Home About us Contact
|
Home About us Contact | ||
|
|
||
Phenyl Substituents (phenyl + substituent)
Selected AbstractsNovel Photochromic Indolinospiropyrans Containing Phenyl Substituents in the Condensed Furan MoietyCHEMINFORM, Issue 41 2006B. S. Lukyanov Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Deformed Phthalocyanines: Synthesis and Characterization of Zinc Phthalocyanines Bearing Phenyl Substituents at the 1-, 4-, 8-, 11-, 15-, 18-, 22-, and/or 25-PositionsCHEMISTRY - A EUROPEAN JOURNAL, Issue 18 2005Takamitsu Fukuda Dr. Abstract The synthesis of a series of zinc phthalocyanines partially phenyl-substituted at the 1-, 4-, 8-, 11-, 15-, 18-, 22-, and/or 25-positions (the so-called ,-positions) is reported. Macrocycle formation based on 3,6-diphenylphthalonitrile, o -phthalonitrile, and zinc acetate predominantly yielded the near-planar disubstituted complex and opposite tetrasubstituted isomer, while the lithium method yielded the sterically hindered hexasubstituted complex and adjacent tetrasubstituted isomer. All compounds have been characterized by 1H NMR, MALDI-TOF-MS, and elemental analysis methods. In addition, crystal structures have been solved for the di-, hexa-, and octasubstituted complexes and the adjacent tetrasubstituted isomer. DFT geometry optimization calculations predict more highly deformed structures than those observed in the crystals. The packing force of the crystals cannot therefore be ignored, particularly for the less phenyl-substituted derivatives. The crystal structures have revealed that overlap of the phenyl groups causes substantial deformation of the phthalocyanine (Pc) ligands within the crystals, while strong ,,, stacking in the remainder of the Pc moiety lacking phenyl substituents can suppress the impact of the deformation. Absorption spectra show sizable red shifts of the Q-band with increasing number of phenyl groups. Analysis of the results of absorption spectra and electrochemical measurements reveals that a substantial portion of the red shift is attributable to the ring deformations. Molecular orbital calculations lend further support to this conclusion. A moderately intense absorption band emerging at around 430 nm for highly deformed octaphenyl-substituted zinc Pc can be assigned to the HOMO,LUMO+3 transition, which is parity-forbidden for planar Pcs, but becomes allowed since the ring deformations remove the center of symmetry. [source] Visible and FTIR Microscopic Observation of Bisthiourea Ionophore Aggregates in Ion-Selective Electrode MembranesELECTROANALYSIS, Issue 22 2005Katherine Abstract Since conventional response models for ionophore-based ISEs are based on the assumption of a homogeneous membrane phase, they cannot accurately predict the response of membranes containing self-aggregating ionophores. However, meaningful conclusions about the relationship between ionophore structure and potentiometric responses can only be drawn if ionophore aggregation is properly recognized. This study demonstrates that dark field visible microscopy and FTIR microspectroscopy are valuable tools for the observation of such ionophore self-aggregation and, thereby, the development of new ionophore-based ISEs. Sulfate selective electrodes with solvent polymeric membranes containing bisthiourea ionophores that differ only by peripheral nonpolar substituents were shown to exhibit very different interferences from the sample pH. On one hand, optimized electrodes based on an ionophore with a phenyl substituent on each thiourea group (1) do not respond to pH at all and function well as sulfate-selective electrodes. On the other hand, membranes containing a more lipophilic ionophore with two additional hexyl-substituted adamantyl groups (2) exhibit severe pH interference at pH values as low as pH,5. The observation of membranes containing ionophore 2 with dark field visible microscopy and FTIR microspectroscopy shows supramolecular aggregation, and explains the startling difference between the potentiometric responses of the two types of electrodes. [source] Reactions of ,,, -Enones with Diazo Compounds.HELVETICA CHIMICA ACTA, Issue 2 2004Part In this study, (E)- and (Z)-enones carrying only a phenyl substituent at their C(,) atom were treaced with dimethyl diazomalonate in the presence of (acetylacetonato)copper(II). According to the configuration of the starting enones, the products were dioxole or dihydrofuran derivatives, significant heterocycles in natural products. [source] Synthesis and conformational study of P -heterocyclic androst-5-ene derivativesHETEROATOM CHEMISTRY, Issue 1 2008Éva Frank The reactions of (20R)-3,-acetoxy-21-hydroxymethylpregn-5-en-20-ol (2) and (20R)-3,-acetoxypregn-5-ene-20,21-diol (11) with phenylphosphonic