Spectroscopic studies of the equilibrium between complexes of lasalocid acid with propargylamine and metal cations.

Abstract

The 1:1 complex between lasalocid acid (LAS), a naturally occurring polyether ionophore, and propargylamine (PROP) was characterized using X-ray crystallography, FT-IR, ¹H NMR, ¹³C NMR, and ESI-MS techniques. Stabilization of the complex arises from both intramolecular and intermolecular hydrogen bonding, with protons of the protonated amine interacting with ether and hydroxyl oxygen atoms of the LAS anion. Comparable FT-IR spectra in solid and solution phases indicate structural consistency across states. In solution, LAS was found to form competing complexes with alkali metal cations (Li⁺, Na⁺, K⁺) alongside the amine, existing in dynamic equilibrium. These structural insights contribute to understanding the antibacterial and anticancer properties associated with lasalocid acid.

Mechanism

The LAS-PROP complex is stabilized through intra- and intermolecular hydrogen bonds between the deprotonated ionophore and the protonated amine. In solution, competitive equilibrium exists between amine complexation and alkali metal cation (Li⁺, Na⁺, K⁺) binding.