Surface-Confined Monomers on Electrode Surfaces. 6. Adsorption and Polymerization of 1,6-Diisocyanohexane on Au and Pt

Abstract

Thin films of 1,6-diisocyanohexane (DICH) can be formed on Au and Pt surfaces by immersion of clean substrates in 0.001-1.0 M solutions of DICH. Infrared transitions for both Au-bound and free isocyanide functionalities are observed after Au surfaces have been placed in methanolic solutions with DICH concentrations > 0.001 M, indicating that some portion of the DICH layer is composed of molecules with only one of the isocyanide moieties bound to the Au surface. In addition, poly(DICH) layers are formed on Au as noted by the presence of imine bands in the reflection-absorption infrared (RAIR) spectra of such surfaces and the time-dependent nature of the band intensities of the imine and methylene modes. The resulting DICH-coated Pt and Au surfaces are effective transport barriersssubstantially diminished redox responses of various solution probes are observed at such modified electrodes. In particular, the DICH films on Pt prevent 95% oxidation of the underlying metal surface. It is found that the remaining free isocyanide groups on the DICH-coated surfaces can be further polymerized (cross-linked) to various extents by exposure to oxygenated aqueous Ni 2+ solutions, allowing for control of film permeability. These results point to the possible application of poly(DICH) films in the fields of chemical sensing and corrosion protection.

Creation of Low-Coordination Gold Sites on Au(111) Surface by 1,4-phenylene Diisocyanide Adsorption

“…In addition, the presence of a single CN vibrational mode is consistent with the proposed structure, since the isocyanide groups are symmetrically equivalent and will therefore only give rise to a single, infrared-allowed vibrational mode. The isocyanide stretching frequency is shifted from the gas-phase value of 2123 cm -1 , consistent with the formation of an isocyanide bond with the surface [22][23][24][25][26][39][40][41][42][43][44][45][46][47][48][49]. Both the C-H bending and CN stretching modes shift somewhat with coverage, and this effect is likely to be due to vibrational coupling between modes in adjacent one-dimensional chains as the coverage increases, and they come closer together.…”

“…This shows peaks at 2137 and 813 cm -1 at a saturation PDI coverage. These modes can be assigned quite straightforwardly to the CN stretching mode (at *2137 cm -1 ) [22][23][24][25][26][39][40][41][42][43][44][45][46][47][48][49], and an out-of-plane C-H bending mode for the benzene ring (813 cm -1 ), which is the only detectable mode in the CH fingerprint region. The out-of-plane bending mode, according to the surface infrared selection rules [21], should be allowed for a benzene ring lying parallel to the surface.…”

Self-assembly of 1,4-phenylene diisocyanide and terephthalic acid on Ni, Cu and Pt

“…For example, the isocyanide-metal interaction, may lead to π -electron donation from the isocyanide group to surface Ni atoms, but also back-bonding of electrons from Ni to the antibonding π * orbitals of the bonded isocyanide group. (3) The free isocyanide group disposed away from the substrate may undergo oligomerization to form polyisocyanide [47]. (4) Strong β-substituent effects are expected for the isocyanide group.…”

“…3a, can be fitted with three peaks, at 401.0, 399.9, and 399.1 eV. The lowest binding energy peak at 399.1 eV is tentatively assigned to nitrogen atoms in imine groups, assuming that some of the pending isocyanide groups have undergone rehybridization and oligomerization to polyisocyanide [17,47]. The peaks at 401.0 and 399.9 eV are assigned to nitrogen in free isocyanide groups and surface-bonded isocyanide groups, respectively.…”

Size-dependent adsorption of 1,4-phenylenediisocyanide onto gold nanoparticle surfaces

“…There have been relatively few reports [9][10][11][12][13][14][15] exploring the chemisorption of organoisocyanides onto metal surfaces. Aliphatic and aromatic diisocyanides are known to adsorb onto gold via only one NC group, with the other NC group pendent with respect to the gold surface.…”