An experimental study of the bonding geometry and electronic coupling of cis-bis(isothiocyanato)bis(2,2(')-bipyridyl-4,4(')-dicarboxylato)-ruthenium(II) (N3) adsorbed on rutile TiO(2)(110) is presented, along with supporting theoretical calculations of the bonding geometry. Samples were prepared in situ using ultrahigh vacuum electrospray deposition. Core-level photoemission spectroscopy was used to characterize the system and to deduce the nature of the molecule-surface bonding. Valence band photoemission and N 1s x-ray absorption spectra were aligned in a common binding energy scale to enable a quantitative analysis of the bandgap region. A consideration of the energetics in relation to optical absorption is used to identify the photoexcitation channel between the highest occupied and lowest unoccupied molecular orbitals in this system, and also to quantify the relative binding energies of core and valence excitons. The core-hole clock implementation of resonant photoemission spectroscopy is used to reveal that electron delocalization from N3 occurs within 16 fs.

The spontaneous ordering of molecules into two-dimensional self-assembled arrays is commonly stabilized by directional intermolecular interactions that may be promoted by the addition of specific chemical side groups to a molecule. In this paper, we show that self-assembly may also be driven by anisotropic interactions that arise from the three-dimensional shape of a complex molecule. We study the molecule mn 12 o 12 (o 2 CCH 3 ) 16 (H 2 o) 4 (mn 12 (acetate) 16 ), which is transferred from solution onto a Au(111) substrate held in ultrahigh vacuum using electrospray deposition (uHV-EsD). The deposited mn 12 (acetate) 16 molecules form filamentary aggregates because of the anisotropic nature of the molecule-molecule and molecule-substrate interactions, as confirmed by molecular dynamics calculations. The fragile mn 12 o 12 core of the mn 12 (acetate) 16 molecule is compatible with the uHV-EsD process, which we demonstrate using near-edge X-ray adsorption fine-structure spectroscopy. uHV-EsD of mn 12 (acetate) 16 onto a surface that has been prepatterned with a hydrogen-bonded supramolecular network provides additional control of lateral organization.

Zinc-protoporphyrin, adsorbed on the rutile TiO(2)(110) surface, has been studied using photoemission spectroscopy and near-edge absorption fine structure spectroscopy to deduce the nature of the molecule-surface bonding and the chemical environment of the central metal atom. To overcome the difficulties associated with sublimation of the porphyrin molecules, samples were prepared in situ using ultrahigh vacuum electrospray deposition, a technique which facilitates the deposition of nonvolatile and fragile molecules. Monolayers of Zn protoporphyrin are found to bond to the surface via the oxygen atoms of the deprotonated carboxyl groups. The molecules initially lie largely parallel to the surface, reorienting to an upright geometry as the coverage is increased up to a monolayer. For those molecules directly chemisorbed to the surface, the interaction is sufficiently strong to pull the central metal atom out of the molecule.

Electrospray deposition of fullerenes on gold has been successfully observed by in situ room temperature scanning tunneling microscopy and photoemission spectroscopy. Step-edge decoration and hexagonal close-packed islands with a periodicity of 1 nm are observed at low and multilayer coverages respectively, in agreement with thermal evaporation studies. Photoemission spectroscopy shows that fullerenes are being deposited in high purity and are coupling to the gold surface as for thermal evaporation. These results open a new route for the deposition of thermally labile molecules under ultra-high vacuum conditions for a range of high resolution surface science techniques.

An electrospray technique has been successfully used to deposit C 60 onto a hydrogen-bonded supramolecular template held in an ultrahigh vacuum environment. Characterization of the surface by in situ scanning tunneling microscopy shows the size-selective trapping of C 60 dimers and heptamers within a 3,4,9,10-perylene tetracarboxylic diimide (PTCDI)/melamine network. We demonstrate that ultrahigh vacuum electrospray deposition (UHV-ESD), where energetic molecules impact onto a substrate, is compatible with surfaces which have been functionalized through the incorporation of hydrogen-bonded templates.