Highly symmetrical 24-membered macrocyclic organoantimony(V) complexes constructed from Schiff base ligands possessing two terminal carboxyl groups

Two novel organoantimony(V) complexes Ph₃SbL^a]₂ (1) and Ph₃SbL^b]₂ (2) (H₂L^a = 5-{(2-carboxyphenyl)methylene]amino}-4-chlorobenzoic acid, and H₂L^b = 5-{(2-carboxyphenyl)methylene]amino}-2-chlorobenzoic acid) have been synthesized by the reaction of triphenylantimony dichloride and Schiff base ligands with the ratio of 1:1, and characterized by elemental analysis, IR, ¹H and ¹³C NMR spectroscopy. X-ray single-crystal diffraction analyses reveal that two highly symmetrical 24-membered macrocyclic organoantimony derivatives were found unprecedentedly, in which two antimony atoms are bridged by four terminal carboxyl groups of the Schiff base ligands, and antimony atoms exhibit typical five-coordinated trigonal-bipyramid geometry with two carboxyl oxygen atoms occupying the axial positions. In complexes 1 and 2, there exist several types of secondary interactions (C–H…π, C–Cl…π and C-H…Cl), which contribute to the formation of a 1D infinite chain in 1 and a 2D supramolecular network structure in 2 in their crystal structures, respectively.