Gas permeation properties of poly(2,5-dialkyl-p-phenyleneethynylene) membranes

Dipropynylbenzenes with alkyl groups (CH₃C ≡ CRC₆H₂RC≡CCH₃, R=n-C₆H₁₃, n-C₈H₁₇, n-C₁₀H₂₁, 1a–c, respectively) were polymerized with Mo(CO)₆ to afford solvent-soluble poly(2,5-dialkyl-p-phenyleneethynylene)s (2a–c). The polymers (2a–c) had high molecular weight over 3×10⁴, and gave free-standing membranes by solution casting method. According to thermogravimetric analysis (TGA), these poly(p-phenyleneethynylene)s showed high thermal stability (T₀ ≥380 °C). The densities of membranes of poly(2,5-dialkyl-p-phenyleneethynylene)s (2a–c) were 0.936–0.965, and their fractional free volume (FFV) were relatively large (ca. 0.14–0.15). The oxygen permeability coefficients (PO₂) of membranes of 2a–c were 4.88, 7.06, and 16.6 barrers, respectively.     

Effects of phenyl-based pendent groups on helical conformation of poly(<Emphasis Type="Italic">N</Emphasis>-propargylamides)

Five achiral N-propargylamide monomers with various phenyl-based substitutents, [HC ≡ CCH₂NHCOR, R for M1: C₆H₄CH₃; M2: C₆H₄CH₂CH₃; M3: C₆H₄(CH₂)₂CH₃; M4: C₆H₄(CH₂)₃CH₃; M5: C₆H₄C(CH₃)₃], were synthesized and polymerized with a rhodium catalyst, (nbd)Rh⁺B^-(C₆H₅)₄ (nbd = 2,5-norbornadiene). The corresponding five homopolymers were obtained in high yields of 90–95% and with moderate molecular weights (M _n ≥ 10 000). All the polymers possessed high cis contents (≥95%). Poly(1)–poly(3) exhibited UV-vis absorption peaks at approx. 350 nm, which indicates that the three polymers formed helical conformations, while no UV-vis absorption peaks could be observed in poly(4) and poly(5) in the wavelength range of 320–500 nm, demonstrating that these two polymers could not adopt helical structures under the examined conditions. To confirm the helical structures formed in poly(1)–poly(3), a chiral monomer, M6, was utilized to copolymerize with M2, which was used as the representative for M1−M3. M6 was utilized since its polymer could form stable helices under suited conditions. The resulting copolymers exhibited remarkable CD effects, however, the maximum wavelength in the copolymers varied remarkably, mainly depending on the composition of the copolymers. It is concluded that in the formation of ordered helical conformations, the substitutents of varied bulk led to different steric repulsion and varied synergic effects among the neighboring pendent groups.     

Synthesis and properties of pyrene-functionalized polyacetylene. A stable helical polymer emitting fluorescence

Pyrene-functionalized chiral N-propargylamide, (R)-HC≡CCH₂NHCOCH(CH₃)O-1,4-C₆H₄-OCO(CH₂)₃-1-pyrenyl (1) was polymerized with (nbd)Rh⁺[η⁶-C₆H₅B⁻(C₆H₅)₃] as a catalyst to obtain the corresponding polymer with a moderate weight in a good yield. Poly(1) was soluble in CHCl₃, CH₂Cl₂, and THF. The polarimetric and CD spectroscopic data indicated that poly(1) existed in a helical structure with predominantly one-handed screw sense in these solvents. The helical structure was stable upon heating and addition of MeOH. Poly(1) showed very large excimer-based fluorescence compared with 1.     

