The non-trivial effect of molecular dipoles on the surface work function of metals is explored for the unidirectional ordered arrays forming the first and second layers of chloroaluminum phthalocyanine (ClAlPc) on Au(111). This phthalocyanine is a non-planar molecule with permanent electric dipole perpendicular to its molecular π-plane that can adopt two distinct configurations (Cl-up and Cl-down) when adsorbed on surfaces. The ordered array forming the first layer is known to consist of all Cl-up molecules, while the less studied second layer is formed by molecules in the Cl-down configuration. The inverted orientation of the molecules in these two layers constitutes our benchmark system to investigate the influence of the dipole array orientation on the surface work function. The present study includes an 2 experimental and theoretical approach that combines diverse imaging and spectroscopic scanning probe microscopies, in ultra-high vacuum, with first-principles DFT-based atomistic simulations.Experiment and theory show a chiral organization transferred from the first layer to the growing film that is reflected in the electronic structure. We demonstrate that the obtained surface work function changes are smaller in magnitude than expected from a dipolar approximation due to charge rearrangement at and beyond the monolayer. We provide understanding of the crucial interplay between the inter-layer and organic-metal interactions and quantify their effect on the electron density distribution and on the work function changes.
By employing diverse surface sensitive synchrotron radiation spectroscopies we demonstrate that the fluorine content of initial C60F48 deposited at room temperature on Ag(111) varies with molecular coverage. At the very...
Depending on the metal, C60F48 molecules lose all the fluorine atoms and transform to C60 at room temperature. Molecular dynamics simulations with ReaxFF reactive force field provide a detailed mechanistic picture of the surface-induced de-fluorination.
The design and fabrication of new nanostructures with controlled functionality, size, shape, and position are major goals in nanoscience. 1 The concept of self-assembly of molecular building blocks to generate well-defined architectures based on non-covalent interactions with the supporting substrate is technologically appealing. 2 Such intriguing supramolecular assemblies often possess polymeric characteristics and are referred to as ''supramolecular polymers''. 3 The generation of such organized structures, obtained by controlling supramolecular interactions, makes tuning of the physicochemical properties of these molecule based materials possible. In this context, to combine organic molecules with metal entities is particularly useful. 4,5 On the other hand, the bottom-up approach for forming on-surface nanostructures by direct sublimation of their building blocks under ultra-high vacuum conditions has been shown as an excellent approach to this goal. 6 However, this experimental approach presents a limitation coming from the stability that it is required for the molecule to allow sublimation without structural damage. This is the reason why there are a relatively high number of nanostructures based on organization of ideal organic molecules but few of them are based on the combination of organic molecules with metal fragments. 7 The metal-organic structures formed up to now by sublimation are almost limited to those simple cases obtained by sequential sublimation of both building blocks, organic molecules and metal precursors, or just by sublimation of the organic molecules and their subsequent in situ reaction with the metal atoms coming from the metallic surface. 8,9 In both cases the selection of the building blocks has allowed formation of a large variety of 1D-or 2D-coordination polymer architectures. [10][11][12] In most of the previous studies of large complex molecules on surfaces the molecules were transferred from a solution [13][14][15][16][17][18][19] or by a dry imprint technique 20 to the substrate in order to preserve the fragile core. In this communication we focus on the search of a new metal-organic complex with a robust structure able to be sublimated keeping its molecular integrity and to self-assemble without being disrupted by the surface. We have been able to directly sublimate under ultra-high vacuum (UHV) conditions a large metal-organic cluster that is, as far as we know, the largest molecular complex ever sublimated and in situ characterized by STM. This allows the formation of well-controlled nanoarchitectures readily on a surface and use of advanced surface in situ techniques. To achieve this goal, we combine in situ scanning tunnelling microscopy (STM), X-ray photoemission spectroscopy (XPS), and low energy electron diffraction (LEED) experiments with ab initio calculations.Recently, we have reported on the synthesis and characterization of a robust metal-organic cluster [Cu 4 (m 3 -Cl) 4 (m-pym 2 S 2 ) 4 ] (pym 2 S 2 = dipyrimidinedisulfide) (1) showing interesting physical and...
The dramatic consequences that the orientation adopted by the molecular dipoles, in diverse arrays of chloroaluminum phthalocyanine (ClAlPc) on Au(111), have on the ulterior adsorption and growth of C60 are...
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