Showing papers by "Sean Parkin published in 2002"
Patent•
10 May 2002TL;DR: In this article, novel substituted pentacenes and electronic devices made with those substituted pentaenes are disclosed. But none of the devices are shown to have been used in this paper.
Abstract: Novel substituted pentacenes and electronic devices made with those substituted pentacenes are disclosed.
103 citations
TL;DR: In this paper, the synthesis and characterization of five organotin compounds containing Salophen(t Bu) [Salophen( t Bu) � /N,N?-phenylenebis(3,5-di-tert -butylsalicylidene(1-aminophenylene-2-amine)] ligands is described.
56 citations
TL;DR: In this article, the preparation and characterization of ammonium hexafluorosilicate salts, 2[R]- [SiF6]2− (where R=piperidinium (2), methylammonium (3), quinolinium (4), acridinium, and propylammmonium, was described.
43 citations
TL;DR: The Salen(tBu) ligand and its derivatives were used to prepare binuclear boron complexes that are active towards the dealkylation of many phosphates and catalytically active with a stoichiometric amount of BBr3 to trimethylphosphate.
Abstract: The Salen(tBu) ligand and its derivatives were used to prepare binuclear boron complexes. These compounds have the formula, L(BBr2)2 (L = Salpen(tBu) and Salben(tBu)). These are formed from the reaction of the corresponding L[B(OMe)2]2 with BBr3. They represent a new type of binuclear boron compound. These compounds are active towards the dealkylation of many phosphates. They are also catalytically active with a stoichiometric amount of BBr3 to trimethylphosphate.
41 citations
TL;DR: Combination of the hydrochloride salt of cysteamine (1) with HgCl2 in water affords the unique compound, [Hg{S(CH2)2NH3}2](Cl)2 (2) in which the SHgS angle is nearly linear as discussed by the authors.
37 citations
TL;DR: Crystals of 4-chloro-2'-biphenylol grown at 263 K and studied at both 293 and 142 K are loosely packed and contain OH.
Abstract: Crystals of 4-chloro-2′-biphenylol grown at 263 K and studied at both 293 and 142 K are loosely packed and contain OH⋯O bonded tetramers composed of four crystallographically independent molecules (Z′ = 4). Approximate symmetry relationships between independent molecules are apparent in many, perhaps even most, structures with Z′ > 1, but are not obvious in this structure. The inefficient crystal packing, the surprisingly large value of Z′ and the absence of pseudosymmetry reflect the difficulty of finding a dense molecular arrangement that also allows for hydrogen-bond formation. Impediments to good packing are the steric congestion around the ortho hydroxyl groups and the difficulty in filling space with significantly twisted biphenyl fragments. The packing arrangement adopted is strongly reminiscent of the structure type found for eight simple 4,4′-biphenyl derivatives, but one of the four independent 4-chloro-2′-biphenylol molecules has an orientation that is significantly different from the orientations of the other three and that does not fit the 4,4′-XPhPhY pattern. It is suggested that molecules that crystallize with Z′ > 1 are good candidates for solid-state compound formation.
34 citations
30 citations
TL;DR: The six-coordinate, solution-state species LAlMe(thf) (L = Salophen and Salomphen) were discovered and implicated as intermediates and a possible mechanism for the thf coupling event is presented.
