A lower rim tert-butyl calix[4]arene derivative that binds Ag(I)

EDUARDO E. CASTELLANO; OSCAR. E. PIRO; W. B. APARICIO-ARAGON; A. F. DANIL DE NAMOR

Florencia, Italia

Congreso; XXth Congress and General Assembly of the International Union of Crystallography; 2005

International Union of Crystallography

The X-ray structures  of  a tert-butyl calix[4]arene  derivative with –O–H and  –O–(CH2)2–NH–(P=S)(OCH2CH3)2 pendant arms (EPS) as molecular complexes with methanol, EPS(MeOH), 1, with dichloromethane, EPS(Cl2CH2), 2, and its complex with silver(I) and acetonitrile, AgEPS(MeCN)K.(ClO4)2.H2O, 3, were determined. The structures were solved from 17027 (1), 8810 (2) and 7729 (3) reflections with I>2σ(I) collected at T=100 K, and refined to R1-factors of 0.054 (1), 0.049 (2) and 0.090 (3). In all compounds, a pair of strong O–H…O(pend) bonds in the lower rim produces relatively open chalices. This, in turn, promotes the hydrophobic interaction with the solvent molecules found included in these cavities. The upper half of the EPS pendant arms is anchored by N-H…O(ox) intra-molecular bonds where now the phenol oxydryl oxygen atoms act as H-bond acceptors. Despite the relative rigidity of the upper half of the hydrophilic cavity, the lower half is pre-organized towards soft metal ion complexation at the thiophosphorous sulphur binding site by unhindered torsion movements, mainly around the N-P σ-bond. The silver(I) complex with EPS, exhibits an approximate C2 symmetry around the calix axis. The Ag(I) ion is sited on this axis, linearly coordinated to the sulphur atoms of the pendant arms [Ag-S distances of 2.414(2) and 2.422(2) Å, Ð(S-Ag-S)=171.99(8)o]. We thank FAPESP (Brazil) and EU (Contract ICA CT 2000-30006) for support