Volume 23, Issue 10 p. 2323-2331
Full Paper

The Redox-Active Chromium Phthalocyanine System: Isolation of Five Oxidation States from Pc4−CrI to Pc2−CrIII

Dr. Wen Zhou

Dr. Wen Zhou

Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6 Canada

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John R. Thompson

John R. Thompson

Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6 Canada

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Prof. Clifford C. Leznoff

Prof. Clifford C. Leznoff

Department of Chemistry, York University, 4700 Keele Street, Toronto, ON, M3J 1P3 Canada

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Prof. Daniel B. Leznoff

Corresponding Author

Prof. Daniel B. Leznoff

Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6 Canada

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First published: 17 October 2016
Citations: 22

Graphical Abstract

Many states of PcCr: A series of chromium phthalocyanine (Pc) complexes has been prepared and structurally characterized, spanning five stepwise oxidation states from the ring-reduced Pc4−CrI (which exists as dimers with Cr–Cr interactions) to Pc2−CrIII, illustrating the impressive redox-active nature of PcM systems. The reduced complexes display unique purple colours compared to traditional green/blue PcM materials.

Abstract

The preparation and structural characterization of a series of chromium phthalocyanine complexes with multiple metal and ring oxidation states were achieved using PcCrII (1) (Pc=phthalocyanine) or PcCrII(THF)2 (1⋅THF2) as starting materials. The reaction of soluble 1⋅THF2 with Br2 or I2 gave the PcCrIII halide complexes PcCrX(THF) (X=I/I3, Br; 3, 4, respectively). Treatment of 1 with 0.5 equivalent of PhIO or air generated the dinuclear [PcCr(THF)]2(μ-O) (5), whereas the addition of one equivalent of AgSbF6 to 1 resulted in oxidation to THF-solvated octahedral [PcCrIII(THF)2]SbF6 (6). The reduction of 1 with three sequential equivalents of KEt3BH resulted in the isolation of [K(DME)4][Pc3−CrII] (7), [K(DME)4]2[Pc4−CrII] (8) and [K6(DME)4][Pc4−CrI]2 (9), respectively. The reduced products are deep purple in colour, with visible absorption maxima between 500–580 nm. The ring-reduced complexes 7 and 8 are monomeric, whereas 9 is a 1D chain of dinuclear [PcCr]2 units with intercalated K+ cations and supported by Cr−Cr interactions of 2.988(2) Å. Addition of four equivalents of KC8 resulted in the demetallated product PcK2(DME)4 (10), which has a 1D chain structure. The isolation and structural characterization of new PcCr complexes spanning five oxidation states, including rare examples of crystalline reduced Pc-ring species emphasizes the broad redox activity and stability of phthalocyanine-based complexes.