Solubilities of salen derivatives and their cobalt complex in liquid and supercritical CO2

Abstract

The solubility of N,N′-Bis(salicylidene) ethylenediamine (n-salen) and N,N′-bis(3,5-di-tert-butylsalicylidene) ethylenediamine (t-butyl-salen) was studied with in-situ UV-V1S spectrometer. n-Salen is 3-5 times more soluble than t-butyl-salen in liquid or supercritical CO 2. This behavior may be attributed to Lewis acid-base interaction between salen and CO2. The chelation of salen with Co++ ion in supercritical condition was confirmed to be fast enough above room temperature. However, the metal ion extraction capability of t-butyl salen is relatively poor because of its low solubility and ionic nature of complex.