Synthesis, crystal structure and charge transport properties of one-electron oxidized zirconium diphthalocyanine, [ZrPc2]IBr2

摘要

Crystals of the new one-electron oxidized zirconium diphthalocyanine, [ZrPc2]IBr2 (PC = C32H16N8) were grown directly from phthalonitrile and pure zirconium powder under the oxidation conditions of IBr at 220 degrees C. [ZrPc2]IBr2 crystallises in the space group P2(1)/m of the monoclinic system, with lattice parameters of: a = 6.697(1), b = 25.483(5), c = 16.918(3) A, beta = 100.03(3)degrees and Z = 2. The crystals of [ZrPc2]IBr2 are built up from one-electron oxidized [ZrPc2](+) units that form stacks parallel to a axis of the crystal and mixed electron-rich trihalide ions of IBr2-. The iodine atom of the IBr2- ions is located at the inversion center, so the IBr2- ions are linear and symmetrical. The mutual arrangement of [ZrPc2](+) and IBr2- ions is different to that found in the one-electron oxidized [ZrPc](I3I2)-I-. complex as well as to that found in the tetragonal crystals of partially oxidized [ZrPC2](I-3)(2/3). EPR experiment shows that the oxidation of the diamagnetic ZrPC2 complex by IBr is ligand centered. The UV-Vis spectrum of [ZrPC2]IBr2 shows, besides the bands observed in the spectrum of ZrPc2, one additional band at similar to 496 nm, which indicates the existence of the one-electron oxidized phthalocyaninato(1 -)pi-radical ligand and it is assigned to the electronic transition from a deeper level to the half-occupied HOMO level. The single-crystal electrical conductivity data shows anisotropy and non-metallic character in conductivity (d sigma-dT > 0). The charge transport mainly proceeds along the stacks of one-electron oxidized [ZrPc2](+) units. The relatively high conductivity along the [ZrPc2](+) stack results from the staggered configuration of the Pc-rings (rotation angle 45.0(3)degrees that makes short inter-ring C alpha(pyrrole)-C alpha(pyrrole) contacts (2.858(2)-3.017(3) A) and greatest overlap of the HOMO orbitals that form the conduction band of the molecular materials. (c) 2006 Elsevier Ltd. All rights reserved.