Mixed-Valence, Disordered Structures and Characterization of Iodine-Doped Phthalocyanines: [YbPc₂]I₂ and [(AsPc)(Pc)]I₂

Crystals of C64H32N16YbI2 and C64H32N16AsI2 were grown directly in the reaction of ytterbium or arsenic powder with 1,2-dicyanobenzene under a stream of iodine at 200 °C. Both partially oxidized phthalocyanine complexes crystallize in the P4/mcc space group of the tetragonal system with one molecule per unit cell, with the cell dimensions a = 13.927(2) Å, c = 6.409(1) Å, and a = 13.926(2) Å, c = 6.433(1) Å for the Yb and As complexes, respectively. The space group of P4/mcc requires that both heavy (iodine and metal) atoms are disordered in these structures. The structures show columnar pseudo-monodimensional stacks of [YbPc2] or [(AsPc)(Pc)] units with an average nonintegral charge of +2/3 and linear chains of triiodide I3- ions, which were detected by Raman spectroscopy. The monodimensional chains of I3- ions and pseudo-monodimensional aggregates of [YbPc2]2/3+ or [(AsPc)(Pc)]2/3+ are aligned along the c-axis of the crystals. The Yb3+ ion lies in the center, whereas in the [(AsPc)(Pc)] unit the As3+ ion does not lie in the center between the Pc rings. In the crystal of [(AsPc)(Pc)]I2 both components in the [(AsPc)(Pc)]2/3+ unit (e.g., AsPc and Pc) with opposite charge are electrostatically interacting. The magnetic susceptibility measurement of the [YbPc2]I2 shows typical Curie−Weiss behavior, and the effective magnetic moment is about 4.60 μB. The EPR measurement shows no signal for the Yb complex, while for [(AsPc)(Pc)]I2 two signals are observed: a sharp narrow line at g = 2.0028 of width ≈2 G and a broad line at g = 2.0036 of width ≈9 G. The two EPR signals are associated with two different radical components: a phthalocyaninato (Pc-•) ring and [AsPc-•], respectively. Both free radicals are in resonance: [(As3+Pc2-)(Pc-•)] ↔ [(As3+Pc-•)(Pc2-)]. Oxygen effects on the EPR signal of the [(AsPc)(Pc)]I2 crystal have been detected. The conductivity measured on polycrystalline samples at room temperature equals 2.5−4 × 10-2 and 2.2−3.5 × 10-4 Ω-1 cm-1 for [YbPc2]I2 and [AsPc(Pc)]I2, respectively. Both complexes exhibit nonmetallic character in conductivity (dσ/dT > 0).