Building blocks for n-type molecular and polymeric electronics. Perfluoroalkyl- versus alkyl-functionalized oligothiophenes (nT; n = 2-6). Systematics of thin film microstructure, semiconductor performance, and modeling of majority charge injection in field-effect transistors

The solid-state properties and FET electrical behavior of several series of alpha,omega- and beta,beta'-fluorocarbon- and alkyl-substituted and unsubstituted oligothiophenes nTs (n = 2-6) are compared and contrasted. The thin films were grown by slow vacuum deposition over a range of substrate temperatures and/or by casting from solution and were investigated by X-ray diffraction and scanning electron microscopy. Our results indicate that vacuum deposition at 60-80 degrees C affords films with remarkably similar microstructures despite the extensive H --> F substitution. Trends in observed d spacing versus molecular core extension provide quantitative information on molecular orientation. Field-effect transistor measurements performed for all systems and having the same device structure, components, and fabrication conditions demonstrate that all nTs functionalized with fluorocarbon chains at the thiophene termini are n-type semiconductors, in contrast to the p-type activity of the remaining systems. One of these systems, alpha,omega-diperfluorohexyl-4T, exhibits a mobility of 0.22 cm2/(V s) and an Ion:Ioff ratio of 10(6), one of the highest so far reported for an n-type organic semiconductor. The effect of substitution regiochemistry on FET majority charge carrier was additionally studied, in the case of a 6T core, by shifting the fluorocarbon substituents from the terminal to the central thiophene units. Finally, we propose a simple theoretical model for electrode/organic interfacial carrier injection. The results suggest why modest substituent-induced changes in the injection barrier can produce working n-type materials.     

Theoretical study of long oligothiophene dications: bipolaron vs polaron pair vs triplet state

A series of oligothiophene dications (from the sexithiophene dication to the 50-mer oligothiophene dication, nT2+, n = 6-50) were studied. Density functional theory (DFT) at the B3LYP/6-31G(d) level and, in some cases, also at BLYP/6-31Gd, was applied to study the singlet and triplet states of the whole series. We found that the singlet state is the ground state for all oligothiophene dications up to the 20-mer, and that the singlet and triplet states are degenerate for longer oligomers. Thus, the triplet state is never a pure ground state for these dications. We found that, for short oligothiophenes dication (e.g., 6T2+), the bipolaron state is the more important state, with only a small contribution made by the polaron pair state. For medium size oligothiophene dications (e.g., 14T2+), both the bipolaron state and the polaron-pair state contribute to the electronic structure. Finally, in long oligothiophene dications, such as 30T2+ and 50T2+, the contribution from the polaron pair state becomes dominant, and these molecules can be considered as consisting of two independent cation radicals or a polaron pair. Results from isodesmic reactions show that the stability of oligothiophene cation radicals over dications is inversely proportional to chain length. Small oligothiophene dications (n = 6-12) were studied at the CASSCF(m,m)/6-31G(d) (m = 4, 6, and 10) level. The major conclusions of this paper regarding the relative energy of the singlet state versus the triplet state and regarding the relative stability of the bipolaron versus the polaron pair were also supported by CASSCF calculations.     

Chiral amphiphilic self-assembled alpha,alpha'-linked quinque-, sexi-, and septithiophenes: synthesis, stability and odd-even effects

The synthesis, characterization, and self-assembly in butanol of a series of well-defined alpha,alpha'-linked quinqui-, sexi-, and septithiophenes substituted, via ester links at their termini, by chiral oligo(ethylene oxide) chains carrying an alpha, beta, delta, and epsilon methyl, respectively, are reported. Studies of the self-assembly of these molecules using UV/visible absorption, luminescence, and circular dichroism spectroscopies reveal, for the sexithiophene case, that the magnitude of the observed Cotton effect in the aggregates diminishes progressively as the chiral substituent is moved away from the thiophene segment. The stability of the assemblies increases with the length of the oligothiophene and as the substituent chiral unit is moved away from the aromatic core, being greatest for the unsubstituted case. The sign of the Cotton effect alternates in an "odd/even" manner as the position of the chiral substituent is moved along the oligo(ethylene oxide) chain and on going from the quinquethiophene to the septithiophene having the same side chain. Atomic force microscopy on materials deposited from solution on an aluminum or glass surface and optical measurements show that capsules are formed from the oligothiophenes with H-type packing of the aromatic segments.     

Rh(II) and Rh(I) two-legged piano-stool complexes: structure,reactivity, and electronic properties

