Synthesis and structural characterization of microporous N 4 O 4 -donor Schiff base macrocycle: Study of host–guest interactions and iodine sorption

A novel N4O4-donor macrocyclic Schiff base (1, 6, 20, 25-tetraaza-2, 5:8, 9:17, 18:21, 24:27, 28:36, 37-hexabenzo-10, 16, 29, 35-tetraoxa-cyclooctatriakonta-1, 6, 20, 25-tetraen) (1) was prepared by a [2 + 2] cyclocondensation reaction of the corresponding dialdehyde and diamine. The crystal and molecular structure was determined by the single crystal X-ray diffraction analysis, and the compound was additionally characterized by IR, Raman and NMR spectroscopy, thermal and elemental analysis. In the crystal the molecules of the macrocycle are connected by a series of weak hydrogen bonds into tubular structures, thus forming an open porous structure with nanometre sized pores (around 18% of the void volume). Recrystallization of 1 from chloroform and dichloromethane led to the formation of the chloroform solvate (1×CLF), and the dichloromethane solvatomorph (1×DCM). The chloroform solvate was treated with iodine vapour in a sealed chamber thus forming a stable iodine host–guest complex (1×I2). From the spectroscopic, crystal structure, and thermal analysis studies of 1×CLF, 1×DCM and 1×I2 it can be deduced that the compound forms stable host–guest complexes without any changes in the organic framework. The host:guest ratio was found to be 1:1, 1:3 and 2:1 for chloroform, dichloromethane and iodine complexes, respectively. The adsorption studies of activated 1×CLF showed a small uptake of CO2 at 298 K.