K W Hipps - Structural and Electronic Properties of Columnar Supramolecular Assemblies Formed from Ionic Metal-Free Phthalocyanine on Au(111)

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      Publication Details (including relevant citation   information):

      Nishida, Krista R. A., Wiggins, Bryan, Hipps, K. W., Mazur,   Ursula The Journal of Physical Chemistry C  2011 115 (33) 16305-16314

      Abstract: Highly ordered assemblies prepared   from tetra (4-sulfonatophenyl) phthalocyanine (TSPc) by employing   very acidic aqueous solutions were deposited onto Au(111)   substrates and studied in UHV using X-ray photoelectron   spectroscopy (XPS), scanning tunneling microscopy (STM), and   orbital mediated tunneling spectroscopy (OMTS). XPS of the TSPc   aggregates shows that the ratio of protonated to unprotonated   nitrogens does not change with decreasing solution pH. STM images   of TSPc deposited from pH <1 solutions reveal ordered branched   web-like assemblies hundreds of nanometers in length, generally 2   nm tall and having variable widths. High-resolution UHV-STM   images of TSPc aggregates on Au(111) reveal detailed coherent   columnar architecture with the phthalocyanine macrocycles   orientated parallel to the substrate surface. OMTS was used to   identify high-energy occupied orbitals, the LUMO of the TSPc   aggregates, and the results are contrasted with the same   molecular states in unsubstituted metalated phthalocyanines   (MPc’s). The positions of the filled and the empty states of the   TSPc are comparable to those of other unsubstituted MPc’s,   indicating that the electronegative sulfonate substituents have   minimal effect on the electronic properties of the macrocycle in   this aggregated state on Au. The ****–LUMO separation of the TSPc   is slightly >2 eV, a value consistent with the literature   assignments for the Pc ring band gap.

      Address (URL): http://dx.doi.org/10.1021/jp203252r