A density functional theory study of catalytic sites for oxygen reduction in Fe/N/C catalysts used in H₂/O₂ fuel cells.

The oxygen reduction catalytic activity of carbon-supported FeN4 moieties bridging micropores between two graphene sheets was investigated by density functional theory (DFT). Based on the FeN(2+2)/C structure proposed earlier by our group, two types of FeN(2+2)/C structures were considered: one mostly planar and one in which the Fe ion is significantly displaced out of the graphitic plane. A structure in which the FeN4 moiety is embedded in an extended graphene sheet (FeN/C) was also considered.

Ullmann-type coupling of brominated tetrathienoanthracene on copper and silver.

We report the synthesis of extended two-dimensional organic networks on Cu(111), Ag(111), Cu(110), and Ag(110) from thiophene-based molecules. A combination of scanning tunnelling microscopy and X-ray photoemission spectroscopy yields insight into the reaction pathways from single molecules towards the formation of two-dimensional organometallic and polymeric structures via Ullmann reaction dehalogenation and C-C coupling. The thermal stability of the molecular networks is probed by annealing at elevated temperatures of up to 500 °C.

Unprecedented transformation of tetrathienoanthracene into pentacene on Ni(111).

The imaging and characterization of single-molecule reaction events is essential to both extending our basic understanding of chemistry and applying this understanding to challenges at the frontiers of technology, for example, in nanoelectronics. Specifically, understanding the behavior of individual molecules can elucidate processes critical to the controlled synthesis of materials for applications in multiple nanoscale technologies. Here, we report the synthesis of an important semiconducting organic molecule through an unprecedented reaction observed with submolecular resolution by scanning tunneling microscopy (STM) under ultrahigh vacuum (UHV) conditions.

Laterally extended spiral graphite analogue boron-nitrogen helices.

Ab initio self-consistent field molecular orbital and density functional theory calculations have been performed on a series of extended helical boron-nitrogen analogues of a "spiral graphite", the [N]polymethylenylnaphthalenes (N = 6, 8, and 12), with the molecular formula N(x)B(y)H(z) (where x = 28, 37, and 55, y = 27, 36, and 54, z = 23, 29, and 41). Interchanging the positions of the boron and nitrogen atoms in the helix leads to very similar structures N(x-1)B(y+1)H(z) in all three studied cases. The electronic structure and the optimum geometries of these helices were investigated at the HF/6-31G(d,p) and B3LYP/6-31G(d,p) levels of theory.

Helices of boron-nitrogen hexagons and decagons. A theoretical study.

Ab initio self-consistent field molecular orbital and density functional theory calculations have been performed on a series of helical boron-nitrogen structures comprised of fused hexagons and larger polygons. The presence of an even number N of rings in the boron-nitrogen [N]helicenes leads to the possibility of angular isomers. The electronic structure and stability of three isomeric nonhydrogenated boron-nitrogen helices were investigated at the HF/6-31G(d) and the B3LYP/6-31G(d) levels of theory.

Theoretical study on the structure and stability of some unusual boron-nitrogen helices.

Ab initio self-consistent field molecular orbital and density functional theory calculations have been performed on a series of helical structures comprised of boron-nitrogen analogues of extended helicenes, with helically arranged N fused benzene rings, and alternating N benzene units fused to N - 1 cyclobutadiene rings as reference structures. The electronic structure and stability of boron-nitrogen analogues of angular [N]helicenes, [N]phenylenes (N = 5, 6, 7, 12), and [N]methylenylnaphthalenes (N = 6) were investigated at the HF/6-31G(d) and the B3LYP/6-31G(d) levels of theory. The presence of an even number N of rings in the boron-nitrogen [N]helicenes leads to the possibility of angular isomers.