Ditopic receptors containing urea groups for solvent extraction of Cu(ii) salts

Abstract

The ditopic receptor L3 [1-(2-((7-(4-(tert-butyl)benzyl)-1,4,7,10-tetraazacyclododecan-1-yl)methyl)phenyl)-3-(3-nitrophenyl)urea] containing a macrocyclic cyclen unit for Cu(ii)-coordination and a urea moiety for anion binding was designed for recognition of metal salts. The X-ray structure of [CuL3(SO)] shows that the sulfate anion is involved in cooperative binding via coordination to the metal ion and hydrogen-bonding to the urea unit. This behaviour is similar to that observed for the related receptor L1 [1-(2-((bis(pyridin-2-ylmethyl)amino)methyl)phenyl)-3-(3-nitrophenyl)urea], which forms a dimeric [CuL1(μ-SO)] structure in the solid state. In contrast, the single crystal X-ray structure of [ZnL3(NO)] contains a 1 : 2 complex (metal : anion) where one anion coordinates to the metal and the other is hydrogen-bonded to the urea group. Spectrophotometric titrations performed for the [CuL3(OSMe)] complex indicate that this system is able to bind a wide range of anions with an affinity sequence: MeCO > Cl > HPO > Br > NO > HSO > NO. Lipophilic analogues of L1 and L3 extract CuSO and CuCl from water into chloroform with high selectivity over the corresponding Co(ii), Ni(ii) and Zn(ii) salts.

Exciplex Formation and Aggregation Induced Emission in Di‐(N‐benzyl)cyclen and Its Complexes – Selective Fluorescence with Lead(II), and as the Cadmium(II) Complex, with the Chloride Ion

“…The Cu II has C.N. = 5 and four Cu–N bonds to the cyclen moiety in 2 , averaging 2.024 ± 0.023 Å, with square pyramidal geometry, which has been noted to be usual for Cu II cyclen complexes. There are four Cu–N bonds to sp 3 hybridized N donors.…”

New Insights into the Recovery of Strategic and Critical Metals by Solvent Extraction

“…A series of N-donor ligands, such as macrocyclic cyclen, with attendant urea anion-binding sites has been prepared ( Figure 9) and are shown to selectively solvent extract copper as the salts [Cu(L)(SO4)] in preference to Co(II), Ni(II), and Zn(II), albeit without the loading capacity for an efficient SX process [38]. In the solid state, the cyclen coordinates the metal cation, and the urea hydrogen bonds to the anion.…”

“…Calix [4]pyrroles can be viewed as ditopic receptors, as they can bind metal cations and anions simultaneously and have been used as extractants for cesium halides [39], but unlike those described above (Figure 8), no coordinate bond is formed between the metal cation and a donor atom, with only hydrogen bonding, electrostatic, and ionic Cs-arene p interactions present ( Figure 10) [38].…”

Organotin‐Functionalized Crown Ethers as Ditopic Hosts for Lithium Salts: Synthesis, Structures and Complexation Studies of X3SnCH2[16]‐crown‐5 (X = I, Br, Cl)

“…Ditopic receptors overcome the shortcomings of ion‐pairing effects involved in the recognition processes of simple anion or cation receptors, and therefore have the ability to dissolve hydrophilic inorganic species. Furthermore, they also have a multitude of other applications such as extraction, ion transport, catalysis, and sensing . However, despite of their significance, the number of well‐characterized ditopic receptors is still limited, probably due to the synthetic and purification hurdles associated with the incorporation of two desperate binding sites into a single framework …”