Rigid trisporphyrin with 1,3,5-triazine core: Synthesis, spectroscopy, and DABCO-induced self-assembly properties

Abstract

A rigid Zn–trisporphyrin (1), the Zinc complex of 2,4,6-tris(5,10,15-triphenylporphyrinatozinc)-1,3,5-triazine (2) with three porphyrin moieties bridged by a rigid 1,3,5-triazine group, was synthesized and characterized by a series of spectroscopic methods including mass, 1H NMR, electronic absorption, and IR spectroscopy in addition to elemental analysis. The UV-vis spectrophotometric titration results revealed that along with the addition of the 1,4-diazabicyclo[2.2.2]octane (DABCO) form 0 to 3 equiv, 1 could form a 2:3 sandwich-type coordination cage in chloroform, which then transformed into a 1:3 open complex when the DABCO concentration was more than 3 equiv. Such DABCO-induced self- and disassembly processes were also confirmed by 1H NMR spectrophotometric titrations. In particular, it was demonstrated by comparative studies that the synergistic effect of the three porphyrin moieties linked together by the rigid 1,3,5-triazine group in 1 promoted the formation and stabilization of the 2:3 sandwich-type coordination cage. This result will be helpful towards the fabrication of various self-assembly structures based on metalloporphyrins with application potential in diverse areas such as molecular recognition and separation.