Tandem mass spectroscopy as a tool for investigation of complexes of PNP‐lariat ether derivative with metal ions

Abstract

The novel PNP-lariat ether L with cyclotriphosphazene ring incorporated in the macrocyclic structure was synthesized and checked by the electrospray mass spectrometry (ESI-MS) method for the ability to bind different types of ions Ag , Ca , Cd , Cu , and Pb . Furthermore, the stability constants of the abovementioned ion complexes with the investigated ligand have been determined by direct and competitive potentiometric methods. To evaluate the stability of various complex types and to confirm the way of metal cation binding, the tandem mass spectra of the investigated ligand and its complexes were taken. As a result, we obtained quite a good relationship between the number and main types of complex species observed in ESI-MS experiments and the forms of complexes for which the stabilization constants were determined by potentiometric methods. Moreover, we also concluded that in case of big discrepancies of stability constants, ESI-MS experiments could provide information about the most stable form of the complexes, but they fail when the differences between the strength of the coordination binding are slightly different.

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

“…Furthermore, the interaction is probably strengthened by additional stabilization by oxygen atoms from crown ether moiety (there is no cleavage of the macrocycle skeleton under the influence of the applied voltage during the experiment). Similar fragmentation pathways were also noticed in previous studies of these complexes with morpholinyl and piperidinyl substituents [35,36].…”

“…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.…”

“…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. The studies for other cations comprise of the complexing behavior of PNP-lariat ether with other metal cations (Cd 2+ , Cu 2+ , Ca 2+ , and Pb 2+ ) using ESI-MS and MS/MS techniques [35,36]. Macrocyclic derivatives of cyclotriphosphazene and their complexes were found to reveal antitumor activity as well as anti-AIDS activity [37][38][39].…”

Recent advances in mass spectrometry studies of non-covalent complexes of macrocycles - A review

“…Thus, if the spectra showed clusters, it would be clear that the clusterization takes place in the gas phase, what is the most interesting from an analytical point of view. Another study about lariat ethers, specially about PNP-lariat ethers was carried out by Kwiecień et al [114] In a PNP-lariat ether, the -P-N=P-subunit of the sidearm belongs to the macrocyclic skeleton. In that work, the complexation behavior of PNP-lariat ethers towards different types of ions (Ag + , Ca 2+ , Cd 2+ , Cu 2+ , and Pb 2+ ) was examined using ESI-MS.…”