Dianionic States of Trithiadodecaazahexaphyrin Complexes with Homotrinuclear M II 3 O Clusters (M = Ni and Cu): Crystal Structures, Metal- Or Macrocycle-Centered Reduction, and Doublet-Quartet Transitions in the Dianions.

Metal complexes of trithiadodecaazahexaphyrin (Hhp) that contain M ^II ₃ O clusters inside a π-extended trianionic (Hhp ^3- ) macrocycle have been prepared. Studies of the magnetic properties of Ni ^II ₃ O(Hhp) and Cu ^II ₃ O(Hhp) reveal a diamagnetic and EPR-silent trianionic (Hhp ^3- ) macrocycle and diamagnetic Ni ^II ₃ (O ^2- ) or paramagnetic Cu ^II ₃ (O ^2- ) tetracations. The positive charge of M ^II ₃ O(Hhp) is compensated by one acetate anion {M ^II ₃ O(Hhp)} ⁺ (CH ₃ CO ₂ ^- ). The three-electron reduction of {M ^II ₃ O(Hhp)} ⁺ yields {cryptand(Cs ⁺ )} ₂ {Ni ^II ₂ Ni ^I O(Hhp ^5- )} ^2- ·2C ₇ H ₈ ( 1 ) and {cryptand(Cs ⁺ )} ₂ {Cu ^II ₃ O(Hhp ^•6- )} ^2- ·C ₇ H ₈ ( 2 ) crystalline salts. The magnetic properties of 1 reveal the formation of Hhp ^5- and the reduction of nickel(II) to the paramagnetic Ni ^I ion ( S = 1/2), which is accompanied by the formation of the {Ni ^II ₂ Ni ^I O(Hhp ^5- )} ^2- dianion. As a result, the magnetic moment of 1 is 1.68 μ _B in the 20-220 K range, and a broad EPR signal of Ni ^I was observed. The Hhp ^5- macrocycle has a singlet ground state, but the increase in the magnitude of the magnetic moment of 1 above 220 K is attributed to the population of the triplet excited state in Hhp ^5- . The {Ni ^II ₂ Ni ^I O(Hhp ^5- )} ^2- dianion is transferred from the doublet excited state to the quartet excited state with an energy gap of 1420 ± 50 K. Salt 1 also shows an unusually strong low-energy NIR absorption, which was observed at 1000-2200 nm. In 2 , a highly reduced Hhp ^•6- radical hexaanion ( S = 1/2) coexists with a Cu ^II ₃ (O ^2- ) cluster ( S = 1/2) in the {Cu ^II ₃ O(Hhp ^•6- )} ^2- dianions. The dianions have a triplet ground state with antiferromagnetic exchange between two S = 1/2 spins with J = -6.4 cm ^-1 . The reduction of Hhp in both salts equalizes the initially alternated C-N bonds, supporting the increase in the Hhp macrocycle electron delocalization.