Doubly-bridged PNP-lariat ethers and their complexes with silver(i) ions in methanol solution

Abstract

We report the preparation of four new double-bridged PNP-lariat ether derivatives L1-L4 synthesized from precursor 1 by the subsequent substitution of chlorine atoms. The process consists of two steps. In the first one two reactive chlorine atoms of the -PCl 2 exocyclic moiety are substituted with respective nucleophiles: 2,2 0 -thiodiethanethiol 2 and 2,2 0 -oxydiethanethiol 3. In the second step the other chlorine atoms are substituted by aziridynyl 6 and pyrrolidinyl 7 groups, respectively. Their structures were established by MS, 1 H NMR, 31 P NMR, 13 C NMR spectroscopy. Furthermore, this work includes the investigation of complexation of silver(I) ions with the new ligands L1-L4 in methanol solution. The formation of the novel tetra-nuclear silver(I) complexes were observed. Stability constants were determined using a simple potentiometric titration. 1 H NMR, 31 P NMR, 13 C NMR spectra were recorded to investigate how the complexation of silver(I) ions by the investigated macrocyclic ligands occurs.Scheme 1 Polymacrocyclic structures formed in the reaction of chlorocyclophosphazenes with diamines.

Mass Spectrometry Reveals Complexing Properties of Modified PNP-Lariat Ether Containing Benzyl Derivative of (S)–Prolinamine

“…Contrary to the previously-described PNP-lariat ethers derivatives [31][32][33][34] the sites and way of successive binding of silver ions (as confirmed by NMR and MS studies) were completely different. In the AgL system, the silver ion is bound by exocyclic nitrogen atoms derived from substituents (Scheme 4).…”

“…Also here, the confirmation of the binding of the second silver ion is the NMR spectra (Figure 2c). The shifts of signals from the CH 2 OP group in the range of about 4 ppm are clearly visible and are similar to the ones previously described for such place of the silver ion binding [31][32][33][34]. In this stage of complexation, one can observe the shift of the signals located at about 3.30 ppm assigned to CH 2 -O fragments of the polyether ring.…”

“…Furthermore, silver ion in the AgL complex is preferably attracted to nitrogen atoms from substituents which are attached to the exocyclic phosphorus atom. In the previously described PNP lariat ethers derivatives, binding of the first silver ion was realized by the endocyclic nitrogen atom from the cyclotriphosphazene subunit [30][31][32][33][34][35][36]. The second silver ion is bound by the endocyclic nitrogen atom of the cyclotriphosphazene ring.…”

“…In our research group, the studies of the complexing properties of macrocyclic compounds with particular focus on P-pivot lariat ethers have been conducted for years [30][31][32][33][34]. These studies show that changes of substituents, as well as solvents used during the complexation process, affect the formation of the various structures of the complexes, especially with silver (I) cation.…”

Cryptands with 2,4,6-tris(p-phenylene)-1,3,5-triazine central units and oligoethyleneoxide bridges: synthesis, structure and complexation abilities

“…These types of compounds form selective bindings with silver ions. 65,66 Additionally, recent investigations showed that silver compounds exhibit antibacterial properties. 67 It has been proved that the thiosubstituted PNP-lariat ethers are commonly used to remove highly toxic heavy metal pollutants and for recovery of silver from industrial wastes.…”