Synthesis and properties of polyether nitrile copolymers with pendant methyl groups

Polyether nitrile and polyether nitrile copolymers with pendant methyl groups were prepared by the nucleophilic substitution reaction of 2,6^′-dichlorobenzonitrile with hydroquinone (HQ) and with varying mole proportions of HQ and methyl hydroquinone (MeHQ) using N-methyl pyrrolidone solvent in the presence of anhydrous K₂CO₃. The polymers were characterised by different physico-chemical techniques. The crystallinity of the polymers was found to decrease with increase in concentration of the MeHQ units in the polymer. Thermogravimetric studies showed that all the polymers were stable up to 450 °C with a char yield above 50% at 900 °C in N₂ atmosphere. The glass transition temperature and activation energy of the polymers was found to increase with increase in concentration of the MeHQ units in the polymer.     

Reactions of platinum nitrile complexes with cyclotriphosphazenes containing pyridylalkylamino groups

Reactions of platinum(II) and platinum(IV) nitrile complexes with polydentate ligands, such as pentaphenoxy(2-pyridylmethylamino)cyclotriphosphazene, pentaphenoxy(3-pyridylmethylamino)cyclotriphosphazene, and pentaphenoxy(2-pyridylethylamino)cyclotriphosphazene, were studied. Platinum(IV) is reduced to platinum(II) upon complex formation; the pyridine and alkylamine nitrogen atoms coordinate to platinum(II) to form chelate rings. The compounds obtained were characterized by ¹H and ³¹P NMR and IR spectroscopy, FAB mass spectrometry, and other methods.     

Titanium "constrained geometry" complexes with pendant arene groups

The synthesis of the proligands C(5)Me(4)HSiMe(2)N(H)R) (R = CMe(2)Ph 1, 2-C(6)H(4)Ph 2) was accomplished via a straightforward salt metathesis reaction of the appropriate lithium amide and ClSiMe(2)(C(5)Me(5)H). Generation of the dilithio salt and reaction with TiCl(3)·(THF)(3) followed by oxidation gave C(5)Me(4)SiMe(2)N(C(6)H(4)Ph)TiCl(2) (3) in low yield. In contrast, deprotonation of 1 and 2 and reaction with (Me(2)N)(2)TiCl(2) afforded C(5)Me(4)(SiMe(2)NR)Ti(NMe(2))(2) (R = CMe(2)Ph 4, 2-C(6)H(4)Ph 5), respectively, in good yields Treatment with MeI gave the analogs C(5)Me(4)(SiMe(2)NR)TiI(2) (R = CMe(2)Ph 6, 2-C(6)H(4)Ph 7). Reduction of 7 with potassium graphite afforded C(5)Me(4)(SiMe(2)NC(6)H(4)Ph)Ti 8. Treatment of 6 and 7 with MeMgBr afforded C(5)Me(4)(SiMe(2)NR)TiMe(2) (R = CMe(2)Ph 9, 2-C(6)H(4)Ph 10). Complexes 9 and 10 in combination with the activator [Ph(3)C][B(C(6)F(5))(4)] catalyzed the polymerization of styrene and ethylene. Copolymerization was also investigated. While the catalyst derived from 10 showed poor activity, compound 9 showed markedly higher activity than 10 and (C(5)Me(4))SiMe(2)(NtBu)]TiMe(2).     

Stability constants of metal complexes of macrocyclic ligands with pendant donor groups

Abstract

In our studies of the stability constants of metal complexes, we have investigated a number of macrocyclic ligands with pendant donor groups. The ligands are characterized by the fact that they have nitrogen donors in the macrocyclic ring and oxygen or sulfur donors in the pendant arms. These ligands represent seven different macrocycles, and by varying the pendant donor groups, ten different ligands are indicated. The affinities of these ligands for fifteen metal ions will be described. The Fe(III) complex of triazanonane with o-hydroxypyridyl or o-hydroxybenzyl pendant donor groups are the most stable ferric complexes ever reported. The In(III) complex of triazacyclononane with pendant mercaptoethyl donor groups, is exceptionally stable. Also, the Ca(II) complex of DOTA probably has the highest stability of any calcium(II) complex. These, and other comparisons will be made on the basis of the thermodynamic stability constant data for the ligands described.     

