Adsorption of Mercaptobenzothiazole and Similar Molecules on Cadmiumsulfide:  A Theoretical Study

Abstract

The structure of the adsorbate systems formed by mercaptobenzothiazole (MBT) and analogue molecules on the CdS(101 h0) surface is studied quantum-chemically using density functional theory. Preliminary calculations of the free adsorptive molecules indicate an energetic preference of their thione form compared to the thiol form. For the anions of the adsorptive molecules, the role of the endocyclic nitrogen and the exocyclic sulfur as possible donor atoms is examined by means of known chelate complexes. Clusters with 24 and 28 atoms that are saturated by point charges have been developed as surface models. Geometry optimizations show that the structure of the adsorbate systems is dominated by the formation of two coordinative bonds from the donor atoms of the adsorptive anions to two adjacent cadmium atoms of the surface. It results that the molecular plane of the adsorptives is tilted with respect to the normal of the crystal face. The calculated tilt angle for the MBT adsorbate agrees with angle-dependent XANES measurements, the only structural information presently available from experiment. It is found that the tilt angle changes with the variation of the heteroatom in the five-membered ring of the adsorptives. The molecule-surface interactions leading to these structural differences are analyzed. Further, the relaxation of the surface is included in the investigation. It becomes obvious that the direction of the relaxation of the free surface is reversed by the formation of the adsorbate bonds.

The Cyclopropylmethyl−3-Butenyl Rearrangement on Mo(110): A Radical Clock on a Surface?

“…An optimization of the isolated cyclopropylmethanol molecule in the gas phase with the same method (using a large unit cell with a lattice constant of 25 Å) shows the structural effects of the chemisorption. Mainly, the C−O bond of the molecule is noticably elongated in the adsorbate by 9 pm, which is in the range of what was found before in adsorbates of organic molecules . Closer inspection of Table shows that the C−O bond for the cyclic species is slightly longer than that of the linear species (1.613 vs 1.580 Å).…”

“…yet remain with a molecular system, the cluster approach is the method of choice. Though widely and successfully applied for ionic or covalent substrates, 29 for metals the usual saturation or passivation strategies (point charges or hydrogen atoms) are not chemically intuitive. If metal clusters are used, they are often not saturated at all 47 or treated with special embedding techniques.…”

“…To model the chemical environment of the adsorbed molecule somewhat realistically yet remain with a molecular system, the cluster approach is the method of choice. Though widely and successfully applied for ionic or covalent substrates, for metals the usual saturation or passivation strategies (point charges or hydrogen atoms) are not chemically intuitive. If metal clusters are used, they are often not saturated at all 47 or treated with special embedding techniques …”

“…Mainly, the C-O bond of the molecule is noticably elongated in the adsorbate by 9 pm, which is in the range of what was found before in adsorbates of organic molecules. 29 Closer inspection of Table 2 shows that the C-O bond for the cyclic species is slightly longer than that of the linear species (1.613 vs 1.580 Å).…”

XPS, Static SIMS and NEXAFS Spectroscopic Investigation of Thiol Adsorption on Metals and Metal Sulfides

“…1b) (3). Both the N and exocyclic S in MBT are potential donor atoms (11), and it is expected that MBT will behave as a bidentate ligand in metal mercaptobenzothiazolato complexes. Indeed, this was shown to be the case for the Cd complex, but a polymeric structure rather than Cd(MBT) 2 molecules were produced (20).…”