dichloride 3 and aryl dichlorophosphates 4,6 afforded novel types of P -heterocyclic androst-5-ene derivatives 7,10 and 12 as epimeric pairs. The diastereomers were separated by column chromatography and were characterized by NMR spectroscopy. Estimation of the stereostructures of the corresponding epimers by B3LYP/631G(d) DFT ab initio calculations suggested that the six-membered hetero ring in compounds 7b and 8a,10a adopts predominantly a chair conformation, with the P -substituents in their preferred orientation. The cyclic phosphonate moiety in 7a or 8b,10b, however, seems to exist as an equilibrium mixture of chair,distorted- boat or chair,chair forms. The theoretical calculations indicate that the conformational equilibrium is shifted toward the distorted- boat conformer for 7a, with a pseudoequatorial P -phenyl substituent, whereas for 8b,10b the chair conformer with an equatorial P -phenoxy group predominates. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:7,14, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20372 [source] Enantioselective Copper-Catalysed Allylic Alkylation of Cinnamyl Chlorides by Grignard Reagents using Chiral Phosphine-Phosphite LigandsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2010Wibke Lölsberg Abstract The copper(I)-catalysed SN2,-type allylic substitution of E -3-aryl-allyl chlorides (cinnamyl chlorides) using Grignard reagents represents a powerful method for the synthesis of compounds carrying a benzylic stereocentre. By screening a small library of modular chiral phosphine-phosphite ligands a new copper(I)-based catalyst system was identified which allows the performance of such reactions with exceptional high degrees of regio- and enantioselectivity. Best results were obtained using TADDOL-derived ligands (3,mol%), copper(I) bromide,dimethyl sulfide (CuBr,SMe2) (2.5,mol%) and methyl tert -butyl ether (MTBE) as a solvent. Various (1-alkyl-allyl)benzene derivatives were prepared with up to 99% ee (GC) in isolated yields of up to 99%. In most cases the product contained less than 3% of the linear regioisomer (except for ortho -substituted substrates). Both electron-rich and electron-deficient cinnamyl chlorides were successfully employed. The absolute configuration of the products was assigned by comparison of experimental and calculated CD spectra. The substrates were prepared from the corresponding alcohols by reaction with thionyl chloride. Initially formed mixtures of regioisomeric allylic chlorides were homogenised by treatment with CuBr,SMe2 (2.5,mol%) in the presence of triphenyl phosphine (PPh3) (3,mol%) in MTBE at low temperature to give the pure linear isomers. In reactions with methylmagnesium bromide (MeMgBr) an ortho -diphenylphosphanyl-arylphosphite ligand with an additional phenyl substituent in ortho, -position at the aryl backbone proved to be superior. In contrast, best results were obtained in the case of higher alkyl Grignard reagents (such as ethyl-, n -butyl-, isopropyl-, and 3-butenylmagnesium bromides) with a related ligand carrying an isopropyl substituent in ortho, -position. The method was tested on a multi-mmol scale and is suited for application in natural product synthesis. [source] Aqueous Asymmetric Mukaiyama Aldol Reaction Catalyzed by Chiral Gallium Lewis Acid with Trost-Type Semi-Crown LigandsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2005Hui-Jing Li Abstract The combination of Ga(OTf)3 with chiral semi-crown ligands (1a,e) generates highly effective chiral gallium Lewis acid catalysts for aqueous asymmetric aldol reactions of aromatic silyl enol ethers with aldehydes. A ligand-acceleration effect was observed. Water is essential for obtaining high diastereoselectivity and enantioselectivity. The p -phenyl substituent in aromatic silyl enol ether (2,h) plays an important role and increases the enantioselectivity up to 95% ee. Although aliphatic silyl enol ethers provided low enantioselectivities and silylketene acetal is easily hydrolyzed in aqueous alcohol, the aldol reactions of silylketene thioacetal (12) with aldehydes in the presence of gallium-Lewis acid catalysts give the ,-hydroxy thioester with reasonable yields and high diastereo- (up to 99,:,1) and enantioselectivities (up to 96% ee). [source] Study of the conformational profile of the norbornane analogues of phenylalanineJOURNAL OF PEPTIDE SCIENCE, Issue 6 2002Arnau Cordomí Abstract The conformational profile of the eight stereoisomeric 2-amino-3-phenylnorbornane-2-carboxylic acids (2-amino-3-phenylbicyclo[2.2.1]heptane-2-carboxylic acids) has been assessed by computational methods. These molecules constitute a series of four enantiomeric pairs that can be considered as rigid analogues of either L - or D -phenylalanine. The