T. Hiejima et al., COMPRESSIBILITY AND HIGH-PRESSURE ELECTRICAL-RESISTIVITY OF ONE-DIMENSIONAL PHTHALOCYANINE CONDUCTORS - THE RELATIONSHIP WITH D-PI CHARGE-TRANSFER, Molecular crystals and liquid crystals science and technology. Section A, Molecular crystals and liquid crystals, 296, 1997, pp. 255-268
Powder X-ray diffraction patterns of one-dimensional phthalocyanine co
nductors (phthalocyaninato)-nickel hexafluoroarsenate, NiPc(AsF6)(0.5)
and (phthalocyaninato)-cobalt hexafluoroarsenate, CoPc(AsF6)(0.5), we
re measured under high pressure. The crystal symmetries of the both co
mpounds were maintained in the pressure range of 0-3.5 GPa. In both co
mpounds, the compressibility along the chain axis is larger than that
along the interchain axis. The compressibility of NiPc(AsF6)(0.5) belo
w 0.5 GPa is unusually larger than that of CoPc(AsF6)(0.5). The relati
on between the lattice contraction along the chain axis and the pressu
re-induced d-pi charge transfer (metal-ligand charge transfer) is disc
ussed based on a simple ligand field theory. The enhancement of the el
ectrical resistivity was observed at about 0.5 GPa in NiPc(AsF6)(0.5).
This enhancement is consistent with the suggestion by the analysis of
the pressure-dependent plasmon absorption. This resistivity change is
attributed to the Anderson localization accompanying the metal-ligand
charge transfer.