Chemical hybrids of the porphyrins and calixpyrroles, calix-[n] phyrins, are polypyrrolic macrocycles that contain at least one sp3 hybridized meso-like bridging carbon atom. While examples of calix [4] phyrin derivatives, represented by such classic structures as the phlorins, 1 isoporphyrins, 2 5, 10-or 5, 15-dihydroporphyrins, 3 and porphomethenes, 4 abound, the chemistry of higher order calix-[n] phyrins (n> 4) remains virtually unexplored. ...
[Kishan, M. Radha; Srinivas, N.; Raghavan, K. V.; Kulkarni, S. J.; Sarma, J. A. R. P.; Vairamani, M. Chemical Communications (Cambridge, United Kingdom), 2001 , # 21 p. 2226 - 2227]