Synthesis and electrochemical characterisation of benzylmercapto and dodecylmercapto tetra substituted cobalt, iron, and zinc phthalocyanines complexes

The work reports on cyclic voltammetry (CV), square wave voltammetry and spectroelectrochemistry of the following complexes: tetrakis (benzylmercapto) phthalocyanine complexes of Zn(II) (ZnTBMPc, 4a), Co(II) (CoTBMPc, 5a), and Fe(II) (FeTBMPc 6a); tetrakis (dodecylmercapto) phthalocyanine complexes of Zn(II) (ZnTDMPc, 4b), Co(II) (CoTDMPc, 5b), and Fe(II) (FeTDMPc, 6b). More reversible CV couples were observed for complexes 4a, 5a, and 6a containing thiol phenyl ring substituents. Complexes 4b, 5b, and 6b containing long chain thiol substituents showed less reversible couples. Complexes 6a and 6b showed a relatively large number of redox processes (5 for 6a and 6 for 6b) within the potential window employed in this work. The processes for FePc derivatives (6a) are assigned to Fe^IIIPc⁻¹/Fe^IIIPc⁻², Fe^IIIPc⁻²/Fe^IIPc⁻², Fe^IIPc⁻²/Fe^IPc⁻², Fe^IPc⁻²/Fe^IPc⁻³, and Fe^IPc⁻³/Fe^IPc⁻⁴ and for the CoPc derivative (5a) to Co^IIIPc⁻¹/Co^IIIPc⁻², Co^IIIPc⁻²/Co^IIPc⁻², Co^IIPc⁻²/Co^IPc⁻², and Co^IPc⁻²/Co^IPc⁻³.     

Colorless and high organosoluble polyimides from 2,5-bis(3,4-dicarboxyphenoxy)-t-butylbenzene dianhydride and aromatic bis(ether amine)s bearing pendent trifluoromethyl groups

A series of polyimides III_a-h characterized by colorlessness, high transparency, high solubility, and good mechanical property, was synthesized from the aromatic dianhydride, 2,5-bis(3,4-dicarboxyphenoxy)-t-butylbenzene dianhydride (I), and various aromatic diamines (II_a-h) with pendent trifluoromethyl group via polyaddition, chemical imidization, and direct cast films. The III series showed more colorless than the polyimides (V and VI series) of 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) contained, the VI series was synthesized from the II with 6FDA. These films III had cut-off wavelengths between 371 and 376 nm, as well as b* value (a yellowness index) ranging from 3.0 to 4.7. In fact, it is so far the most colorless aromatic polyimide in our systematical researches. The III series had inherent viscosity ranging from 0.72 to 1.33 dL/g and showed excellent solubility in a variety of organic solvents. They were soluble in a concentration of 5-10% in the amide polar solvent, ether solvent, and chlorinated solvent. These films showed strength tensile of 97-123 MPa, dielectric constants of 2.78-3.28 (1 MHz), and moisture absorptions of 0.11-0.36 wt%. The glass transition temperature of the III series was recorded at 214-259 °C, the 10% weight loss temperature was over 468 °C, and the residue was more than 47% at 800 °C in nitrogen.     

Electrochemical behaviour of tetraazamacrocyclic nickel(II) complexes functionalized with crown ethers

Tetraazamacrocyclic nickel(II) complexes linked by the system of conjugated double bonds with one or two benzo-15-crown-5 moieties (2Ni and 3Ni) were synthesized and characterized. The CV of these complexes in acetonitrile (ACN) solution exhibited reversible Ni^II/III redox process. At more positive potentials oxidation of the bezno-15-crown-5 ether (B15C5) moiety was found. In complexes 2Ni and 3Ni redox potential of Ni^II/III did not change after the interactions of alkali and alkaline earth metal cations with B15C5 unit. However, the presence of guest cations caused a significant change of B15C5 oxidation potential. Complexation of two Cl⁻ anions to the coordinated Ni^II in 2Ni and 3Ni resulted in an appreciable shift of both Ni^II/III and B15C5 redox processes after addition of metal cations. Behaviour of complexes 2Ni and 3Ni was compared with behaviour of similar Cu^II complexes.     

