The study of crown ethers and their capabilities of interacting with various analytes demonstrate the versatility and applicability of supramolecular (host-guest) chemistry across multiple disciplines such as environmental, medical, and, more recently, forensic applications. Using high-resolution mass spectrometry techniques, these metal-ligand structures are easily confirmed by fragmenting precursor ions. We have observed that metalloids like antimony do not readily associate with macrocycles while in the presence of other metals. Two main questions arise from this observation: 1)Which host molecule binds the most efficiently to metal species? 2) What are the main factors most effect by binding? Quantum mechanical simulation methods like density functional theory (DFT) help solve the Schrödinger equation by accounting for the density of electrons by applying functionals and measuring the ground-state of molecules. These calculations yield very similar trends to experimental results. Baseline structures were generated and modeled after 18-crown-6-ether including hexacyclen, and several other aza-crown ethers and thia-crown ethers. Additionally, different heteroatoms mixtures were included to monitor the effects on the binding energies. Factors like natural bond orbital (NBO) analysis along with HOMO-LUMO energy gap evaluations and electrostatic potentials contributed to describing interactions in the metal-ligand complexes. Ten metal species with varying metal charges such as +1, +2, and +3 and their capacity to form nitrate adducts were monitored. Gas and solvent phases at varying protic and aprotic strengths (water, methanol, acetonitrile) were controlled variables. Out of all factors listed, the solvation models mentioned do not cause a high impact on binding, whereas counterions such as nitrates adducts yield a more significant effect on the binding energies.

Theoretical investigations and exploratory methods for simple host-guest chemistry

ACS Spring Meeting 2021

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