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

Maxim A Faraonov; Ilya A Yakushev; Evgeniya I Yudanova; Marius Pelmus; Sergiu M Gorun; Akihiro Otsuka; Hideki Yamochi; Hiroshi Kitagawa; Dmitri V Konarev

doi:10.1021/acs.inorgchem.3c00887

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

Inorg Chem. 2023 Jul 24;62(29):11390-11401. doi: 10.1021/acs.inorgchem.3c00887. Epub 2023 Jul 12.

Authors

Maxim A Faraonov¹, Ilya A Yakushev², Evgeniya I Yudanova¹, Marius Pelmus³, Sergiu M Gorun³, Akihiro Otsuka⁴, Hideki Yamochi⁴, Hiroshi Kitagawa⁴, Dmitri V Konarev¹

Affiliations

¹ Federal Research Center of Problems of Chemical Physics and Medical Chemistry, Russian Academy of Sciences, Moscow Region, Chernogolovka 142432, Russia.
² Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Moscow 119991, Russia.
³ Department of Chemistry and Biochemistry and Center for Functional Materials, Seton Hall University, South Orange, New Jersey 07079, United States.
⁴ Division of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.

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 (Cu^IIF₆₄Pc) in o-dichlorobenzene (C₆H₄Cl₂) by potassium graphite in the presence of cryptand(K⁺), abbreviated L⁺, results in the formation of (L⁺)[Cu^II(F₆₄Pc^•3-)]^-·2C₆H₄Cl₂ (1), (L⁺)₂[Cu^II(F₆₄Pc^4-)]^2-·C₆H₄Cl₂ (2), and (L⁺)₂[Cu^II(F₆₄Pc^4-)]^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 N_meso-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, [Cu^II(F₆₄Pc^•3-)]^-, is a diradical, exhibiting broad electron paramagnetic resonance (EPR) signals, with intermediate parameters between those typical to Cu^II and F₆₄Pc^•3-. The two-electron reduced complexes, [Cu^II(F₆₄Pc^4-)]^2-, contain a diamagnetic F₆₄Pc^4- macrocycle and a single spin, S = 1/2, on Cu^II. The bulky perfluoroisopropyl groups are suppressing intermolecular π-π interactions between Pcs in the [Cu^II(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 Cu^II(F₈Pc^•3-) and Cu^II(F₁₆Pc^•3-), a testimony to the F accretion effect of rendering the Pc macrocycle progressively more electron-deficient. The data for Cu^II(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 Cu^II(F_xPc), 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.