An experimental and theoretical investigation of the thiophene/aluminum interface

Abstract

The adsorption of thiophene and 2, 2′-bithiophene on Al(111) has been studied using thermal desorption spectroscopy (TDS), angle-resolved UV photoemission (ARUPS), and work function measurements. Ab initio density functional theory calculations have been performed for thiophene on Al(111). Both thiophene and bithiophene bond only very weakly to Al(111), as indicated by TDS and calculations of the thiophene absorption energy, which is found to be only 0.54 eV. There is no indication of π-bonding in either the ARUPS data or the calculations. The calculated S–Al distance, 3.7 Å, is much greater than either measured or calculated S–metal distances for covalent bonding. The bonding is shown to be almost entirely electrostatic, with a small contribution from the sulfur lone pair. This is in direct contrast to calculations for Al–thiophene complexes which show covalent bonds between the Al atoms and the thiophene α carbons. The calculations show the molecule to be essentially flat, with a tilt angle of only 2° of the molecular plane relative to the surface. There is some indication of self-assembly of bithiophene on Al(111).

Adsorption of thiophene and pyridine on W(110)

“…It was found that aluminum interacts strongly with thiophene in the latter case, but only weakly in the former one. This was in agreement with previously observed weak bonding of thiophene on Al(1 1 1) by Blyth et al [8] and studies of aluminum deposition on oligo-and polythiophenes [1].…”

Hydrodesulfurization reaction pathways on MoS2 nanoclusters revealed by scanning tunneling microscopy

“…The metallic states associated with the brim sites, on the other hand, have the ability to donate and accept electrons and thus act as catalytic sites very much like ordinary catalytically active metal surfaces. Whereas many catalytically active metal surfaces (Fe, Ni, Mo to mention a few [50][51][52][53][54]) are poisoned by H 2 S and strongly bonded sulfur residues, the fully sulfurcoordinated brim sites of the MoS 2 nanoclusters are clearly not. Compared to the reactive metals on one hand and the inert basal plane of the MoS 2 nanoclusters on the other, the metallic brim sites seem to offer a more optimum bonding strength for the adsorption of thiophene.…”

Molecules and Electronic Materials

“…The molecules interact with the metal in several ways (see Fig. 2), i.e., metal polarization (e.g., tris-(hydroxyquinoline)Al (Alq) on Ag, [15] or naphthalene on Cu [26] ), coupling of electronic states (e.g., C 6 F 5 S ± on Cu [14] ), partial charge exchange (ionic bond formation by thiophene on Al [27] ), or even formation of new chemical species by covalent bond formation, (organometallic complex formation of Alq on Mg [28] ). The importance of metal±molecule interactions is also clear from the inversion of dipole direction upon adsorption of benzoic acids on indium tin oxide (ITO) or on Al.…”