Dispersion Of Molecular Orbitals Research Articles

Dielectric Relaxation Processes, Electronic Structure, and Band Gap Engineering of MFU‐4‐type Metal‐Organic Frameworks: Towards a Rational Design of Semiconducting Microporous Materials

The electronic structures and band gaps of MFU‐4‐type metal‐organic frameworks can be systematically engineered leading to a family of isostructural microporous solids. Electrical properties of the microcrystalline samples are investigated by temperature‐dependent broad‐band dielectric and optical spectroscopy, which are corroborated by full band structure calculations performed for framework and cluster model compounds at multiple levels of density functional theory. The combined results glean a detailed picture of relative shifts and dispersion of molecular orbitals when going from zero‐dimensional clusters to three‐dimensional periodic solids, thus allowing to develop guidelines for tailoring the electronic properties of this class of semiconducting microporous solids via a versatile building block approach. Thus, engineering of the band gap in MFU‐4 type compounds can be achieved by adjusting the degree of conjugation of the organic ligand or by choosing an appropriate metal whose partially occupied d‐orbitals generate bands below the LUMO energy of the ligand which, for example, is accomplished by octahedral Co(II) ions in Co‐MFU‐4.

Electronic structure and polymerization of a self-assembled monolayer with multiple arene rings

We find evidence of intermolecular interactions for a self-assembled monolayer (SAM) formed from a large molecular adsorbate, [1,${1}^{\ensuremath{'}}$;${4}^{\ensuremath{'}}$,${1}^{\ensuremath{''}}$-terphenyl]-4,${4}^{\ensuremath{''}}$-dimethanethiol, from the dispersion of the molecular orbitals with changing wave vector $k$. With the formation self-assembled molecular (SAM) layer, the molecular orbitals hybridize to electronic bands, with indications of significant band dispersion of the unoccupied molecular orbitals. The electronic structure is also seen to be dependent upon temperature, and cross linking between the neighbor molecules, indicating that the electronic structure may be subtly altered by changes in molecular conformation and packing.

Electronic structure of molecular icosahedra films

Using angle-resolved photoemission and inverse photoemission, the electronic structure of films of the molecular icosahedron orthocarborane (C2B10H12) on Cu(100) has been studied. The measured gap between the highest occupied molecular orbitals and the lowest unoccupied molecular orbitals is in good agreement with modified neglect of differential overlap calculations. An unoccupied exopolyhedral state has been found and is ascribed to molecular orbital hybridization. This hybridization is consistent with the observed dispersion of the orthocarborane molecular orbitals. This molecular orbital dispersion indicates a surface Brillouin zone edge with an average radius of 0.7 AA-1, and suggests that the molecules adopt local close-packed ordering in the overlayers, with an intermolecular distance of 5.58 AA.