A preparative study of some coronands and their complexation of silver(I), zinc(II), cadmium(II) and lead(II)

A study of the complexation of heavy metal ions by the coronands 3,12,20,29-tetraoxa-35,36-diazapentacyclo29.3.1.1.^14,18.0^5,10.0^22,27]-hexatriaconta-1(35),5(10),6,8,14,16,18(36),22(27),23,25,31,33-dodecaene (1); 2,3,11,12-bis (4^′-methylbenzo)-1,4,10,13-tetrathia-7,16-dioxacyclo-octadeca-2,11-diene (2); 7,16-diaza-1,4,10,13-tetraoxa-2,3,11,12-dibenzocyclooctadeca-2,11-diene (3); 2-19-(2-hydroxy-2-phenylethyl)-7,8,9,10, 18,19,20,21-octahydro-6H,17H-dibenzob,k]1,4,10,13,7,16]tetraoxadiazacyclooctadecin-8-yl]-1-phenyl-1-ethanol (4); 1,4,10,13-tetraoxa-7,16-diazacyclo-octadecane (5); and 2-16-(2-hydroxy-2-phenylethyl)-1,4,10,13-tetraoxa-7,16-diazacyclo-octadecanyl]-1-phenyl-1-ethanol (6) is described. Coronands 1 and 3 were prepared by literature methods, improved methods were used to prepare 2, and 4 and 6 were prepared from 3 and 5 (obtained commercially), respectively. Potentiometric studies in N,N-dimethylformamide yielded (logK/dm³ mol⁻¹)=5.50, 6.49, 9.42 and 7.52 for Ag · 1]⁺, Ag · 2]⁺, Ag · 5]⁺ and Ag · 6]⁺, respectively; <2, <2, 4.30 and <2 for Zn · 1]²⁺, Zn · 2]²⁺, Zn · 5]²⁺ and Zn · 6]²⁺, respectively, <2, <2, 5.92 and >7.52 for Cd · 1]²⁺, Cd · 2]²⁺, Cd · 5]²⁺, and Cd · 6]²⁺, respectively, and 2.62, 2.38, 6.71 and >7.52 for Pb · 1]²⁺, Pb · 2]²⁺, Pb · 5]²⁺, and Pb · 6]²⁺, respectively. ESI-MS studies of the interactions of 1-6 with Ag⁺, Zn²⁺, Cd²⁺ and Pb²⁺ are also reported.