In situ synthesis and structure of FeCl4(4,4′-diethyl-4,4′-bipyh) (bipy = bipyridine)

A novel viologen(4,4′-bipyridinium)-based compound FeCl₄(4,4′-diethyl-4,4′-bipyH) (1) (bipy = bipyridine), in which 4,4′-diethyl-4,4′-bipyH (MQ ⁺) was generated in situ, is synthesized via the hydrothermal reaction and structurally characterized by single crystal X-ray diffraction. The crystal structure analysis reveals that the title compound features an isolated structure based on 4,4′-diethyl-4,4′-bipyH moieties and an iron atom terminally bound by four chlorine atoms. The 4,4′-diethyl-4,4′-bipyH moieties and (FeCl₄)^? anions are interconnected by hydrogen bonds to form a 3D supramolecular framework.     

Kondesationen mit hydrazin-N,N′-dicarbonsäurediamidin,XXIII [1] fluorierte β-diketone als reaktionspartner

Application of a 30% aqueous potassium carbonate solution for the condensation of 1,2-hydrazinedicaboxamidine with 1,1,1-trifluoro-2,4-pentanedione leads to the formation of 4,4′-dimethyl-6,6′-bis(trifluoromethyl)-2,2′-hydrazopyrimidine, with 1,1,1-trifluoro-2,4-hexanedione to 4,4′-diethyl-6,6′-bis-(trifluoromethyl)-2,2′-hydrazopyrimidine. 2-Guanidinoamino-4-methyl-6-trifluoromethylpyridine formed as an intermediate in this reacton may be isolated, while 4-ethyl-2-guanidinoamino-6-trifluoromethylpyrimidine undergoes cyclization to yield 2-amino-5-ethyl-7-trifluoromethyl-s-triazolo[1,5-a]pyrimidine.     

Chromium(VI) oxide-mediated oxidation of polyalkyl-polypyridines to polypyridine-polycarboxylic acids with periodic acid

4,4′-Dicarboxy-2,2′-bipyridine was synthesized quantitatively by chromium(VI) oxide-mediated oxidation of 4,4′-dimethyl-2,2′-bipyridine or 4,4′-diethyl-2,2′-bipyridine with periodic acid as the terminal oxidant in sulfuric acid. 5,5′-Dicarboxy-2,2′-bipyridine and 6,6’-dicarboxy-2,2′-bipyridine were also synthesized by the method from the corresponding dimethyl bipyridines in excellent yields. 4,4′,4″-Tricarboxy-2,2′:6′,2″-terpyridine was obtained in 80% yield from 4,4′,4″-triethyl-2,2′:6′,2″-terpyridine, and 4,4′,4″,4′″-tetracarboxy-2,2′:6′,2″:6″,2′″-quaterpyridine was obtained in 72% yield from 4,4′,4″,4′″-tetraethyl-2,2′:6′,2″:6″,2′″-quaterpyridine by the same procedure.     

Pyrromethene–BF2 complexes as laser dyes:1.