The ligand 1,4-bis[4-(diphenylphosphino)butyl]-2,3,5,6-tetramethylbenzene, 3, was used to synthesize a mononuclear Rh(II) complex [(eta(1):eta(6):eta(1)-1,4-bis[4-(diphenylphosphino)butyl]-2,3,5,6-tetramethylbenzene)Rh][PF(6)](2), 6+, in a two-legged piano-stool geometry. The structural and electronic properties of this novel complex including a single-crystal EPR analysis are reported. The complex can be cleanly interconverted with its Rh(I) form, allowing for a comparison of the structural properties and reactivity of both oxidation states. The Rh(I) form 6 reacts with CO, tert-butyl isocyanide, and acetonitrile to form a series of 15-membered mononuclear cyclophanes [(eta(1):eta(1)-1,4-bis[4-(diphenylphosphino)butyl]-2,3,5,6-tetramethylbenzene)Rh(CO)(3)][PF(6)] (8), [(eta(1):eta(1)-1,4-bis[4-(diphenylphosphino)butyl]-2,3,5,6-tetramethylbenzene)Rh(CNC(CH(3))(3))(2)][PF(6)] (10), and [(eta(1):eta(1)-1,4-bis[4-(diphenylphosphino)butyl]-2,3,5,6-tetramethylbenzene)Rh(CO)(CH(3)CN)][PF(6)] (11). The Rh(II) complex 6+ reacts with the same small molecules, but over shorter periods of time, to form the same Rh(I) products. In addition, a model two-legged piano-stool complex [(eta(1):eta(6):eta(1)-1,4-bis[3-(diphenylphosphino)propoxy]-2,3,5,6-tetramethylbenzene)Rh][B(C(6)F(5))(4)], 5, has been synthesized and characterized for comparison purposes. The solid-state structures of complexes 5, 6, 6+, and 11 are reported. Structure data for 5: triclinic; P(-)1; a = 10.1587(7) A; b = 11.5228(8) A; c = 17.2381(12) A; alpha = 96.4379(13) degrees; beta = 91.1870(12) degrees; gamma = 106.1470(13) degrees; Z = 2. 6: triclinic; P(-)1; a = 11.1934(5) A; b = 12.4807(6) A; c = 16.1771(7) A; alpha = 81.935(7) degrees; beta = 89.943(1) degrees; gamma = 78.292(1) degrees; Z = 2. 6+: monoclinic; P2(1)/n; a = 11.9371(18) A; b = 32.401(5) A; c = 12.782(2) A; beta = 102.890(3) degrees; Z = 4. 11: triclinic; P(-)1; a = 13.5476(7) A; b = 13.8306(7) A; c = 14.9948(8) A; alpha = 74.551(1) degrees; beta = 73.895(1) degrees; gamma = 66.046(1) degrees; Z = 2.     

Water-solubilized, cap-stabilized, helical polyalanines: calibration standards for NMR and CD analyses

NMR and CD studies are reported for two length series of solubilized, spaced, highly helical polyalanines that are N-capped by the optimal helix stabilizer (beta)Asp-Hel and C-capped by beta-aminoalanine beta and that are studied in water at 2 degrees C, pH 1-8. NMR analysis yields a structural characterization of the peptide Ac(beta)AspHelAla(8)betaNH(2) and selected members of one (beta)AspHelAla(n)beta series. At pH > 4.5 the (beta)AspHel cap provides a preorganized triad of carboxylate anion and two amide residues that is complementary to the helical polyalanine N-terminus. The C-terminal beta-aminoalanine assumes a helix-stabilizing conformation consistent with literature precedents. H(N)CO NMR experiments applied to capped, uniformly (13)C- and (15)N-labeled Ala(8) and Ala(12) peptides define Ala(n) hydrogen bonding signatures as alpha-helical without detectable 3(10) character. Relative NH-->ND exchange rates yield site protection factors PF(i) that define uniquely high fractional helicities FH for the peptide Ala(n) regions. These Ala(n) calibration series, studied in water and lacking helix-stabilizing tertiary structure, yield the first (13)C NMR chemical shifts, (3)J(HNH)(alpha) coupling constants, and CD ellipticities [theta(Molar)](lambda,n) characteristic of a fully helical alanine within an Ala(n) context. CD data are used to assign parameters X and [theta](lambda,infinity), required for rigorous calculation of FH values from CD ellipticities.     

Polyynes as a model for carbyne: synthesis, physical properties, and nonlinear optical response

With the Fritsch-Buttenberg-Wiechell rearrangement as a primary synthetic route, a series of conjugated, triisopropylsilyl end-capped polyynes containing 2-10 acetylene units has been assembled. In a few steps, significant quantities of the polyynes are made available, which allow for a thorough analysis of their structural, physical, and optical properties. Molecules in the series have been characterized in detail using (13)C NMR spectroscopy, differential scanning calorimetry, mass spectrometry, and, for four derivatives including octayne 6, X-ray crystallography. UV-vis spectroscopy of the polyynes 1-7 shows a consistent lowering of the HOMO-LUMO gap (E(g)) as a function of the number of acetylene units (n), fitting a power-law relationship of E(g) approximately n(-)(0.379)(+/-)(0.002). The third-order nonlinear optical (NLO) properties of the polyyne series have been examined, and the nonresonant molecular second hyperpolarizabilities (gamma) increase as a function of length according to the power-law gamma approximately n(4.28)(+/-)(0.13). This result exhibits an exponent that is larger than theoretically predicted for polyynes and higher than is observed for polyenes and polyenynes. The combined linear and nonlinear optical results confirm recent theoretical studies that suggest polyynes as model 1-D conjugated systems. On the basis of UV-vis spectroscopic analysis, the effective conjugation length for this series of polyynes is estimated to be ca. n = 32, providing insight into characteristics of carbyne.     

