Comparison of Adsorbed Orthocarborane and Metacarborane on Metal Surfaces

Abstract

We compare the adsorption, bonding, and electronic structure of closo-1,2 dicarbadodecaborane (orthocarborane, C2B10H12) and closo-1,7 dicarbadodecaborane (metacarborane, C2B10H12) on metal surfaces. The electronic structure (molecular orbitals) of these two isomer molecules are calculated to be very similar, but there are significant differences in the experimental binding energies for each isomer as an adsorbed species. Metacarborane adsorbs on both Co and Au with the Fermi level (chemical potential) placed closer to the lowest unoccupied molecular orbital than is observed with orthocarborane adsorbed on Co and Cu.

Defect contributions to conductivity in poly(3‐hexylthiophene)?

“…As is typical [5,11,[15][16][17][18][19], except for the lowest unoccupied molecular orbitals of RR-P3HT, there is good qualitative agreement with experiment ( Figure 1).…”

“…Similar semiempirical molecular orbitals calculations have recovered much of the detail observed in large molecular systems using photoemission and inverse photoemission, including reproducing with reasonable agreement the highest occupied molecular orbital (HOMO) to lowest unoccupied molecular orbital (LUMO) gap for closo-carborane molecular fi lms [15], fl uorinated polymer fi lms [16], multilayer fi lms of biphenyldiisocyanide [17], biphenyldimethyldithiol [18], and tris(8-hydroxyquinoline) aluminum (Alq3) [19]. The model calculations were undertaken on short chain length polymers (from one to 16 repeat units) that were hydrogen terminated to prevent excessive folding as is typical of such calculations [5].…”

“…The difference between orbital energies for RR-P3HT obtained in theory (referenced to the vacuum level) and the experimental binding energies with respect to the Fermi level, obtained for RR-P3HT from the photoemission spectra is about 5.3 eV. This value is typical in comparing the calculated spectra with other conducting polymers [5,15] and molecular adsorbates [11,[16][17][18].…”

Photohole Screening Effects in Polythiophenes with Pendant Groups

“…4,10,15,[21][22][23][24][25] The difference between orbital energies (Figure 2), obtained in theory and referenced to the vacuum level, and the experimental binding energies with respect to the Fermi level, obtained for regioregular poly(3-hexylthiophene) from the photoemission spectra, is about 5.3 eV, as was observed in comparing the calculated spectra with other conducting polymers. 10 This shift between theory and experiment is similar to that observed for closocarborane molecular films, 21 fluorinated polymer films, 22 multilayer films of biphenyldiisocyanide, 23 biphenyldimethyldithiol, 24 poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylenevinylene] (MEH-PPV), 10 and like molecules. 15 As seen from Figure 2, many features, from the photoemission and inverse photoemission spectra (Figure 1), can be assigned to groups of molecular orbitals such as the features at -3.8 eV (a), -7.5 eV (b), -10.2 eV (c), and -11.3 eV (d), but father away from the Fermi level the calculation underestimates the…”

“…19,20 Similar semiempirical molecular orbitals calculations have recovered much of the detail observed in large molecular systems using photoemission and inverse photoemission, including reproducing, with reasonable agreement, the highest occupied molecular orbital (HOMO) to lowest unoccupied molecular orbital (LUMO) gap for closo-carborane molecular films, 21 fluorinated polymer films, 22 multilayer films of biphenyldiisocyanide, 23 biphenyldimethyldithiol, 24 and tris(8-hydroxyquinoline) aluminum (Alq 3 ). 25 Hydrogen terminated (to prevent excessive folding) short chain length (from 1 to 16 repeat units for P3HT and 1 unit for PEDOT) polymers were used for our simplistic model calculations, as has been done elsewhere.…”