Two isomeric calix(4)arene complexes with mercury(II)

O. E. PIRO; E. E. CASTELLANO; S. CHAHINE; 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 two isomeric complexes of partially derivatized 5,11,17,23-tetra-tert-butyl[25,27-bis(hydroxy)-26,28-bis(ethylthio ethoxy)]-calix[4]arene (L) with mercury(II) were determined at 120K. The one obtained by slow evaporation from ethanol solvent, LHg(ClO4)2, crystallizes in the space group Pbca with a=15.568(1), b=18.696(1), c=40.322(1) Å, and Z=8. The other one, obtained from an acetonitrile solution, LHg(ClO4)2.2MeCN, crystallizes in the space group Pccn with a=21.794(1), b=45.754(1), c=12.395(1) Å, and Z=8. The structures were solved from 6870 [LHg(ClO4)2] and 7660 [LHg(ClO4)2.2MeCN] reflections with I>2s(I) and refined to R1-values of 0.053 and 0.073, respectively. The calix[4]arene ligand in both complexes shows hydrophobic cavities with a quite similar squashed cone conformation. In contrast, the hydrophilic cavities exhibit substantial differences in the conformation adopted by the opposite sulfur-containing pendant arms: in LHg(ClO4)2 they are roughly related by a pseudo two-fold axis, while in LHg(ClO4)2.2MeCN these pendant arms are approximately related through a local mirror plane. Despite these lower rim conformational differences, the Hg(II) ion in both complexes is in a similar environment, trans coordinated to the sulfur atoms of the opposite pendant arms, conforming a nearly linear S-Hg-S bond. This work was supported by FAPESP, Brazil and the EU (Contract ICA CT 2000-30006).