Condensations between 3-X-2,4-dimethylpyrroles (X = H, CH₃, C₂H₅, and CO₂C₂H₅) and acyl chlorides gave derivatives of 3,5,3′,5′-tetramethylpyrromethene (isolated as their hydrochloride salts): 6-methyl, 6-ethyl, 4,4′,6-trimethyl, 4,4′-diethyl-6-methyl, and 4,4′-dicarboethoxy-6-ethyl derivatives for conversion on treatment with boron trifluoride to 1,3,5,7-tetramethylpyrromethene–BF₂ complex (TMP–BF₂) and its 8-methyl (PMP–BF₂), 8-ethyl, 2,6,8-trimethyl (HMP–BF₂),2,6,-diethyl-8-methyl (PMDEP–BF₂), and 2,6-dicarboethoxy-8-ethyl derivatives. Chlorosulfonation converted, 1,3,5,7,8-pentamethylpyrromethene–BF₂ complex to its 2,6-disulfonic acid isolated as the lithium, sodium (PMPDS–BF₂), potassium, rubidium, cesium, ammonium, and tetramethylammonium disulfonate salts and the methyl disulfonate ester. Sodium 1,3,5,7-tetramethyl-8-ethylpyrromethene-2,6-disulfonate–BF₂ complex was obtained from the 8-ethyl derivative of TMP–BF₂. Nitration and bromination converted PMP–BF₂ to its 2,6-dinitro-(PMDNP–BF₂) and 2,6-dibromo- derivatives. The time required for loss of fluorescence by irradiation from a sunlamp showed the following order for P–BF₂ compounds (10⁻³ to 10⁻⁴ M) in ethanol: PMPDS–BF₂, 7 weeks; PMP–BF₂, 5 days; PMDNP–BF₂, 72 h; HMP–BF₂, 70 h; and PMDEP–BF₂, 65 h. Under similar irradiation PMPDS–BF₂ in water lost fluorescence after 55 h. The dibromo derivative was inactive, but each of the other pyrromethene–BF₂ complexes under flashlamp excitation showed broadband laser activity in the region λ 530–580 nm. In methanol PMPDS–BF₂ was six times more resistant to degradation by flashlamp pulses than was observed for Rhodamine-6G (R-6G). An improvement (up to 66%) in the laser power efficiency of PMPDS–BF₂ (10⁻⁴ M in methanol) in the presence of caffeine (a filter for light <300 nm) was dependent on flashlamp pulse width (2.0 to 7.0 μsec).     

Structure–property correlations of sulfonated polyimides. II. Effect of substituent groups on membrane properties

A series of sulfonated polyimides with increasing alkyl substituents in the o‐position to diamine were synthesized from 4,4′‐methylene dianiline, 4,4′‐diamine‐3,3′‐dimethyl‐diphenylmethane, and 4,4′‐diamine‐3,5,3′,5′‐tetraethyl‐diphenylmethane using 1,4,5,8‐naphthalenetetracarboxylic dianhydride and perylenetetracarboxylic dianhydride by chemical imidization method. 4,4′‐Diaminobiphenyl 2,2′‐disulfonic acid was used as sulfonated diamine. The variation in the membrane properties with increase in substitution was analyzed. Solubility increased with substitution whereas the thermal stability decreased with increase in substitution. Ion exchange capacity and water uptake reduced with increase in substitution because of the low sulfonic acid content at a particular weight due to the increased molecular weight of the repeating unit. The conductivity of the substituted diamines was higher than the unsubstituted diamines at higher temperature regardless of low ion exchange capacity and water uptake. The increase in conductivity with increase in temperature was more rapid in polyimides than in Nafion®115. Hydrolytic stability of the polyimides with substitution is more than the unsubstituted diamines. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3621–3630, 2004     

Manganese(III) acetate‐catalyzed synthesis of polyguaiacol

Polyguaiacol was synthesized in the mixtures of water and various organic solvents using manganese(III) acetate as a new catalyst for radical polymerization and a biomimetic model for manganese peroxidase. Aqueous solutions of 30–70% (v/v) acetonitrile, 1,4‐dioxane, and methanol were used as model solvent mixtures. The polymer yield in the methanol (<30%) solution was lower than that in the acetonitrile or 1,4‐dioxane solution (60–90%). The average molecular weight of the polymer was also lowest in the methanol solution. Difference UV absorption spectroscopy analysis revealed that nonhydrated guaiacol clusters were found to be dominant in acetonitrile and 1,4‐dioxane solutions, especially when the content of 1,4‐dioxane was 50% (v/v) or higher. In the methanol solution, only the hydrated guaiacol clusters were observed. From the comparison of ¹H NMR data for polyguaiacol and products of guaiacol oxidation by manganese(III) acetate, 3‐(4‐hydroxy‐3‐methoxy‐phenyl)‐5,3′‐dimethoxy‐4,4′‐biphenol and a mixture of 5‐(4‐hydroxy‐3‐methoxyphenyl)‐3,3′‐dimethoxy‐4,4′‐biphenoquinone and 3‐(4‐hydroxy‐3‐methoxyphenyl)‐5,3′‐dimethoxy‐4,4′‐biphenoquinone were found to be the major structural units of polyguaiacol. Water molecule is not involved in the formation of these compounds. Therefore, the polymerization should take place readily not in methanol but in acetonitrile and 1,4‐dioxane solutions. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6009–6015, 2008     