Crown ether bridged homo- and heterodinuclear copper(II) and nickel(II) cyclidene complexes: Interaction with anions

Homodinuclear (3CuCu, 3NiNi) and heterdionuclear (3CuNi) cyclidene complexes linked by two 1,10-diaza-18-crown-6 ethers were synthesized and their properties characterized. For the 3CuCu in the negative potential range the mixed-valence state Cu^I-Cu^II was observed and the comproportionation constants were determined. The redox potentials of M^II/III showed a good correlation with DN of the solvent. In acetonitrile solution containing 0.1 mol dm⁻³ Bu₄NPF₆ reversible M^II/III redox processes were observed. However, in the presence of stronger ion pairing anions (e.g. BF₄⁻ and ClO₄⁻) the “potential inversion” occurred. Redox potentials of dinuclear complexes were compared with mononuclear cyclidene complexes. The influence of selected anions (Cl⁻ and NO₃⁻) on the redox process M^II/III was studied. The effect of Cl⁻ anion was different for 3CuCu and 3NiNi. In 3CuCu coordination of two chloride anions took place after oxidation of copper centers. In the 3NiNi complex two Cl⁻ anions were coordinated to one of the nickel(II) centers facilitating oxidation, at different potentials, of both nickel(II) cations. The behaviour of heteronuclear complex with Cl⁻ anions was similar to 3NiNi. All dinuclear complexes interacted with NO₃⁻ anions and the observed potential shifts were larger for nickel(II) than for copper(II) cations.     

Paired electrochemical synthesis of new organosulfone derivatives

Electrochemical oxidation of “cathodically generated 4-aminocatechol (2)” has been studied in the presence of 4-toluenesulfinic acid (4a) and benzenesulfinic acid (4b) as nucleophiles in aqueous solutions, using cyclic voltammetry and controlled-potential coulometry. The results indicate that the o-benzoquinone derived from 4-aminocatechol (2) participates in Michael addition reaction with 4a or 4b to form the corresponding new organosulfone derivatives (5a and 5b). In this work we have proposed a mechanism for the electrode process. A Fe(CN)₆³⁻/Fe(CN)₆⁴⁻ redox mediator was used for the anodic oxidation of 4-aminocatechol (2) to the corresponding o-quinone 3. The indirect electrochemical process consists of a multi-step such as (a) cathodic reduction of 4-nitrocatechol (1) to 4-aminocatechol (2), (b) chemical oxidation of 4-aminocatechol (2) to 4-aminoquinone (3) with the resulting Fe(CN)₆³⁻, (c) the chemical reaction of 4-aminoquinone (3) with 4-toluenesulfinic acid (4a) or benzenesulfinic acid (4b), and (d) the anodic regeneration of Fe(CN)₆³⁻. The paired electrochemical synthesis of organosulfone derivatives (5a and 5b) has been successfully performed in an one-pot process at carbon rod electrode as a working and platinum as a counter electrode in an undivided cell.     

Synthesis of a pyridine substituted polycarbodiimide and its use as a solid support for chemical reagents

Optically active, polycarbodiimides 3(a, b & c) with pyridine pendant groups were synthesized using [(R) - 2,2′- binaphthoxy] (di-isopropoxy) titanium(IV) catalyst. The polymers were characterized by ¹H and ¹³C NMR, and IR. Thermal stability of these polymers (up to 162 °C by TGA), allows thermally demanding chemical transformations on their side chains without decomposition. Advantages include fine-tunability of the other pendant group of the carbodiimide monomer. This allows one to optimize the properties of the polymer without undergoing copolymerization or further post-polymerization modifications. Borane (BH₃) was coordinated to poly 3 (a & b) to prepare the functional polymers 4 (a & b) respectively. A strong IR signature peak at 2368 cm⁻¹ supports BH₃ coordination. Gravimetric analysis indicates 97-99% borane complexation of the pyridine units. In addition, the thermal stability increased to 194 °C in poly 4a is consistent with the incorporation of BH₃ to the pendant pyridine of the helical polycarbodiimide 3a. Poly 4 (a & b) can be used as supported reagents and successfully reduced the carbonyl compounds (5 a-e) in moderate to excellent yields (60-100%) and are shown to be efficient, non-volatile, stable, and mild supported-reducing reagents. Upon completion of the reduction reaction, the polymer support was quantitatively recycled as required for a green solid catalyst support.     

