Understanding the electronic structure between porphyrins and ultrathin metal-oxide film interfaces is vital for the rational design of functional molecular architectures. Here, we have studied the interfacial electronic properties of porphyrin molecular thin films on well-ordered thin layers of CoO(111) and metallic Co(100) surfaces by means of X-ray and ultraviolet photoemission spectroscopies. In this work, we observed the direct self-metalation of free-base porphyrin molecules at the interface to CoO(111) at room temperature by monitoring the N 1s core-level evolution. On metallic Co(100) films, no metalation occurs, but it can be induced by exposure to oxygen. The oxygen-induced metalation has, to the best of our knowledge, not been reported until now and might play an important role in processes where porphyrins are exposed to metals in a reactive environment.

Temperature Programmed Desorption (TPD) spectroscopy was used to determine the binding energies of polycyclic aromatic hydrocarbons CnHm (22 ≤ n ≤ 60) with highly oriented pyrolytic graphite. These energies were then used to estimate the dispersive graphite interlayer cohesion by means of a refined extrapolation method proposed by Björk et al. This yields a cohesion energy of 44.0 ± 3.8 meV per carbon atom. We discuss some limits of the TPD-based approach and contrast our values with previous determinations of the interlayer cohesion energy of graphite.

Electron impact ionization was used to generate dehydrogenated monocationic fragments of polycyclic aromatic hydrocarbons (PAHs) coronene, pentacene, hexabenzocoronene, dicoronylene, and rubrene. Upon mass-selective soft-landing deposition onto highly oriented pyrolytic graphite (HOPG) surfaces, these dehydrogenated monomeric species can form strongly bound dimers and oligomers interlinked via newly formed annulated benzene rings as detected by subsequent desorption experiments. The oligomerization degree can be influenced by varying the cation beam composition. The largest desorbable oligomers ranged up to pentamers for both coronene and pentacene fragments. PAH oligomers formed in this way can be considered as short sublimable graphene nanoribbons (GNRs).

In-situ high temperature micro-Raman investigation of annealing behavior of high-pressure phases of Si

We compare the intersystem crossing rate, k ISC , of Rose Bengal (RB) in an aqueous pH 12 solution with the corresponding relaxation rates of four different RB-derived anion and dianion species isolated in the gas phase: the doubly deprotonated dianion ([RB-2H] 2− ), the singly deprotonated monoanion ([RB-H] − ), and the corresponding singly negatively charged sodium and cesium adducts ([RB-2H + Na] − and [RB-2H + Cs] − , respectively). Each of them was probed following photoexcitation of their first singlet excited states (S 1 ) at or near room temperature. The solution was studied by transient absorption spectroscopy, whereas the massselected anions were characterized by time-resolved photoelectron spectroscopy�all with ca. 50 femtosecond temporal resolution. [RB-H] − shows an S 1 lifetime of ca. 80 ps; the solution ensemble, thought to consist primarily of solvated dianion chromophores, shows a similar lifetime of ca. 70 ps. By contrast, the isolated dianion, [RB-2H] 2− , has a much longer lifetime. Superimposed on S 1 decay attributable mainly to intersystem crossing, all four isolated anions also show some rapid oscillatory features of the transient photoelectron signal on a 4−5 ps timescale after excitation. Interestingly, an analogous phenomenon is also seen in the transient absorption measurements. We attribute it to a librational oscillation as the S 1 state, initially populated in the S 0 geometry, relaxes into its excited state equilibrium structure. Some implications of these observations for RB photophysics and interpretation of solution measurements are discussed� also in terms of density functional theory and time-dependent density functional theory calculations of ground and excited states.