Conformation and selectivity towards silver of thiocrown ethers based on Xylyl subunits

Abstract

Studies intended to relate the conformational behaviour and selectivity (towards silver) of arene thiocrown ether ligands with one fused SCCSCCS unit have been made. The cyclophane isomers 2,5,8-trithia[9]-o-benzenophane 1 and 2,5,8-trithia[9]-p-benzenophane 3 have been characterised by single-crystal X-ray crystallography: 1, monoclinic, space group P2₁/c, a= 8.855(2), b= 15.892(2), c= 9.943(2)Å, β= 111.52(1)°, Z= 4, R= 0.052, R′= 0.046, based on 1392 observed reflections; 3, monoclinic, space group P2₁/n, a= 10.363(5), b= 7.574(3), c= 16.647(2), β= 101.64(2)°, Z= 4, R= 0.039, R′= 0.041, based on 1704 observed reflections. New NMR information on solution conformations of 1 and 3 and of the m-isomer 2, is compared with crystal structure data, and with the patterns of conformational change seen when molecular dynamics (MD) simulations are performed on the molecules (using the crystal data as starting conformation). The separations between non-bonded sulfurs in the crystal structures, MD simulations, and in a series of metal complex crystal structures obtained from the Cambridge Structural Database or the literature have been analysed. The MD simulation provides a new perspective on preorganisation of the ligands studied prior to metal-ion co-ordination.