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Mixed-Valence, Disordered Structures and Characterization of Iodine-Doped Phthalocyanines: [YbPc(2)]I(2) and
Jan Janczak1, Ryszard Kubiak, Adam Jezierski
1W. Trzebiatowski Institute of Low Temperature and Structure Research, Polish Academy of Sciences, 2 Okólna Str., P.O. Box 1410, 50-950 Wroclaw, Poland, and Institute of Chemistry, University of Wroclaw, 14 F. Joliot-Curie Str., 50-383 Wroclaw, Poland.
Abstract:
Crystals of C(64)H(32)N(16)YbI(2) and C(64)H(32)N(16)AsI(2) were grown directly in the reaction of ytterbium or arsenic powder with 1,2-dicyanobenzene under a stream of iodine at 200 degrees 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 [YbPc(2)] or [(AsPc)(Pc)] units with an average nonintegral charge of +(2)/(3) and linear chains of triiodide I(3)(-) ions, which were detected by Raman spectroscopy. The monodimensional chains of I(3)(-) ions and pseudo-monodimensional aggregates of [YbPc(2)](2/3+) or [(AsPc)(Pc)](2/3+) are aligned along the c-axis of the crystals. The Yb(3+) ion lies in the center, whereas in the [(AsPc)(Pc)] unit the As(3+) ion does not lie in the center between the Pc rings. In the crystal of [(AsPc)(Pc)]I(2) 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 [YbPc(2)]I(2) shows typical Curie-Weiss behavior, and the effective magnetic moment is about 4.60 &mgr;(B). The EPR measurement shows no signal for the Yb complex, while for [(AsPc)(Pc)]I(2) two signals are observed: a sharp narrow line at g = 2.0028 of width approximately 2 G and a broad line at g = 2.0036 of width approximately 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: [(As(3+)Pc(2)(-))(Pc(-)(*))] <--> [(As(3+)Pc(-)(*))(Pc(2)(-))]. Oxygen effects on the EPR signal of the [(AsPc)(Pc)]I(2) crystal have been detected. The conductivity measured on polycrystalline samples at room temperature equals 2.5-4 x 10(-)(2) and 2.2-3.5 x 10(-)(4) Omega(-)(1) cm(-)(1) for [YbPc(2)]I(2) and [AsPc(Pc)]I(2), respectively. Both complexes exhibit nonmetallic character in conductivity (dsigma/dT > 0).
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