Electrocatalytic four-electron reductions of O2 to H2O with cytochrome c oxidase model compounds

Three different complexes, heme-Cu ([(⁶L)Fe^IICu^I]⁺ (1), ⁶L=a binucleating ligand having a heme and covalently tethered copper binding tris(2-pyridyl)methylamine tetradentate moiety), heme complex ((⁶L)Fe^II (4), (with “empty” tethered chelate)), and the “parent” iron-porphyrinate ((F₈TPP)Fe^II (5), F₈TPP=tetrakis(2,6-difluorophenyl)porphyrinate) were employed for the electrocatalytic reduction of O₂. Complexes 1 and 4 reduce O₂ to water (four-electron reduction) with good efficiency (74 and 59%, respectively), but complex 5 exhibited only an ∼20% efficiency, thus primarily the two-electron reduction to hydrogen peroxide occurred. The results of the present electrochemical O₂-reduction studies and the previous studies have elucidated the O₂-binding nature of these three complexes, indicating the formation of quite stable Fe^III(O₂²⁻)Cu^II (peroxo) or Fe^IIIO₂⁻ (superoxo) species. In line with the thinking of other researchers, the fact that both 1 and 4 can well stabilize Fe^IIIO₂⁻ superoxo species may suggest that the formation of the latter is a key to the pathway favoring four-electron reduction of dioxygen to water.     

Thermal behavior of 1,4-bis(4-trimellitimido-2-trifluoromethyl phenoxy)benzene (DIDA) solvated with polar organic solvents and properties of DIDA-based poly(amide-imide)s

Fluorinated diimide-dicarboxylic acid (DIDA, Code: IV), 1,4-bis(4-trimellitimido-2-trifluoromethylphenoxy) benzene, synthesized by reacting 1,4-bis(4-amino-2-trifluoromethyl phenoxy)benzene (I) with trimellitic anhydride in polar solvents (PSv), was found to crystallize easily in amide-type solvents, such as N-methyl-2-pyrrolidinone (NMP), N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAc), or 1,3-dimethyl-2-imidazolidinone (DMI) media, to form a series of stable crystalline solvates (III_(NMP), III_(DMAc), III_DMF), III_(DMI)) containing a certain quantity of crystalline solvent. The solvates III_(PSv) were characterized and proven by DSC, TGA, and X-ray analysis. The decomposition point temperature (T_d) was different with the type of polar solvents in III_(PSv). Elemental analysis and NMR showed that most of the III_(PSv) were formed from IV and polar solvents in the ratio of 1:2, and the solvation processes were found to be reversible. Furthermore, a series of soluble fluorinated poly(amide-imide)s (VI_a-h) were synthesized from reacting either the NMP-solvates III_(NMP) or dry/non-solvates IV with an equivalent amount of diamines by direct polycondensation using triphenyl phosphate and pyridine as condensing agents. Thermal and mechanical properties of the fluorinated VI_a-h were measured, and compared with counterparts of non-fluorinated PAI's (Code: VI′s). In comparison, the fluorinated VI_a-h poly(amide-imide)s exhibited better solubility, tensile, and thermal properties than the non-fluorinated VI′s.     

Highly optically transparent/low color polyimide films prepared from hydroquinone- or resorcinol-based bis(ether anhydride) and trifluoromethyl-containing bis(ether amine)s

Two series of novel polyimides (5a-g and 6a-g) containing flexible ether linkages and pendent trifluoromethyl (CF₃) groups were synthesized from 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride (3a) and 1,3-bis(3,4-dicarboxyphenoxy)benzene dianhydride (3b) with various CF₃-substituted aromatic bis(ether amine)s (4a-g) via ring-opening polyaddition to poly(amic acid)s, followed by thermal or chemical imidization. These polyimides were readily soluble in a variety of organic solvents and could be solution-cast into flexible and tough films. The cast films exhibited high optical transparency and almost no color, with a UV-vis absorption edge of 368-382 nm and a very low b^∗ value (a yellowness index) of 6.2-15.5. They had good thermal stability with glass-transition temperatures of 186-288 °C, and most of them did not show significant decomposition before 500 °C. Moreover, these polyimide films also possessed low dielectric constants of 2.79-3.49 (at 1 MHz) and low water uptakes (<0.65 wt%).     