Synthesis and Gas Permeability of Novel Poly(diphenylacetylenes) Having Polyethylene Glycol Moieties

4-Trimethylsilyldiphenylacetylenes with methyl group or bromine atom (Me₃SiC₆H₄C≡CC₆H₄R, R = m-CH₃, p-CH₃, m-Br, p-Br, 1a–d, respectively) were polymerized with TaCl₅/ n-Bu₄Sn to afford poly(diphenylacetylene) derivatives (2a–d). The polymers (2a–d) had high molecular weight over 5×10⁵, and gave free-standing membranes by solution casting method. Chlorination of the obtained poly[1-(3-methylphenyl)-2-(4-trimethylsilyl)phenylacetylene] was carried out by using sulfuryl chloride, and then substitution of polyethylene glycol was performed to give poly(diphenylacetylene) possessing polyethylene glycol moieties. Its carbon dioxide permeability (P_{CO 2}) and permselectivity (P_{CO 2}/P_{N 2}) were 2,970 barrers and 9.0, respectively.     

Radical polymerization of (trimethylsilylethynyl)styrene and thermal properties of polystyrene with ethynyl group

The radical polymerizations of 2-, 3-, and 4-(trimethylsilylethynyl)styrenes (1 a – c) and copolymerizations of 1 a – c (M₁) with styrene (M₂) have been studied. Copolymerization parameters were determined as r₁ = 1.22 and r₂ = 0.54 for 1 a, ₁ = 1.10 and r₂ = 0.90 for 1 b, and r₁ = 1.42 and r₂ = 0.38 for 1 c. The deprotection of the trimethylsilyl groups in poly[(trimethylsilylethynyl)styrene] (2 a – c) and poly[(trimethylsilylethynyl)styrene-co-styrene] (4 a – c) using (C₄H₉)₄NF smoothly proceeded to yield poly(ethynylstyrene) (3 a – c) and poly(ethynylstyrene-co-styrene) (5 a – c), respectively, which underwent curing reactions at elevated temperature to form crosslinking polystyrenes. Received: 31 March 1997/Revised: 2 June 1997/Accepted: 3 June 1997     

Synthesis and properties of polyacetylenes carrying N-phenylcarbazole and triphenylamine moieties

Novel acetylene monomers containing N-phenyl-substituted carbazole (Cz) and triphenylamine (TPA) groups, namely, 3-ethynyl-9-phenylcarbazole (1) and p-(N,N-diphenylamino)phenylacetylene (2) were synthesized, and polymerized with several Rh-, W-, and Mo-based catalysts. Poly(1) and poly(2) with high number-average molecular weights (15?500-974?000) were obtained in good yields (77-97%), when [(nbd)RhCl]₂-Et₃N (nbd = norbornadiene) was used as a catalyst. The polymers exhibited UV-vis absorption peaks derived from the Cz and TPA moieties at 250-350 nm and polyacetylene backbone above 350 nm. The UV-vis absorption band edge wavelengths of the polymers were longer than those of the corresponding monomers. Poly(2) exhibited a UV-vis absorption peak at a longer wavelength than poly(1) did, which indicates that poly(2) has main chain conjugation longer than that of poly(1). The molecular weights and photoluminescence quantum yields of the polymers obtained by the polymerization using [(nbd)RhCl]₂-Et₃N were larger than those of the Rh⁺(nbd)[η⁶-C₆H₅B⁻(C₆H₅)₃]-based counterparts. The cyclic voltammograms of the polymers indicated that they had clear electrochemical properties; the onset oxidation voltage of poly(1) was higher than those of N-alkyl-substituted Cz derivatives. The polymers showed electrochromism and changed the color from pale yellow to blue by application of voltage, presumably caused by the formation of charged polaron at the Cz and TPA moieties. The temperatures for 5% weight loss of the polymers were around 350-420 °C under air, indicating the high thermal stability.     