Kinetics of Uncatalyzed Reactions of 2,4′‐ and 4,4′‐Diphenylmethane‐Diisocyanate with Primary and Secondary Alcohols

The kinetics of the uncatalyzed reaction of an industrially important 50/50 blend of isomers of 4,4′‐diphenylmethane‐diisocyanate (4,4‐MDI) and 2,4′‐diphenylmethane‐diisocyanate (2,4′‐MDI) with primary and secondary alcohols was studied using high‐performance liquid chromatography coupled with photodiode array detector. The alcohols such as 1‐propanol, 2‐propanol, 1‐hexanol, 2‐hexanol, 3‐hexanol, 1‐methoxy‐2‐propanol, and 3‐methoxy‐1‐propanol were used in high molar excess to diisocyanate in toluene at 80°C, and pseudo–first‐order dependences on the concentrations of 4,4′‐MDI and 2,4′‐MDI were found. Appropriate treatments of the kinetic data allowed us to determine the corresponding pseudo–first‐order rate constants. According to the kinetic results, the reactivity of the isocyanate group in the para‐position is about four to six times higher than that of the ortho‐positioned isocyanate group, depending on the reacting alcohol. Furthermore, the substitution effect, i.e., change in the reactivity of the free isocyanate group after the other has been reacted, was found for both 4,4′‐MDI and 2,4′‐MDI isomers. The differences in the reactivities of the isocyanate groups of 2,4′‐MDI and 4,4′‐MDI isomers before and after one of two isocyanate groups has been reacted are explained in terms of partial positive charges on the corresponding carbonyl carbon atom calculated by high‐level quantum chemical calculations. In addition, the UV‐spectral properties of the products obtained by quenching the reaction mixture with methanol are also discussed in light of practical implications.     

Transient absorption spectra of pinacyanol and cyanine photoisomers obtained with a sync-pumped picosecond dye laser and independently tunable probe light

We have measured the absorption difference spectra and quantum yields of photoisomers of pinacyanol iodide and 1,1′-diethyl-4,4′-cyanine iodide on a picosecond time scale using syne-pumped picosecond dye laser pulses for excitation and independently tunable analyzing light.     

Oxidation of 2,6-Di-tert-butylphenol by dioxygen catalyzed by tetrasodium phthalocyaninatocobalt(II) tetrasulfonate in aqueous micellar media

The oxidation of 2,6-di-tert-butylphenol by dioxygen has been investigated in aqueous micellar aggregates of cetyltrimethylammonium bromide (CTAB) using tetrasodium phthalocyaninatocobalt(II) tetrasulfonate (CoPcTsNa₄) as catalyst. The CTAB/CoPcTsNa4 system showed enhanced catalytic activity in the oxidation of 2,6-di-tert-butylphenol compared to that observed in the oxidation reaction in the absence of CTAB. 2,6-Di-tert-butyl-1,4-benzoquinone and 3,5,3′,5′-tetra-tert-butyl-4,4-diphenoquinone were identified as reaction products. The initial rate constants of auto-oxidation reaction was found to increase with increasing the pH range from 7.0 to 13.0. The rate constants k_obs of auto-oxidation reaction showed linear dependence on catalyst concentration. The rate of auto-oxidation reaction was found to fit a Michealis-Menten kinetic model for the saturation of catalyst sites with increasing 2,6-di-tert-butylphenol concentration and dioxygen pressure. Tetrasodium phthalocyaninatocobalt(II) tetrasulfonate in aqueous micellar solution of CTAB was found to be mainly monomeric.     

