Electrical Conduction through Linear Porphyrin Arrays

Abstract

Electrical conduction measurements were made on two extreme types of directly linked porphyrin arrays by using nanoelectrodes. One type is the directly linked Zn(II)porphyrin arrays, consisting of 48 Zn(II)porphyrin moieties (Z48), and the other type is the completely flat, tape-shaped Zn(II)porphyrin arrays, consisting of eight Zn(II)porphyrin units (T8). The I-V curve for Z48 exhibits the diode-like behavior and the hysteresis depending on the voltage sweep direction presumably due to the conformational heterogeneity arising from the dihedral angle distribution in Z48. On the other hand, the I-V curve for T8 is nearly symmetric without any hysteresis, leading to the higher conductivity and the smaller band gap. These results illustrate that the stronger pi-electron conjugation in T8, as compared with that of Z48, results in better electrical conduction.

Comparison of the Conductance of Three Types of Porphyrin‐Based Molecular Wires: β,meso,β‐Fused Tapes, meso‐Butadiyne‐Linked and Twisted meso‐meso Linked Oligomers

“…[20,32] Porphyrins are also remarkably stable, both thermally and chemically, [33] and they display great synthetic versatility, making it possible to prepare oligomers with lengths ranging from about 1 nm to more than 10 nm. [34,35] Many different varieties of porphyrinbased molecular wires have been investigated, [20,31,32,[34][35][36][37][38][39][40][41][42] and potential applications in molecular electronics and other fields have been identified. [43][44][45] The axial coordination chemistry of metalloporphyrins provides unique opportunities for controlling the three-dimensional conformations of porphyrin-based molecular wires via formation of double-stranded ladders, and other types of supramolecular assemblies.…”

“…[20, 41,42,[57][58][59][60] Yoon et al and Kang et al constructed arrays of small (but indeterminate) numbers of porphyrin molecules bridging gold nanoelectrodes and measured their I-V response. [41,42] More recently it has become possible to measure the single-molecule conductance of porphyrin molecular wires, which have been trapped between gold contacts in an STM break-junction configuration.…”

“…[41,42] More recently it has become possible to measure the single-molecule conductance of porphyrin molecular wires, which have been trapped between gold contacts in an STM break-junction configuration. Sedghi et al evaluated the conductance of a series of porphyrin oligomers.…”

Structural Aspects of Porphyrins for Functional Materials Applications

“…This is consistent with the higher macrocycle co-planarity in (C) and the resulting increase in conjugation. Yoon et al [34] measured electrical conduction through two types of porphyrin wires using nanoelectrodes. One type consisted of directly meso-meso-linked Zn(II) porphyrin arrays with 48 Zn(II) porphyrin moieties.…”

Excitation Energy Migration in Multiporphyrin Arrays

“…To explore the electrical property, we have performed electrical transport measurements of two extreme types of porphyrin arrays (Z48 and T8), where two kinds of Au/Ti nanoelectrodes were used for molecular level measurements. 12 For Z48 with the length of about 40 nm, nanoelectrodes with a spacing of about 20-30 nm were fabricated by electron-beam lithography and a double-angle evaporation technique onto degenerately doped silicon substrate with a top SiO 2 layer of 0.5 µm (Figure 4a). On the other hand, for T8 with about 7 nm in its length, Au/Ti nanoelectrodes with a spacing of less than 7 nm were prepared by utilizing the electromigration induced breakjunction technique (Figure 4b).…”