A solid-state NMR investigation of single-source precursors for group 12 metal selenides; M[N(iPr2PSe)2]2 (M = Zn, Cd, Hg)

The first solid-state NMR investigation of dichalcogenoimidodiphosphinato complexes, M[N(R(2)PE)(2)](n), is presented. The single-source precursors for metal-selenide materials, M[N((i)Pr(2)PSe)(2)](2) (M = Zn, Cd, Hg), were studied by solid-state (31)P, (77)Se, (113)Cd, and (199)Hg NMR at 4.7, 7.0, and 11.7 T, representing the only (77)Se NMR measurements, and in the case of Cd[N((i)Pr(2)PSe)(2)](2)(113)Cd NMR measurements, to have been performed on these complexes. Residual dipolar coupling between (14)N and (31)P was observed in solid-state (31)P NMR spectra at 4.7 and 7.0 T yielding average values of R((31)P,(14)N)(eff) = 880 Hz, C(Q)((14)N) = 3.0 MHz, (1)J((31)P,(14)N)(iso) = 15 Hz, alpha = 90 degrees , beta = 26 degrees . The solid-state NMR spectra obtained were used to determine the respective phosphorus, selenium, cadmium, and mercury chemical shift tensors along with the indirect spin-spin coupling constants: (1)J((77)Se,(31)P)(iso), (1)J((111/113)Cd,(77)Se)(iso), (1)J((199)Hg,(77)Se)(iso), and (2)J((199)Hg,(31)P)(iso). Density functional theory magnetic shielding tensor calculations were performed yielding the orientations of the corresponding chemical shift tensors. For this series of complexes the phosphorus magnetic shielding tensors are essentially identical, the selenium magnetic shielding tensors are also very similar with respect to each other, and the magnetic shielding tensors of the central metals, cadmium and mercury, display near axial symmetry demonstrating an expected deviation from local S(4) symmetry.     

203,205Tl NMR studies of crystallographically characterized thallium alkoxides. X-ray Structures of [TI(OCH2CMe3)]4 and [TI(OAr)]infinity, where OAr = OC6H3(Me)2-2,6 and OC6H3(CHMe2)2-2,6

[Tl(OCH2Me)]4 (1) was reacted with excess HOR to prepare a series of [Tl(OR)]n, where OR = OCHMe2 (2, n = 4), OCMe3 (3, n = 4), OCH2CMe3 (4, n = 4), OC6H3(Me)2-2,6 (5, n = infinity), and OC6H3(CHMe2)2-2,6 (6, n = infinity). Single-crystal X-ray diffraction experiments revealed that in the solid state the alkoxide-ligated compound 4 adopts a cubane structure, whereas the aryloxide derivatives, 5 and 6, formed polymeric chains. Compounds 1-6 were also characterized by 203,205Tl solution and 205Tl solid-state NMR spectroscopy. In solution it was determined that 1-4 retained the [Tl-O]4 cube structure, whereas the polymeric species 5 and 6 appeared to be fluxional. Variations in the solution and solid-state structures for the [Tl(OR)]4 cubes and polymeric [Tl(OAr)]infinity are influenced by the steric hindrance of the ligand. The acidity of the parent alcohol influences the degree of covalency at the Tl metal center, which is reflected in the 203,205Tl chemical shifts for 1-6.     

Synthesis, pH-dependent structural characterization, and solution behavior of aqueous aluminum and gallium citrate complexes

Reactions of Al(III) and Ga(III) with citric acid in aqueous solutions, yielded the complexes (NH(4))(5)[M(C(6)H(4)O(7))(2)].2H(2)O (M(III) = Al (1), Ga (2)) at alkaline pH, and the complexes (Cat)(4)[M(C(6)H(5)O(7))(C(6)H(4)O(7))].nH(2)O (M(III) = Al (3), Ga (4), Cat. = NH(4)(+), n = 3; M(III) = Al (5), Ga (6), Cat. = K(+), n = 4) at acidic pH. All compounds were characterized by spectroscopic (FT-IR, (1)H, (13)C, and (27)Al NMR, (13)C-MAS NMR) and X-ray techniques. Complex 1 crystallizes in space group P1, with a = 9.638(5) A, b = 9.715(5) A, c = 7.237(4) A, alpha = 90.96(1) degrees, beta = 105.72(1) degrees, gamma = 119.74(1) degrees, V = 557.1(3) A(3), and Z = 1. Complex 2 crystallizes in space group P1, with a = 9.659(6) A, b = 9.762(7) A, c = 7.258(5) A, alpha = 90.95(2) degrees, beta = 105.86(2) degrees, gamma = 119.28(1) degrees, V = 564.9(7) A(3), and Z = 1. Complex 3 crystallizes in space group I2/a, with a = 19.347(3) A, b = 9.857(1) A, c = 23.412(4) A, beta = 100.549(5) degrees, V = 4389(1) A(3), and Z = 8. Complex 4 crystallizes in space group I2/a, with a = 19.275(1) A, b = 9.9697(6) A, c = 23.476(1) A, beta = 100.694(2) degrees, V = 4432.8(5) A(3), and Z = 8. Complex 5 crystallizes in space group P1, with a = 7.316(1) A, b = 9.454(2) A, c = 9.569(2) A, alpha = 64.218(4) degrees, beta = 69.872(3) degrees, gamma = 69.985(4) degrees, V = 544.9(2) A(3), and Z = 1. Complex 6 crystallizes in space group P1, with a = 7.3242(2) A, b = 9.4363(5) A, c = 9.6435(5) A, alpha = 63.751(2) degrees, beta = 70.091(2) degrees, gamma = 69.941(2) degrees, V = 547.22(4) A(3), and Z = 1. The crystal structures of 1-6 reveal mononuclear octahedral complexes of Al(III) (or Ga(III)) bound to two citrates. Solution NMR, on both 4- and 5- species, reveals rapid intramolecular exchange of the bound and unbound terminal carboxylates. Upon dissolution in water, the complexes, through a complicated reaction cascade, transform to oligonuclear 1:1 species that, in agreement with previous studies, represent the thermodynamically stable state in solution. The data provide, for the first time, structural details of low MW, mononuclear complexes of Al(III) (or Ga(III)) with citrate that are dictated, among other factors, by pH. The properties of 1-6 may provide clues relevant to their biological association with humans.     

