Synthesis and Studies of Dibenzofuran Embedded Bis‐(Calix)‐Pentaphyrins

Abstract

AbstractCondensation of dibenzofuran based tripyrrane with dipyrroethene diol under acid catalyzed porphyrin forming conditions resulted in the formation of dibenzofuran embedded calix pentaphyrins with two meso‐sp3 carbons instead of expected fully conjugated dibenzofuran (DBF) embedded pentaphyrins. Three examples of DBF embedded calix pentaphyrins have been synthesized by adopting the [3+2] condensation methodology and characterized by various spectroscopic and theoretical methods. The NMR studies that include COSY, NOESY, HMBC and HSQC clearly confirmed the molecular structures of DBF embedded bis‐(calix)‐pentaphyrins. The optimized structures showed that the DBF embedded bis‐(calix)‐pentaphyrin macrocycles adopted figure eight conformation due to presence of two sp3 carbon atoms (C1 and C22) at meso positions which obstructed the conjugation throughout the macrocycle. The absorption spectra of macrocycles showed non‐aromatic features with a sharp strong band at 480 nm and a broad band in the region of 600–800 nm which were significantly red shifted with distinct colour change in protonated derivatives of DBF embedded bis‐(calix)‐pentaphyrins.