The self-assembly of two dimensional (2D) ordered monolayers of four-coordinate metalloporphyrins on atomically flat substrates has been extensively studied. Much less attention has been devoted to the possibility that the axial metal coordination sites of metalloporphyrin monolayers could serve as attachment points for producing organized 3D arrays of functional molecules. We report that gallium(III) meso-tetradecylporphyrins (Ga(TC10P)L), where L is a supported (or a support for a) functional molecule, have been synthesized and found to form ordered monolayers on highly oriented pyrolytic graphite (HOPG) when deposited from solution under ambient conditions, as determined by STM imaging. Molecular supports derived from Ga–acetylide, –aryloxide, and –arylcarboxylate linkages have been investigated. In all cases, the monolayer is formed with the porphyrin parallel to the HOPG surface and the L linkage oriented perpendicular to this plane. One class of supports consists of axial oligo-phenylene-ethynylene (OPE) wires in complexes of form Ga(TC10P)[(CCC6H4)nH] (n = 1, 2, 3; see figure). At the solid–liquid interface, the structure of the initial 2D lattice formed by these compounds is a function of the OPE ligand. The wires in these monolayers project ~1.0–2.5 nm above the surface, with the upper limit being larger than the longest dimension within the 2D unit cell. A second class of supports, based on aryloxide linkages, allow formation of porphyrin–luminophore dyads, as exemplified by Ga(TC10P)(fluorescein). In addition to the synthetic and surface studies outlined above, structural modeling and electronic-spectroscopic studies of these compounds will be described.

Organized arrays of functional molecules supported by gallium-porphyrin monolayers on HOPG

249th National Meeting (2015)

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