Oxidation of Benzylic Methyl Groups by Supported MnO2/Al2O3 Oxidant

An investigation of benzylic oxidations with manganese dioxide supported on neutral alumina has been carried out. Isolation of intermediated products, which is possible in some cases, gives strong support for the reaction mechanism proposed. With 2,6-di-tert-butyl-4-methylphenol, 4,4′-dihydroxy-3,5,3′,5′-tetra-tert-butyldiphenylmethane,2,6-di-tert-butylphenol and 4-methyl-phenol, selective formation of essentially a single product in excellent yield was obtained.     

On the methylation of 5-(4-alkoxyphenyl)-15-(4-pyridyl)porphyrins

Mixed condensation of 3,3′-diethyl-4,4′-dimethyl-2,2′-dipyrrolylmethane 1 with 4-formylpyridine 2 and 4-alkoxybenzaldehyde 3 in acid medium and subsequent oxidation of the reaction mixture with DDQ gives, among other compounds, title compound 5 . An efficient methylation procedure of the pyridyl group in 5-(4-alkyoxyphenyl)-15-(4-pyridyl)porphyrins is described. Mixed condensation of 1 with N-methyl-4-formylpyridinium salt 9 and 3 yields among other compounds 5-(4-N-methylpyridiniumiodide)porphyrin 10 .     

Oxidation of 3,5,3',5'-Tetra-tert-butyl-4,4'-dihydroxybiphenyl with Atmospheric Oxygen in the Absence of Base Catalysts

Use of dimethylformamide as solvent and preliminary addition of 3,5,3',5'-tetra-tert-butyl-4,4'-diphenoquinone allow oxidation of 3,5,3',5'-tetra-tert-butyl-4,4'-dihydroxybiphenyl with atmospheric oxygen to be efficiently performed in the absence of base catalysts.     

Steroidal heterocycles. 15. 4,4-Dialkyl-delta 5-3-oxosteroids, 1,4'-spiro [cycloalkyl-delta 5-3-oxo-steroids] and derivatives

Homologs of 17-hydroxy-4,4-17α-trimethyl-3-oxo-androst-5-ene-2α-carbonitrile ( 6d ), such as the 4,4-diethyl-( 6a ), 4,4-cyclopentyl-( 6c ) and 4,4-cyclohexyl-( 6b ) analogs were synthesized.     

Substituted 2,2′‐Bis(2‐oxidobenzylideneamino)‐4,4′‐dimethyl‐1,1′‐biphenyl Complexes of Zinc

The condensation reaction of 2,2′‐diamino‐4,4′‐dimethyl‐6,6'‐dibromo‐1,1′‐biphenyl with 2‐hydroxybenzaldehyde as well as 5‐methoxy‐, 4‐methoxy‐, and 3‐methoxy‐2‐hydroxybenzaldehyde yields 2,2′‐bis(salicylideneamino)‐4,4′‐dimethyl‐6,6′‐dibromo‐1,1′‐biphenyl ( 1a ) as well as the 5‐, 4‐, and 3‐methoxy‐substituted derivatives 1b , 1c , and 1d , respectively. Deprotonation of substituted 2,2′‐bis(salicylideneamino)‐4,4′‐dimethyl‐1,1′‐biphenyls with diethylzinc yields the corresponding substituted zinc 2,2′‐bis(2‐oxidobenzylideneamino)‐4,4′‐dimethyl‐1,1′‐biphenyls ( 2 ) or zinc 2,2′‐bis(2‐oxidobenzylideneamino)‐4,4′‐dimethyl‐6,6′‐dibromo‐1,1′‐biphenyls ( 3 ). Recrystallization from a mixture of CH₂Cl₂ and methanol can lead to the formation of methanol adducts. The methanol ligands can either bind as Lewis base to the central zinc atom or as Lewis acid via a weak O–H ··· O hydrogen bridge to a phenoxide moiety. Methanol‐free complexes precipitate as dimers with central Zn₂O₂ rings.     