A conformational study of phospha(III)- and phospha(V)-guanidine compounds

Spectroscopic, crystallographic, and computational studies of the substituent distribution about the "NCN" unit in a series of phospha(III)- and phospha(V)-guanidines, R(2)PC{NR'}{NHR'} and R(2)P(E)C{NR'}{NHR'} (R = Ph, Cy; R' = (i)Pr, Cy; E = S, Se), are reported. In the phosphorus(III) systems, the P-diphenyl substituted compounds are observed as only one isomer, shown by NMR spectroscopy to be the E(syn)-(alpha) configuration. In contrast, the corresponding P-dicyclohexyl derivatives exist as a mixture of E(syn)-(alpha) and Z(anti) in solution. Spectroscopic techniques are unable to determine whether the latter isomer exists as the alpha- or beta-conformer relative to rotation about the P-C(amidine)() bond; however, DFT calculations indicate a low-energy structure for the N,N'-dimethyl model complex in the beta-conformation. In their oxidized sulfo and seleno forms, the P-diphenyl compounds are present as an interconverting equilibrium mixture of the E(syn)-(beta) and Z(syn)-(beta) isomers in solution ( approximately 3:2 ratio), whereas for the P-dicyclohexyl analogues, the latter configuration (in which the nitrogen substituents are in a more sterically unfavorably cisoid arrangement about the imine double bond) is the dominant form. Intramolecular E...HN (E = S, Se) interactions are observed in solution for the Z(syn)-(beta) configuration of both P-substituted species, characterized by J(SeH) coupling in the NMR spectrum for the P(V)-seleno compounds and a bathochromic shift of the NH absorption in the infrared spectrum. An X-ray crystallographic analysis of representative Ph(2)P(E)- and Cy(2)P(E)-substituted species shows exclusively the E(syn)-(beta) configuration for the P-diphenyl substituted compounds and the Z(syn)-(beta) form for the P-dicyclohexyl derivatives, independent of the chalcogen and the nitrogen substituents. Results from a DFT analysis of model compounds fail to identify a compelling electronic argument for the observed preferences in substituent orientation, suggesting that steric factors play an important role in determining the subtle energetic differences at work in these systems.     

New insights into the structural and dynamical features of lithium hexaoxometalates Li7MO6 (M = Nb, Ta, Sb, Bi)

We present a (re)investigation of the hexaoxometalates Li(8)MO(6) (M = Sn, Pb, Zr, Hf) and Li(7)MO(6) (M = Nb, Ta, Sb, Bi). Lithium motion and ionic conductivity in the hexaoxometalates were studied using impedance spectroscopy (for Li(7)MO(6), M = Sb, Bi, Ta) and (6)Li and (7)Li solid-state nuclear magnetic resonance (for Li(7)TaO(6)). The NMR data indicate a considerable exchange of Li among the tetrahedral and octahedral voids even at ambient temperature. In an investigation of the crystal structures using laboratory and synchrotron X-ray powder diffraction techniques, the structures of Li(7)TaO(6), Li(7)NbO(6), and Li(7)SbO(6) could be solved and refined. All three reveal a triclinic metric (Li(7)SbO(6), triclinic, P1, a = 5.38503(6) A, b = 5.89164(7) A, c = 5.43074(6) A, alpha = 117.2210(6) degrees, beta = 119.6311(6) degrees, gamma = 63.2520(7) degrees, V = 127.454(3) A(3), Z = 1; Li(7)NbO(6), triclinic, P1, a = 5.37932(9) A, b = 5.91942(11) A, c = 5.37922(9) A, alpha = 117.0033(9) degrees, beta = 119.6023(7) degrees, gamma = 63.2570(9) degrees, V = 126.938(4) A(3), Z = 1; Li(7)TaO(6), triclinic, P1, a = 5.38486(2) A, b = 5.92014(3) A, c = 5.38551(2) A, alpha = 117.0108(2) degrees, beta = 119.6132(2) degrees, gamma = 63.2492(2) degrees, V = 127.208(1) A(3), Z = 1.     

