A new type of polytopic coordination compound: The synthesis and NMR studies of the first hybrid thiacalix[4]arenoclathrochelates

Abstract

Nucleophilic substitution of the reactive chlorine atoms of iron(II) dichloroclathrochelate with thiol-terminated thiacalix[4]arene nucleophiles in the 1,3-alternate conformation afforded the first hybrid calixarenoclathrochelates with both ring-closed and ring-opened structures. The 1:1, 1:2 and 1:3 condensations of tetra-O-substituted thiacalix[4]arenes with thiol-terminated spacer substituents at the lower rim of the macrocyclic platform were performed. These thiol-terminated calixarene precursors were obtained from their O-ω-bromoalkyl precursors in the 1,3-alternate conformation, which are the products of alkylation of the parent thiacalix[4]arene with a series of homological α,ω-dibromoalkanes. The complexes obtained were characterized using elemental analysis, MALDI-TOF and ESI mass spectrometry, IR, 1H, 19F, 11B and 13C{1H} NMR spectra; their molecular structures in solution were thoroughly studied by one- and two-dimensional NMR spectroscopy as well as by molecular mechanics calculations. The formation of the thiacalix[4]arenoclathrochelates depends on the length of their ribbed spacer substituents in the chelate α-dioximate fragments of the cage frameworks; those with four bridging methylene groups seem to be optimal for the synthesis of the ring-closed hybrid molecules with two metal-encapsulating macrobicycles. © 2012 Elsevier Ltd. All rights reserved.