Novel poly(diphenylacetylene)s with both alkyl and silyl groups as gas permeable membranes: Synthesis, desilylation, and gas permeability

Diphenylacetylenes having a dimethyloctylsilyl group and an alkyl group at para positions [Me₂n-C₈H₁₇SiC₆H₄CCC₆H₄R; R = H (1a), i-Pr (1b), t-Bu (1c), n-Bu (1d)] and having only an alkyl group [PhCCC₆H₄R; R = i-Pr (1B), t-Bu (1C)] were synthesized and then polymerized with TaCl₅/n-Bu₄Sn catalyst to provide the corresponding poly(diphenylacetylene)s (2a, 2b, 2c, 2d, 2B, and 2C). The formed polymers afforded tough free-standing membranes by casting from toluene solutions. Desilylation reaction of Si-containing membranes (2a-d) was carried out with trifluoroacetic acid to give the desilylated membranes (3a-d). The permeability of these membranes to O₂, N₂, and CO₂ were determined. All the Si-containing membranes exhibited almost the same gas permeability. The desilylation of Si-containing membranes of 2a-c resulted in large increase of gas permeability. No apparent increasing of gas permeability was observed in the desilylation of 2d. To clarify the effects of desilylation, CO₂ diffusivity (D(CO₂)), CO₂ solubility (S(CO₂)), and fractional free volume (FFV) of the polymer membranes were investigated. The S(CO₂) values of desilylated membranes were much larger than that of Si-containing counterparts. The D(CO₂) and FFV of membranes of 2a-c increased through desilylation. The desilylated membrane of 3d had small D(CO₂) value and almost the same FFV compared with 2d. Further, the comparison of the permeability between three types of membranes with the same chemical structure revealed that the microvoids were not generated by the desilylation of membranes of poly(diphenylacetylene)s containing alkyl groups.     

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 poly(1-β-naphthyl-2-phenylacetylene) membranes through desilylation and their properties

The polymerization of 1-β-naphthyl-2-[(p-trimethylsilyl)phenyl]acetylene (8a) with TaCl₅-n-Bu₄Sn in cyclohexane provided a high molecular weight polymer (9a) (M_w=3.4×10⁶). The corresponding monomers having p-dimethyl-t-butylsilyl and p-dimethyl(10-pinanyl)silyl groups in place of p-trimethylsilyl group in 8a also polymerized in a similar way to give high molecular weight polymers (9b, 9c, respectively; M_w>1×10⁶). All these polymers were soluble in many common solvents such as toluene and chloroform, and provided free-standing membranes by casting from toluene solution. The oxygen permeability coefficients (P_O2) of 9a at 25 °C was as high as 3500 barrers. The membrane of poly(1-β-naphthyl-2-phenylacetylene) (10a) was prepared by desilylation of the membrane of 9a with trifluoroacetic acid. Polymer 10a was insoluble in any solvents, and showed high thermal stability (the onset temperature of weight loss in air ∼470 °C). The P_O2 value of 10a reached 4300 barrers. Not only the membrane of 9c but also its desilylation product 10c exhibited large optical rotations ([α]_D=+2924 and +9800°, respectively) and strong CD signals. This indicates that the membrane of 10c maintains the helical main chain conformation of 9c with a large excess one-handed helix sense.     

Electrochemical characterisation of tetra- and octa-substituted oxo(phthalocyaninato)titanium(IV) complexes

The synthesis and electrochemical characterisation of the following oxotitanium tetra-substituted phthalocyanines are reported: 1,(4)-(tetrabenzyloxyphthalocyaninato)titanium(IV) oxide (5a); 1,(4)-{tetrakis[4-(benzyloxy)phenoxy]phthalocyaninato}titanium(IV) oxide (5b); 2,(3)-(tetrabenzyloxyphthalocyaninato)titanium(IV) oxide (6a) and 2,(3)-{tetrakis[4-(benzyloxy)phenoxy]phthalocyaninato}titanium(IV) oxide (6b). The electrochemical characterisation of complexes octa-substituted with 4-(benzyloxy)phenoxy (9b), phenoxy (9c) and tert-butylphenoxy (9d) groups is also reported. The cyclic voltammograms of the complexes exhibit reversible couples I-III and couple IV is quasi-reversible for complexes 5a, 5b, 6a and 6b. The first two reductions are metal-based processes, confirmed by spectroelectrochemistry to be due to Ti^IVPc²⁻/Ti^IIIPc²⁻ and Ti^IIIPc²⁻/Ti^IIPc²⁻ redox processes and the last two reductions are ring-based processes due to Ti^IIPc²⁻/Ti^IIPc³⁻ and Ti^IIPc³⁻/Ti^IIPc⁴⁻. Chronocoulometry confirmed a one-electron transfer at each reduction step. The electrochemistry of the above complexes is also compared to the previously reported 5c, 5d, 6c and 6d.     