Donor-Free Alkali Metal Thiolates: Synthesis and Structure of Dimeric, Trimeric, and Tetrameric Complexes with Sterically Encumbered Terphenyl Substituents

The synthesis and characterization of the tetrameric lithium thiolate (LiSC(6)H(2)-2,4,6-Ph(3))(4).C(7)H(8) (1), the trimeric lithium thiolate (LiSC(6)H(3)-2,6-Mes(2))(3).C(6)H(14)()()(2) (Mes = 2,4,6-Me(3)C(6)H(2)), the thiol HSC(6)H(3)-2,6-Trip(2) (3) (Trip = 2,4,6-i-Pr(3)C(6)H(2)), and the complete alkali metal series of dimeric thiolates (MSC(6)H(3)-2,6-Trip(2))(2) (M = Li (4, 5), Na (6), K (7), Rb (8), Cs (9)) are described. The compounds were characterized by (1)H, (7)Li, and (13)C NMR and IR spectroscopy and by X-ray crystallography. The compounds 1 and 2 crystallize as four- and three-rung ladder framework structures. The compounds 4-9 crystallize as dimers with M(2)S(2) cores. In addition, the metal ions interact with the ortho aryl groups to varying degrees in all the structures. The extent of these interactions appears to be determined mainly by ionic sizes and geometric factors. The coordination geometry of the thiolato sulfurs also varies from pyramidal in 1, 2, 4, 5, and 6 and one planar and one slightly pyramidal sulfur geometry in 7 to both sulfurs being planar coordinated in 8 and 9. Crystal data at 130 K are as follows: (LiSC(6)H(2)-2,4,6-Ph(3))(4).C(7)H(8) (1), a = 15.961(2) ?, b = 16.243(3) ?, c = 17.114(3) ?, alpha = 89.375(14) degrees, beta = 85.334(14) degrees, gamma = 63.343(12) degrees, V = 3950(1) ?(3), space group P&onemacr;, Z = 2, R(1) = 0.082; (LiSC(6)H(3)-2,6-Mes(2))(3).C(6)H(14)()()(2), a = 14.554(4) ?, b = 14.010(4) ?, c = 32.832(8) ?, beta = 95.20(2) degrees, V = 6667(2) ?(3), space group P2(1)/n, Z = 4, R(1) = 0.089; HSC(6)H(3)-2,6-Trip(2) (3), a = 8.180(2) ?, b = 25.437(5) ?, c = 15.752(3) ?, V = 3278(1) ?(3), space group Pnma, Z = 4, R(1) = 0.045; (LiC(6)H(3)-2,6-Trip(2))(2) (4), a = 12.652(2) ?, b = 14.218(1) ?, c = 18.713(2) ?, alpha = 83.56(1) degrees, beta = 84.36(1) degrees, gamma = 73.82(1) degrees, V = 3205(1) ?(3), space group P&onemacr;, Z = 2, R(1) = 0.055; (LiC(6)H(3)-2,6-Trip(2))(2).C(7)H(8) (5), a = 15.383(3) ?, b = 14.381(2) ?, c = 16.524(2) ?, beta = 111.10(1), V = 3410.3(9) ?(3), space group P2(1)/n, Z = 2, R(1) = 0.086; (NaSC(6)H(3)-2,6-Trip(2))(2).0.5C(7)H(8) (6), a = 13.952(2) ?, b = 20.267(2) ?, c = 24.475(3) ?, beta = 98.673(9) degrees, V = 6842(1) ?(3), space group P2(1)/n, Z = 4, R(1) = 0.068; (KSC(6)H(3)-2,6-Trip(2))(2).C(7)H(8) (7), a = 13.683(4) ?, b = 15.071(4) ?, c = 17.824(5) ?, alpha = 82.73(2), beta = 86.09(2), gamma = 88.46(2), V = 3637(2) ?(3), space group P&onemacr;, Z = 2, R(1) = 0.072; (RbSC(6)H(3)-2,6-Trip(2))(2).C(7)H(8) (8), a = 19.710(3) ?, b = 20.892(3) ?, c = 18.755(2) ?, beta = 106.900(9) degrees, V = 7389(2) ?(3), space group P2(1)/n, Z = 4, R(1) = 0.069; (CsSC(6)H(3)-2,6-Trip(2))(2) (9), a = 13.109(3) ?, b = 15.941(3) ?, c = 17.748(4) ?, alpha = 101.65(2) degrees, beta = 100.76(2) degrees, gamma = 104.25(2) degrees, V = 3410(1) ?(3), space group P&onemacr;, Z = 2, R(1) = 0.048.     

Synthesis of a library of stereo- and regiochemically diverse aminoglycoside derivatives

A library of forty modified aminoglycosides was prepared in which the configuration and regiochemistry of two or three rings was widely varied. The library was based around three core ring systems: the 2-deoxystreptamine ring system found in the natural products, and both enantiomers of (1R*,2R*,4R*,5R*)-2,5-diamino-cyclohexane-1,4-diol and (1R*,3R*,4R*,6R*)-4,6-diaminocyclohexane-1,3-diol. In each case, the core was modified by glycosylation with one or two sugar rings. The absolute configuration of the sugar substituents (d or l), the configuration of the anomeric centres (alpha or beta), and the regiochemical arrangement of the amine(s) were varied.     

