{CpFe^II(CO)₂Sn^II(Macrocycle^•3-)} Radicals with Intrinsic Charge Transfer from CpFe(CO)₂ to Macrocycles (Cp: Cp or Cp*); Effective Magnetic Coupling between Radical Trianionic Macrocycles^•3.

ABSTRACT: Neutral {CpFe^II(CO)₂[Sn^II(Pc^•3-)]} {Cp is cyclopentadienyl (1, 2) or Cp* is pentamethylcyclopentadienyl (3); Pc: phthalocyanine}, {Cp*Fe^II(CO)₂[Sn^II(Nc^•3-)]} (4, Nc: naphthalocyanine), and {CpFe^II(CO)₂[Sn^II(TPP^•3-)]} (5, TPP: tetraphenylporphyrin) complexes in which CpFe^II(CO)₂ fragments (Cp: Cp or Cp*) are coordinated to Sn^II(macrocycle^•3-) have been obtained. The product complexes were obtained at the reaction of charge transfer from CpFe^I(CO)₂ (Cp: Cp or Cp*) to [Sn^II(macrocycle^2-)] to form the diamagnetic Fe^II and paramagnetic radical trianionic macrocycles. As a result, these formally neutral complexes contain S = 1/2 spins delocalized over the macrocycles. This provides alternation of the C-N_imine or C-C_meso bonds in the macrocycles, the appearance of new bands in the near-infrared spectra of the complexes, and blue shift of both Soret and Q-bands. The {CpFe^II(CO)₂Sn^II(macrocycle^•3-)} units (Cp: Cp or Cp*, macrocycle: Pc or Nc) form closely packed ?-stacking dimers in 1 and 3 or one-dimensional chains in 2 and 4 with effective ?-? interaction between the macrocycles. Such packing allows strong antiferromagnetic coupling between S = 1/2 spins. Magnetic interaction can be described well by the Heisenberg model for the isolated dimers in 1 and 3 with exchange interaction J/k _B = -78 and -85 K, respectively. Magnetic behavior of 2 and 4 is described well by the model that includes contributions from an antiferromagnetically coupled S = 1/2 dimer (J _intra) and a Heisenberg S = 1/2 chain with alternating antiferromagnetic spin exchange between the neighbors (J _inter). Compound 2 demonstrates large intradimer interaction of J _intra/k _B = -54 K and essentially weaker interdimer exchange interactions of J _inter/k _B = -6 K, whereas compound 4 shows strong magnetic coupling of spins within the dimers (J _intra/k _B = -170 K) as well as between the dimers (J _inter/k _B = -40 K). Compound {CpFe^II(CO)₂[Sn^II(TPP^•3-)]} (5) shows no ?-? interactions between the porphyrin macrocycles, and magnetic coupling is weak in this case (Weiss temperature is -5 K). Preparation of a similar complex with indium(III) chloride phthalocyanine yields {CpFe(CO)₂[In(Pc^2-)]} (6). In this complex, indium(III) atoms are reduced instead of the phthalocyanine macrocycles that explains electron paramagnetic resonance silence of 6 in the 4-295 K range.

SUBMITTER: Konarev DV 

PROVIDER: S-EPMC6644027 | biostudies-literature | 2018 Nov

REPOSITORIES: biostudies-literature