Trifluoromethanesulfonate salt of 5,10,15,20-tetrakis(1-benzylpyridin-1-ium-4-yl)-21H,23H-porphyrin and its CaII complex

The synthesis, crystallization and characterization of a trifluoromethanesulfonate salt of 5,10,15,20-tetrakis(1-benzylpyridin-1-ium-4-yl)-21H,23H-porphyrin, C68H54N84+center dot 4CF(3)SO(3)(-)center dot 4H(2)O, 1 center dot OTf, are reported in this work. The reaction between 5,10,15,20-tetrakis(pyridin-4-yl)-21H,23H-porphyrin and benzyl bromide in the presence of 0.1 equiv. of Ca(OH)(2) in CH3CN under reflux with an N-2 atmosphere and subsequent treatment with silver trifluoromethanesulfonate (AgOTf) salt produced a red-brown solution. This reaction mixture was filtered and the solvent was allowed to evaporate at room temperature for 3 d to give 1 center dot OTf. Crystal structure determination by single-crystal X-ray diffraction (SCXD) revealed that 1 center dot OTf crystallizes in the space group P2(1)/c. The asymmetric unit contains half a porphyrin molecule, two trifluoromethanesulfonate anions and two water molecules of crystallization. The macrocycle of tetrapyrrole moieties is planar and unexpectedly it has coordinated Ca-II ions in occupational disorder. This Ca-II ion has only 10% occupancy (C72H61.80Ca0.10F12N8O16S4). The pyridinium rings bonded to methylene groups from porphyrin are located in two different arrangements in almost orthogonal positions between the plane formed by the porphyrin and the pyridinium rings. The crystal structure features cation center dot center dot center dot pi interactions between the Ca-II atom and the pi-system of the phenyl ring of neighboring molecules. Both trifluoromethanesulfonate anions are found at the periphery of 1, forming hydrogen bonds with water molecules.