Showing papers by "Sean Parkin published in 2001"
TL;DR: The preparation of two functionalized pentacene derivatives, and the effect of this functionalization on both the solid-state ordering and the electronic properties of the resulting crystals is reported.
Abstract: Molecular order has proven to be a significant factor in the performance of devices based on organic semiconductors. Recent studies involving solubilized versus unsubstituted thiophene oligomers have demonstrated that modifications which increase orbital overlap in the solid state can improve device performance by more than an order of magnitude. 1 Similar studies on pentacene, a compound which has already demonstrated remarkable potential for device applications, 2 have also focused on maximizing orbital overlap by inducing order in films. 3 However, these pentacene studies have thus far relied on substrate modification, rather than on pentacene functionalization, 4 to achieve the desired goals. We report here the preparation of two functionalized pentacene derivatives, and the effect of this functionalization on both the solid-state ordering and the electronic properties of the resulting crystals. Our goal for a functionalized pentacene was two-fold: First, the substituents should impart solubility to the acene, to simplify purification and processing. Second, the substituents should induce some capability for self-assembly of the aromatic moieties into ﷿-stacked arrays to enhance intermolecular orbital overlap. We anticipated that both of these goals could be accomplished by exploiting a rigid spacer to hold the necessarily bulky solubilizing groups well away from the aromatic core, allowing the closest possible contact between the aromatic rings. 5 Our initial targets were the bis(triisopropylsilylethynyl)pentacenes 1 and 2. Both of these compounds are easily prepared in near quantitative yield in a one-pot reaction from 6,13-pentacenequinone and 5,14pentacenequinone, respectively. 6
1,211 citations
TL;DR: Several of the compounds were explored as potential catalysts for the living polymerization of propylene oxide and the first structurally characterized five-coordinate monomeric amide was prepared by a salt elimination utilizing Salcen((t)Bu)AlCl (4).
Abstract: The convenient five-coordinate starting materials, Salen((t)Bu)AlCl (Salen((t)Bu) = N,N'-alkylene (or arylene) bis (3,5-di-tert-butyl-2-hydroxybenzylideneamine) (1-4) can be used in a wide range of reactions to form five-coordinate aluminum compounds. Herein, these reagents were used to produce new five-coordinate azides, LAlN(3) (L = Salen((t)Bu) (5), Salpen((t)Bu) (6), and Salomphen((t)Bu) (7)) through trimethylsilylhalide elimination. The decomposition of the azides produce first hydroxide (LAlOH (L = Salen((t)Bu) (8)) and, subsequently in the presence of chlorotrimethylsilane, the siloxide compounds, LAlOSiMe(3) (L = Salen((t)Bu) (9), Salpen((t)Bu) (10), and Salomphen((t)Bu) (11)). Alkane elimination reactions may also be used to access this type of compound as evidenced by the formation of Salomphen((t)Bu)AlOSiPh(3) (12). Additionally, the first structurally characterized five-coordinate monomeric amide, Salcen((t)Bu)AlN(SiMe(3))(2) (13), can prepared by a salt elimination utilizing Salcen((t)Bu)AlCl (4). The compounds were characterized by spectroscopic methods ((1)H and (27)Al NMR, MS, and IR) and, in the case of 2 (Salpen((t)Bu)AlCl), 3 (Salomphen((t)Bu)AlCl) 9, 11, 12, and 13, by X-ray analysis. Several of the compounds were explored as potential catalysts for the living polymerization of propylene oxide.
107 citations
TL;DR: The acid dissociation constants of 2,4,6-trimercaptotriazine (H(3)TMT, 1) were determined and now can be employed in the preparation of complexes having specific M-TMT ratios.
Abstract: The acid dissociation constants of 2,4,6-trimercaptotriazine (H(3)TMT, 1) were determined and now can be employed in the preparation of complexes having specific M-TMT (M = divalent metal; TMT = 2,4,6-trimercapto-1,3,5-triazinide, C(3)N(3)S(3)(3-)) ratios. For example, the combination of H(3)TMT (1) with Mg(OH)(2) at pH 7.1 leads to the crystallization of Mg(H(2)TMT)(2).6H(2)O (4). With the appropriate pH adjustment, the contiguous series of compounds Ba(3)(TMT)(2).8H(2)O (3), Ba(H(2)TMT)(2).7H(2)O (5), and BaHTMT.3H(2)O (6) can be isolated. The compounds were characterized by mp, IR, TGA, elemental analysis, and, in the cases of 4, 5, and 6, crystallography. The comparison of 4 with 5 and 6 offers an interesting view of the difference in hard and soft bonding with TMT. In the saltlike Mg structure of 4, there is extensive hydrogen bonding, but in the Ba structures, 5 and 6, covalent Ba-S bonding dominates.
56 citations
TL;DR: In this paper, the authors describe physical measurements on a unique class of pentacene-based compounds where additional symmetric side groups have been added to enhance their solubility in common organic solvents.
28 citations
TL;DR: In this paper, the bidentate ligand Sal(tBu)H is prepared by the condensation of one equivalent of a bulky amine with 3,5-di-tert-butylsalicylaldehyde.
27 citations
TL;DR: The substituents at the peri positions of dehydro[14]annulenes 1 have a dramatic effect on the stability of these macrocycles, and lead to derivatives that are stable even at elevated temperatures (up to 190°C).
Abstract: The substituents at the peri positions of dehydro[14]annulenes 1 have a dramatic effect on the stability of these macrocycles, and lead to derivatives that are stable even at elevated temperatures (up to 190°C).
19 citations
TL;DR: The complexes [Cu(imH)5]-AsF6)2·H2O and [Cu[imH]4Cl]Cl (imH = imidazole) were prepared and characterized on the basis of elemental analyses and X-ray crystallography as mentioned in this paper.
Abstract: The complexes [Cu(imH)5](AsF6)2·H2O and [Cu(imH)4Cl]Cl (imH = imidazole) were prepared and characterized on the basis of elemental analyses, infrared spectroscopy, electronic spectroscopy, magnetic moment measurements and X-ray crystallography. The complex cation in each species contains a five-coordinate copper atom with a distorted square-pyramidal geometry.
12 citations
TL;DR: The pronounced pseudosymmetry in the P1 and P2(1)/c structures that have Z' = 2 has been investigated by analysing the atomic coordinates, performing refinements in the smaller pseudocells and by making separate Wilson plots for the classes of reflections which are systematically strong and systematically weak.
Abstract: Numerous printing errors in the paper by Xia et al. [Acta Cryst. (2001), B57, 507–516] are corrected.
10 citations
6 citations
TL;DR: In this article, the crystal structure of a metabolite of 4-chloro-bi-phenyl (PCB 3) was described and the dihedral angle of the title compound is 43.1 1/3°, which is in reasonable agreement with the calculated value of 37.2°.
Abstract: The crystal structure of a metabolite of 4-chlorobiphenyl (PCB 3), 4-chloro-3′,4′-dihydroxybiphenyl (C12H9ClO2), is described. The dihedral angle of the title compound is 43.1 (3)°, which is in reasonable agreement with the calculated value of 37.2°.
4 citations
TL;DR: The substituents at the peri positions of dehydro[14]annulenes 1 have a dramatic effect on the stability of these macrocycles, and lead to derivatives that are stable even at elevated temperatures (up to 190°C) as discussed by the authors.
Abstract: The substituents at the peri positions of dehydro[14]annulenes 1 have a dramatic effect on the stability of these macrocycles, and lead to derivatives that are stable even at elevated temperatures (up to 190°C).