A silver complex of chloroquine: synthesis, characterization and structural properties

Abstract

A new silver–chloroquine (CQ–Ag) complex [CQAgNO₃, CQ = chloroquine, C₁₈H₂₆N₃Cl] has been synthesized and characterized by using a combination of NMR (solution and solid-state), FTIR, molar conductivity and ESI/FT-ICR high resolution mass spectroscopy with DFT calculations. The CQ–Ag complex is formed by silver–CQ cations and nitrate counter anions, where the silver atoms are di-coordinated to chloroquines (CQ₂2Ag²⁺2+) through the quinoline sp² N and diethylamino sp³ N nitrogen basic sites. These cations presumably form polymeric structures mainly as head–head catemers. The most important cationic fragments of the CQ–Ag complex, detected by ESI/FT-ICR, were CQAg⁺, CQ₂Ag⁺, chloroquine singly (CQH⁺) and doubly protonated (CQH₂²⁺), whose formations are clearly favored by proton-displacement of the Ag⁺ cations.