A multimode analysis of the gas-phase photoelectron spectra in oligoacenes

We present a multimode vibrational analysis of the gas-phase ultraviolet photoelectron spectra of the first ionization in anthracene, tetracene, and pentacene, using electron-vibration constants computed at the density functional theory level. The first ionization of each molecule exhibits a high-frequency vibronic structure; it is shown that this regularly spaced feature is actually the consequence of the collective action of several vibrational modes rather than the result of the interaction with a single mode. We interpret this feature in terms of the missing mode effect. We also discuss the vibronic coupling constants and relaxation energies obtained from the fit of the photoelectron spectra with the linear vibronic model.     

Characterization of the molecular parameters determining charge transport in anthradithiophene

The molecular parameters that govern charge transport in anthradithiophene (ADT) are studied by a joint experimental/theoretical approach involving high-resolution gas-phase photoelectron spectroscopy and quantum-mechanical methods. The hole reorganization energy of ADT has been determined by an analysis of the vibrational structure of the lowest ionization band in the gas-phase photoelectron spectrum as well as by density-functional theory calculations. In addition, various dimers and clusters of ADT molecules have been considered in order to understand the effect of molecular packing on the hole and electron intermolecular transfer integrals. The results indicate that the intrinsic electronic structure, the relevant intramolecular vibrational modes, and the intermolecular interactions in ADT are very similar to those in pentacene.     

Crystal and molecular structures of [Co(<Emphasis Type="Italic">D</Emphasis>H)(<Emphasis Type="Italic">o-phen</Emphasis>)<Subscript>2</Subscript>][BF<Subscript>4</Subscript>]<Subscript>2</Subscript> · 2H<Subscript>2</Subscript>O

The crystal structure of a new mixed-ligand complex [Co(DH)(o-phen)₂][BF₄]₂ · 2H₂O is determined by X-ray diffraction. The crystal is monoclinic, a = 12.2081(11) Å, b = 14.3474(9) Å, c = 17.7393(16) Å, β = 104.95(1)°, and space group P2₁/c. The coordination octahedron of Co³⁺ is formed by two nitrogen atoms of the dimethylglyoxime molecule and four nitrogen atoms of o-phenanthroline molecules. The dimethylglyoxime molecule is singly deprotonated and acts as DH^?. The mean Co-N distances for dioxime and o-phenanthroline are 1.911 and 1.964 Å, respectively. The key role in the formation of the crystal structure is played by [BF₄]^? outer-sphere anions and crystallization water molecules, which form an extended hydrogen-bond system.     

Synthesis and structure of cobalt(III) α-dimethylglyoximates containing thiourea and [ZrF<Subscript>6</Subscript>]<Superscript>2−</Superscript> anion

Two novel coordination compounds of thiourea-containing trans-octahedral trans-dioximates of trivalent cobalt [Co(DH)₂(Tu)₂]₂[ZrF₆]·H₂O and [Co(NioxH)₂(Tu)₂]₂[ZrF₆]·3H²O, where DH^? is the monoanion of dimethylglyoxime, NioxH^? is the monoanion of 1,2-cyclohexanone dioxime, Tu is thiourea, are prepared and characterized by single crystal X-ray diffraction. The structures manifest pairwise an almost parallel and perpendicular arrangement of the Tu fragment in respect to the equatorial plane of the coordination core, accompanied by a development of non-bonding intramolecular π-π-and N-H...O-interactions affecting the structures of the compounds in question. The formation of the crystal structures is primarily governed by outer-sphere [ZrF₆]^2? anions and crystallization water molecules.     

Charge transport parameters of the pentathienoacene crystal

Pentathienoacene, the thiophene equivalent of pentacene, is one of the latest additions to the family of organic crystal semiconductors with a great potential for use in thin film transistors. By using density functional theory and gas-phase ultraviolet photoelectron spectroscopy, we investigate the microscopic charge transport parameters of the pentathienoacene crystal. We find that the valence band exhibits a stronger dispersion than those in the pentacene and rubrene single crystals with marked uniaxial characteristics within the molecular layer due to the presence of one-dimensional pi-stacks; a small hole effective mass is also found along the direction perpendicular to the molecular layers. In the conduction band, strong intermolecular sulfur-sulfur interactions give rise to a significant interstack electronic coupling whereas the intrastack dispersion is greatly reduced. The intramolecular vibronic coupling (reorganization energy) is stronger than that in pentacene but comparable to that in sexithiophene; it is larger for holes than for electrons, as a result of low-frequency modes induced by the sulfur atoms. The polarization energy is large, but its effect on the vibronic coupling remains small. Charge transport is discussed in the framework of both band and hopping models.     

New Co(III) dioximates with hexafluorophosphate ion as stimulators of the proteolytic activity of the micromycete Fusarium gibbosum CNMN FD 12

The coordination compounds [Co(DH)₂(An)₂][PF₆] (I) and [Co(NioxH)₂(Thio)₂][PF₆] · 0.5DMF · 0.5H₂O (II), where DH- and NioxH-are dimethylglyoxime and 1,2-cyclohexanedione dioxime monoanions, respectively; An is aniline; and Thio is thiourea, were synthesized. The composition and structure of the complexes were determined by elemental analysis, IR spectroscopy, and X-ray diffraction. Compounds I and II are ionic and consist of complex cations [Co(DioxH)₂(A)₂]⁺, where DioxH is the α-dioxime residue, A is neutral organic molecule (aniline or thiourea), and [PF₆]^? anions. The coordination polyhedra of the Co(III) complex cations are octahedra formed by the set of N6 donor atoms of monodeprotonated DH-residues and two An molecules (in I) or by the N₄S₂ atoms of two NioxH-anions and two Thio molecules (in II). The formation of the crystal structure of I and II is largely determined by the [PF₆]-anions in which the fluorine atoms serve as acceptors in various hydrogen bonds. The compounds were tested as stimulators of biosynthesis of extracellular proteases of the micromycete Fusarium gibbosum CNMN FD 12. The introduction of the test complexes in optimized concentrations into the nutrition medium for cultivation of the producing strain enhances the biosynthesis of acid and neutral proteases by 63.6 and 92.5%, respectively.