Sb(V) dihalide corroles: efficient singlet oxygen photosensitisers

Sb(V) dihalide corrole complexes, in particular difluoro-5,15-di(4-cyanophenyl)-10-(2,4,5-trimethoxyphenyl)corrolatoantimony(V) (complex 1), show distinct emission properties and efficient intersystem crossing rates. Furthermore, complex 1 is characterised by its extended triplet excited state lifetime and an impressive singlet oxygen quantum yield exceeding 95%. This emphasises its potential for effective photooxidation reactions, positioning it as a leader in Sb(V) complex applications.

Do Corroles Stabilize Tetravalent Antimony?

Antimony corrole cations have been prepared by one-electron oxidation of antimony(III) congeners with silver(I) and copper(II) salts. Isolation and crystallization was successful for the first time, and the X-ray crystallographic investigation unraveled structural similarities with antimony(III)corroles. EPR experiments showed strong hyperfine interactions of the unpaired electron with the 121Sb (I = 5/2) and 123Sb nuclei (I = 7/2). A DFT analysis supports the description of the oxidized form as a Sb(III) corrole radical with less than 2% Sb(IV) character. In the presence of water or a fluoride source like PF6-, the compounds undergo a redox disproportionation to yield known antimony(III)corroles and either difluorido-antimony(V)corroles, or bis-μ-oxido-di[antimony(V)corroles] via novel cationic hydroxo-antimony(V) derivatives.