Group 4 metallocene complexes with non-bridged and tetramethyldisiloxane-bridged methyl-phenyl-cyclopentadienyl ligands: synthesis, characterization and olefin polymerization studies

The non-vicinal methyl-phenyl-substituted zirconocene dichlorides meso-and rac-[Zr{η⁵-(1-Ph-3-Me-C₅H₃)}₂Cl₂] and [Zr(η⁵-C₅H₅){η⁵-(1-Ph-3-Me-C₅H₃)}Cl₂] have been isolated by transmetallation of the lithium salt Li(1-Ph-3-Me-C₅H₃) to ZrCl₄(THF)₂ and [Zr(η⁵-C₅H₅)Cl₃ · DME] (DME = dimethoxyethane), respectively. Similar transmetallation of the lithium salt Li₂[(Me-Ph-C₅H₂SiMe₂)₂O] to MCl₄ gave the ansa-metallocenes [M{η⁵-(Me-Ph-C₅H₂SiMe₂)₂O}Cl₂] (M = Zr, Hf) for which the meso- and rac-diastereomers were separated. The dimethyl and dibenzyl derivatives of these metallocenes were also prepared and the structure of all of these compounds determined by NMR spectroscopy. The molecular structure of rac-[Zr{η⁵-(2-Me-4-Ph-C₅H₂SiMe₂)₂O}Cl₂] was determined by single crystal X-ray diffraction methods. The activity of the dichlorometallocenes/MAO catalysts for ethene and propene polymerization was evaluated.     

Aromatic polyisophthalamides with N-benzylidene pendant groups

A new series of modified polyisophthalamides bearing N-benzylidene pendant groups was prepared by reacting various aromatic diamines with 5-(N-benzylidene) isophthalic acid. The latter was synthesized from the reaction of 5-aminoisophthalic acid with benzaldehyde and characterized by IR and ¹H-NMR spectroscopy. Triphenyl phosphite and pyridine was used as condensing agents for preparing polyamides. In addition, the corresponding unsubstituted polyisophthalamides were prepared under identical experimental conditions for comparative purposes. Characterization of modified polyamides was accomplished by IR as well as inherent viscosity measurements. They showed a slightly lower solubility in various media than the corresponding unsubstituted polyamides. The cured modified polyamides displayed significantly higher thermal stability than the cured unsubstituted polyamides. They were stable up to 355–308°C in N₂ or air and afforded anaerobic char yield of 66–61% at 800°C. © 1992 John Wiley & Sons, Inc.     

Aromatic polyisophthalamides with iminobenzoyl pendant groups

Polyisophthalamides were prepared from aromatic diamines and 5-iminobenzoylisophthalic acid by the Yamazaki method of direct polyamidation catalyzed by triphenylphosphite. The properties of the polymers were measured and compared with the analogous unsubstituted polyisophthalamides. The incorporation of one iminobenzoyl pendant group per repeating unit gave rise to better solubility in strongly polar solvents. Higher content of amide groups per repeating unit allowed the modified polymers to absorb moisture to a greater extent than the parent polyisophthalamides. The glass transition temperatures were raised 20–30 by the presence of the pendant groups and they ranged from 290 to 317°. On the contrary, the substituted polymers showed lower initial decomposition temperatures, as measured by TGA, all of them beginning to decompose at about 410°. The mechanical properties of polymer films seemed not to be greatly affected by the pendant groups and only small differences were observed between substituted and unsubstituted polymers.     

Photoactive Eu(III) and Tb(III) complexes of calix[4]arenes with pyridine-N-oxide pendant groups

Two calix[4]arenes with four 2-pyridyhnethyl-l-oxide pendant groups at the lower rim have been synthesized, and their Tb(III) and Eu(III) complexes are fluorescent upon UV light excitation at 312 nm. The complexes are not stable in aqueous solution, completely losing their luminescent properties.     

Novel photocurable polyethers with methacrylate pendant groups

A method for preparation of novel fast photocurable polyethers is described. Thus, novel polyether, poly(3-methacryloxy propylene oxide) was obtained in low molecular weights (M_n: 1700 Da) by cationic ring opening polymerization of the epoxy group of glycidyl methacrylate (GMA) in presence of trimethylsilyl trifilate (TMSTF) as initiator. Copolymerization of the monomer with cyclohexene oxide (CHO) in the same reaction conditions yielded copolyethers with methacylate pendant groups. A series of copolymers with various GMA contents (10-100% mol/mol) were prepared using CHO as diluting comonomer. ¹H NMR spectra showed that oxirane function of GMA is somewhat less reactive than CHO. Having methacylate pendant groups the resulting waxy polymers underwent rapid photocrosslinking to give glassy hard materials upon UV irradiation at 350 nm, in the presence of benzoin as photoinitiator. Photocuring abilities of the copolymers were investigated by real time FT-IR using in dimethoxyethane solutions (14.7% w/w). The results showed that, 60% double bonds disappear within 150-300 s by irradiation of diluted copolymer solutions with Xenon lamp (150 W).     

