Synthesis, X-ray Structures, and Optical and Magnetic Properties of Cu(II) Octafluoro-octakisperfluoro(isopropyl)phthalocyanine: The Effects of Electron Addition and Fluorine Accretion

Abstract

The stepwise reduction of copper­(II) 1,4,8,11,15,18,22,25-octafluoro-2,3,9,10,16,17,23,24-octakisperfluoro­(isopropyl) phthalocyanine (CuIIF64Pc) in o-dichlorobenzene (C6H4Cl2) by potassium graphite in the presence of cryptand­(K+), abbreviated L+, results in the formation of (L+)­[CuII(F64Pc•3–)]−·2C6H4Cl2 (1), (L+)2[CuII(F64Pc4–)]2–·C6H4Cl2 (2), and (L+)2[CuII(F64Pc4–)]2– (3) complexes. Single-crystal X-ray structures revealed their composition and a monotonic increase with increased phthalocyanine (Pc) negative charges of the magnitude of alternative shortening and elongation of the prior equivalent Nmeso–C bonds. The complexes are separated by bulky i-C3F7 substituents, large cryptand counterions, and solvent molecules. Weak, new bands are generated in the visible and near-infrared (NIR) domains upon reductions. The one-electron reduced complex, [CuII(F64Pc•3–)]−, is a diradical, exhibiting broad electron paramagnetic resonance (EPR) signals, with intermediate parameters between those typical to CuII and F64Pc•3–. The two-electron reduced complexes, [CuII(F64Pc4–)]2–, contain a diamagnetic F64Pc4– macrocycle and a single spin, S = 1/2, on CuII. The bulky perfluoroisopropyl groups are suppressing intermolecular π–π interactions between Pcs in the [CuII(F64Pc n–)](n−2)– (n = 3, 4) anions, 1–3, similar to the case of the nonreduced complex. However, π–π interactions between 1 and o-dichlorobenzene are observed. The d9 and Pc electrons in 1 are antiferromagnetically coupled, J = −0.56 cm–1, as revealed by superconducting quantum interference device (SQUID) magnetometry, but the coupling is at least 1 order of magnitude smaller compared with the coupling observed for CuII(F8Pc•3–) and CuII(F16Pc•3–), a testimony to the F accretion effect of rendering the Pc macrocycle progressively more electron-deficient. The data for CuII(F64Pc) provide structural, spectroscopic, and magnetochemical insights, which establish a trend of the effects of fluorine and charge variations of fluorinated Pcs within the macrocycle series CuII(F x Pc), x = 8, 16, 64. Diamagnetic Pcs might be useful for photodynamic therapy (PDT) and related biomedical applications, while the solvent-processable biradicalic nature of the monoanion salts may constitute the basis for designing robust, air-stable electronic, and magnetically condensed materials.