Synthesis,Characterization, and Reactivity of trans-Ru(X)(Cl)(nbd)(dppb) (X = H,Cl; nbd = 2,5-norbornadiene; dppb = 1,4-bis(diphenylphosphino)butane), Including the X-ray Crystal Structure of the Dichloride

The ruthenium (II) diene complexes [Ru(X)(Cl)(nbd)(dppb)] (X = Cl, H; nbd = 2,5-norbornadiene; dppb = PPh₂(CH₂)₄PPh₂) have been prepared and characterized spectroscopically. The X-ray crystal structure of RuCl₂(nbd)(dppb) (crystal data at 22°C: space group P1, a = 10.896 (1) Å, b = 15.168(2) Å, c = 10.829 (1) Å, α = 103.02(1)°, β = 107.08(1)°, γ = 81.65(1)°, Z = 2, R = 0.054 for 6420 reflections) shows an octahedral geometry at Ru, with the chloro ligands slightly distorted from a trans configuration (Cl)(1)-Ru-C1(2) = 168.4°); the unit cell contains two molecules of the complex and one molecule of benzene. Reaction of this complex with H₂, in presence of Proton Sponge (PS, 1,8-bis(dimethylamino)naphthalene) as base, is complicated by initial dissociation of nbd, and [Ru₂Cl₅(dppb)₂]⁻-PSH⁺ is the major product. A minor product, the hydrido(diene) complex trans-RuCl(nbd)(dppb) 5 , characterized spectroscopically, is more effectively synthesized from (a) trans-Ru(H)Cl(nbd)(PPh₃)₂, 1 , and dppb, or (b) reaction of RuCl₂(dppb)-(PPh₃) with H₂ in presence of nbd and PS. Complex 5 is unreactive toward H₂ or CO while 1 has been shown previously to give η²-H₂ and norbornenoyl derivatives, respectively; the differences in reactivity are discussed.     

Developing a fulvene route to C1-bridged “constrained geometry” Ziegler catalyst systems

6-dimethylamino-6-methylfulvene (7) was converted to the [(C₅H₄)–CMe₂–NMe₂]⁻ ligand system (8) by treatment with methyllithium. Its reaction with MCl₄ (M = Zr, Ti) followed by treatment with CH₃Li gave the respective [(C₅H₄)–CMe₂–NMe₂]₂M(CH₃)₂ complexes (12). Their reaction with B(C₆F₅)₃ led to reactive metallocene cation complexes that instantaneously underwent CH activation at a N–CH₃ group to yield the metallacyclic cation complexes 15. (tert-butylaminomethyl)fluorene was prepared by the addition of tert-butylisocyanate to fluorenyllithium followed by hydride reduction. Deprotonation by a variety of bases gave rise to a series of competing and consecutive reactions to yield several unusually structured products, among them a fluorenyl-anellated η⁵-1-azapentadienyl anion equivalent (25) and [(flu)-CH₂–NCMe₃]Li₂ (23). An improved way of generating synthetically useful C₁-linked [Cp–C₁(R) _n –NR¹]^2- dianion equivalents was developed starting from 6-amino-6-methylfulvene (26). N-silylation followed by double deprotonation with, e.g., lithium diisopropylamide cleanly furnished the respective [(C₅H₄)–C(=CH₂)–NSiMe₃]^2- dianion 33 (isolated as the dilithio derivative). Its reaction with Cl₂Zr(NEt₂)₂ in THF gave [η⁵:κ-N-(C₅H₄)–C(=CH₂)–NSiMe₃]Zr(NEt₂)₂ 36. Activation of 36 with methylalumoxane in toluene led to the formation of a C₁-linked “constrained geometry” Ziegler catalyst that polymerized ethylene similarly as the [(C₅Me₄)SiMe₂NCMe₃]ZrCl₂ derived literature system. This revised version was published online in June 2006 with corrections to the Cover Date.     

