PR0494
Synthesis of Partially-Oxidized Salts of Metal Phthalocyanine with Axial Halides○Derrick Ethelbhert Yu, Toshio Naito, and Tamotsu Inabe
Division of Chemistry, Graduate School of Science, Hokkaido University,Sapporo 060-0810, Hokkaido, Japan
Axially-ligated metal phthalocyanines (MPc’s) are promising candidates as acomponent of molecular conductors. Their outstanding feature is the variation of the π-πstacking structure in their molecular assemblies. Without axial ligands, the planar MPc
molecules are expected to form a face-to-face stacking one-dimensional column. Any intercolumnar interaction may be negligible, since their π-orbitals are not overlapped between thecolumns. On the other hand, axially substituted species form completely different stacking
structure. The adjacent π-ligands shift away from the protruding axial ligands and overlap
with the planar parts where the charge carriers are accommodated in a variety of π-π stacking
networks.

Axially-substituted metal phthalocyanines (Cyano-ligated; M = Co, Fe) have beenfound to form conducting species upon oxidation. Studies have shown that the axialsubstitution plays a major role in the effectiveness of π-π stacking and consequently on thesolid state properties.
The development of phthalocyanines (Pc), particularly in the field of materials science
hinges largely on the synthesis of new Pc derivatives. Employing halogens as axial ligands
opens a new avenue for this exploration, due to some of the distinct and variable properties ofthis group in contrast with other known axially-ligated MPc’s, particularly the dicyano-MPc.
We report herein the syntheses (multi-step and one-pot) of partially-oxidized
crystalline salts of MPc’s (M = Co, Fe) with axial halides (X = Cl, Br), utilizing
tetraphenylphosphonium (TPP) as the cation, TPP[M(Pc)X2]2. Their crystal structures havebeen found to be isomorphous with TPP[Co(Pc)(CN)2]2.
TPP[M(Pc)X2]2 is synthesized by electrochemical oxidation of K[M(Pc)(SCN)2] and
TPPX, or by direct one-pot electrochemical oxidation of MPc and TPPX. The first method
involves initial chloro axial ligation by reacting MPc with thionyl chloride (SOCl2) thereby
producing the hardly soluble M(Pc)Cl2. The proceeding step is axial ligand substitution byutilizing potassium thiocyanide (KSCN) to afford K[M(Pc)(SCN)2] salt which can beoxidized with TPPX to get TPP[M(Pc)X2]2 using acetone as solvent. The electrochemical
crystallization process usually takes 2-3 weeks. The current also influences crystal quality,
usually 1-3 µA yields good crystals.

The second procedure is a one-pot synthesis involving direct electrochemical reaction
between MPc and TPPX. This method is more delicate in terms of solvent utilization. Someorganic solvents were able to generate neutral radicals [M(Pc)X2]. Tetrahydrofuran (THF)
gave TPP[Co(Pc)X2]2, while an acetone-dimethylformamide (DMF) solvent system provided
TPP[Fe(Pc)X2]2. Both partially-oxidized salts form dark green needle-like crystals.
As indicated by x-ray structure analysis, TPP[M(Pc)X2]2 forms one-dimensional π-πstacking network that results in a tetragonal crystal system. The MPc unit is formally
oxidized by 0.5e, which translates into one MPc unit per TPP counter ion.
Since differing thickness of the axial ligands results into varying distances between
neighboring molecules, as further evidenced by their overlap integrals (s) which indicatedlower value for bulkier axial ligands (TPP[Co(Pc)(CN)2]2: s = 10.0 x 10-3, TPP[Co(Pc)Cl2]2 :s = 9.0 x 10-3, TPP[Co(Pc)Br2]2: s = 8.1 x 10-3). This variation influences the electrical andmagnetic properties of the system.

Crystal Structure of TPP[M(Pc)X2]2; Space group = P42/n; Crystal system = Tetragonal4103ρ / Ω cm102101

10010Br

10-1

10-210-3ClCN
050100150200250300T/K
Temperature dependence of the electrical resistivity

Compared with its partially metallic dicyano-ligated counterpart, TPP[Co(Pc)X2]2
record one-order lower conductivity because of the lesser π-π overlap interaction, and they
exhibit semiconducting properties.
A detailed characterization of TPP[M(Pc)X2]2 will be presented at the conference.