Synthesis of 1,9-bis[glycidyloxypropyl]penta(1′H,1′H,2′H,2′H-perfluoroalkylmethylsiloxane)s and copolymerization with piperazine

A series of 1,9-bis[glycidyloxypropyl]pentasiloxanes (IV-VI) were prepared by the platinum catalyzed hydrosilylation of 1,9-dihydridodecamethylpentasiloxane (I), 1,9-dihydrido-3,5,7-tris(3′,3′,3′-trifluoropropyl)heptamethylpentasiloxane (II), and 1,9-dihydrido-3,5,7-tris(1′H,1′H,2′H,2′H-perfluorooctyl)heptamethylpentasiloxane (III) with allyl glycidyl ether. Subsequently, IV-VI were copolymerized with piperazine to form high molecular weight copoly(carbosiloxane)s (VII-IX). The structures of the 1,9-bis[glycidyloxypropyl]penta-siloxanes (IV-VI) and copoly(carbosiloxane)s (VII-IX) were determined by ¹H, ¹³C, ²⁹Si, and ¹⁹F NMR as well as IR spectroscopy. The molecular weight distributions (M_w/M_n) of VII-IX have been characterized by gel permeation chromatography and their thermal properties measured by differential scanning calorimetry and thermal gravimetric analysis.     

Highly active and trans-1,4 specific polymerization of 1,3-butadiene catalyzed by 2-pyrazolyl substituted 1,10-phenanthroline ligated iron (II) complexes

A new family of iron (II) complexes (2a–h) bearing tridentate 2-pyrazolyl substituted 1,10-phenanthroline ligands were successfully prepared and characterized by IR spectroscopy, elemental analysis, and mass spectra. Complexes 2a–f and 2h were further confirmed by the X-ray crystallographic analysis. 2a, 2b, 2e, and 2f adopted distorted trigonal bipyramidal configuration. 2c displayed a distorted octahedron formed by six coordinated nitrogen atoms of the two ligands. Linked by two bridged chloride atoms, complex 2d was a centrosymmetric dimmer, and complex 2h adopted a six-coordinate distorted octahedral geometry due to the coordination of two solvent molecules. These complexes activated by alkylaluminum were examined in butadiene polymerization. In combination with AlⁱBu₃, complexes 2a–c exhibited high catalytic activity (73.5%–94.3%) at 20 °C, whereas other complexes exhibited much lower activity. Interestingly, the activity and selectivity of the complexes increased as increasing polymerization temperature. In particular, 2b and 2c displayed both high activity (99% and 80%, respectively) and trans-1,4 selectivity (95.6% and 96.2%, respectively) at 60 °C. The trans-1,4 selectivity of 2b varied as alkylaluminum used as a cocatalyst, in the following order: AlⁱBu₃ > AlOct₃ > AlEt₃ > AlMe₃, whereas much lower trans-1,4 selectivity was observed in the cases of using MAO and MMAO.     

Colorless polyimides from 2,3,3′,4′-biphenyltetracarboxylic dianhydride (α-BPDA) and various aromatic bis(ether amine)s bearing pendent trifluoromethyl groups

A series of organosoluble and light-colored polyimides (III) was prepared from 2,3,3′,4′-biphenyltetracarboxylic dianhydride (α-BPDA) with various fluorinated aromatic bis(ether amine)s via two-step method with thermal or chemical imidization of poly(amic acid)s yielded polyimides. The III series had inherent viscosity of 0.74-1.01 dl/g and showed excellent solubility in a variety of organic solvents. They were soluble in the amide polar solvent, ether-type solvent, and chlorinated solvent. These polyimide films also showed a high optical transparency and less color intensity, with an ultraviolet-visible absorption edge of 369-382 nm and low b^* values (a yellowness index) of 5.0-11.7. Glass-transition temperature of the III series was recorded at 244-319 °C and higher than the isomeric polyimides V series. Compared with the nonfluorinated polyimides IV, the III series showed lighter-colored and lower dielectric constants and moisture absorptions. The good tensile properties and excellent thermal properties of the III series were also observed.     

Polymeric molecular shuttles: Polypseudorotaxanes & polyrotaxanes based on viologen (paraquat) urethane backbones & bis(p-phenylene)-34-crown-10

Reaction of di(p-isocyanatophenyl)methane (MDI, 4) with N,N′-di(2-hydroxyethyl)- (1b) or N,N′-di[2-(2′-hydroxyethoxy)ethyl]-4,4′-bipyridinium di(hexafluorophosphate) (1e) and other diols [oligo(ethylene glycol)s and poly(tetramethylene oxide)s] in the presence of bis(p-phenylene)-34-crown-10 (2) afforded polyurethane (pseudo)rotaxanes as statistical (7P or 7R) and segmented analogs 10P (P = pseudorotaxane, R = rotaxane). In 7R a bulky alcohol was incorporated at the chain ends and in 13R a bulky diol as in-chain units to form polyrotaxanes and preclude the possibility of dethreading. The crown ether 2 in 10P and 13R was shown by ¹H NMR spectroscopy to be shuttling between the viologen (paraquat) and urethane sites; in DMSO the crown ether prefers the urethane site, probably because of H-bonding with the N–H moieties and complexation of the pyridinium site by the dipolar solvent, while in acetone at low temperatures the viologen site is preferred by the crown ether, with ΔH = −6.91 kcal/mol and ΔS = −22.9 eu for 13R.     