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.     

Tyrosine-based poly(m-phenyleneethynylene-p-phenyleneethynylene)s. Helix folding and responsiveness to a base

The Sonogashira-Hagihara polymerization of 3′,5′-diiodo-N-α-tert-butoxycarbonyl-l-tyrosine methyl ester (1) and 3′,5′-diiodo-N-α-tert-butoxycarbonyl-O-methyl-l-tyrosine methyl ester (2) with para-diethynylbenzene (3) was carried out to obtain optically active poly(m-phenyleneethynylene-p-phenyleneethynylene)s [poly(1) and poly(2)] with M_n’s ranging from 9900 to 15,000 in 80-87% yields. Poly(1) exhibited intense CD signals in DMSO and THF, but did not in CH₂Cl₂, indicating that it took a predominantly one-handed helical conformation in the former two solvents. On the other hand, there was no evidence for poly(2) to take a helical structure in these solvents. Poly(1) turned the CD sign at 390 nm from plus to minus in DMSO/H₂O = 9/1 (v/v) by the addition of NaOH. Alkaline hydrolysis of ester moieties of poly(1) and poly(2) gave the corresponding polymers having carboxy groups [poly(1a) and poly(2a)]. Poly(1a) and poly(2a) increased the CD intensity by the addition of NaOH.     

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.     

Synthesis, characterization, and high gas permeability of poly(diarylacetylene)s having fluorenyl groups

Diarylacetylenes having fluorenyl groups and other substituents (trimethylsilyl, t-butyl, bromine, fluorine) (1a-1) were polymerized with TaCl₅-n-Bu₄Sn. Monomers 1a-l produced high molecular weight polymers 2a-l (M_w 5.1 × 10⁵-1.3 × 10⁶) in 12-59% yields. All of the polymers were soluble in common organic solvents, and gave tough free-standing membranes by the solution casting method. The onset temperatures of weight loss of polymers 2a-l in air were over 400 °C, indicating considerably high thermal stability. All the polymer membranes showed high gas permeability; e.g., the oxygen permeability coefficient (PO₂) of 2a was as large as 4800 barrers. Membrane 2d possessing two fluorine atoms at meta and para positions of the phenyl ring showed the highest oxygen permeability (PO₂ = 6600 barrers) among the present polymers.     

Ionic liquid as catalytic and reusable media for cyanoethoxycarbonylation of aldehydes

Various ionic liquids (IL 1-9) based on N-methyl N′-alkyl imidazolium salts were explored as catalytic media in cyanoethoxycarbonylation of various aldehydes. The study revealed that the alkyl chain length and counter ion of the ionic liquid are critical for the product yield. The highest product yield of cyanohydrin carbonate (up to 96%) was obtained with C₅ alkyl chain with Br⁻ as counter ion (IL 3). On the other hand PF₆⁻ as counter ion failed to catalyze the cyanoethoxycarbonylation reaction.     

Synthesis and properties of ornithine- and lysine-based poly(N-propargylamides). Responsiveness of the helical structure to acids

Ornithine- and lysine-based novel N-propargylamides, N-α-tert-butoxycarbonyl-N-δ-fluorenylmethoxycarbonyl-l-ornithine-N′-propargylamide (1), N-α-tert-butoxycarbonyl-N-?-fluorenylmethoxycarbonyl-l-lysine-N′-propargylamide (2), N-α-fluorenylmethoxycarbonyl-N-δ-tert-butoxycarbonyl-l-ornithine-N′-propargylamide (3), and N-α-fluorenylmethoxycarbonyl-N-?-tert-butoxycarbonyl-l-lysine-N′-propargylamide (4) were synthesized and polymerized with a rhodium catalyst. Polymers with moderate molecular weights were obtained in good yields. Poly(1)-poly(4) showed strong Cotton effects in THF, whose sign and wavelength depended on the substituents. They were satisfactorily converted into the corresponding polymers [poly(1a)-poly(4a)] with free amino groups. Poly(1a) and poly(2a) also formed a helix, while poly(3a) and poly(4a) did not. Poly(1a) and poly(2a) decreased the CD intensity by the addition of m- and o-phthalic acids.     

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.     

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.     

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.     

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.     