Synthesis and characterization of new coordination polymers generated from bent bis(cyanophenyl)oxadiazole ligands and Ag(I) salts

Two new bent bis(cyanophenyl)oxadiazole ligands, 2,5-bis(4-cyanophenyl)-1,3,4-oxadiazole (L7) and 2,5-bis(3-cyanophenyl)-1,3,4-oxadiazole (L8), were synthesized. The coordination chemistry of these ligands with various Ag(I) salts has been investigated. Seven new coordination polymers, namely, {[Ag(L7)(H2O)]ClO4}n) (1) (triclinic, P1, a = 9.342(4) A, b = 9.889(4) A, c = 10.512(4) A, alpha = 68.978(6) degrees, beta = 78.217(6) degrees, gamma = 81.851(7) degrees, Z = 2), {[Ag(L7)]SO3CF3}n (2) (monoclinic, P2(1)/n, a = 7.559(2) A, b = 23.739(6) A, c = 10.426(3) A, beta = 108.071(4) degrees, Z = 4), {[Ag(L8)]BF4 x 0.5(C6H6) x H2O}n (3) (triclinic, P1, a = 7.498(3) A, b = 10.649(4) A, c = 13.673(5) A, alpha = 98.602(5) degrees, beta = 100.004(5) degrees, gamma =110.232(5) degrees, Z = 2), {[Ag(L8)SbF6] x H2O}n (4) (triclinic, P1, a = 8.2621(9) A, b = 10.6127(12) A, c = 13.3685(15) A, alpha = 98.012(2) degrees, beta = 106.259(2) degrees, gamma = 112.362(2) degrees, Z = 2), {[Ag2(L8)2(SO3CF3)] x H2O}n (5) (triclinic, P1, a = 10.713(4) A, b = 13.449(5) A, c = 15.423(5) A, alpha = 65.908(5) degrees, beta = 74.231(5) degrees, gamma = 83.255(5) degrees, Z = 2), {[Ag2(L8)(C6H6)(ClO4)] x ClO4}n (6) (monoclinic, P2(1)/n, a = 6.9681(17) A, b = 20.627(5) A, c = 17.437(4) A, beta = 95.880(4) degrees, Z = 4), and {[Ag2(L8)(H2PO4)2]}n (7) (triclinic, P1, a = 7.956(2) A, b = 9.938(3) A, c = 14.242(4) A, alpha = 106.191(4) degrees, beta = 97.322(4) degrees, gamma = 107.392(4) degrees, Z = 1), were obtained by the combination of L7 and L8 with Ag(I) salts in a benzene/methylene chloride mixed-solvent system and fully characterized by infrared spectroscopy, elemental analysis, and single-crystal X-ray diffraction. In addition, the luminescence and electrical conductance properties of compounds 1-6 and the host-guest chemistry of compound 3 were investigated.     

Organocadmium aminoalcoholates: synthesis, structure, and materials chemistry

The novel methylcadmium aminoalkoxides MeCd(dmae) (Hdmae = dimethylaminoethanol), MeCd(bdmap) [Hbdmap = 1,3- bis-(dimethylamino)-propan-2-ol], and MeCd(tdmap) [tdmap = 1,3- bis(dimethylamino)-2-(dimethylaminomethyl)-propan-2-ol] have been synthesized and structurally characterized. MeCd(dmae) (1) forms a tetrameric heterocubane with a Cd4O4 core, while MeCd(bdmap) (2) is trimeric and MeCd(tdmap) (3) is a dimer. Only in the case of MeCd(dmae) are all the ligand donors fully utilized. In solution, MeCd(tdmap) undergoes a Schlenk equilibrium, with Me2Cd and Cd(tdmap)2 evident at 218 K. The structure and solution-state chemistry of Cd(tdmap)2 (5) have been independently studied and, in the solid-state, found to exist as a dimer whose coordination number at cadmium (CN = 6) is greater than in the organocadmium complexes (CN = 4, 5). MeCd(tdmap) has been used as a single-source precursor for CdO films by LPCVD with a glass substrate temperature of only 140 degrees C. Evidence is also presented for the formation of a heterometallic precursor, [(MeZn)(MeCd)(tdmap)2] (6), which has been used to deposit films of CdO mixed with ZnO by LPCVD at 140 degrees C. The structure of Me4Cd4(tdmap)2Cl2 (4), obtained serendipitously, is also included. Crystal data: 1, C20H52Cd4N4O4, FW 862.26, triclinic, P1, a = 11.47560(10), b = 13.55400(10), c = 21.5966(2) A, alpha = 99.7869(4), beta = 90.7476(4), gamma = 98.7823(4) degrees, V = 3268.82(5) A(3), Z = 4; 2, C27H67Cd3N6O3, FW 861.07, triclinic, P1, a = 11.4148(2), b =13.1886(2), c = 14.3139(3) A, alpha = 102.1962(10), beta = 108.3064(10), gamma = 100.8446(10) degrees, V = 1923.09(6) A(3), Z = 4; 3, C22H54Cd2N6O2, FW 659.51, monoclinic, P2(1)/n, a = 10.2912(1), b = 13.46930(1), c = 11.79130(1) A, beta = 112.8051(1) degrees, V = 1506.59(2) A(3), Z = 2; 4, C24H60Cd4Cl2N6O2, FW 985.28, monoclinic, P2(1)/c, a = 10.89780(10), b = 20.3529(2), c = 16.5317(2) A, beta = 94.8550(10) degrees, V = 3653.61(7) A(3), Z = 4; 5, C40H96Cd2N12O4, FW 1034.09, orthorhombic, P2(1)cn, a = 12.33290(10), b = 14.25060(10), c = 29.9003(2) A, V = 5255.01(7) A(3), Z = 4.     