Synthesis and characterization of poly(arylene ether sulfone) copolymers with sulfonimide side groups for a proton‐exchange membrane

A sulfonimide‐containing comonomer derived from 4,4′‐dichlorodiphenylsulfone was synthesized and copolymerized with 4,4′‐dichlorodiphenylsulfone and 4,4′‐biphenol to prepare sulfonimide‐containing poly(arylene ether sulfone) random copolymers (BPSIs). These copolymers showed slightly higher water uptake than disulfonated poly(arylene ether sulfone) copolymer (BPSH) controls, but their proton‐conductivity values were very comparable to those of the BPSH series with similar ion contents. The proton conductivity increased with the temperature for both systems. For samples with 30 mol % ionic groups, BPSI showed less temperature dependence in proton conductivity and slightly higher methanol permeability in comparison with BPSH. The thermal characterization of the sulfonimide copolymers showed that both the acid and salt forms were stable up to 250 °C under a nitrogen atmosphere. The results suggested that the presumed enhanced stability of the sulfonimide systems did not translate into higher protonic conductivity in liquid water. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6007–6014, 2006     

Preparation and photophysics of polyimide/silica organic/inorganic hybrid composites

In this work, polyimide/silica hybrid composites were prepared by the sol-gel reaction of tetraethoxysilane(TEOS) and the thermal imidization of poly(amic acid) from 3,3′,4,4′-biphenyltetracarboxylic dianhydride(BPDA) and 4,4′-oxydianiline(ODA), and their photophysical properties were investigated using a fluorescence spectroscopy. It was found that the intrinsic fluorescence of poly(4,4′-oxydiphenylene-3,3′4,4′-biphenyltetracarboximide)(BPDA-ODA) such as emission intensity and emission wavelength depends strongly on the changes in the molecular conformations during the sol-gel reaction and the thermal imidization. In conclusion, we found that the fluorescence spectroscopy can provide an insight into how the intermolecular or intramolecular interaction of polyimide in the hybrid composite system is affected by the silica contents, depending on the sample states.     

Trennung und absolute Konfiguration der C(8)-epimeren (all-E)-Neochrome (Trollichrome) und -Dinochrome

Separation and Absolute Configuration of the C(8)-Epimeric (app-E)-Neochromes (Trollichromes) and -Dinochromes The C(8′)-epimers of (all-E)-neochrome were separated by HPLC and carefully characterized. The faster eluted isomer, m.p. 197.8–198.3°, is shown to have structure 3 ((3S,5R,6R,3′S,5′R,8′R)-5′,8′-epoxy-6,7-dodehydro-5,6,5′,8′-tetrahydro-β,β-carotene-3,5,3′-triol). To the other isomer, m.p. 195-195.5°, we assign structure 6 , ((3S,5R,6R,3′S,5′R,8′R)-5′,8′-epoxy-6,7-didehydro-5,6,5′,8′-tetrahydro-β,β-carotene-3,5,3′-triol). The already known epimeric dinochromes (= 3-O-acetylneochromes) can now be formulated as 4 and 5 , (‘epimer 1’ and its trimethylsilyl ether) and 7 and 8 , (‘epimer 2’ and its trimethylsilyl ether), respectively.     

On the long-lived transient absorption observed in nanosecond laser photolysis studies of two polymethine cyanine dyes

It is shown that the long-lived transient absorption which is observed when solutions of cryptocyanine and DDI (1, 1′-diethyl-2, 2′-dicarbocyanine iodide) in methanol and other alcohols are exposed to nanosecond ruby laser pulses arises from a photoproduct whose formation requires consecutive absorption of two photons.     