Synthesis and gas permeation properties of various Si-containing poly(diarylacetylene)s and their desilylated membranes

Diarylacetylene monomers having trimethylsilyl groups and other substituents (substituted biphenyl, 1a and 1b; trimethylsilylmethylphenyl, 1c-e) were synthesized and polymerized with TaCl₅-n-Bu₄Sn catalyst to produce the corresponding poly(diarylacetylene)s (2a-d). Polymers 2a-c had high molecular weights and were soluble in common organic solvents. Free-standing membranes of 2a-c as well as previously reported 2f-h were prepared by the solution-casting method. Desilylation of these Si-containing polymer membranes was carried out with trifluoroacetic acid to afford 3a, 3b, and 3f-h. Upon desilylation, biphenyl-containing membranes became less permeable (3a, b), whereas fluorene-containing membranes became more permeable (3f-h). In particular, 3h exhibited extremely high gas permeability (PO₂ = 9800 barrers), which is about the same as that of poly(1-trimethylsilyl-1-propyne). Desilylated membranes 3a and 3f-h showed different gas permeability from that of polymers 2i-k which have the identical chemical structures and obtained directly by the polymerization of the corresponding monomers.     

Synthesis and properties of organosoluble polyimides based on 1,1-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]cyclohexane

New aromatic diamine with cyclohexane cardo group substituted with trifluoromethyl group in the side chain, 1,1-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]cyclohexane (II), was prepared through the nucleophilic substitution reaction of 1,1-bis(4-hydroxyphenyl)cyclohexane and 2-chloro-5-nitrobenzotrifluoride in the presence of potassium carbonate, to yield the intermediate dinitro compound I, followed by catalytic reduction with hydrazine and Pd/C to afford the diamine II. Fluorinated polyimides (IVa-g) were prepared from the II with various aromatic dianhydrides via thermal or chemical imidization of poly(amic acid). These polyimides had inherent viscosity ranging from 0.72 to 1.16 dl/g and showed excellent solubility in a variety of organic solvents. They were soluble in a concentration of 10% in the amide polar solvent, and 1-5% in the other testing solvents. IV films showed good mechanical properties, excellent thermal stability. The 10% weight loss temperature was above 476 °C in nitrogen or air, and the glass transition temperature was recorded at 214-278 °C. In comparison of the IV series with the analogous nonfluorinated polyimides (V series) based on 1,1-bis[4-(4-aminophenoxy)phenyl]cyclohexane (II′), IV series revealed better solubility, lighter-colored and lower dielectric constants and moisture absorptions. Their films had cut-off wavelengths in the range of 364-414 nm, b^* value (a yellowness index) ranging from 3.3 to 66.3, dielectric constants of 3.02-3.55 (1 MHz), with moisture absorption of 0.16-0.36 wt%.     

Electrochemical study of stable N-alkoxyarylaminyl radicals

The electrochemical study of N-tert-butoxy-2,4-diphenyl-6-tert-butylphenylaminyl (1a), N-tert-butoxy-2,4-bis(4-chlorophenyl)-6-tert-butylphenylaminyl (1b), N-[2-(methoxycarbonyl)-2-propyl]-2,4-diphenyl-6-tert-butylphenylaminyl (2), and N-tert-butoxy-2,4,6-tris(4-chlorophenyl)phenylaminyl radicals (3) was performed by cyclic voltammetry using acetonitrile as the solvent and Bu₄NPF₆ as the supporting electrolyte. On cathodic scan (100 mV/s), all the radicals gave chemically reversible cyclic voltammograms, and the were determined to be −1.405 V (1a), −1.310 V (2a), −1.282 V (2b), and −1.195 V (3) (versus Fc⁺/Fc), respectively. On anodic scan (100 mV/s), on the other hand, 1a, 1b and 2 showed chemically reversible cyclic voltammograms, but 3 exhibited a partially reversible couple even on a scan rate of 500 mV/s, indicating that the cation species of 3 was less stable. The determined for 1a, 1b, 2 and 3 were 0.220, 0.280, 0.318 and 0.294 V (versus Fc⁺/Fc), respectively. The electrochemical data were compared with those of thioaminyl radicals, the corresponding sulfur analogues of 1-3.     

