K W Hipps - A Scanning Tunneling Microscopy Study of Self-Assembled Nickel(II) Octaethylporphyrin Deposited from Solutions on HOPG

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  Ogunrinde, Ayowale, Hipps, K. W., Scudiero, L. Langmuir  2006 22 (13) 5697-5701

  Abstract: The adsorption of nickel(II)   octaethylporphyrin (NiOEP) from benzene and chloroform solutions   on highly ordered pyrolytic graphite (HOPG) was investigated with   a scanning tunneling microscope (STM) operated in ambient   conditions. STM images show that NiOEP self-assembles on the   graphite surface and that the molecules lie flat and form 2D   lattices with spacings of 1.58 ± 0.03 nm by 1.46 ± 0.06 nm with a   lattice angle of 69° ± 4° averaged over both solvents. We were   unable to eliminate the possibility that one unit cell distance   is twice the above-reported distance. The corresponding molecular   packing density, 4.5 ± 0.3 × 1013 molecules/cm2, was essentially   the same for benzene and chloroform solution deposition. These   results differ somewhat from the structure revealed by   high-resolution STM images of NiOEP on Au (111). The lack of   apparent height (image intensity) in the constant current STM   image of the alkane region of alkane-substituted metal porphyrins   is attributed to a combination of changes in alkane configuration   relative to the ring and associated changes in electronic   coupling with **** and LUMO.

  Address (URL): http://dx.doi.org/10.1021/la060233p