Cation complexation by chemically modified calixarenes. Part 10. Thioamide derivatives of p-tert-butylcalix[4]-, [5]- and [6]-arenes with selectivity for copper, silver, cadmium and lead. X-Ray molecular structures of calix[4]arene thioamide–lead(II) and calix[4]arene amide–copper(II) complexes

Abstract

The effect of chemical modification of the lower rim of p-tert-butylcalix[4]-, [5]-and [6]-arenes has beenanalysed with respect to cation binding by thioamide podands. Extraction data for metal picrates from water into dichloromethane are discussed. Cu II , Pb II and Ag I ions are extracted efficiently by all the thioamides studied, whereas extraction of Cd II only reaches significant levels with the pentamer derivative. Unlike their calixarene amide counterparts, these thioamides have no affinity in extraction for either alkali or alkaline earth metals. The X-ray molecular structure of a thioamide-Pb II (ClO 4 ) 2 complex and, for comparison, that of an amide-Cu II (ClO 4 ) 2 complex have been determined. Both complexes exist in the cone conformation with the metal ion encapsulated by the heteroatoms on the lower rin. The crystal structure of the lead complex derivative 5ؒPb(ClO 4 ) 2 ؒEtOHؒ0.5H 2 O, was solved by Patterson methods and refined by block diagonal least-squares analysis. The crystals are triclinic, space group P1 , a = 13.394(6), b = 13.459(6), c = 26.711(4) Å, a = 78.33(2), = 87.62(2), = 60.46(2)Њ with R = 0.108 for 4417 observed reflections. The Pb 2+ is bonded to the four ethereal oxygen and four thiocarbonyl sulfur atoms, [Pb᎐O, 2.65(2) to 2.72(2), mean value 2.68(3) Å; Pb᎐S, 2.82(1) to 2.95(1) with a mean of 2.91(3) Å]. The crystal structure of the copper calixarene complex 2ؒCu(ClO 4 ) 2 ؒH 2 Oؒ1.4CH 3 OHؒEtOH, was solved by direct methods and refined by block-diagonal least-squares methods. The crystals are tetragonal, space group P4/ncc a = 17.147(2), c = 28.054(4) Å, with R = 0.079 for 1482 observed reflections. The Cu 2+ resides on a four-fold axis and is bonded to the four carbonyl oxygen atoms [Cu᎐O, 1.926(6) Å]. Four ethereal oxygen atoms are at a distance of 2.963(6) Å from the metal ion.Chemical modification of calixarenes 1 1,2 on the lower rim represents a simple though effective and versatile way of producing receptors with very selective cation binding properties. We and others have demonstrated complexation of alkali and alkaline cations using calixarenes with pendant ether, 3 ester, 4-9 ketone, 10 carboxylic acid, 11 amide, 12-15 crown ether 16 and hemispherand 17 groups attached to the calixarene substructure through the phenolic oxygen atoms. In some cases the selectivity and strength of complexation were sufficiently favourable to allow the incorporation of the calixarene into ion-selective electrodes 18 and ISFETS, 19 e.g. for Na + and Cs + ion. Alkaline earth salts are strongly bound by calixarene amides, the diethyl amide 1 in the tetramer series exhibiting a large preference in stability constant (ca. 10 8 ) for Ca 2+ over Mg 2+ in methanol. 13 Calixarene ring size is also important with the larger pentamer and hexamer derivatives favouring the larger cations. We have extended our research into chemically modified calixarenes to include systems with binding potential for metallic ions in other regions of the periodic table and we now describe the synthesis and complexati...

Calixarene-Based Molecules for Cation Recognition

“…Thiocarbamoyl groups [159,160] or dithiocarbamoyl groups when attached to the calixarene skeleton such as in ligand 30 [161,162] provide selectivity for Ag + , Pd 2+ , Hg 2+ and other 'soft' metal ions over 'hard' ones.…”

Lower Rim Substituted p‐tert‐Butyl‐Calix[4]arene. Part 15. Pb(II)‐Ion‐Selective Electrodes Based on p‐tert‐Butyl‐calix[4]arene Thioamides

“…Here, we present four new calix [4]thioamide ionophores design with the aim of using them as active material in Pb(II)-selective electrodes and compound 2, known earlier [13,14]. The structure of the studied ligands are presented in Figure 1.…”

“…Tetrakis(diethyl)thioamide 2 is known as good Pb(II)-extractant but also for Cu 2þ and Ag þ cations [13]. The crystal structure of its complex with lead was already published [14]. It was revealed that Pb 2þ cation is bonded by four ethereal oxygen atoms and four sulfur atoms of the thiocarbonyls.…”

Self-assembly of a hybrid organic–inorganic dicopper(II) coordination polymer with a calix[4]arene-derived nitrogenous ligand

“…The corresponding Cu(II) species feature non-coordinating anions, such as PF À 6 , ClO À 4 , and NO À 3 , and have thus far eluded structural characterization. Moreover, the number of reports on the solid state structures of calixarene-derived copper(II) complexes is scarce [11][12][13][14][15]. Herein we report the preparation, spectroscopic properties, and solid state structure of a new organic-inorganic hybrid polymer with dinuclear Cu(II) linear connectors linked by the ditopic pro-ligand L 1 [16] (Scheme 1, R = H).…”