ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Synthesis, silver (I) extraction and silver (I) binding studies of novel N¹,N³-bis(2-(benzylthio)ethyl)propanediamide derivatives

Abiodun D. Aderibigbe and Andrew J. Clark

Department of Chemistry, University of Warwick, Coventry, UK

E-mail: abiodunadaderibigbe23@gmail.com

Received: 21 May 2020  Accepted: 6 August 2020

Abstract:

Abstract

Solvent or liquid–liquid extraction represents a highly valuable technique for the selective recovery of metals from the aqueous phase due to the ease of operation and short turnaround times. Ligands bearing soft donor atoms including nitrogen and sulfur are ideal candidates for selective silver recovery due to their preference for silver binding. Herein, novel N¹,N³-bis(2-(benzylthio)ethyl)propanediamide derivatives bearing sulfur and nitrogen donor atoms were prepared in low to high yields and tested for Ag⁺ extraction from ternary aqueous solutions also containing Cu²⁺ and Pb²⁺ following a well-established solvent extraction protocol. It was observed that electronics effects at the 4-aryl position in the propanediamide (or malondiamide) derivatives had a significant effect on the selectivity, but little effect on the efficiency of Ag⁺ extraction with the 4-methoxy analogue proving the most selective. Steric hindrance provided by dimethyl substitutions at the α-positions to the sulfur atoms had negative effects on Ag⁺ extraction efficiency and selectivity, while diethyl steric hindrance at the methylene center lowered selectivity but increased extraction efficiency for Ag⁺. Detailed binding studies reveal that one of the malondiamide derivatives which lacked the electronic and steric hindrance groups studied coordinated Ag⁺ in a 1:1 fashion suggesting a tetrahedral complex geometry. Overall, the results show that simple modification of the electronics and sterics of the N¹,N³-bis(2-(benzylthio)ethyl)propanediamides, can improve their selectivity for Ag⁺ recovery from the aqueous phase.

Graphic abstract

Keywords: Malondiamide derivatives; Selective silver(I) extraction; Electronics; Sterics; Job plot; 1H NMR titration

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-020-01307-x

Chemical Papers 75 (1) 397–410 (2021)