Imidotitanium Tris(pyrazolyl)hydroborates: Synthesis, Solution Dynamics, and Solid-State Structure

Reaction of [Ti(NBu(t))Cl(2)(py-Bu(t))(2)] (1; py-Bu(t) = 4-tert-butyl pyridine) with 1 equivalent of K[Tp(Me2)], K[Tp(Pri)] or K[Tp(Pri,Br)] affords the corresponding complexes [Tp(Me2)Ti(NBu(t))Cl(py-Bu(t))] (2), [Tp(Pri)Ti(NBu(t))Cl(py-Bu(t))] (3), and [Tp(Pri,Br)Ti(NBu(t))Cl(py-Bu(t))] (4), respectively, which are the first examples of imido Group 4 tris(pyrazolyl)hydroborates [Tp(Me2) = tris(3,5-dimethylpyrazolyl)hydroborate; Tp(Pri) = tris(3-isopropylpyrazolyl)hydroborate; Tp(Pri,Br) = tris(3-isopropyl-4-bromopyrazolyl)hydroborate]. Complexes 2-4 are fluxional on the (1)H and (13)C NMR time scales, the spectra indicating restricted rotation about the Ti-py-Bu(t) bond. Activation parameters for this dynamic process have been determined both by (13)C NMR lineshape analysis and by coalescence measurements. The solution-state structure for 2 has been unambiguously assigned from a low temperature, phase-sensitive (1)H NOESY DQF spectrum and the solid-state X-ray crystal structure of the dichloromethane solvate of 3 has been determined (space group P2(1)/n; a = 12.539(3), b = 14.686(3), c = 21.747(4) ?; beta = 91.28(3) degrees; R(1) = 0.0694 and wR(2) = 0.154 for 1578 observed reflections). (13)C NMR Deltadelta values (Deltadelta = delta(C(alpha)) - delta(C(beta))) for the tert-butyl imido ligand in 2-4 suggest that the donor ability of the tris(pyrazolyl)hydroborate ligands increases in the order Tp(Pri,Br) < Tp(Pri) < Tp(Me2). None of these ligands, however, is as effective a donor to the metal center as either eta-C(5)H(5) or eta-C(5)Me(5).     

Synthesis, structure, and reactions of binuclear gold(I) complexes containing two different bridging ligands

The binuclear cycloaurated compounds [Au(2)(mu-C(6)H(3)-2-PPh(2)-n-Me)(2)] (n = 5, 1a; n = 6, 1b) react with the digold(I) complexes [Au(2)(mu-S(2)CN(n)()Bu(2))(2)] and [Au(2)(mu-dppm)(2)](PF(6))(2) to give heterobridged dinuclear complexes [Au(2)(mu-C(6)H(3)-2-PPh(2)-n-Me)(mu-S(2)CN(n)Bu(2))] (n = 5, 5a; n = 6, 5b) and [Au(2)(mu-C(6)H(3)-2-PPh(2)-n-Me)(mu-dppm)]PF(6), (n = 5, 9a; n = 6, 9b), respectively. Complex 5a exists in the solid state as an infinite zigzag chain of dimeric units with intramolecular Au-Au separations of 2.8331(3) and 2.8243(3) A for independent molecules and intermolecular Au-Au separations of 3.0653(3) and 3.1304(3) A. Both 5a and 5b undergo oxidative addition with halogens to give the heterovalent, gold(I)-gold(III) compounds [XAu(I)(mu-2-Ph(2)PC(6)H(3)-n-Me)Au(III)X(eta(2)-S(2)CN(n)Bu(2))] [n = 5, X = Cl (6a), I (8a); n = 6, X = Cl (6b), Br (7b), I (8b)]. Compound 8a has been shown by X-ray crystallography to contain a gold(III) atom coordinated in a planar array by bidentate, chelating di-n-butyldithiocarbamate, iodide, and the sigma-aryl carbon atom, together with a gold(I) atom that is linearly coordinated by the phosphorus atom of the arylphosphine and by iodide. The intramolecular gold-gold distance of 3.2201(3) A indicates little or no interaction between the metal atoms. In contrast to the behavior of the homobridged complexes 1a and 1b, the heterobridged dithiocarbamate complexes 5a and 5b give structurally similar products on reaction with halogens, irrespective of the position of the ring methyl substituent. Crystal data for [Au(2)(mu-C(6)H(3)-2-PPh(2)-5-Me)(mu-S(2)CN(n)Bu(2))] (5a): triclinic, space group P1 (No. 2), with a = 11.3398(1), b = 15.9750(2), c = 16.4400(3) A, alpha = 91.0735(9), beta = 109.3130(7), gamma = 90.7666(8) degrees, V = 2809.47(6) A(3), and Z = 4. Crystal data for [IAu(I)(mu-2-Ph(2)PC(6)H(3)-5-Me)Au(III)I(eta(2)- S(2)CN(n)Bu(2))] (8a): triclinic, space group P1 (No. 2), with a = 8.6136(2), b = 9.3273, c = 21.1518(4) A, alpha = 84.008(1), beta = 84.945(1), gamma = 75.181(1) degrees, V = 1630.54(6) A(3), and Z = 2.     

