High-Band-Gap Polycrystalline Monolayers of a 12-Vertex p-Carborane on Au(111)

Abstract

Experimental manipulations were carried out using standard vacuum and inert atmosphere techniques. All chemicals were obtained from Sigma-Aldrich and used as received. closo-1,12-Dicarbadodecaborane was purchased from Katchem Ltd., E. Krásnohorské 6, 110 00 Prague 1, Czech Republic. Diethyl ether and THF were dried over Na metal and NaK, respectively, and distilled fresh prior to use. Deuterated solvents were obtained from Cambridge Isotopes Laboratories and used as received. NMR spectra were recorded either on a Varian INOVA 500 spectrometer at 500 MHz or a Bruker Avance-III 300 spectrometer at 300 MHz. Chemical shifts are given in ppm with positive shifts downfield: all 1 H and 13 C chemical shifts were referenced relative to internal residual protons from a lock solvent. For 11 B decoupled 1 H NMR spectra, the decoupling was not complete and BH proton peaks did not integrate to expected values. The values listed are the actual values observed and the expected values are in brackets. IR spectra were recorded eith a Nicolet Nexus 670 FT-IR spectrophotometer either in KBr pellets or neat compound deposited onto a Ge window. Mass spectra were recorded using a Thermo Finnigan Polaris Q GC/MS instrument using a Phenomenex ZB-5ms general purpose column (30 m, 0.25 mm ID, 0.25 um film thickness, max. 320 ºC isotherm/340 ºC program) in electron impact (70 eV) ionization mode. Elemental analysis was performed by Columbia Analytical Services, 3860 S. Palo Verde Road, Suite 302, Tucson, AZ 85714. closo-1-Iodo-1,12-dicarbadodecaborane 1. The synthesis of 1 was adapted from a literature procedure. 1 To a flame-dried round bottom flask were added p-carborane (0.2 g, 1.39 mmol) and anhydrous diethyl ether (5 mL). The solution was stirred at room temperature under nitrogen while n-BuLi (1.6 M, 1.6 mmol, 1.0 mL) was added dropwise from a syringe. The reactants were stirred for

Adsorption of oriented carborane dipoles on a silver surface

“…The surface concentration of thiolate sulfur atoms calculated using XPS is 6.5 × 10 14 cm −2 for sample A (10 min immersion time), 8.0 × 10 14 S atoms per cm 2 for sample A (16 h immersion time) and 8.0 × 10 14 S atoms per cm 2 for sample B (10 min immersion time). These experimentally determined concentrations are close to the estimation of ∼2.5 × 10 14 molecules in a densely packed monolayer per one squared centimeter determined from the literature . The value of the sulfur surface concentration for sample B (16 h immersion time) was not calculated with regard to the thicker layer of Ag film affected by molecules of B in this sample.…”

“…. These experimentally determined concentrations are close to the estimation of $2.5 Â 10 14 molecules in a densely packed monolayer per one squared centimeter determined from the literature [18,28,45]. The value of the sulfur surface concentration for sample B (16 h immersion time) was not calculated with regard to the thicker layer of Ag film affected by molecules of B in this sample.…”

“…The concentration of boron in a silver film exposed to the solution for 16 h was significantly higher than the concentration which corresponds to a densely packed monolayer. The number of molecules in a densely packed monolayer per one squared centimeter is estimated $2.5 Â 10 14 [18,28,45]. The concentration of boron atoms in a silver film exposed for 16 h to B in MeOH thus corresponds to $35 monolayers.…”

Carboranes in the chemist's toolbox

“…107,108 Both isomers modify the surface potential of flat metal surfaces, but the 1,2 isomer increases the surface potential of modified Ag film more effectively than does the 9,12 compound, a finding attributed to the higher inductive electron withdrawal by the carboranyl carbon atoms in the 1,2-dithiol. 107 In other work, mixed self-assembled monolayers of 1-and 9-HS-m-carboranes on gold and silver were found to modulate the work functions in a controllable way, furnishing another potentially useful strategy for developing organic field-effect transistors. 107 In other work, mixed self-assembled monolayers of 1-and 9-HS-m-carboranes on gold and silver were found to modulate the work functions in a controllable way, furnishing another potentially useful strategy for developing organic field-effect transistors.…”

Defect-Tolerant Aligned Dipoles within Two-Dimensional Plastic Lattices

“…The most common defects in these monolayers are substrate step edges and molecular domain boundaries in which there is a translational (phase) and/or rotational offset of the registry of the lattice of attachment to the substrate. 37,39,40,42,43 …”