Structure and properties of radical anion and dianion salts of organic dye trans-perinone and its mixed salt with gallium(iii) phthalocyanine

Abstract

Reduction of organic dye trans-perinone (its abbreviation is perinone) in different experimental conditions allows us to obtain and characterize radical anion {cryptand(K⁺)}[perinone˙⁻] (1) and dianion {PPN⁺}₂[perinone²⁻]·2C₆H₄Cl₂ (2) salts of this dye. The salts have layered structures. Perinone˙⁻ radical anions form π–π stacked dimers in 1 with an effective interaction between them, whereas perinone²⁻ dianions are isolated in 2. Reduction of perinone is accompanied by an essential red shift of the absorption bands of the starting dye and, as a result, the salts have absorption nearly in the whole visible range. Strong coupling of spins is observed in the π-stacking [perinone˙⁻]₂ dimers of 1, which are described by the Heisenberg model for isolated pairs of antiferromagnetically interacting spins with J/k_B = −38 K. The triplet excited state of the dimers is populated above 50 K. The EPR signal of 1 shows features characteristic of triplets, and the average separation of spins within the dimers estimated in the point-dipole approximation is 8.7 Å. The dimers manifest an intense charge transfer band with a maximum at 1356 nm. A mixed {cryptand(K⁺)}[(perinone)_0.5(Ga^IIIClPc)]⁻·3C₆H₄Cl₂ (3) salt with two anionic chromophores – perinone and gallium chloride phthalocyanine – is also obtained in the crystalline form. It has only one negative charge and spin per [(perinone)_0.5(Ga^IIIClPc)] unit. As a result, the magnetic behavior of 3 is described well by contributions from isolated perinone˙⁻ radical anions and {Ga^IIIClPc}₂˙⁻ dimers with effective π–π stacking between phthalocyanines and one negative charge and S = 1/2 spin per dimer.