Synthesis and properties of various poly(diphenylacetylenes) containing tert-amine moieties

The polymerization of diphenylacetylene derivatives possessing tert-amine moieties, such as triphenylamine, N-substituted carbazole and indole, was examined in the presence of TaCl₅-n-Bu₄Sn (1:2) catalyst. A polymer with high molecular weight (M_w = 570 × 10³) was obtained in good yield by the polymerization of diphenylamine-containing monomer 1b, whereas the isopropylphenylamine derivative (1c) gave a polymer with relatively low molecular weight (M_w = 2.4 × 10³). The polymerization of monomer 1d containing cyclohexylphenylamine group did not proceed; however, carbazolyl- and indolyl-containing monomers also produced polymers. Poly(1b), poly(2f) and poly(4b) could be fabricated into free-standing membranes by casting toluene solutions of these polymers. The gas permeability of poly(1b) was too low to be evaluated accurately whereas poly(4b) possessing two chlorine atoms in the repeating unit showed higher gas permeability than that of poly(1b); furthermore, poly(2f) having trimethylsilyl and 3-methylindolyl groups exhibited relatively high gas permeability (). In the cyclic voltammograms of diphenylamino group-containing polymers, poly(1b) and poly(2b), the intensities of oxidation and reduction peaks decreased more than those of carbazolyl-containing poly(2a). The molar absorptivity (?) of poly(1b) at ∼700 nm increased with increasing applied voltage in the UV-vis spectrum.     

Preparation of π-conjugated polymers consisting of 2-decylbenzimidazole and thiophene units and chemical properties of the polymers

Polycondensation by Stille coupling of 2-decyl-4,7-dibromobenzimidazoles and N-methyl-2-decyl-4,7-dibromobenzimidazole with 2,5-bis(trimethylstannyl)thiophene and 5,5′-bis(trimethylstannyl)-2,2′-bithiophene gave the corresponding π-conjugated polymers, poly(2-decylbenzimidazole-4,7-diyl-thiophene-2,5-diyl) 1b, poly(2-decylbenzimidazole-4,7-diyl-bithiophene-2,5-diyl) 1c and poly(N-methyl-2-decylbenzimidazole-4,7-diyl-thiophene-2,5-diyl) 2b, in 98-99% yields. The polymers 1b and 2b were fully soluble in CF₃COOH, and partially soluble in DMF (about 60 and 40% for 1b and 2b, respectively) and NMP (about 70 and 40%, respectively). The NMP soluble part of 1b and DMF soluble part of 2b gave values of 0.36 and 0.24 dl g⁻¹ in NMP and DMF, respectively. The DMF soluble part of 1b, 1c and 2b showed absorption peaks at about 458, 465 and 388 nm, respectively, in DMF. In an alkaline medium the absorption peaks of 1b and 1c are shifted to a longer wavelength by 92-101 nm; the observed shifts in the acidic medium and alkaline medium were much larger than those observed with usual benzimidazoles with low molecular weights. Packing structures of 1b, 1c and 2b are discussed based on their XRD patterns.     

Pd-catalyzed hydrosilylation polymerization of a dihydrosilane with diyne/triyne mixed systems affording crosslinked silylene-divinylene polymers and their properties

Treatment of a dihydrosilane (methylphenylsilane, 1) with mixtures of a diyne (p- or m-diethynylbenzene, 2a or 2b) and a triyne (1,3,5-triethynylbenzene, 3a or B,B′,B″-triethynyl-N,N′,N″-trimethylborazine, 3b; 1:2:3=100:95:5, 100:90:10, 100:80:20) in the presence of Pd-PCy₃ (Cy=cyclohexyl) catalyst gave new crosslinked silylenedivinylene polycarbosilanes. In TGA the resulting crosslinked polymers tended to show higher Td₅ values and higher char yields than the corresponding linear polymers. On the other hand, UV/vis absorption spectra of the crosslinked polymers obtained in the reactions of 2a or 2b with 3a exhibited increased broad peaks around 390 nm for 2a or 360 nm for 2b. Coincidently, their fluorescence spectra showed significant increase of the emission peaks in 400-550 nm. The crosslinked polymer derived from 2a and 3b, however, showed decrease of the absorption peak around 390 nm and profound depression of fluorescence peaks in 400-550 nm.