conformational space of their N -acetyl methylamide derivatives has been explored within the molecular mechanics framework, using the parm94 set of parameters of the AMBER force field. Local minimum energy conformations have been further investigated at the ab initio level by means of the Hartree-Fock and second order Moller-Plesset perturbation energy calculations using a 6,31G(d) basis set. The results of the present work suggest that the bulky norbornane structure induces two kinds of conformational constraints on the residues. On one hand, those of a steric nature directly imposed by the bicycle on the peptide backbone and, on the other hand, those that limit the orientations attainable by the phenyl ring which, in turn, reduces further the flexibility of the peptide backbone. A comparative analysis of the conformational profile of the phenylnorbornane amino acids with that of the norbornane amino acids devoid of the ,-phenyl substituent suggests that the norbornane system hampers the residue to adopt extended conformations in favour of C7-like structures. However, the bicycle itself does not impart a clear preference for any of the two possible C7 minima. It is the aromatic side chain, which is forced to adopt an almost eclipsed orientation, that breaks this symmetry introducing a marked preference for a single region of the (,, ,) conformational space in each of the phenylalanine norbornane analogues investigated. Copyright © 2002 European Peptide Society and John Wiley & Sons, Ltd. [source] 4-Alkylbenzopyrylium perchlorates as C,H Acidic compoundsJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 7 2002U.-W. Grummt Abstract 7-Alkyl-5,6-dihydro-3-methoxy(naphtho[1,2b]-1-benzopyrylium) compounds are acidochromic due to CH acidity of the 7-alkyl substituent. Their acidity exponents are 4 < pKa < 5 and 1 < pKa < 3 regardless of whether the carbocation generated by deprotonation is resonance stabilized by a phenyl substituent or not. The thermodynamic equilibrium data were obtained via UV,vis spectroscopy. The activation parameters for protonation and deprotonation reactions were derived from rapid mixing experiments. Ab initio calculations with model compounds are presented in order to rationalize the experimental findings. The title compounds are useful objects to study the kinetics of proton-transfer kinetics to and from carbon. Copyright © 2002 John Wiley & Sons, Ltd. [source] Synthesis and properties of novel conjugated poly(silylacetylene silazane)sJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 12 2004Ji Dong Hu Abstract A series of novel conjugated polymers, poly(silylacetylene silazane)s having different substituents, were prepared by ammonolysis of the corresponding ,,,-dichlorosilyleneacetylene oligomers. The structures and properties of the poly(silylacetylene silazane)s were characterized by Fourier transform infrared, 1H, 13C, 29Si NMR, and elemental analyses, gel permeation chromatography, thermogravimetric analysis, differential scanning calorimetry, and spectrofluorophotometry. The resulting polymers had good thermal properties and were moderately fluorescent. Their thermal stability was improved, and obvious red shift was observed when a phenyl substituent was attached on a silicon atom of polymers in the emission spectra. These polymers have the potential to be used as light-emitting materials with good thermal stability. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2897,2903, 2004 [source] Promoted random orientation of the phenyl substituent of phenylhydroquinone,terephthalic acid polyesters prepared with a diphenyl chlorophosphate/pyridine condensing agentJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2001Fukuji Higashi Abstract The reaction of sterically hindered hydroxyl groups at the 2-position of methylhydroquinone and phenylhydroquinone (PhHQ) to form esters was largely promoted by their slow addition to benzoic acid activated by diphenyl chlorophosphate in pyridine. A modification of this reaction was applied to the preparation of thermotropic terephthalic acid/PhHQ and 2,5-dichloroterephthalic acid/PhHQ polymers with randomly oriented phenyl substituents, and the properties of the polymers were studied in terms of their transition temperatures, which were determined by differential scanning calorimetry and microscopic observation. The melting points were lowered by about 30,50 °C by the dropwise addition of PhHQ over 10,30 min. The molecular structures of the 2,5-dichloroterephthalic acid/PhHQ polymers were studied by 13C NMR. