Dianionic States of Trithiadodecaazahexaphyrin Complexes with Homotrinuclear MII3O Clusters (M = Ni and Cu): Crystal Structures, Metal- Or Macrocycle-Centered Reduction, and Doublet–Quartet Transitions in the Dianionsстатья
Статья опубликована в высокорейтинговом журнале
Информация о цитировании статьи получена из
Web of Science
Статья опубликована в журнале из списка Web of Science и/или Scopus
Дата последнего поиска статьи во внешних источниках: 17 августа 2021 г.
Аннотация:Metal complexes of trithiadodecaazahexaphyrin (Hhp) that contain MII3O clusters inside a π-extended trianionic (Hhp3–) macrocycle have been prepared. Studies of the magnetic properties of NiII3O(Hhp) and CuII3O(Hhp) reveal a diamagnetic and EPR-silent trianionic (Hhp3–) macrocycle and diamagnetic NiII3(O2–) or paramagnetic CuII3(O2–) tetracations. The positive charge of MII3O(Hhp) is compensated by one acetate anion {MII3O(Hhp)}+(CH3CO2–). The three-electron reduction of {MII3O(Hhp)}+ yields {cryptand(Cs+)}2{NiII2NiIO(Hhp5–)}2–·2C7H8 (1) and {cryptand(Cs+)}2{CuII3O(Hhp•6–)}2–·C7H8 (2) crystalline salts. The magnetic properties of 1 reveal the formation of Hhp(5–) and the reduction of nickel(II) to the paramagnetic NiI ion (S = 1/2), which is accompanied by the formation of the {NiII2NiIO(Hhp5–)}2– dianion. As a result, the magnetic moment of 1 is 1.68 μB in the 20–220 K range, and a broad EPR signal of NiI was observed. The Hhp5– 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 {NiII2NiIO(Hhp5–)}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 hexaanione (S = 1/2) coexists with a CuII3(O2–) cluster (S = 1/2) in the {CuII3O(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.