Syn-Anti Isomerism in a Mixed-Ligand Oxorhenium Complex, ReO[SN(R)S][S

The simultaneous action of the tridentate ligand (C(2)H(5))(2)NCH(2)CH(2)N(CH(2)CH(2)SH)(2) and the monodentate coligand HSC(6)H(4)OCH(3) on a suitable ReO(3+) precursor results in a mixture of syn- and anti-oxorhenium complexes, ReO[(C(2)H(5))(2)NCH(2)CH(2)N(CH(2)CH(2)S)(2)] [SC(6)H(4)OCH(3)], in a ratio of 25/1. The complexes are prepared by a ligand exchange reaction using ReO(eg)(2) (eg = ethylene glycol), ReOCl(3)(PPh(3))(2), or Re(V)-citrate as precursor. Both complexes have been characterized by elemental analysis, FT-IR, UV-vis, X-ray crystallography, and NMR spectroscopy. The syn isomer C(17)H(29)N(2)O(2)S(3)Re crystallizes in the monoclinic space group P2(1)/n, a = 14.109(4) ?, b = 7.518(2) ?, c = 20.900(5) ?, beta = 103.07(1) degrees, V = 2159.4(9) ?(3), Z = 4. The anti isomer C(17)H(29)N(2)O(2)S(3)Re crystallizes in P2(1)/n, a = 9.3850(7) ?, b = 27.979(2) ?, c = 8.3648(6) ?, beta = 99.86(1) degrees, V = 2163.9(3) ?(3), Z = 4. Complete NMR studies show that the orientation of the N substituent chain with respect to the Re=O core greatly influences the observed chemical shifts. Complexes were also prepared at the tracer ((186)Re) level by using (186)Re-citrate as precursor. Corroboration of the structure at tracer level was achieved by comparative HPLC studies.     

Relative energies of alpha and beta isomers of Keggin dodecatungstogallate

The relative energies of beta Keggin heteropolytungstates, X(n+) W12O40(8-n)-, decrease as X(n+) is varied within period 3, from P5+ to Si4+ to Al3+. With heating of alpha-H5Ga3+ W12O40 at 200 degrees C in water, an equilibrated mixture of alpha (T(d); one 183W NMR signal) and beta (C(3v); three signals; 1:2:1 ratio) isomers is obtained. From deltaG(exp) = -RT ln K(beta-->alpha), in which (from 71Ga NMR spectra) K(beta-->alpha) (= [alpha]/[beta]) = 5.0, beta-GaW12O40(5-) is 0.65 kcal mol(-1) higher in energy than alpha-GaW12O40(5-). This finding is evaluated by analysis of the X-ray crystal structure alpha-K2Na3[GaW12O40] x 9.3 H2O [trigonal, space group P3(2)21, a = 18.9201(13) A, b = 18.9201(13) A, c = 12.5108(12) A, Z = 3, T = 100(2)K], comparison of the Shannon and Prewitt radii and Pauling electronegativities of Al3+ and Ga3+, and insight from density functional theory calculations, which predicted Ebeta - Ealpha = 0.32 kcal mol(-1).     

The synthesis and characterization of compounds of the type Hg[1-C(6)H(4)-2-C(H)=NC(6)H(5-n)R(n)](2)

The organomercurial compounds Hg[1-C(6)H(4)-2-C(H)=NC(6)H(5-n)R(n)](2) (R = 4-NMe(2), 6a; 4-Me, 6b; 4-I, 6c; 4-NO(2), 6d; 2-(i)Pr, 6e; 2-Me, 6f; 2,6-(i)Pr(2), 6g; 2,6-Me(2), 6h) have been prepared in good overall yield from 2-bromobenzaldehyde. All of the compounds have been characterized by elemental analysis, (1)H NMR, (13)C[(1)H] NMR, and infrared spectroscopy. In addition, compounds 6a [C(30)H(30)HgN(4), triclinic, P, a = 6.20000(10) A, b = 9.2315(2) A, c = 10.9069(3) A, alpha = 85.8510(10) degrees, beta = 89.3570(10) degrees, gamma = 87.206(2) degrees, Z = 1], 6b [C(28)H(24)HgN(2), monoclinic, P2(1)/c, a = 12.8260(5) A, b = 14.0675(4) A, c = 6.1032(2) A, beta = 90.0990(10) degrees, Z = 2], 6g [C(38)H(44)HgN(2), triclinic, P, a = 8.2626(2) A, b = 9.8317(2) A, c = 11.8873(3) A, alpha = 103.6650(10) degrees, beta = 109.3350(10) degrees, gamma = 104.627(2) degrees, Z = 1], and 6h [C(30)H(28)HgN(2), monoclinic, P2(1)/c, a = 12.5307(2) A, b = 10.9852(2) A, c = 18.2112(2) A, beta = 104.0190(10) degrees, gamma = 87.206(2) degrees, Z = 4] have been characterized by low-temperature single-crystal X-ray diffraction studies, and two different molecular geometries about the central mercury atom have been observed; intramolecular contacts suggest a van der Waals radius for Hg of 2.1-2.2 A.