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1726,1732, 2001 [source] A nitrogen-15 NMR study of hydrogen bonding in 1-alkyl-4-imino-1,4-dihydro-3-quinolinecarboxylic acids and related compoundsMAGNETIC RESONANCE IN CHEMISTRY, Issue 5 2006Laurence Carlton Abstract The title compounds contain groups (amine, amide, imine, carboxylic acid) that are capable of forming intramolecular hydrogen bonds involving a six-membered ring. In compounds where the two interacting functional groups are imine and carboxylic acid, the imine is protonated to give a zwitterion; where the two groups are imine and amide, the amide remains intact and forms a hydrogen bond to the imine nitrogen. The former is confirmed by the iminium 15N signal, which shows the coupling of 1J(15N,1H) ,85 to ,86.8 Hz and 3J(1H,1H) 3.7,4.2 Hz between the iminium proton and the methine proton of a cyclopropyl substituent on the iminium nitrogen. Hydrogen bonding of the amide is confirmed by its high 1H chemical shift and by coupling of the amide hydrogen to (amide) nitrogen [(1J(15N,1H) ,84.7 to ,90.7 Hz)] and to ortho carbons of a phenyl substituent. Data obtained from N,N -dimethylanthranilic acid show 15N1H coupling of (,)8.2 Hz at 223 K (increasing to (,)5.3 Hz at 243 K) consistent with the presence of a N··· HO hydrogen bond. Copyright © 2006 John Wiley & Sons, Ltd. [source] Predictive 3D-Quantitative Structure-Activity Relationship for A1 and A2A Adenosine Receptor LigandsMOLECULAR INFORMATICS, Issue 11-12 2009Olga Yuzlenko Abstract The use of QSAR applications to develop adenosine receptor (AR) antagonists is not so common. A library of all xanthine derivatives, obtained at the Department of Technology and Biotechnology of Drugs, was created. Sixty-three active adenosine A1 receptor ligands and one hundred thirty nine active adenosine A2A receptor ligands were used for 3D-QSAR investigation. The 3D-QSAR equations with a high predictive power in estimating the binding affinity values of potential A1 and A2A ARs ligands were derived. For the first time, hybrid shape-property descriptors were used in 3D-QSAR for xanthine ARs ligands. The obtained models were characterized by a high regression and cross-validation coefficients. Two types of the model validation were tested , dividing the library into the training set for model development and external set for model validation and increasing the number of library components and checking the model by cross-validated regression coefficient. The analysis of the results depicts that for the A1 AR binding activity it is important for ligands to possess R1 -propyl substituents along with the phenyl or benzyl substituents bearing halogen atom and phenethyl moiety. For A2A AR affinity it could be favorable to introduce phenethyl or phenyl substituent connected with the tricyclic ring by the alkoxy chain. The nature of R1 group may not significantly affect the A2A AR affinity. High predictive power of the equations suggests their use for further development of adenosine receptor antagonists within xanthine derivatives. [source] 5-Acetyl-2-amino-6-methyl-4-phenyl-4H -pyran-3-carbonitrile and 2-amino-5-benzoyl-6-methyl-4-phenyl-4H -pyran-3-carbonitrile acetonitrile solvateACTA CRYSTALLOGRAPHICA SECTION C, Issue 12 2006Vladimir N. Nesterov The syntheses, X-ray structural investigations and calculations of the conformational preferences of the carbonyl substituent with respect to the pyran ring have been carried out for the two title compounds, viz. C15H14N2O2, (II), and C20H16N2O2·C2H3N, (III), respectively. In both molecules, the heterocyclic ring adopts a flattened boat conformation. In (II), the carbonyl group and a double bond of the heterocyclic ring are syn, but in (III) they are anti. The carbonyl group forms a short contact with a methyl group H atom in (II). The dihedral angles between the pseudo-axial phenyl substituent and the flat part of the pyran ring are 92.7,(1) and 93.2,(1)° in (II) and (III), respectively. In the crystal structure of (II), intermolecular N,H,N and N,H,O hydrogen bonds link the molecules into a sheet along the (103) plane, while in (III), they link the molecules into ribbons along the a axis. [source] O -Acylated 2-Phosphanylphenol Derivatives , Useful Ligands in the Nickel-Catalyzed Polymerization of EthyleneEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 9 2009Dmitry G. Yakhvarov Abstract The title ligands were prepared by O -acylation of 2-diphenylphosphanyl-4-methylphenol (1) or directly by double lithiation of 2-bromo-4-methylphenol and stepwise coupling with ClPPh2 and ClP(O)Ph2 or RC(O)Cl (R = Me, tBu, Ph, 4-MeOC6H4) to afford diphenylphosphinate 2 and carboxylic esters 3a,d. X-ray crystal structure analyses of 3b,d show conformations in which the P -phenyl substituents are rotated away from the ester group and the C(O)O , planes are nearly perpendicular to the phenol ring , plane. O -Acylated phosphanylphenols 2 and 3a,d form highly active