The syntheses and comprehensive characterization of 14 organic semiconductors based on perylene bisimide (PBI) dyes that are equipped with up to four halogen substituents in the bay area of the perylene core and five different highly fluorinated imide substituents are described. The influence of the substituents on the LUMO level and the solid state packing of PBIs was examined by cyclic voltammetry and single crystal structure analyses of seven PBI derivatives, respectively. Top-contact/bottom-gate organic thin film transistor (OTFT) devices were constructed by vacuum deposition of these PBIs on SiO(2) gate dielectrics that had been pretreated with n-octadecyl triethoxysilane in vapor phase (OTS-V) or solution phase (OTS-S). The electrical characterization of all devices was accomplished in a nitrogen atmosphere as well as in air, and the structural features of thin films were explored by grazing incidence X-ray diffraction (GIXD) and atomic force microscopy (AFM). Several of those PBIs that bear only hydrogen or up to two fluorine substitutents at the concomitantly flat PBI core afforded excellent n-channel transistors, in particular, on OTS-S substrate and even in air (mu > 0.5 cm(2) V(-1) s(-1); I(on)/I(off) > 10(6)). The best OTFTs were obtained for 2,2,3,3,4,4,4-heptafluorobutyl-substituted PBI 1a ("PTCDI-C4F7") on OTS-S with n-channel field effect mobilities consistently >1 cm(2) V(-1) s(-1) and on-to-off current rations of 10(6) in a nitrogen atmosphere and in air. For distorted core-tetrahalogenated (fluorine, chlorine, or bromine) PBIs, less advantageous solid state packing properties were found and high performance OTFTs were obtained from only one tetrachlorinated derivative (2d on OTS-S). The excellent on-to-off current modulation combined with high mobility in air makes these PBIs suitable for a wide range of practical applications.

Currently, the only compounds known to support fixation and functionalization of dinitrogen (N) under nonmatrix conditions are based on metals. Here we present the observation of N binding and reduction by a nonmetal, specifically a dicoordinate borylene. Depending on the reaction conditions under which potassium graphite is introduced as a reductant, N binding to two borylene units results in either neutral (BN) or dianionic ([BN]) products that can be interconverted by respective exposure to further reductant or to air. The N isotopologues of the neutral and dianionic molecules were prepared withN-labeled dinitrogen, allowing observation of the nitrogen nuclei by N nuclear magnetic resonance spectroscopy. Protonation of the dianionic compound with distilled water furnishes a diradical product with a central hydrazido BNH unit. All three products were characterized spectroscopically and crystallographically.

Homoatomic triple bonds between main-group elements have been restricted to alkynes, dinitrogen, and a handful of reactive compounds featuring trans-bent heavier elements of groups 13 and 14. Previous attempts to prepare a compound with a boron-boron triple bond that is stable at ambient temperature have been unsuccessful, despite numerous computational studies predicting their viability. We found that reduction of a bis(N-heterocyclic carbene)-stabilized tetrabromodiborane with either two or four equivalents of sodium naphthalenide, a one-electron reducing agent, yields isolable diborene and diboryne compounds. Crystallographic and spectroscopic characterization confirm that the latter is a halide-free linear system containing a boron-boron triple bond.

progress made in late-transition metal boryl complexes, a field which has seen a number of exciting developments in the past couple of years. Reviews covering other forms of metal-boron covalent and dative interactions have since appeared in a number of publications. [20][21][22][23][24][25][26][27][28][29][30][31][32] We have attempted to comprehensively cover the remaining sections regarding complexes with two-center M f B dative interactions ("borane"), B-R fragments as terminal or bridging ligands ('borylene'), and a lone boron atom as ligand ("boride").

The metals of the s block of the periodic table are well known to be exceptional electron donors, and the vast majority of their molecular complexes therefore contain these metals in their fully oxidized form. Low-valent main-group compounds have recently become desirable synthetic targets owing to their interesting reactivities, sometimes on a par with those of transition-metal complexes. In this work, we used stabilizing cyclic (alkyl)(amino)carbene ligands to isolate and characterize the first neutral compounds that contain a zero-valent s-block metal, beryllium. These brightly coloured complexes display very short beryllium-carbon bond lengths and linear beryllium coordination geometries, indicative of strong multiple Be-C bonding. Structural, spectroscopic and theoretical results show that the complexes adopt a closed-shell singlet configuration with a Be(0) metal centre. The surprising stability of the molecule can be ascribed to an unusually strong three-centre two-electron π bond across the C-Be-C unit.

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The ability of an atom or molecular fragment to bind multiple carbon monoxide (CO) molecules to form multicarbonyl adducts is a fundamental trait of transition metals. Transition-metal carbonyl complexes are vital to industry, appear naturally in the active sites of a number of enzymes (such as hydrogenases), are promising therapeutic agents, and have even been observed in interstellar dust clouds. Despite the wealth of established transition-metal multicarbonyl complexes, no elements outside groups 4 to 12 of the periodic table have yet been shown to react directly with two or more CO units to form stable multicarbonyl adducts. Here we present the synthesis of a borylene dicarbonyl complex, the first multicarbonyl complex of a main-group element prepared using CO. The compound is additionally stable towards ambient air and moisture. The synthetic strategy used--liberation of a borylene ligand from a transition metal using donor ligands--is broadly applicable, leading to a number of unprecedented monovalent boron species with different Lewis basic groups. The similarity of these compounds to conventional transition-metal carbonyl complexes is demonstrated by photolytic liberation of CO and subsequent intramolecular carbon-carbon bond activation.

Monomeric oxoboranes have hitherto been detected only as short-lived species in gas-phase or low-temperature matrix experiments. Here, we report formation of the oxoboryl complex trans-[(Cy3P)2BrPt(B[triple bond]O)] (Cy being cyclohexyl) by means of reversible liberation of trimethylsilylbromide from the boron-bromine oxidative addition product of dibromo(trimethylsiloxy)borane and [Pt(PCy3)2] in room-temperature toluene solution. The platinum complex is inert toward oligomerization, even under photolytic conditions and at elevated temperatures. The bromide was substituted by thiophenolate, and spectral parameters of both products as well as results of computational and x-ray diffraction studies are in agreement with the formulation of a triple bond between boron and oxygen. The boron-oxygen distance of 120.5(7) picometers shows a bond shortening of 7.2% as compared with a double bond, which is similar to the shortening observed in carbon-carbon analogs.