Abstract: When the reagents LAlMe (L = N,N'-(alkylene or arylene)bis(3,5-di-tert-butyl)salicylideneimine (alkylene = ethylene (Salen(tBu))(1), propylene (Salpen(tBu))(2), and butylene (Salben(tBu)) (3); arylene = phenylene (Salophen(tBu) (4), 3,4-dimethylphenylene (Salomphen(tBu) (5)) are combined with Ph(H)P(O)OH in tetrahydrofuran (thf) the unique aluminophosphinate compounds, [L(tBu)Al[O(2)P(H)Ph]](n) with L, n = Salen,(infinity)(6), Salpen, 2 (7), Salben, 2 (8), Salophen, (infinity)(9) and Salomphen, (infinity)(10) are produced The yields for the latter two reactions are low, and it was subsequently found that the unique thf-coupled compounds appear in the thf filtrates of the original reaction mixture These compounds are, [L-thf(tBu)Al[O(2)P(H)Ph]](2), L = Salophen (13) and Salomphen (14) The thf connects through an alpha-carbon to only one of the two possible imine carbons of the ligand While trying to determine how this coupling proceeds, the six-coordinate, solution-state species LAlMe(thf) (L = Salophen (11) and Salomphen (12) were discovered and implicated as intermediates All of the compounds are characterized by melting point, NMR, IR, and X-ray analyses for 5-8, 13, and 14 A possible mechanism for the thf coupling event is presented
29 citations
TL;DR: Six new calcium and strontium compounds were prepared by the reaction of various salen(t-Bu)H(2) ligands with the metals in ethanol, structurally characterized by single-crystal X-ray diffraction.
Abstract: Salen complexes of the heavy alkaline-earth metals, calcium and strontium, were prepared by the reaction of various salen(t-Bu)H2 ligands with the metals in ethanol. Six new calcium and strontium compounds, [Ca(salen(t-Bu))(HOEt)2(thf)] (1), [Ca(salen(t-Bu))(HOEt)2] (2), [Ca(salpen(t-Bu))(HOEt)3] (3), [Ca(salophen(t-Bu))(HOEt)(thf)] (4), [Sr(salen(t-Bu))(HOEt)3] (5), and [Sr(salophen(t-Bu))(HOEt)(thf)2] (6), were formed in this way with the quatridentate Schiff-base ligands N,N‘-bis(3,5-di-tert-butylsalicylidene)ethylenediamine (salen(t-Bu)H2), N,N‘-bis(3,5-di-tert-butylsalicylidene)-1,3-propanediamine (salpen(t-Bu)H2), and N,N‘-o-phenylenebis(3,5-di-tert-butylsalicylideneimine (salophen(t-Bu)H2). Initially, ammonia solutions of the metals were combined with the salen(t-Bu)H2 ligands, and in the reaction of strontium with salen(t-Bu)H2, the unusual tetrametallic cluster [{OC6H2(t-Bu)2CHN(CH2)2NH2}Sr(μ3-salean(t-Bu)H2)Sr(μ3-OH)]2 (7) was produced (salean(t-Bu)H4 = N,N‘-bis(3,5-di-tert-butyl-2-hydroxybenzyl...
26 citations
TL;DR: In this article, the photoresponse of a recently synthesized class of organic semiconductors based on functionalized pentacene was investigated in terms of carrier activation versus heating effects.
Abstract: We report the investigation of the photoresponse of the conductivity of a recently synthesized class of organic semiconductors based on functionalized pentacene. These materials form high quality single crystals that exhibit a thermally activated resistivity. Unlike pure pentacene, the functionalized derivatives are readily soluble in acetone, and can be evaporated or spincast as thin films for potential device applications. The electrical conductivity of the single crystal materials is noticeably sensitive to ambient light changes. The purpose, therefore, of the present study, is to determine the nature of the photoresponse in terms of carrier activation versus heating effects, and also to measure the dependence of the photoresponse on photon energy. We describe a method, involving the temperature dependent photoresponse, which allows an unambiguous identification of the signature of heating effects in materials with a thermally activated conductivity. We find strong evidence that the photoresponse in th...
25 citations
TL;DR: In this paper, the photo-response of a new class of organic semiconductors based on functionalized pentacene was investigated, and the authors found strong evidence that the photo response in the materials investigated is predominantly a highly localized heating mechanism.
