Calixarene/azolium cyclophane hybrids: synthesis, structure and conformations

Abstract

The synthesis, structure, and conformational behaviour of three imidazolium cyclophanes that incorporate one or two 4-tert-butylphenol or 4-tert-butylanisole groups as meta-disubstituted linkers in the macrocycle is described. The cyclophanes containing anisole moieties adopt a cone conformation in the solid state, which, in solution, is not labile on the NMR timescale. The cyclophanes containing one or two phenol moieties adopt conformations other than the cone in the solid state and are labile in solution on the NMR timescale. The phenol cyclophanes are readily deprotonated, and structural and conformational studies for a variety of the associated cyclophanes are also reported.

Dinuclear Au(i) N-heterocyclic carbene complexes derived from unsymmetrical azolium cyclophane salts: potential probes for live cell imaging applications

“…Cyclophanes have been of significant interest during the last decade, spurred on by studies into their interesting conformational behaviour, [1][2][3][4][5][6] their application for anion recognition, 4,[7][8][9][10] and in the case of azolium cyclophanes, for their use as precursors to N-heterocyclic carbene (NHC) metal complexes. 5,[11][12][13][14][15][16][17][18][19][20][21] In recent years there has been a high level of interest in the antitumour properties of Au(I)-NHC complexes.…”

Mercury complexes of an N-heterocyclic carbene derived from a calixarene/azolium cyclophane hybrid

“…Complex 10 2+ was also formed when 9.2Br or the binuclear salt 11.2Br [15] (Scheme 3) were heated with mercuric acetate in DMF or acetonitrile respectively. From one such experiment, the complex crystallised from DMF as 10.HgBr 4 , an adduct with tetrabromidomercurate (see below).…”

“…When 9.2Br was treated with titanium(IV) tetra(isopropoxide) in THF at reflux, no reaction occurred. When 9.2Br was treated with silver(I) oxide in DMF or copper(I) oxide in CH 2 Cl 2 , 9 2+ was partially deprotonated, to form the dimeric cation 11 2+ [15], which was identified by 1 H NMR spectroscopy, but no evidence for metal complexes was seen. We also explored the possibility of preparing metal complexes from NHC ligands derived from the hexafluorophosphate salt of the mono-phenol imidazolium cyclophane 12 2+ (Scheme 3).…”

“…The general procedure is described in a preceding paper [15], but with the following minor variations. In 10.HgBr 4 .8DMF, two t-butyl groups, one coordinated DMF and one solvent DMF were modelled as disordered over two sets of sites.…”

“…In the preceding contribution [15], we explored a further macrocycle 9 2+ (Scheme 1) in which the azolium cyclophane form was combined with the calix [4]arene form (which has certain similarities). Here, the imidazolium rings are now coupled with 2,6-phenolic linkages, the latter functionalized and potential donors (cf.…”