Non-covalent synthesis of calixarene capped porphyrins can be achieved in polar solvents (up to 45% molar fraction of water) via ionic interaction. Thus tetracationic meso-tetrakis(N-alkylpyridinium-3-yl) porphyrins 1a–d and tetra anionic 25,26,27,28-tetrakis(2-ethoxyethoxy)-calixarene tetrasulfonate 2 self-assemble in an entropy driven process in 1:1 stoichiometry with association constants K1·2 as high as 107 M−1 in methanol. The thermodynamic stability remains high even in the presence of competing salts: 10−2 M Bu4NClO4 (4500 times the concentration of the building blocks) gives a reduction in K1·2 of only 10 times. Ternary complexes 1a·2·L using 1-methylimidazole or pyridine as axial ligands (L) have been obtained with L residing outside the assembly cavity.
Fiammengo, R., Timmerman, P., Huskens, J., Versluis, K., Heck, A. J. R., & Reinhoudt, D. (2002). Non-covalent synthesis of calixarene-capped porphyrins in polar solvents via ionic interactions. Tetrahedron, 58(4), 757-764. https://doi.org/10.1016/S0040-4020(01)01097-3