Synthesis and luminescence of poly(phenylacetylene)s with pendant iridium complexes and carbazole groups

Poly(phenylacetylene)s containing pendant phosphorescent iridium complexes have been synthesized and their electrochemical, photo‐ and electroluminescent properties studied. The polymers have been synthesized by rhodium‐catalyzed copolymerization of 9‐(4‐ethynylphenyl)carbazole (CzPA) and phenylacetylenes (C∧N)₂Ir(κ²‐O,O′‐MeC(O)CHC(O)C₆H₄C?CH‐4) (C∧N = κ²‐N,C¹‐2‐(pyridin‐2‐yl)phenyl (Ir^ppyPA) or κ²‐N,C¹‐2‐(isoquinolin‐1‐yl)phenyl (Ir^piqPA)). In addition, organic poly(phenylacetylene)s with pendant carbazole groups have been synthesized by rhodium‐catalyzed copolymerization of CzPA and 1‐ethynyl‐4‐pentylbenzene. Complex (C∧N)₂Ir(κ²‐O,O′‐MeC(O)CHC(O)Ph) (Ir^piqPh; C∧N = 2‐(isoquinolin‐1‐yl)phenyl‐κ²‐N,C¹) was prepared and characterized. While the copolymers of the Ir^ppy series were weakly phosphorescent, those of the Ir^piq series displayed at room temperature intense emissions from the carbazole (fluorescence) and iridium (phosphorescence) emitters, being the latter dominant when the spectra were recorded using polymer films. Triple layer OLED devices employing copolymers of the Ir^piq series or the model complex Ir^piqPh yielded electroluminescence with an emission spectra originating from the iridium complex and maximum external quantum efficiencies of 0.46% and 2.99%, respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3744–3757, 2010     

Europium(III) macrocyclic complexes with alcohol pendant groups as chemical exchange saturation transfer agents

Paramagnetic lanthanide(III) complexes that contain hyperfine-shifted exchangeable protons offer considerable advantages over diamagnetic molecules as chemical exchange saturation transfer (CEST) agents for MRI. As part of a program to investigate avenues to improve the sensitivity of such agents, the CEST characteristics of europium(III) macrocyclic complexes having appended hydroxyethyl groups were investigated. The CEST spectrum of the asymmetrical complex, EuCNPHC3+, shows five distinct peaks for each magnetically nonequivalent exchangeable proton in the molecule. The CEST spectra of this complex were fitted to NMR Bloch theory to yield exchange rates between each of six exchanging proton pools (five on the agent plus bulk water). Exchange between the Eu3+-bound hydroxyl protons and bulk water protons was slow in dry acetonitrile but accelerated incrementally upon stepwise addition of water. In pure water, exchange was too fast to observe a CEST effect. The utility of this class of europium(III) complex for CEST imaging applications is ultimately limited by the small chemical shifts induced by the hydroxyl-appended ligands of this type and the resulting small Deltaomega values for the exchangeable hydroxyl protons.     

Synthesis of dibenzocrown ethers with pendant thioamide groups

The synthesis of eighteen crown ether compounds with pendant thioamide, N-alkylthioamide, and N,N-dialkylthioamide groups is reported. The new crown ether compounds are obtained by one-step reactions from the corresponding sym-dibenzo-16-crown-5-oxyacetamides and sym-(propyl)dibenzo-16-crown-5-oxyacetamides with Lawesson's reagent.     

Synthesis of new terpolymers with heterocyclic pendant groups

Chemical modifications of polyacrylonitrile (PAN), an inexpensive and commercial homopolymer, to obtain terpolymers containing 1,2,4 or 1,3,4 oxadiazolic pendant groups are described. These new materials are physically and spectroscopically characterized.     

Photohole screening effects in polythiophenes with pendant groups

We compare two mechanisms that dominate the temperature-dependent changes in electronic structure for poly(3-hexylthiophene-2,5 diyl) (P3HT). Structural changes in the relative orientation and configuration of the aromatic ring backbone are observed to occur over a wide range in temperature and affect the local final state screening in photoemission. There are also changes in conductivity and carrier concentration at lower temperatures leading to altered long-range intramolecular screening of photoholes and final state effects that affect excitation spectroscopies including photoemission. For polyethylenedioxythiophene (PEDOT), temperature-dependent changes in the structure and configuration of the polymer backbone are not as significant, although temperature-dependent final state effects are observed.     

Miscibility of methacrylic polymers with different pendant groups

Miscibility is not always common in blends of homologous polymers that differ in structure but possess the same functional groups. In this study, two methacrylate polymers, which differ by a methylene unit, were found to be miscible in accordance with morphology and thermal transition criteria of polymer miscibility. Miscibility of the pair poly(phenyl methacrylate) and poly‐(benzyl methacrylate) is quite unusual. Interactions between carbonyl units and phenyl rings of these two polymers are discussed. FT‐IR results indicate an intimate mixing state between these two polymers leading to mutual influence in the absorbance wavenumbers for C=O, ether groups and, possibly, phenyl rings.     

