Phthalocyanine adlayers

Since the first report on a copper(II) Pc adlayer on Cu(100) [178], several studies describing the formation of Pc adlayers in air, in ultra-high vacuum (UHV), or at the solid-liquid interface have been reported [179-183], most of them involving the use of scanning tunneling microscopy (STM), a widely used technique for studying the organization of Pc derivatives on surfaces. 

Symmetrically substituted chloro-[184,185] and phenoxy-substituted [186] Pcs have been organized on Ag(l 11) and Au(l 11) by sublimation techniques. It has been demonstrated that in the case of the alkoxy-substituted Pc, the rotational degrees of the bulky phenoxy substituents imposes a bowl-like structure to the adsorbed Pc units, which in turn enables the interaction of the macrocycle core with the metal surface. 

Two-dimensional (2-D), two-component systems composed of Pcs and porphyrins self-organized by UHV techniques on Au(lll) have also been reported [188-192], It is interesting to note that, in some cases, depending on the substituent groups on the Pc and the porphyrin systems, the intermolecular interactions between these macrocycles give rise to a 2-D crystalline architecture that presents a higher stability than that of the films resulting from either parent compound [188], 

The metastable, 2-D packing motif presented by some Pcs adsorbed on Ag(l 11) has also prompted the utilization of such ensembles as templates for the organization of complementary guest molecules such as fullerenes [193] or corannulenes [194], giving rise to the formation of two-component, 2-D architectures. More recently, a similar approach has been used to prepare a surface-supported, three-component system. In fact, the immersion of an Au substrate into a solution containing both a ZnPc and a Zn porphyrin led to the formation of a highly ordered, 2-D arrangement of both Pc and porphyrin which can act as a bimolecular chessboard toward the supramolecular assembly of a third component (i.e., C6o fullerene) which is selectively trapped in the open spaces (Fig. 25) [195], 

Complexation of metal ions by Pcs adsorbed on metal surfaces has also been reported. In fact, a CoPc adsorbed on Au(lll) is able to complex two Ca(II) ions by two of its four peripherally substituted crown ether macrocycles as demonstrated by high-resolution STM studies [196], Furthermore, it was demonstrated by using a Au(100)-(1 x 1) lattice surface that the relationship between the crown ether moieties of the CoPc and the underlying Au lattice is important in the trapping of the Ca(II) ions within the crown macrocycles [197], 

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More EC-STM studies have been devoted to porphyrin and phthalocyanine adlayers on singlecrystal metal electrodes than to any other type of organic adlayers. Becanse extensive reviews have discussed this particular topic, we will limit the discussion of this subject here to a few examples that emphasize the particular features of porphyrin and phthalocyanine adlayers and emphasize the versatility that they offer for the design of functional surfaces under electrochemical control. 

Among the main goals of electrochemical research are the design, characterization and understanding of electrocatalytic systems, (1-2) both in solution and on electrode surfaces. (3.) Of particular importance are the nature and structure of reactive intermediates involved in the electrocatalytic reactions.(A) The nature of an electrocatalytic system can be quite varied and can include activation of the electrode surface by specific pretreatments (5-9) to generate active sites, deposition or adsorption of metallic adlayers (10-111 or transition metal complexes. (12-161 In addition the electrode can act as a simple electron shuttle to an active species in solution such as a metallo-porphyrin or phthalocyanine. 

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