Abstract: We report the first investigation of the photo-response of the conductivity of a new class of organic semiconductors based on functionalized pentacene. These materials form high quality single crystals that exhibit a thermally activated resistivity. Unlike pure pentacene, the functionalized derivatives are readily soluble in acetone, and can be evaporated or spin-cast as thin films for potential device applications. The electrical conductivity of the single crystal materials is noticeably sensitive to ambient light changes. The purpose, therefore, of the present study, is to determine the nature of the photo-response in terms of carrier activation vs. heating effects, and also to measure the dependence of the photo-response on photon energy. We describe a new method, involving the temperature dependent photo-response, which allows an unambiguous identification of the signature of heating effects in materials with a thermally activated conductivity. We find strong evidence that the photo-response in the materials investigated is predominantly a highly localized heating mechanism. Wavelength dependent studies of the photo-response reveal resonant features and cut-offs that indicate the photon energy absorption is related to the electronic structure of the material.
TL;DR: Because metallapinacolate intermediates have been implicated in important C-C bond-forming reactions, such as pinacol coupling and McMurry chemistry, the mechanism of the fragmentation reactions was studied.
Abstract: Reactions between terminal alkynes or aromatic ketones and titanapinacolate complexes (DMSC)Ti(OCAr(2)CAr(2)O) (2, Ar = Ph, and 3, Ar = p-MeC(6)H(4); DMSC = 1,2-alternate dimethylsilyl-bridged p-tert-butylcalix[4]arene dianion) occur via rupture of the C-C bond of the titanacycle. Thus, reactions of 2 and 3 with terminal alkynes produce 2-oxatitanacyclopent-4-ene or 2-oxatitanacycloheptadiene complexes along with free Ar(2)CO. These compounds have been characterized spectroscopically and by X-ray crystallography. Because metallapinacolate intermediates have been implicated in important C-C bond-forming reactions, such as pinacol coupling and McMurry chemistry, the mechanism of the fragmentation reactions was studied. Analysis of the kinetics of the reaction of (DMSC)Ti[OC(p-MeC(6)H(4))(2)C(p-MeC(6)H(4))(2)O] (3) with Bu(t)Ctbd1;CH revealed that the fragmentation reactions proceed via a preequilibrium mechanism, involving reversible dissociation of titanapinacolate complexes into (DMSC)Ti(eta(2)-OCAr(2)) species with release of a ketone molecule, followed by rate-limiting reaction of (DMSC)Ti(eta(2)-OCAr(2)) species with an alkyne or ketone molecule.
TL;DR: In this paper, six boron compounds have been synthesized through the combination of phenylboronic acid and various Salen ( N, N ′-ethylenebis(2-hydroxy)benzylidenimine) ligands.
TL;DR: The crystal structure of a "coplanar" polychlorinated biphenyl (PCB) derivative, 4-methoxy-3, 3', 5'-trichlorobiphenyl(C13H9Cl3O), is described, which is in good agreement with the calculated torsion angle.
TL;DR: Salen(t-Bu)H2 (N,N-ethylenebis(3,5-di-tert-butyl(2-hydroxy)benzylidenimine) and its derivatives were used to prepare boron compounds having the formula L(BCl2)2 as mentioned in this paper.
Abstract: Salen(t-Bu)H2 (N,N-ethylenebis(3,5-di-tert-butyl(2-hydroxy)benzylidenimine) and its derivatives were used to prepare boron compounds having the formula L(BCl2)2 (L = salen(t-Bu) (1), salpen(t-Bu) (2), salben(t-Bu) (3), salpten(t-Bu) (4), salhen(t-Bu) (5)). These are formed from the reaction of the corresponding L(B(OMe)2)2 with BCl3. In addition to being a new type of boron compound, they are also potential two-point Lewis acids. Indeed, they dem- onstrate Lewis acidic behavior in the dealkylation of trimethylphosphate. All of the compounds were characterized by mp, elemental analysis, 1 H and 11 B NMR, IR, MS, and in the case of 2 by X-ray crystallography.
TL;DR: The diacylaminal represents a new supramolecular synthon, one perhaps more suited to the design of three-dimensional architectures, and the first examples of cyclic hexamers held together by hydrogen bonds in which the hydrogen-bonded atoms are not coplanar.
