synthesis from an appropriate isatin and 1-indanone, followed by various oxidative steps, to generate the required carboxylic acids. The 4- and 6-carboxamides (with the side chain on a terminal ring, off the short axis of the chromophore) were effective cytotoxins. The dimeric 4- and 6-linked analogues were considerably more cytotoxic than the parent monomers, but had broadly similar activities. In contrast, analogues with side chains at the 8-position (on a terminal ring but off the long axis of the chromophore) or 10-position (off the short axis of the chromophore but in a central ring) were drastically less effective. The 4,10- and 6,10-biscarboxamides had activities between those of the corresponding parent monocarboxamides. The first of these showed good activity against advanced subcutaneous colon 38 tumours in mice.

Theoretical investigations on (CO) n(CO 2) m cyclic cooligomers

Ab initio calculations have been performed on the (CO) n (CO 2) m cyclic copolymers, where n, m=1,2 with m≥ n. The cyclic molecules were studied at the HF/6-311G, HF/6-311+G(df), MP2/6-311+G(df) levels and Gaussian-2 theory with reduced Møller–Plesset order, G2MP2. The structures of the three cyclic oligomers investigated, C 2O 3, C 3O 5 and C 4O 6 are found to have a minimum and the geometries are planar. The energy releases of the dissociation reactions indicate that these molecules are thermodynamically unstable with respect to the parent monomers CO and CO 2. In addition, the heats of formation for the cyclic molecules were evaluated at the G2MP2 level using an isodesmic approach and bond separation energies.

Evaluation of norbornene- beta-cyclodextrin-based monomers and oligomers as chiral selectors by means of nonaqueous capillary electrophoresis.

Norbornen-5-yl carboxylic acid and norbornen-5-ylmethylsilyl ether-based beta-cyclodextrins (beta-CDs) containing up to three norbornene ester and up to five norbornene silyl ether units have been prepared from beta-CD and norbornen-5-carboxylic chloride and norbornen-5-ylmethyldichlorosilane, respectively. Oligomers (n = 2-4) were prepared therefrom using ring-opening metathesis polymerization (ROMP). Monomeric and oligomeric substituted beta-CDs were evaluated as chiral selectors in nonaqueous capillary zone electrophoresis using 35 mM sodium bicarbonate in N-methylformamide (NMF) as background electrolyte. Both monomeric and oligomeric norbornene ester- and norbornene silyl ether-type selectors showed good enantioresolution for dansylated (DNS-) amino acids using concentrations of the chiral selector of up to 4% w/v. A significant improvement in resolution was observed upon the introduction of up to five norbornene silyl ether units into a beta-CD molecule, whereas higher degrees of substitution with norbornen-5-yl-carboxyl groups lead to a reduction in enantioresolution of DNS-amino acids. Thus, pentakis(norbornen-5-ylmethylhydroxysiloxyl)-beta-CD turned out to be superior to mono(norbornen-5-ylmethylhydroxysiloxyl)-beta-CD in terms of enantioresolution. Moreover, norbornene silyl ether-type selectors were found to be more efficient than norbornene ester-type selectors. Finally, oligomeric selectors were found to possess superior or at least comparable enantioselectivity in the separation of DNS-amino acids compared to the parent monomers. A maximum in enantioresolution was obtained with oligo(pentakis(norbornen-5-ylmethylhydroxysiloxyl)beta-CD).

Synthesis of polymers with isolated thiophene-arylidene-thiophene chromophores for enhanced and specific electron/hole transport

The synthesis of nine new polymers intended for future use in light-emitting diodes is described. The polymers consist of alternating units of thiophene–arylidene–thiophene chromophores and saturated silicon-containing spacers. The arylidene moieties include benzene-1,4-, 2,5-dimethoxybenzene-1,4-, naphthalene-1,4-, anthracene-9,10-, pyridine-2,5-, pyridine-2,6-, N-methylcarbazole-3,6-, 1,3,4-oxadiazole-2,5-, and 4,4′-dimethyl-2,2′-bithiazole-5,5′-. The syntheses involved dibromination of the central arene followed by Suzuki or Kumada cross-coupling reactions with two thiophene units. Subsequent dilithiation and reaction with dihalosilylalkanes provided the polymers. Their optical properties, including ultraviolet–visible absorption and emission in solution, were comparable to those of the parent monomer units, and they possessed the physical characteristics of macromolecules. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 872–879, 2001