catalysts with Ni(1,5-cod)2 (as does 1) for polymerization of ethylene, whereas phosphanylphenyl ethers do not give catalysts under the same conditions. The reason is the cleavage of the O -acyl bond upon heating with nickel(0) precursor compounds in the presence of ethylene. The precursors are P-coordinated Ni0 complexes, which are formed at room temperature, such as 4d obtained from 3d and Ni(cod)2 (in a 2:1 molar ratio), and characterized by multinuclear NMR spectroscopy. Upon heating in the presence of ethylene, the precatalysts are activated. Catalysts 2Ni and 3a,dNi convert ethylene nearly quantitatively, 2Ni slowly, and 3a,dNi rapidly, into linear polyethylene with vinyl and methyl end groups, and in the latter case, C(O)R end groups are also detectable. This proves insertion of Ni0 into the O,C(O)R bond of 3a,d ligands for formation of the primary catalyst. Termination of the first chain growing cycle by ,-hydride elimination changes the mechanism to the phosphanylphenolate,NiH initiated polymerization providing the main body of the polymer. A small retardation in the ethylene consumption rate with 3a,dNi catalysts relative to that observed for 1Ni and stabilization of the catalyst, which gives rise to reproducibly high ethylene conversion, is observed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Synthesis and Reactivity of 23 - tert -Butyl- and 23 -Phenyltetraarylazuliporphyrins: an Analysis of the Effect of Bulky Substituents on Oxidative Ring Contractions to Benzocarbaporphyrins,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 24 2007Jessica A. El-Beck Abstract 6- tert -Butyl- and 6-phenylazulene reacted with pyrrole and benzaldehyde in a molar ratio of 1:3:4 in the presence of BF3·Et2O in chloroform, followed by oxidation with DDQ, to give 23 -substituted tetraphenylazuliporphyrins in 15,20,% yield. Slightly higher yields of the related meso -tetrakis(4-chlorophenyl)azuliporphyrins were obtained using 4-chlorobenzaldehyde. The presence of an electron-donating tert -butyl substituent increased the diatropic character of the azuliporphyrin system as determined by the proton NMR chemical shifts for the internal CH resonance, while intermediary results were noted for 23 -phenylazuliporphyrins. Addition of TFA afforded dications with increased aromatic ring currents, but electron-donating substituents (tBu,>,Ph) again produced a larger upfield shift for the internal CH signal due to stabilization of the tropylium character that is required so that the system can attain carbaporphyrin-type aromaticity. The substituted azuliporphyrins reacted with nickel(II) acetate or palladium(II) acetate to give the corresponding organometallic derivatives. In addition, oxidations with tBuOOH and KOH afforded benzocarbaporphyrin products in approximately 50,% yield. The presence of tert -butyl or phenyl substituents did not block these oxidative ring contraction processes, and the rate of reaction was slightly increased compared to 23 -unsubstituted azuliporphyrins. The major products were 22 - tert -butyl or phenyl-substituted benzocarbaporphyrins and minor products with an additional formyl substituent were also isolated. These products are consistent with an initial nucleophilic addition occurring at the position adjacent to the R group on the azulene ring. Detailed mechanisms are proposed to explain these observations. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Further Studies on the Synthesis of meso -Tetraarylazuliporphyrins under Lindsey,Rothemund Reaction Conditions and Their Conversion into BenzocarbaporphyrinsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 23 2003Timothy D. Lash Abstract Azulene has been shown to react with pyrrole and a series of aromatic aldehydes in the presence of boron trifluoride etherate to give meso -tetraarylazuliporphyrins 6. Good yields of azuliporphyrins were obtained for benzaldehyde, 4-chlorobenzaldehyde, 4-bromobenzaldehyde, and 4-iodobenzaldehyde, and under dilute conditions p -tolualdehyde gave respectable yields. In each case, substantial amounts of meso -tetraarylporphyrins were also formed and a minor fraction of carbaporphyrin by-products could be detected, but otherwise no other macrocyclic products could be identified. 