Syntheses and Crystal Structures of Di- and Trimethyltin Carboxylates: Ladders and 1D Zig–Zag Chains Polymers

A series of organotin(IV) carboxylates complexes; namely, [(Me₂Sn)₄O₂(RCOO)₄] (R = C₁₂H₁₅ 1, C₉H₁₁ 2, C₈H₈ClO 3, C₇H₉ 4) and [Me₃(RCOO)]_n (R = C₁₂H₁₅ 5, C₉H₁₁ 6, C₈H₈ClO 7, C₇H₉ 8) have been synthesized. All complexes were characterized by elemental analysis, FT-IR, and NMR (¹H, ¹³C and ¹¹⁹Sn) spectroscopy. Among them, the structures of complexes 1–3 and 5–8 were also determined by X-ray crystallography. The structural analysis showed that complexes 1–3 are the same tetranuclear monomer, and complexes 5–8 are the same 1D zigzag chain coordination polymer. Furthermore, each complex 1, 2 and 3, can form a supramolecular chain through weak intermolecular interactions.     

Organometallic–Inorganic Conjugated Unsymmetrical Schiff-Base Hybrids. Synthesis,Characterization, Electrochemistry and X-ray Crystal Structures of Functionalized Trinuclear Iron–Nickel–Ruthenium Dipolar Chromophores

The synthesis of neutral dinuclear iron–nickel unsymmetrical Schiff base complexes 3 and 4 was achieved via a template reaction involving equimolar amounts of alkyl or aryl “half-unit” precursors, respectively, Fc–C(O)CH=C(CH₃)N(H)R (1: R = CH₂CH₂NH₂; 2: R = o-C₆H₄NH₂; Fc = CpFe(η⁵-C₅H₄); Cp = η⁵-C₅H₅), 5-bromosalicylaldehyde and nickel(II) acetate tetrahydrate in a refluxing CH₂Cl₂/MeOH (1:1) mixture. The ionic trinuclear unsymmetrical complex 5 was prepared by reacting its dinuclear precursor 3 with the arenophile source, [Cp*Ru(NCCH₃)₃]PF₆ (Cp* = η⁵-C₅(CH₃)₅), in refluxing CH₂Cl₂ for 2 h, whereas the trinuclear species 6 was formed upon regioselective π-complexation of the 5-bromosalicylidene ring of 4 by [Cp*Ru]⁺ at room temperature overnight. All the new compounds were adequately characterized by analytical and spectroscopic techniques and, in addition, the crystal and molecular structures of the “half-unit” 1, the binuclear complex 4 and its hemisolvate adduct 4 · 0.5CH₃OH, the trinuclear Schiff base compound 5 · 2(CH₃)₂CO, and the mixed sandwich metalloligand 7 have been determined by X-ray crystallography. Both organometallic–inorganic hybrids 5 and 6 contain the neutral electron-releasing ferrocenyl group, and the cationic electron-withdrawing ruthenium mixed sandwich, linked through the unsymmetrical tetradentate Schiff base complex {Ni(ONNO)}. UV–vis, ¹H and ¹³C NMR as well as electrochemical data clearly indicate a mutual donor–acceptor electronic influence between the organometallic termini. Furthermore, X-ray crystal structure analysis of 5 · 2(CH₃)₂CO reveals the partial delocalization of bonding electron density throughout the dinucleating nickel Schiff base ligand. Dedicated to Prof. Didier Astruc, a true friend, an outstanding lecturer and scientist, in honor of his pioneering research efforts and accomplishments in the fields of organometallic chemistry, dendrimers and their applications in nanocatalysis.     

Kinetic Study of the Prooxidant Effect of α-Tocopherol. Hydrogen Abstraction from Lipids by α-Tocopheroxyl Radical

