Metallic One-Dimensional Conductors Composed of Axially Ligated (Phthalocyanato)CoIII with Supramolecular Cations of A(EtOH)4 (A = Na and K)

Yasuhiro Tanaka,Yukihiro Takahashi,Manabu Ishikawa,Tamotsu Inabe,Toshio Naito,Naoko Watanabe

doi:10.3390/cryst2030946

Abstract

Electrolysis of Na and K salts of the anion dicyano(phthalocyaninato)cobalt(III) (Co(Pc)(CN)2) in ethanol yields one-dimensional partially oxidized salts of A[Co(Pc)(CN)2]2.4(EtOH) (A = Na and K). The cationic component is the supramolecular cation [A(EtOH)4]+, which forms hydrogen bonds with the CN ligands of the Co(Pc)(CN)2 units. The crystal shows metallic conductivity, in contrast to the thermally activated conductivity observed in the isomorphous tetraphenylphosphonium (TPP) salt of TPP[Co(Pc)(CN)2]2. Since the π-π interactions in these isomorphous crystals are nearly the same, the distinctive behavior of the Na and K salts may be attributed to the difference in the degree of charge disproportionation in these crystals.

Highlights

It is well known that planar phthalocyanine (Pc) complexes give one-dimensional (1-D) partially oxidized salts of [M(Pc)]Xy (M = Ni, Cu, Co, H2, etc., X = I3, BF4, PF6, etc., 0 < y < 1) in which the Pc complexes stack by metal-over-metal type overlaps whenchemically oxidized [1]
In this 1-D system, the π-π interaction increases in the order Na salt < K salt < TPP salt, showing that lattice contraction does not increase the π-π interaction
A[Co(Pc)(CN)2]2.4(EtOH) with A = Na and K is a one-dimensional conductor that is isomorphous with TPP[Co(Pc)(CN)2]2

Summary

Introduction

External magnetic fields break the short-range magnetic order, which is thought to delocalize the π-electron charge carriers At present, it remains unclear how the degree of charge disproportionation of the π-electrons and the magnitude of the antiferromagnetic interactions between the d-spins correlate to the appearance of negative magnetoresistance. With the exception of the anisotropic 2-D system, the Fe analogs were successfully fabricated, and all of them were found to show giant negative magnetoresistance [4,11,12] They were not suitable for a systematic study on the role of electron correlation effects in their magneto-transport properties, since their structural, electronic, and magnetic features were all different. We describe the structural features of the alkaline metal salts, and discuss the reasons why their charge disproportionation was depressed compared with that of the TPP salt

Crystal Structures

Physical Properties

Materials and Crystal Growth

X-ray Structure Determination

Measurements

Conclusions