Beyond Size Complementary Factors in Anion-Tetralactam Macrocycle Complexes: From Intrinsic Gas-Phase to Solvent-Predicted Stabilities.

Magdalena Zimnicka,Witold Danikiewicz,Kinga Kozłowska

doi:10.1021/acs.joc.0c00917

Abstract

The gas-phase affinities of different types of anions X– (halogen anions, oxoanions, and hydrogenated anions) toward a model tetralactam-based macrocycle receptor (1), defined in terms of stability of an anion–receptor complex (1 + X–) against its disintegration, were evaluated by dissociation studies using a mass spectrometry-based methodology and supported by theoretical calculations (density functional theory–PBE0). The gas-phase complex with Cl– was found to be tailor-made for the macrocycle 1, while 1 + SA– (SA– = salicylate anion) and 1 + HSO4– were the weakest ones. Other complexes displayed a relatively low-stability dispersion (<1.2 kcal·mol–1). The 1/εr approach of the electrostatic contribution scaling method was used to predict the stability trends in a dimethyl sulfoxide solvent from the gas-phase binding energy partition using the symmetry-adapted perturbation theory. High deformation energy and differences in solvation energies were suggested to be the main sources of inconsistency in the predicted and experimental stabilities of 1 + F– and 1 + H2PO4– complexes.

Highlights

Anions are ubiquitous in our artificial and natural environments
In the presence of an anion X− (Scheme 1), tetralactam 1 readily forms an associate, which is detected in the mass spectrum as a 1:1 complex, denoted as 1 + X−
The relative gas-phase stabilities of 1 + X− complexes were evaluated by comparison of their dissociation energies using collision-induced dissociation (CID) experiments performed in a triple quadrupole mass spectrometer

Summary

■ INTRODUCTION

Anions are ubiquitous in our artificial and natural environments. Their increasing omnipresence resulting from various industrial, agricultural, and daily life sources is both intended and harmful to the nature and living beings;[1] the manipulation of anion concentrations in order to regulate and remediate their unsustainable environmental and health exposure is widely applied by taking advantage from the anion recognition process. Beyond the specificity and selectivity of anion recognition in solutions, the intrinsic properties of an anion−receptor complex in the gas phase are of great importance because many computer-aided designs of new receptors and guided criteria are introduced in the solvent-free environment.[4] Earlier reported findings provided an approach to solution-phase anion affinities based on the gasphase properties.[3] In this study, we evaluate the impact of anion properties on the gas-phase stability of an anion−. In many anion−receptor attractive systems, employing the hydrogen bonding interactions as widely explored in urea-based receptors, the anion selectivity follows the basicity trends,[5−8] any deviation from this trend may be ascribed to additional factors that are important for a given molecular system. Previous findings performed in DMSO solvent have found size complementarity as a dominant factor in the anion affinity properties of 1, the analysis of the other stability components was not performed and is studied in detail in this study

■ RESULTS AND DISCUSSION

■ CONCLUSIONS

■ ACKNOWLEDGMENTS

■ REFERENCES