Synthesis of diazadithiol calix[4]arene for heavy metal ions separation

Abstract

Four diazadithiol calix[4]arenes, 25,27-((2,2'-diethoxy)benzyl)-3,7-dithianonane-1,9-diimine-p-tert-butylcalix[4]arene, 3, 25,27-((4,4'-diethoxy)benzyl)-3,7-dithianonane-1,9-diimine-p-tert-butylcalix[4]arene, 4, 25,27-((2,2'-diethoxy)benzyl)-3,6-dithiaoctane-1,8-diimine-p-tert-butylcalix[4]arene, 5 and 25,27-((4,4'-diethoxy)benzyl)-3,6-dithiaoctane-1,8-diimine-p-tert-butylcalix[4]arene, 6, have been prepared by condensation reaction reactions of appropriate dithia diamines and 25,27-((2,2'-diethoxy)benzaldehyde)-p-tert-butylcalix[4]arene, 1, as well as 25,27-((4,4'-diethoxy)benzaldehyde)-p-tert-butylcalix[4]arene, 2, Reduction of 3 and 4 with NaBH4 and subsequent protonat protonation by HCl/CH3OH resulting in 25,27-((2,2'-diethoxy)benzyl)-3,7-dithianonane-1,9-diamine-p-tert-butylcalix[4]arene dihydrogenchloride, 7, and 25,27-((4,4'-diethoxy)benzyl)-3,7-dithianonane-1,9-diamine-p-tert-butylcalix[4]arene dihydrogenchloride, 8, respectively. The compounds 7 and 8 were then used for protonation and complexation studies of the neutral derivatives, 25,27-((2,2'-diethoxy)benzyl)-3,7-dithianonane-1,9-diamine-p-tert-butylcalix[4]arene, 9, and 25,27-((4,4'-diethoxy)benzyl)-3,7-dithianonane-1,9-diamine-p-tert-butylcalix[4]arene, 10. Protonation constants of the compouds 9 and 10 in 1.0x10 -2 M NMe4Cl in 10% CH2Cl2/CH3OH at 25 ํC by potentiometric titrations are log K1 = 9.30+-0.04, log K2 = 7.80+-0.09 and log K1 = 8.67+-0.01, log K2 = 7.82+-0.03 and in 5.0x10 -2 M NBu4CF3SO3 are log K1 = 9.23+-0.05, log K2 = 7.82+-0.10 ตามลำดับ สำหรับใน 5.0x10 -2 M NBu4CF3SO3 พบว่า log K1 = 8.67+-0.01 and log K1 = 8.47+-0.02, log K2 = 7.87+-0.04, respectively. Complexation studies of 9 and 10 with Cu 2+, Zn2+, Cd2+ and Hg2+ ions in 5.0x10 -2 M NBu4CF3SO3 in 10% Ch2Cl2/CH3OH ที่ 25 ํC were performed by potentiometric titrations. The compounds 9 and 10 form 1:1 complexes with Cu2+, and their stability constants (log K's) were estimated to be 8.81+-0.04 and 7.21+-0.07, respectively. Both compounds also form 1:1 complexes with Hg2+, and their stability constants (log K's) were estimated to be 4.47+-0.08 and 3.20+-0.13, respectively. From species distribution plots, the highest amount of 1:1 complexes of 9 with Cu2+ and Hg2+ occurred at pH 5.8 and 8.7, respectively. For 10, the highest amount of 1:1 complexes with Cu2+ and Hg+ occurred at pH 6.2 and 9.1, respectively.