Synthetic access to calix[3]pyrroles via meso-expansion: hosts with diverse guest chemistry.

Calix[3]pyrroles were synthesized for the first time. These macrocycles display versatile guest binding ability based on the bridges connecting the two α-positions of the tripyrrane moiety e.g. with an ethene bridge they showed colorimetric sensing of fluoride and cyanide ions, whereas with a phenylene spacer they exhibited fluorometric sensing of fluoride ions only, and the macrocycle with an ethylene unit acted as a host towards the water molecule with unique penta-coordinated oxygen in the solid state.

ß-Hexaalkylporphycenes: Positional Effect of Alkyl Groups toward Design and Control of Structural and Photophysical Properties in Isomeric Hexaethylporphycenes.

Two novel ß-hexaalkylated porphycenes, i.e., 2,3,7,12,13,17- (HOT) and 2,3,6,12,13,16-hexaethylporphycenes (HIT) were introduced for the first time in porphycene chemistry. These were synthesized through McMurry coupling reactions of new isomeric unsymmetrically substituted triethylbipyrrole dialdehydes. The positional effects of alkyl groups could be manifested through significant alteration in structure of porphycene cores and, as a consequence their photophysical properties, not noticed in ß-octaethylporphycene. HOT displays significant fluorescence accompanied by reasonable singlet oxygen generation ability.

Calix[2]bispyrrolylarenes: new expanded calix[4]pyrroles for fluorometric sensing of anions via extended π-conjugation.

Two new expanded calix[4]pyrroles 3 and 4 were synthesized by '2 + 2' cyclocoupling of easily prepared diboryldipyrromethane 7 (by Ir-catalyzed CH-bond activation) with appropriate diiodoarenes using the Suzuki protocol. Owing to the unique design, both macrocycles exhibited extended π-conjugation and enhanced fluorescence. Upon complexation with anions (fluoride and acetate), receptor 3 displayed turn-on sensing of fluorescence, whereas 4 showed turn-off sensing.