Polyimide-polydimethylsiloxane copolymers containing nitrile groups

A novel series of nitrile-containing polyimide-polydimethylsiloxane copolymers was prepared by polycondensation reaction of 4,4′-oxydiphthalic anhydride with a mixture of an aromatic diamine, namely 2,6-bis(3-aminophenoxy)benzonitrile, and bis(aminopropyl)oligodimethylsiloxane of controlled molecular weight, in different ratios. The polymers were easily soluble in polar organic solvents, such as N-methylpyrrolidone, N,N-dimethylformamide as well as in less polar solvents such as chloroform, and can be cast from solution into thin flexible films. The inherent viscosity was in the range of 0.43-0.55 dL/g. The polymers showed good thermal stability, the decomposition temperature being above 430 °C. They exhibited a glass transition temperature in the range of 149-219 °C, with reasonable interval between glass transition temperature and decomposition temperature. The surface morphology was investigated by scanning electron microscopy. The water dynamic contact angles were measured by tensiometric method. The free surface energy was evaluated based on Owens and Wendt equation. A composite film based on a polyimide-polydimethylsiloxane copolymer and pyrite ash powder has been prepared and its nanoactuation has been investigated.     

Synthesis of hydronaphthalenes through coupling of enyne-carbonyl compounds that contain pendant alkane groups with Fischer carbene complexes

The coupling of enyne-carbonyl compounds that contain pendant alkene groups with Fischer carbene complexes to afford furans that contain pendant alkene groups is described. Subsequent intramolecular Diels-Alder reactions are effective in selected cases, resulting in hydronaphthalene systems after dehydration. Although the Diels-Alder event is thermodynamically unfavorable, the overall transformation of alkene-furans to dihydronaphthalenes is a favorable process.     

Developing some functional group chemistry at the Group 4 bent metallocene frameworks

Four series of reactions were explored that are aimed at the development of a functional group chemistry at the sensitive bent metallocenes of the Group 4 metals. First, we have tested and employed the olefin metathesis reaction. Two [C₅H₄-(CH₂)_n-CHCH₂]₂ZrCl₂ complexes (with n=4 and n=1) were treated with the Cl₂(PCy₃)₂RuCHPh catalyst in dilute solution. Intramolecular metathesis took place readily with liberation of ethene to yield the corresponding ansa-metallocene complexes [C₅H₄-(CH₂)_n-CHCH-(CH₂)_n-C₅H₄]ZrCl₂ that were isolated in ca. 28% (n=4, trans-CHCH-) or ca. 50% (n=1, cis-CHCH-) yield. Intermolecular olefin metathesis could also be effected using either a first or a second generation Grubbs catalyst to metathetically couple a variety of (L)Cl₂M(C₅H₄-CH₂CHCH₂)-type titanium or zirconium complexes to yield the respective dimetallic products. Alkenyl substituents were attached at the ligand stage at the indenyl 2-positions by means of a nickel-catalyzed cross-coupling reaction. Transmetallation eventually gave the bis(2-alkenylindenyl)ZrCl₂ complexes. Photolysis of three examples of this type of complexes (with 1-alkenyl substituents being methyl, cyclohexyl, or phenyl) resulted in a very efficient intramolecular [2 + 2] cycloaddition to yield the respective substituted cyclobutylene-bridged ansa-metallocenes. These complexes were MAO activated to give very active homogeneous metallocene catalysts for, e.g., ethene/1-octene copolymerization. The corresponding (s-trans-butadiene)-ansa-zirconocene complexes feature a pronounced C-H/phenylene π-interaction that probably helps to stabilize the s-trans-diene complex relative to its s-cis-isomer. Deprotonation of 7-dialkylaminofulvenes provides an easy access to enamino-cyclopentadienides. Transmetallation under carefully controlled conditions gave the respective bis(enamino-C₅H₄)ZrCl₂ complexes. Their treatment with a catalytic amount of a Lewis acid (TiCl₄) or a Brønsted-acid ([HNMe₂Ph⁺][BPh₄⁻]) led to a rapid intramolecular Mannich-type carbon-carbon coupling reaction that gave novel, very rigid C₃-bridged, -NR₂ functionalized ansa-metallocene systems. The analogous, readily performed Mannich-coupling reaction starting from 1,1^′-diacetylferrocene and a variety of secondary amines provided an interesting and useful novel entry to [3]ferrocenophane systems. Catalytic hydrogenation of the unsaturated bridge followed by additional functionalization opened a novel pathway to ferrocenophane-based chelate ligands (some optically active) for stereoselective catalytic transformations. Eventually, examples of direct attack of the electrophilic boranes B(C₆F₅)₃ or HB(C₆F₅)₂, respectively, to the Cp rings of bis(cyclopentadienyl)zirconacyclopentadienes are described, leading to novel types of Cp-borylated Group 4 metallocene complexes.