4-Nitrobenzaldehyde gave relatively poor yields of the corresponding azuliporphyrin, while p -anisaldehyde only gave trace amounts of product. Pentafluorobenzaldehyde gave variable results, although in this case a large number of additional by-products were identified including N -fused pentaphyrin, hexaphyrin, and higher order porphyrinoids, but no expanded azulene-containing macrocycles could be detected. Azuliporphyrins undergo reversible nucleophilic substitution on the seven-membered ring with pyrrolidine, benzenethiol, hydrazine, or benzylamine to give carbaporphyrin adducts. This property appears to facilitate an oxidative ring contraction of azuliporphyrins 6 with tert -butyl hydroperoxide in the presence of potassium hydroxide to produce mixtures of benzocarbaporphyrins 19 and 20. Tetraaryl-benzocarbaporphyrins exhibit slightly reduced diatropic ring currents compared to their meso -unsubstituted counterparts, although their UV/Vis spectra are very porphyrin-like and exhibit strong Soret bands near 450 nm. The benzocarbaporphyrins undergo reversible protonation to give monocationic and dicationic species. The latter involves C -protonation to generate an internal CH2 within the macrocyclic cavity. X-ray crystallography of tetraphenylbenzocarbaporphyrin 19a confirms that the preferred tautomer has the two NHs on either side of the indene subunit, in agreement with previous theoretical and spectroscopic studies. In addition, the presence of phenyl substituents at the 5,20-positions was found to tilt the indene moiety substantially by 27.4(1)° relative to the [18]annulene substructure. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Study of Energy Transfer and Triplet Exciton Diffusion in Hole-Transporting Host MaterialsADVANCED FUNCTIONAL MATERIALS, Issue 19 2009Chao Wu Abstract A device structure is used in which the hole-transporting layer (HTL) of an OLED is doped with either fluorescent or phosphorescent emitters, that is, anode/HTL-host/hole blocker/electron-transporting layer/cathode. The HTL hosts have higher HOMO energy allowing holes to be transported without being trapped by dopant molecules, avoiding direct recombination on the dopant. The unconventional mismatch of HOMO energies between host and dopant allow for the study of energy transfer in these host/guest systems and triplet exciton diffusion in the HTL-host layers of OLED devices, without the complication of charge trapping at dopants. The host materials examined here are tetraaryl- p- phenylenediamines. Data shows that Förster energy transfer between these hosts and emissive dopant in devices is inefficient. Triplet exciton diffusion in these host materials is closely related to molecular structure and the degree of intermolecular interaction. Host materials that contain naphthyl groups demonstrate longer triplet exciton diffusion lengths than those with phenyl substituents, consistent with DFT calculations and photophysical measurements. [source] B3LYP calculations on bishomoaromaticity in substituted semibullvalenes*JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 13 2001David A. Hrovat Abstract B3LYP/6-31G* calculations on the degenerate rearrangements of substituted semibullvalenes spuriously predict the relative enthalpies of the bishomoaromatic TSs to be lower than the experimental values. However, the calculations do make the useful and experimentally testable prediction that the two cyano and two phenyl substituents in 2,6-dicyano-4,8-diphenylsemibullvalene (9d) are more likely than four cyano substituents in 2,4,6,8-tetracyanosemibullvalene (9f) or the four phenyl substituents in 2,4,6,8-tetraphenylsemibullvalene (9g) to produce a semibullvalene that has a bishomoaromatic equilibrium geometry in the gas phase. The major reason for the surprising finding that 9d is more likely to be bishomoaromatic than 9g is shown to be steric interactions between the phenyl groups at C-2 and C-8 and at C-4 and C-6 in bishomoaromatic structure 10g. These interactions inhibit the conjugative stabilization of 10g; but they are absent in bishomoaromatic structure 10d, where cyano groups replace the phenyl groups at C-2 and C-6 in 10g. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1565,1573, 2001 [source] Stability studies of oxazolidine-based compounds using 1H NMR spectroscopyJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 8 2010Gerard P. Moloney Abstract A series of oxazolidine-based compounds with a variety of substituents in positions 2 and 3 was synthesized and their stability studied. Ring opened intermediates formed on addition of limiting amounts of D2O to oxazolidine solutions, as observed by NMR. As the hydrolysis reactions proceeded, a series of novel dimeric ,-amino alcohol compounds formed via an internal reaction between ephedrine and the ring opened intermediates. 