A kinetic study of the prooxidant effect of α-tocopherol was performed. The rates of allylic hydrogen abstraction from various unsaturated fatty acid esters (ethyl stearate 1, ethyl oleate 2, ethyl linoleate 3, ethyl linolenate 4, and ethyl arachidonate 5) by α-tocopheroxyl radical in toluene were determined, using a double-mixing stopped-flow spectrophotometer. The second-order rate constants (k _p) obtained are <1 × 10⁻² M⁻¹ s⁻¹ for 1, 1.90 × 10⁻² M⁻¹ s⁻¹ for 2, 8.33 × 10⁻² M⁻¹ s⁻¹ for 3, 1.92 × 10⁻¹ M⁻¹ s⁻¹ for 4, and 2.43 × 10⁻¹ M⁻¹ s⁻¹ for 5 at 25.0 °C. Fatty acid esters 3, 4, and 5 contain two, four, and six –CH₂– hydrogen atoms activated by two π-electron systems (–C=C–CH₂–C=C–). On the other hand, fatty acid ester 2 has four –CH₂– hydrogen atoms activated by a single π-electron system (–CH₂–C=C–CH₂–). Thus, the rate constants, k _abstr/H, given on an available hydrogen basis are k _p/4 = 4.75 × 10⁻³ M⁻¹ s⁻¹ for 2, k _p/2 = 4.16 × 10⁻² M⁻¹ s⁻¹ for 3, k _p/4 = 4.79 × 10⁻² M⁻¹ s⁻¹ for 4, and k _p/6 = 4.05 × 10⁻² M⁻¹ s⁻¹ for 5. The k _abstr/H values obtained for 3, 4, and 5 are similar to each other, and are by about one order of magnitude higher than that for 2. From these results, it is suggested that the prooxidant effect of α-tocopherol in edible oils, fats, and low-density lipoproteins may be induced by the above hydrogen abstraction reaction.     

Synthesis and properties of poly(phenylacetylene)s having dialkylamino groups

Summary Poly(phenylacetylene)s bearing dialkylamino groups were prepared by the polymerization of p-(N,N-dialkylamino)phenylacetylenes with [Rh(nbd)Cl]₂, and their electrochemical behavior was examined. Rh-catalyzed polymerization of p-(N,N-diethylamino)phenylacetylene (DEAPA) and p-(N,N-di-n-butylamino)phenylacetylene (DBAPA) in toluene in the presence of triethylamine gave good yields of the polymers (86 and 90%, respectively). Poly(DEAPA) was soluble in chloroform and dichloromethane, and poly(DBAPA) dissolved in various solvents such as toluene, THF, dichloromethane and chloroform. Poly(DEAPA) and poly(DBAPA) showed onset temperatures at 248 and 190°C, respectively, and absorptions around 300–400 nm. Electrochemical doping of the polymer films resulted in the shift of the absorptions to a region around 680 nm, which accompanied a color change of the polymer films from green ocher to deep blue. Received: 26 October 1998/Revised version: 6 November 1998/Accepted: 12 November 1998     

Synthesis and gas permeability of poly(<Emphasis Type="Italic">p</Emphasis>-phenyleneethynylene)s having bulky alkoxy or alkyl groups

Dipropynylbenzene with branched alkoxy and alkyl groups [CH₃C≡CRC₆H₂RC≡CCH₃, R = 2-methylpropoxy (1a), 3-methylbutoxy (1b), 4-methylpentoxy (1c), cyclohexylmethoxy (1d), 2-ethylhexoxy (1e), 2-octoxy (1f), 2-ethylhexyl (1g), and 2-octyl (1h)] were polymerized with Mo(CO)₆ in the presence of 4-(trifluoromethyl)phenyl to afford poly(2,5-di(alkoxy or alkyl)-p-phenyleneethynylene)s (2a–h). Polymer 2a was insoluble in any solvents, but the other polymers (2b–h) were soluble in common organic solvents. The polymers with relatively long side chains (2e–h) had high molecular weight over 1.6 × 10⁴ and gave free-standing membranes by solution-casting method. The densities of membranes of 2e–h were 0.914–0.998, and their fractional-free volume values were relatively large (0.094–0.158). The oxygen permeability coefficients of membranes of 2e–h were 18.4, 12.7, 4.85, and 19.3 barrers, respectively. It was found that poly(p-phenyleneethynylene) with 2-octyl side groups, which have the branch at the nearest position from main chain, exhibited the highest gas permeability.     