Abstract: A cage-shaped N,N'-diacylaminal crystallizes from some aromatic solvents as "supramolecular chair cyclohexanes", squat cylindrical hexamers with approximate D3d symmetry containing two arene molecules, and from other aromatic and nonaromatic solvents as infinite tapes. A homologous diacylaminal crystallizes only as an infinite tape. The hexamers represent the first examples of cyclic hexamers held together by %@mt;sys@%%@bold@%R%@rsf@%%@sx@%2%@be@%2%@sxx@%%@fn;(;vis;full;auto@%8%@fnx;);vis;full@%-type%@mx@% hydrogen bonds in which the hydrogen-bonded atoms are not coplanar. The diacylaminal represents a new supramolecular synthon, one perhaps more suited to the design of three-dimensional architectures.
TL;DR: The structure of poly-μ-pyrazine-bis(pyrazines) with bidentate pyrazine groups has been investigated by X-ray diffraction as discussed by the authors.
Abstract: The structure of poly-μ-pyrazine-bis(pyrazine)(dinitrato-O)copper(II), Cu(pyz)3(NO3)2, has been investigated by X-ray diffraction. The compound crystallizes in the triclinic space group
$$P\bar 1$$
with a = 6.8040 (10), b = 7.2860 (10), c = 9.289 (2) A, α = 69.65 (2), β = 68.51 (2), γ = 67.51 (2)°, and Z = 1. The structure consists of linear chains of copper ions bridged by bidentate pyrazine groups, with monodentate terminal pyrazine and nitrate groups completing the distorted octahedral geometry about the copper ions.
TL;DR: In this article, the condensation of cyclopentadienyl-derived γ-diketones and arylhydrazines was utilized to synthesize 4-(1,4-diphenyl-2H-cyclopent[d]-pyridazin-2-yl)benzenesulfonamide in better than 80% yield.
Abstract: The condensation of cyclopentadienyl-derived γ-diketones and arylhydrazines was utilized to synthesize 4-(1,4-diphenyl-2H-cyclopent[d]-pyridazin-2-yl)benzenesulfonamide and 4-(1,4-di-(4-methylphenyl)-2H-cyclopent[d]pyridazin-2-yl)benzenesulfonamide in better than 80% yield. The crystal structures of the precursor hydroxyfulvene, {(5Z)-5-[hydroxy(4-methylphenyl)-methylene]cyclopenta-1,3-dien-1-yl}(4-methylphenyl)methanone, and the derived pyridazine 4-(1,4-diphenyl-2H-cyclopent[d]pyridazin-2-yl)benzene-sulfonamide, were also obtained.
TL;DR: In this paper, the X-ray data indicate that the lack of the expected distortion can be accounted for by the presence of either static Jahn-Teller disorder or dynamic Jahn Teller distortion.
Abstract: The reaction of Cu(ClO4)2·6H2O, NaAsF6 and excess pyrazole yields hexakis(pyrazole-κN2)copper(II) bis(hexafluoroarsenate), [Cu(C3H4N2)6](AsF6)2 or [Cu(pzH)6](AsF6)2 (pzH is pyrazole), (I). The analogous hexakis(pyrazole-κN2)copper(II) hexafluorophosphate perchlorate complex, [Cu(C3H4N2)6](PF6)1.29(ClO4)0.71 or [Cu(pzH)6](PF6)1.29(ClO4)0.71, (II), is obtained in a similar fashion, using KPF6 in place of NaAsF6. Both compounds contain the hitherto unknown [Cu(pzH)6]2+ complex cation, in which the copper(II) ion lies at the center of a regular octahedron of coordinated N atoms. The cation has crystallographically imposed \overline 3 symmetry. The X-ray data indicate that the lack of the expected distortion can be accounted for by the presence of either static Jahn–Teller disorder or dynamic Jahn–Teller distortion.
TL;DR: The title compound, C10H9N2+·Br−·H2O, crystallizes in the orthorhombic crystal system as discussed by the authors, which consists of separate bipyridinium cations stacked along the a axis.