Effects of internal linkage groups of fluorinated diamine on the optical and dielectric properties of polyimide thin films

To investigate the difference of the trifluoromethyl (CF₃) group and ether group affecting the optical property of fluorinated polyimides (PIs), we prepared 4,4′-bis(4-amino-2-trifluoromethylphenoxy)diphenyl ether (4) with three ether groups and 2,2-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]hexafluoropropane (5) with four CF₃ groups with 2-chloro-5-nitrobenzotrifluoride and 4,4′-dihydroxydiphenyl ether or 2,2-bis(4-hydroxyphenol)hexafluoropropane. Two series of organosoluble and light-colored PIs (4a-4c, 5a-5c) were synthesized from 4 and 5 with various aromatic dianhydrides: 3,3,4,4-benzophenonetetracarboxylic dianhydride (BTDA) (a), 4,4-oxydiphthalic anhydride (ODPA) (b), and 4,4-hexafluoroisopropylidenediphthalic anhydride (6FDA) (c), prepared through a typical two-step polymerization method. These PIs were soluble in amide polar solvents and even in less polar solvents. The glass-transition temperatures (T_g) of 4a-5c were 221-249 °C and the 10% weight-loss temperatures were above 530 °C. Their films had cutoff wavelengths between 339 and 399 nm and yellowness index ranges from 1.95 to 42.60. The dielectric constants estimated from the average refractive indices are 2.59-2.93 (1 MHz). In a comparison of the PI series based on 4, 5, and 4,4′-bis(4-amino-2-trifluoromethylphenoxy)biphenyl (6), we found that the CF₃ group and ether group on the diamine had almost same effect in lowering the color, but the ether group had better thermal stability. The color intensity of the three PI series was lowered in the following order: 6 > 4 > 5. The PI 5c, synthesized from diamine 5 and dianhydride c, had six CF₃ groups in a repeated segment and ether group at the same time, so it exhibited the lightest color among the three series.     

Synthesis and characterization of chiral polythiophenes: Poly [(R)-(−) and (S)-(+)-2-(3′-thienyl)ethyl N-(3″,5″-dinitrobenzoyl)-α-phenylglycinate]

(R)-(−) (1) and (S)-(+)-2-(3′-Thienyl)ethyl N-(3″,5″-dinitrobenzoyl)-α-phenylglycinate (2) monomers were synthesized, characterized, and polymerized in chloroform using FeCl₃ as an oxidizing agent. Molecular weights of 2.6 × 10⁴ and 3.2 × 10⁴ for poly1 and poly2, respectively, were determined by SEC analysis. FTIR spectra of the polymers indicated the coupling of monomers through the α positions. UV-vis spectra showed absorption bands at λ_max = 226 and 423 nm for poly1 and poly2, ascribed to transitions of side groups and polythiophene backbone, respectively. Poly1 and poly2 remained stable up to 210 °C. At higher temperatures, a two step weight loss degradation process was observed for both polymers by TGA analysis. ¹H NMR, in the presence of Eu(tfc)₃, and optical rotation measurements indicate the chiral properties of the monomers 1 ([α]_D²⁸ = −76.2) and 2 ([α]_D²⁸ = +76.0), and the maintenance of chirality after polymerization (poly1 [α]_D²⁸ = −29.0 and poly2 [α]_D²⁸ = +28.4, c = 2.5 in THF). According to scanning electron microscopic analysis, the polymers are highly porous.     

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.     

A facile galvanostatic method for the synthesis of quinoxalinediones

Electrochemical oxidation of catechols (1a-d) has been studied in the presence of N,N-dimethylethylendiamine (3) as a nucleophile in aqueous solutions, using cyclic voltammetry, constant-current coulometry and controlled-potential coulometry. The results indicate that the quinones derived from catechols (2a-d) participate in Michael addition reactions with N,N′-dimethylethylendiamine (3) via the ECECE mechanism to form the corresponding quinoxalinedione derivatives (6a-c).     

Synthesis, characterization and third-order non-linear optical properties of novel fluorene monomers and their cross-conjugated polymers

We designed and synthesized two novel fluorene monomers of D-A-D (donor-acceptor-donor) type (M1 and M2), and their two corresponding polymers (PM1 and PM2) and a copolymer (CPM). These high molecular weight, film-forming polymers were obtained from metal-free, superacid-catalyzed reactions of the monomers with N-phenylisatin. The cubic NLO response (χ⁽³⁾) for these new compounds, in solid thin films, was measured through the use of third-harmonic generation (THG) Maker-Fringes technique at IR wavelengths given values of the order of 10⁻¹² esu from which, the corresponding second hyperpolarizabilities (γ) were estimated to be of the order of 10⁻³³ esu for monomers and 10⁻³¹ esu for polymers. Second hyperpolarizabilities have also been estimated theoretically at B3LYP/6-31G(d) level of theory in gas phase and related with the electronic structure of the synthesized molecules.