Homo- and R/S-copolymerizations of chiral methylpropargyl esters carrying pyrene moieties, and optical properties of the formed polymers

Pyrene-functionalized chiral methylpropargyl esters, (R)-3-butyn-2-yl-1-pyrenebutyrate [(R)-1], (S)-3-butyn-2-yl-1-pyrenebutyrate [(S)-1], (R)-3-butyn-2-yl-1-pyrenecarboxylate [(R)-2], and 3-butyn-2-yl-1-pyrenecarboxylate [(R,S)-2] were polymerized with (nbd)Rh⁺[η⁶-C₆H₅B⁻(C₆H₅)₃] to obtain the corresponding polymers with moderate molecular weights (M_n: 10?500-66?500) in good yields (82-97%). All the polymers were soluble in CHCl₃, CH₂Cl₂, and THF. The polarimetric and CD spectroscopic data indicated that poly[(R)-1], poly[(S)-1], and poly[(R)-2] existed in a helical structure with predominantly one-handed screw sense in these solvents. The helical structure of poly[(R)-1] and poly[(S)-1] was stable upon heating and addition of MeOH, while that of poly[(R)-2] changed upon MeOH addition. The copolymerization of (R)-1 with (S)-1 was also conducted to obtain the copolymers satisfactorily. Poly[(R)-1], poly[(S)-1], and poly[(R)-2] emitted fluorescence smaller than the corresponding racemic copolymers. The fluorescence intensity was tuned by the addition of MeOH to THF solutions of the polymers.     

Stimuli-responsive conjugated polymers. Synthesis and chiroptical properties of polyacetylene carrying l-glutamic acid and azobenzene in the side chain

A glutamic acid- and azobenzene-containing novel N-propargylamide, (S)-CHCCH₂NHCOCH(CH₂CH₂CO₂CH₂C₆H₅)NHCO₂CH₂CH₂-p-C₆H₄NNC₆H₅ (1) was synthesized and polymerized with (nbd)Rh⁺[η⁶-C₆H₅B⁻(C₆H₅)₃] as a catalyst to obtain the corresponding polymer [poly(1)] with the moderate number-average molecular weight of 12,200 in 93% yield. The chiroptical studies revealed that poly(1) took a helical structure in THF, CHCl₃, CH₂Cl₂ and toluene. Poly(1) underwent solvent and heat-driven helix-helix transition. The trans-azobenzene of the side chain isomerized into cis upon UV-irradiation, accompanying decrease in helicity. The cis-azobenzene moiety reisomerized into trans upon visible-light irradiation, while the polymer did not recover the original helicity.     

Hydrosilylation Synthesis of New Ferrocenylene Copolymers Containing Carbosilylene,Carbosiloxy and Cyclopentadienyliron Dicarbonyl Bridges

Bifunctional organometallic silicon precursor monomers and substrates FC(SiMe₂H)₂ (1) [FC = (η⁵-C₅H₄)Fe(η⁵-C₅H₄)]; FC(SiMe₂(CH₂)_xCH=CH₂)₂ [x = 0 (2), 1 (3)], [η⁵-C₅H₄-SiMe₂(CH₂)_xCH=CH₂)]Fe(CO)₂SiMe₂(CH₂)_xCH=CH₂ x = 0 (4), 1 (5) and (η⁵-C₅H₄-SiMe₂H)Fe(CO)₂SiMe₂H (6) have been used to make a series of new iron containing polymers via hydrosilylation reactions. In addition to the vinyl- and allyl-containing substrates 2, 3, 4 and 5 the organosilicon compounds [CH₂=CHSiMe₂]₂O, 1,4-(H₂C=CH-SiMe₂)₂C₆H₄ and (HC≡CH–SiMe₂)₂O were also used as substrates for the hydrosilylation reaction. The reactions between the various SiH and CH=CH₂ and C≡C functionalities were performed in the presence of Pt(0) catalyst and resulted in regioselective (β-isomer and β-(E) isomer) products as determined by NMR spectroscopy. Molecular weights of all the polymers were determined by Gel Permeation Chromatography, which revealed oligomeric materials with narrow polydispersity. Cyclic voltammetric studies of exhibited single reversible redox processes due to the Fe(II)/Fe(III) couple when present, and irreversible oxidation for the presence of any Fp Fe atom. This article is dedicated to Professor Astruc.     

