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Keywords:

  • Molecular design;
  • Iron;
  • ­Phthalocyanines;
  • Layered compounds;
  • EPR spectroscopy;
  • Magnetic properties

Abstract

Iron hexadecachlorophthalocyanine (Cl16Pc) salts with a layered arrangement of phthalocyanine (Pc) macrocycles were obtained by the reduction of FeCl16Pc with sodium fluorenone ketyl in the presence of PPNCl [PPN+: bis(triphenylphosphine)iminium cation] and TBABr (TBA+: tetrabutylammonium cation). (PPN+)[(FeICl16Pc)]·0.78C6H4Cl2·0.22C6H14 (1) contains π–π stacking columns formed by dimerized (FeICl16Pc) anions. The side-by-side arrangement of neighboring columns results in the formation of a layered iron hexadecachlorophthalocyanine structure. (TBA+)3{[(FeCl16Pc)2]3–} (2) contains hexagonal layers formed by [(FeCl16Pc)2]3– dimers and separated by TBA+ cations. The dimers bear –3 charge and, according to optical and X-ray diffraction data, consist of a [FeI(Cl16Pc)] monoanion and a [Fe0(Cl16Pc)]2– dianion. These anions are bonded in the dimer by a Fe–Fe bond of 2.899(4) Å length. It was shown that the negative charge in both anions is localized on the iron atoms to form FeI and Fe0, respectively, and no electron transfer to the hexadecachlorophthalocyanine macrocycles is observed. Magnetic data indicate the presence of only one S = 1/2 spin per [(FeCl16Pc)2]3– dimer. This result is in agreement with the formation of iron(I) and iron(0) hexadecachlorophthalocyanine anions, which have the iron atoms in d7 and diamagnetic d8 electron configuration, respectively. The spins of the iron(I) atoms are arranged in a hexagonal manner and only weakly interact, which results in a Weiss temperature of –1 K because of the long distances between them (>18 Å). Previously studied anionic salts with a columnar arrangement of [FeI(Cl16Pc)] do not show EPR signals from FeI. In contrast, salt 2 shows an intense EPR signal with main components at g = 2.249 and g = 1.989, which are characteristic of FeI with d7 electron configuration.