Synthesis, Structure, and Properties of Corona[6]arenes and Their Assembly with Anions in the Crystalline State

The
synthesis, conformational structure, electronic property, and
anion complexation of novel coronarenes were systematically studied.
A number of corona[4]­arene[2]­tetrazines that contain different combinations
of nitrogen atoms with O, S, SO2, and CH2 as
bridging units were synthesized conveniently by means of a fragment
coupling strategy based on efficient nucleophilic aromatic substitution
reaction of easily available aromatic dinucleophiles and 3,6-dichlorotetrazine.
The resulting macrocycles adopt crownlike conformational structures
with the nitrogen bridge(s) forming conjugation with carbonyl and
the other heteroatom linkages with tetrazine. CV and DPV measurements
showed that the tetrazine-bearing coronarenes were electron deficient
with reduction potentials ranging from −896 to −960
mV. Owing mainly to noncovalent anion−π attractive interactions,
N2,O4-corona­[4]­arene­[2]­tetrazine formed complexes
with anions of varied geometries and shapes yielding diverse assembled
structures in the solid state.