Tooru Miyajima

Synthesis of thiophene-containing hybrid calixphyrins of the 5,10-porphodimethene type

The synthesis, structure, and optical and electrochemical properties of thiophene-containing hybrid calixphyrins are reported. The 5,10-porphodimethene type 14pi- and 16pi-S,N2,X-hybrid calixphyrins (X = NH, O, S) were prepared by acid-promoted dehydrative condensation between a thiatripyrrane and the corresponding 2,5-bis[hydroxy(phenyl)methyl]heteroles followed by DDQ oxidation. Both crystallographic and spectroscopic analyses of the newly prepared hybrid calixphyrins have revealed that the combination of heteroles explicitly influences the electronic structures of the pi-conjugated framework. The 14pi-S,N2,X-hybrid calixphyrins have proven to be fluorescent in solution.

Zinc-Induced Fluorescence Enhancement of the 5,10-Porphodimethene-Type Thiophene-Containing Calixphyrins

The synthesis, structure, and electrochemical/optical properties of the zinc complexes of 5,10-porphodimethene-type thiophene-containing (S,N3-) and phosphole-containing (P,N3-) calixphyrins are reported. The S,N3- and P,N3-calixphyrin free bases react with zinc(II) salts to give the corresponding zinc complexes in good yields. The S,N3-calixphyrin–ZnI complex adopts a distorted square pyramidal geometry, with the S and N atoms at the basal positions. The S,N3-calixphyrin–ZnX complexes emit red fluorescence with fluorescent quantum yields up to 23%, whereas the P,N3-calixphyrin–ZnCl complex is weakly fluorescent. Among the first-row transition metals (Fe2+, Cu2+, and Zn2+) examined, the chelation-enhanced fluorescence is observed specifically for the Zn2+ ion. These results indicate that the 5,10-porphodimethene-type S,N3-hybrid calixphyrin is a promising turn-on fluorescent probe for Zn2+ sensing.