Synthesis and structural studies of copper(ii) complex with N2S2 based N-substituted pendant phosphonic acid arms.Dalton Trans. 2020 Mar 21; 49(11):3545-3552.DT
The synthesis of a heteromacrocyclic bifunctional chelator with phosphonic acid pendent arms is presented along copper(ii) complexation. Ligand N2S2-POH featuring N,N'-bis-substituted phosphonate pendent arms was isolated in respectable yields, characterized, and chelated to copper(ii). Implementation of both Moedritzer-Irani and Kabachnik-Fields conditions using aza-thia macrocycle 1,8-dithia-4,11-diazacyclotetradecane afforded 1,8-dithia-4,11-diazacyclotetradecane-4,11-diyl-bis-(methylene)-bis-(phosphonic acid) (N2S2-POH). Kinetic NMR studies provided four acid dissociation constants with respect to hydronium ion concentration. Benesi-Hildebrand binding experiment provided a conditional formation constant of 2.8 × 104 M-1. Heteromacrocycle N2S2-POH readily formed an encapsulated copper(ii) chelate at room temperature, which was examined through EPR analysis.