Cystine-based cyclic oligoureas: a new class of hydrogen-bonding electroneutral anion receptorsElectronic supplementary information (ESI) available: 1H NMR of 1 (Fig. S1), 2 (Fig. S2); ROESY NMR of 1 (Fig. S3), 2 (Fig. S4); ES-MS of 1 (Fig. S5), 2 (Fig. S6), FAB-MS of 1 (Fig. S7); NMR titration of 2 with squarate TBA salt (Fig. S8); 1H NMR of 1 in CDCl3 (host alone) (Fig. S9), 1 with Cl− in 1∶1 molar ratio (Fig. S10), 1 with Br− in 1∶1 molar ratio (Fig. S11), 1 with NO3− in 1∶1 molar ratio (Fig. S12), 2 in CDCl3 (host alone) (Fig. S13), 2 with squarate dianion in 1∶1 molar ratio (Fig. S14). See http://www.rsc.org/suppdata/cc/b1/b102720b/

Abstract

Cystine-based symmetrical cyclic oligoureas, synthesized in a one-pot reaction from L-cystine dimethyl ester and triphosgene, are demonstrated to act as versatile neutral receptors for both inorganic and organic anions operating exclusively through hydrogen bonds; ¹H NMR studies have shown that while the cyclic triurea prefers to complex with spherical (halides) and trigonal planar (nitrate) anions, the higher oligomer tetraurea can trap the tetragonal planar squarate dianion with modest efficiency.