Abstract: The title compound, C10H9N2+·Br−·H2O, crystallizes in the orthorhombic crystal system. The structure consists of separate bipyridinium cations stacked along the a axis. The pyridine and pyridinium rings deviate from coplanarity by 29.6 (4)° about the C—C bridging bond. The Br− ions and the water molecules are situated between the stacks.
TL;DR: In this article, the effect of an interfacial layer between the antiferromagnetic and the ferromagnetic layers on the magnetometer response was investigated using a three-layer model for the exchange anisotropy.
Abstract: Recent x-ray absorption measurements have indicated that the interface between the antiferromagnetic (AF) and the ferromagnetic (FM) layers in AF/FM bilayers instead of being abrupt, consists of a thin layer with uncompensated spins. Here the effect of an interfacial layer between the AF and FM layers on the ferromagnetic resonance response is investigated using a three-layer model for the exchange anisotropy. The calculated dependence of the resonance field with the azimuthal angle of the in-plane external field agrees quite well with experimental data in several samples, lending support to the existence of the uncompensated interfacial layer.
TL;DR: In this article, Salen ligands (Salen(tBu)H2=N, N′-ethylenebis(3,5-di-tertbutyl(2-hydroxy)benzylidenimine) were used to prepare borosilyl and μ-O bridged borosallyl compounds.
Abstract: Various Salen ligands (Salen(tBu)H2=N, N′-ethylenebis(3,5-di-tertbutyl(2-hydroxy)benzylidenimine) were used to prepare borosilyl and μ-O bridged borosilyl compounds having the formula, L{B(OSiMe3)2}2 (L=Salen(tBu) (1), Salpen(tBu) (2), Salben(tBu) (3), Salhen(tBu) (4) and L(BOSiMe3)2(μ-O) (L=Salen(tBu) (5) and Salben(tBu) (6)). In the case of 5 and 6 the formation of the B–O–B linkage takes precedence over the formation of a B–O–Si linkage. All of the compounds were characterized by Mp, elemental analysis, 1H and 11B NMR, IR, MS and in the case of 1, 2, and6 by X-ray crystallography.
TL;DR: In the case of C12H6Cl5O2, the dihedral angle between the two rings is 37° as discussed by the authors, which is different from the calculated dihedral angles in aqueous solution (48°).
Abstract: In the title compound, C12H6Cl5O2, the dihedral angle between the two rings is 37°. This dihedral angle is different from the calculated dihedral angle in aqueous solution (48°), a likely cause being the influence of crystal packing.
TL;DR: The copper(II) ion in the title compound, [Cu(NO3)(mepyz)4(H2O)]NO3, has a distorted octahedral geometry with four N atoms of the methylpyrazine ligands in the equatorial positions and two O atoms from water and semi-coordinated nitrate moieties in the axial sites.
Abstract: The copper(II) ion in the title compound, [Cu(NO3)(mepyz)4(H2O)]NO3, where mepyz is 2-methylpyrazine (C5H6N2), has a distorted octahedral geometry with four N atoms of the methylpyrazine ligands in the equatorial positions and two O atoms from water and semi-coordinated nitrate moieties in the axial sites.
TL;DR: A new crystal form of concanavalin A, a well studied lectin from the jack bean (Canavalia ensiformis) is reported, with the symmetry of orthorhombic space group C222(1), grow as large roughly equi-dimensional blocks.
Abstract: A new crystal form of concanavalin A, a well studied lectin from the jack bean (Canavalia ensiformis) is reported. These crystals, with the symmetry of orthorhombic space group C2221, grow as large roughly equi-dimensional blocks. Unit-cell parameters at 120 K are a = 118.67 (12), b = 101.36 (13), c = 111.94 (9) A. On density considerations for two molecules per asymmetric unit, the water content is ∼60%. Data to a nominal resolution of 1.5 A were collected.
01 Jan 2002
Abstract: An error has been noted within Fig. 1 of the paper by Howard & Stokes (1998). There is a group–subgroup relationship between I4/mcm (a0a0c−) and C2/c (a−b−b−), and this should be indicated on the figure by a continuous line joining the corresponding boxes. The corrected version of the figure is shown here.