Pyrromethene–BF2 complexes as laser dyes: 2

Pyrromethene–BF₂ complexes (P–BF₂) 7 were obtained from α-unsubstituted pyrroles 5 by acylation and condensation to give intermediate pyrromethene hydrohalides 6 followed by treatment with boron trifluoride etherate. Conversion of ethyl α-pyrrolecarboxylates 4 to α-unsubstituted pyrroles 5 was brought about by thermolysis in phosphoric acid at 160°C, or by saponification followed by decarboxylation in ethanolamine at 180°C, or as unisolated intermediates in the conversion of esters 4 to pyrromethene hydrobromides 6 by heating in a mixture of formic and hydrobromic acids. Addition of hydrogen cyanide followed by dehydrogenation by treatment with bromine converted 3,5,3′,5′-tetramethyl-4,4′-diethylpyrromethene hydrobromide 9 to 3,5,-3′,5′-tetramethyl-4,4′-diethyl-6-cyanopyrromethene hydrobromide 6bb , confirmed by the further conversion to 1,3,5,7-tetramethyl-2,6-diethyl-8-cyanopyrromethene–BF₂ complex 7bb on treatment with boron trifluoride etherate. An alternation effect in the relative efficiency (RE) of laser activity in 1,3,5,7,8-pentamethyl-2,6-di-n-alkylpyrromethene–BF₂ dyes depended on the number of methylene units in the n-alkyl substituent, -(CH₂)_nH, to give RE ≥ 100 when n = 0,2,4 and RE 65, 85 when n = 1,3. (The RE 100 was arbitrarily assigned to the dye rhodamine 6G). The absence of fluorescence and laser activity in 1,3,5,7-tetramethyl-2,6-diethyl-8-isopropylpyrromethene–BF₂ complex 7p and a markedly diminished fluorescence quantum yield (Φ 0.23) and lack of laser activity in 1,3,5,7-tetramethyl-2,6-diethyl-8-cyclohexylpyrromethene–BF₂ complex 7q were attributed to molecular nonplanarity brought about by the steric interference between each of the two bulky 8-substituents with the 1,7-dimethyl substituents. An atypically low RE 20 for a peralkylated dye without steric interference was observed for 1,2,6,7-bistrimethylene-3,5,8-trimethylpyrromethene–BF₂ complex 7j . Comparisons with peralkylated dyes revealed a major reduction in RE 0–40 for the six dyes 7u–z lacking substitution at the 8-position. Low laser activity RE was brought about by functional group (polar) substitution in the 2,6-diphenyl derivative 7I , RE 20, and the 2,6-diacetamido derivative 7m , RE 5, of 1,3,5,7,8-pentamethylpyrromethene–BF₂ complex (PMP–BF₂) 7a and in 1,7-dimethoxy-2,3,5,6,8-pentamethylpyrromethene–BF₂ complex 7n , RE 30. Diethyl 1,3,5,7-tetramethyl-8-cyanopyrromethene-2,6-dicarboxylate–BF₂ complex, 7aa , and 1,3,5,7-tetramethyl-2,6-diethyl-8-cyanopyrromethene–BF₂ complex, 7bb , offered examples of P–BF₂ dyes with electron withdrawing substituents at the 8-position. The dye 7aa , λ_las 617 nm, showed nearly twice the power efficiency that was obtained from rhodamine B, λ_las 611 nm.     

Synthesis and transformations of bis(polychloroethylideneaminosulfonyl)- and bis(polychloroethylideneaminosulfonyl)-substituted derivatives of biphenyl, diphenyl oxide, and diphenylmethane

Reactions of N,N,N′,N′-tetrachlorobiphenyl-4,4′-disulfonamide, 4,4′-methylenebis(N,N-dichlorobenzenesulfonamide), and 4,4′-oxybis(N,N-dichlorobenzenesulfonamide) with 1,2-dichloroethylene and trichloroethylene open convenient synthetic approach to highly electrophilic bissulfony limines of dichloroacetic aldehyde and chloral: N,N′-bis(polychloroethylidene)biphenyl-4,4′-disulfonamides, 4,4′-methylenebis[N-(polychloroethylidene)benzenesulfonamides] and 4,4′-oxybis[N-(polychloroethylidene)benzenesulfonamides]. The synthetic opportunities of the bisazomethines obtained were demonstrated by examples of their reactions with water, methanol, chloroacetamide, and toluene where products of O-, N-nucleophiles addition to the azomethine bond and products of C-amidoalkylation of aromatic compound with imines were formed.