Synthesis,Characterization, and Singlet Oxygen Sensitization by Antimony (III/V) Corrole Complexes

The synthesis, structural, spectroscopic characterization, and DFT/TD-DFT calculations of antimony corroles are reported herein. The studied complexes can be described as (Corr)Sb^III] and (Corr)(oxo)Sb^V]₂, where Corr is the trianion of corrole. All these complexes are diamagnetic in nature as is evident from sharp peaks with normal chemical shifts in the ¹H NMR spectra. Single crystal XRD analysis reveals that the antimony(V) corrole complex is the bis-μ-oxo-bridged dinuclear antimony(V). Both the tetra and hexa-coordinated (Corr)Sb^III] and (Corr)(oxo)Sb^V]₂ antimony complexes adopt domed-structure with weak d-π electron coupling. The Sb?O bond distances in the co-facial dimer of (Corr)(oxo)Sb^V]₂ are 1.9802(16) Å (DFT: 2.0141 Å ) (for Sb1?O1), and 1.9639(17) Å (DFT: 1.9957 Å ) (for Sb2?O2) respectively. We observed that even though iodosobenzene is frequently used to oxidize (Corr)Sb^III] species, the oxidation of (Corr)Sb^III] is indeed very facile in nature and it even occurred in the air-equilibrated CHCl₃ solution while storing for few days. Excitation of these antimony (III/V) corrole complexes in DCM/MeOH (1 : 1) at 77 K results in red emission with maxima at 640–720 nm. The singlet oxygen production of (Corr)(oxo)Sb^V]₂ has a quantum yield of 69 % and is two times higher than the analogous (Corr)Sb^III] derivatives.