# Metal-dependant structural families of aminomethylphosphonic acid assemblies differentiated by ion mobility mass spectrometry and density functional theory

## TL;DR

This paper shows how different metal ions affect the structure of aminomethylphosphonic acid assemblies using advanced analytical techniques.

## Contribution

The study identifies two distinct structural families of AMPA–metal aggregates based on metal type using ion mobility and DFT.

## Key findings

- AMPA–metal aggregates with Ca2+, Sr2+, and Ba2+ form a square pyramidal geometry.
- AMPA–metal aggregates with Mg2+, Mn2+, Cu2+, and Zn2+ form a seesaw geometry.
- Ion mobility mass spectrometry and DFT can distinguish structural families at early assembly stages.

## Abstract

Herein the morphology of aminomethylphosphonic acid (AMPA)–metal aggregates are analysed by ion mobility-mass spectrometry, DFT and IRMPD spectroscopy. Matching experimental collision cross section to the DFT predicted minima allowed unambiguous assignment of [M(AMPA)(AMPA-H)]+ where M = Mg2+, Ca2+, and Mn2+. Two distinct structural families of [M(AMPA)(AMPA-H)]+ where M = Mg2+, Ca2+, Sr2+, Ba2+, Mn2+, Cu2+, and Zn2+ were differentiated by ion mobility mass spectrometry. Groupings of experimental collision cross sections were observed for a square pyramidal geometry, (M = Ca2+, Sr2+, Ba2+) versus a seesaw geometry (M = Mg2+, Mn2+, Cu2+, and Zn2+), paving the way for distinction of aggregates at the earliest stages of assembly.

Aminomethylphosphonic acid (AMPA)–metal aggregates are effectively distinguished by ion mobility-mass spectrometry, and complementary DFT, giving insight into the earliest stages of assembly.