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 H-1 NMR spectra. Single crystal XRD analysis reveals that the antimony(V) corrole complex is the bis-& mu;-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-& pi; electron coupling. The Sb-O bond distances in the co-facial dimer of [(Corr)(oxo)Sb-V](2) are 1.9802(16) & ANGS; (DFT: 2.0141 & ANGS;) (for Sb1-O1), and 1.9639(17) & ANGS; (DFT: 1.9957 & ANGS;) (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.