A Novel Bimetallic Chain Based on [Mo(CN)<Subscript>8</Subscript>]<Superscript>3−</Superscript> and Yb<Superscript>3+</Superscript> Ions as Building Blocks in Which Containing Many Intriguing Structural Features

A novel Mo^V–Yb^III bimetallic chain, {[Yb^III(bpy)₂(DMF)(H₂O)][Mo^V(CN)₈]·0.5bpy·4.5H₂O}_n (1) (DMF = N,N′-dimethylformamide; bpy = 2,2′-bipyridine), has been constructed by the reaction of [Mo(CN)₈]³⁻ with Yb³⁺ and 2,2′-bipyridine. Complex 1 is confirmed as a host–guest supramolecular structure by X-ray structural analysis. The neighboring chains interact with each other with two types of hydrogen bonds and two types of π···π interactions. Thus complex 1 has a unique 3D network. Magnetic analysis of 1 indicates the presence of a strong Yb^III single-ion effect owing to spin–orbital coupling within this system.     

Copper (II) Ions into Polyphosphazenes: Solid-Like Solution Behavior

Reaction of Cu(BF₄)₂ salt with the polymer [NP(OC₆H₄C(O)C–OC₆H₅)₂] _n (1) in THF affords three new polymers gels containing varied copper (II) ions contents, (2), (3), and (4). The nature of the copper (II) ions in the gel (2)–(4) was examined by IR spectroscopy, solid state ³¹P, ¹³C and ⁶³Cu NMR spectroscopy and EPR spectroscopy. Despite the copper content, the gels were insulators as measured by complex impedance spectroscopy. SEM images show a uniform distribution of the Cu (II) ions and a most porous morphology than those without copper polymer. TEM images show the formation of small aggregates being smallest for, gel (2) of about 200 nm. All the data suggest the Cu²⁺ centers behave as a solid dilute into the polyphosphazenes.     

Synthesis and properties of conjugated copolymers having a tricarbonyl(arene)chromium and thiophene units in the main chain

Summary Palladium-catalyzed polymerization of η ⁶-(1,4-diethynylbenzene)tricarbonyl chromium (1) with 3-alkyl-2,5-dibromothiophene (2a-c) was carried out to give the corresponding alternating conjugated copolymers (5a-c) in good yields. The structures of the polymers were supported by ¹H NMR and IR spectra. The polymers obtained were soluble in common solvents such as THF, CH₂Cl₂, CHCl₃ and toluene. The molecular weights of the polymers were determined by GPC. Their thermal, optical and electrical properties were investigated in detail. Received: 18 March 2002 /Accepted: 1 April 2002     

New photocatalysts based on mixed-metal pyridine dicarboxylates

New photocatalytically active isostructural two-dimensional mixed metal-pyridine dicarboxylates, [M(H₂O)₃Co{C₅N₁H₃(COO)₂}₃])_∞], M = Gd (1), Dy (2) and Y (3) have been prepared under hydrothermal conditions. The structure consists of a network of MO₆(H₂O)₃, CoO₃N₃ polyhedral units connected by the pyridine dicarboxylates forming two-dimensional layers, which are arranged in an AAAA... fashion. The photocatalytic studies on 1 – 3 indicate that they are active catalysts for the degradation of simple organic dyes, such as Remazol brilliant blue R (RBBR) and Orange G (OG) in the presence of UV light. The compounds have also been characterized by powder XRD, IR, TGA, UV-Vis and magnetic studies.