Hexaphyrin GeIV and SnIV complexes were synthesized in high yields by reactions of hexaphyrin with GeCl4 or SnCl4 in the presence of triethylamine. Both complexes display distinct 28π Möbius aromatic character and possess a trigonal bipyramidal geometry at the central GeIV or SnIV atom. The equatorial hydroxy group of the GeIV complex was smoothly exchanged with neutral nucleophiles, such as phenol derivatives and thiophenol, with retention of configuration. In the SnIV complex, intersystem crossing to the T1 state is remarkably enhanced owing to the effective heavy-atom effect, thus allowing the formation of the T1 state in high yield. The T1 states of the GeIV and SnVI complexes were found to be antiaromatic on the basis of the transient absorption features in line with the Baird rule.
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The research at Kyoto and Osaka was supported by JSPS KAKENHI grants 25220802, 16K13952, 26810021, JP16H00909, JP15H03779, JP15K13642, and JP15H01087. S.-i.I. acknowledges a JSPS Fellowship for Young Scientists. The research at Yonsei University was supported by Global Research Laboratory grant 2013K1A1A2A02050183. The quantum-mechanical calculations were supported by the National Institute of Supercomputing and Network (NISN)/Korea Institute of Science and Technology Information (KISTI) with supercomputing resources, including technical support (KSC-2015-C3-024).
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