2-Phenyl substituted oxazolidine compounds containing electron withdrawing nitro substituents were more rapidly hydrolyzed than the unsubstituted derivative and methoxy substituted compounds, with the nitro substituents appearing to stabilize the ring opened intermediates. Two oxazolidine derivatives, with a methyl and proton at position 2, were found to be more stable to oxazolidine hydrolysis than the 2-phenyl substituted compounds. Oxazolidines incorporating phenyl substituents at position 3 were synthesized and found to be less stable than those incorporating a methyl substituent at position 3. These fundamental structure,activity relationships may be useful when choosing oxazolidine derivatives as synthetic intermediates and as prodrugs for the delivery of compounds containing either ,-amino alcohol or aldehyde components. © 2010 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99:3362,3371, 2010 [source] Evidence for extended ,,n-participation in solvolysis of some benzyl chloridesJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 12 2003Sandra Juri Abstract Chlorides 3 (1-aryl-1-chloro-4-methyl-7-methoxy-4-heptene) and 4 (1-aryl-1-chloro-4-methyl-4-hexene) with various phenyl substituents were prepared (Y=p -OCH3, p -CH3, H and m -Br) and the solvolysis rates were measured in 80% (v/v) aqueous ethanol. The rate constants of 3 correlate well with ,+, and the ,+ value obtained is ,1.45±0.15, whereas with 4 breakdown of the Hammett plot occurs, and the ,+ value without the p -anisyl group is ,2.55±0.20, indicating extended ,,n-participation in 3 and simple ,-participation in 4. The drastically smaller activation parameters obtained with 3 than with 4 are consistent with the proposed mechanism in which the high degree of order required in the transition state (large negative ,S,) is overcompensated by a small ,H,. Copyright © 2003 John Wiley & Sons, Ltd. [source] Structural studies of 1-(2-hydroxy-4-bromophenyl)-4-methyl-4-imidazolin-2-onesJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 6 2001Michal K. Cyra Abstract The crystal structure of 1-(2-hydroxy-4-bromophenyl)-3-methyl-4-methyl-4-imidazolin-2-one was determined by x-ray diffraction. The structure is stabilized by intermolecular hydrogen bonds formed between the 2-hydroxy and central groups. Molecular modelling including ab initio calculations at the HF/6,31+G** level revealed that in the gas phase the molecule is stabilized by an intramolecular hydrogen bond. The derivatives with 3-alkyl, benzyl and phenyl substituents were studied by 13C NMR including solid-state 13C CP/MAS NMR [for 1-(2-hydroxy-4-bromophenyl)-3-methyl-4-methyl-4-imidazolin-2-one] and FT-IR methods. The differences in chemical shifts ,,=,,liquid,,,,solid are significant for aromatic carbons C(3) (,2.9,ppm), C(4) (3.6,ppm) and C(5) (,3.9,ppm) and, on the other side of the imidazoline ring, of C(7) (,1.5,ppm). These carbons are adjacent to N(1),C(4), and are subject to the largest changes of the environment during reorientation of the imidazolin-2-one moiety. Copyright © 2001 John Wiley & Sons, Ltd. [source] Promoted random orientation of the phenyl substituent of phenylhydroquinone,terephthalic acid polyesters prepared with a diphenyl chlorophosphate/pyridine condensing agentJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2001Fukuji Higashi Abstract The reaction of sterically hindered hydroxyl groups at the 2-position of methylhydroquinone and phenylhydroquinone (PhHQ) to form esters was largely promoted by their slow addition to benzoic acid activated by diphenyl chlorophosphate in pyridine. A modification of this reaction was applied to the preparation of thermotropic terephthalic acid/PhHQ and 2,5-dichloroterephthalic acid/PhHQ polymers with randomly oriented phenyl substituents, and the properties of the polymers were studied in terms of their transition temperatures, which were determined by differential scanning calorimetry and microscopic observation. The melting points were lowered by about 30,50 °C by the dropwise addition of PhHQ over 10,30 min. The molecular structures of the 2,5-dichloroterephthalic acid/PhHQ polymers were studied by 13C NMR. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1726,1732, 2001 [source] Ortho Effects in Quantitative Structure Activity Relationships for Lipase Inhibition by Aryl CarbamatesMOLECULAR INFORMATICS, Issue 8 2003Gialih Lin Abstract Ortho -substituted phenyl- N -butyl carbamates (1,11) are synthesized and evaluated for their inhibition effects on Pseudomonas species lipase. Carbamates 1,11 are characterized as pseudo-substrate inhibitors of the enzyme. The logarithms of dissociation constant (Ki), carbamylation constant (k2), and bimolecular inhibition constant (ki) multiply linearly correlate with Hammett substituent constant (,), Taft-Kutter-Hansch ortho steric constant (ES), and Swan-Lupton field constant (F). For ,logKi -, logk2 -, and logki -correlations, values of ,, ,, f, ,XR are 0.2, ,0.06, ,1.7, 0.8; 0.0, 0.0, 1.0, ,0.07; and ,1.8, 7, 0.6, 5; respectively. The enzyme inhibition mechanism is composed of four steps: 1) the first step which is protonation of carbamates 1,11, 2) the second step (Ki1) which involves in the proton 1,3-shift of protonated carbamates 1,11 then the pseudo- trans to cis conformational change, 3) the third step (Ki2) which is formation of a negative charged enzyme-inhibitor tetrahedral intermediate, and 4) the fourth step (k2) which is the carbamylation step. The former three steps are likely composed of the Ki step. There is little ortho steric enhancement effect in the Ki step. From cross-interaction correlations, distance between carbamate and phenyl substituents in transition state for the Ki step is relatively short due to a large ,XR value of 7. The k2 step is insensitive to ortho steric effect. The k2 step involves in departure of leaving group, substituted phenol in which is protonated from the proton 1,3-shift but not from the active site histidine of the enzyme. From cross-interaction correlations, the distance between carbamate and phenyl substituents in transition state for the k2 step is relatively long due to a small ,XR value of 0.6. [source] Molecular-selective adsorption property of chemically surface modified nanoporous alumina membrane by di(1-naphthyl)silanediol to anthracenesAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 3 2010Kenji Kakiage Abstract Nano-porous alumina membrane (NPAM) formed by the anodic oxidation of aluminum is an attractive composite as the base material for a functional filter, because of its honeycombed ordered structure with large surface area per weight and also high shape stability. In this work, we investigated the adsorption properties of the NPAM possessing ,-electron systems on the surface, which were produced through chemical surface modification by di(1-naphthyl)silanediol, to aromatic compounds using anthracenes as typical aromatic compounds. The chemically surface-modified NPAM exhibited strong affinity to anthracene molecules and the affinity was observed to be weakened remarkably with the introduction of methyl and phenyl substituents to anthracene, indicating a molecular-selective adsorption property of the NPAM. Copyright © 2009 John Wiley & Sons, Ltd. [source] ChemInform Abstract: Chiral 1-Phenylethylamine-Derived Phosphine,Phosphoramidite Ligands for Highly Enantioselective Rh-Catalyzed Hydrogenation of ,-(Acylamino)acrylates: Significant Effect of Substituents on 3,3,-Positions of Binaphthyl Moiety.CHEMINFORM, Issue 36 2010Xiao-Mao Zhou Abstract Introduction of phenyl substituents at the phosphoramidite backbone of PEAPhos ligand (PEAPP) significantly increases its catalytic activity in the Rh-catalyzed asymmetric hydrogenation of ,-(acylamino)acrylates. [source] Deformed Phthalocyanines: Synthesis and Characterization of Zinc Phthalocyanines Bearing Phenyl Substituents at the 1-, 4-, 8-, 11-, 15-, 18-, 22-, and/or 25-PositionsCHEMISTRY - A EUROPEAN JOURNAL, Issue 18 2005Takamitsu Fukuda Dr. Abstract The synthesis of a series of zinc phthalocyanines partially phenyl-substituted at the 1-, 4-, 8-, 11-, 15-, 18-, 22-, and/or 25-positions (the so-called ,-positions) is reported. Macrocycle formation based on 3,6-diphenylphthalonitrile, o -phthalonitrile, and zinc acetate predominantly yielded the near-planar disubstituted complex and opposite tetrasubstituted isomer, while the lithium method yielded the sterically hindered hexasubstituted complex and adjacent tetrasubstituted isomer. All compounds have been characterized by 1H NMR, MALDI-TOF-MS, and elemental analysis methods. In addition, crystal structures have been solved for the di-, hexa-, and octasubstituted complexes and the adjacent tetrasubstituted isomer. DFT geometry optimization calculations predict more highly deformed structures than those observed in the crystals. The packing force of the crystals cannot therefore be ignored, particularly for the less phenyl-substituted derivatives. The crystal structures have revealed that overlap of the phenyl groups causes substantial deformation of the phthalocyanine (Pc) ligands within the crystals, while strong ,,, stacking in the remainder of the Pc moiety lacking phenyl substituents can suppress the impact of the deformation. Absorption spectra show sizable red shifts of the Q-band with increasing number of phenyl groups. Analysis of the results of absorption spectra and electrochemical measurements reveals that a substantial portion of the red shift is attributable to the ring deformations. Molecular orbital calculations lend further support to this conclusion. A moderately intense absorption band emerging at around 430 nm for highly deformed octaphenyl-substituted zinc Pc can be assigned to the HOMO,LUMO+3 transition, which is parity-forbidden for planar Pcs, but becomes allowed since the ring deformations remove the center of symmetry. [source] | ||||||||||||||||||||||||||||||||||