Cationic manganese(II)-based metal-organic framework constructed from viologen derivative with multifunctional properties

Abstract

Utilizing the rigid and linear viologen carboxylic ligand as an organic linker, we have successfully synthesized and structurally characterized a multifunctional Mn-based cationic metal-organic framework (1). Compound 1 features a three-dimensional framework structure with a positively charged skeleton, wherein triangular pores accommodate [MnCl4]2− anions to preserve charge neutrality. Notably, compound 1 demonstrates a chemical chromism phenomenon, transitioning from yellow-brown to deep green upon exposure to ammonia. This color change is attributed to the nucleophilic attack of electron-rich ammonia molecules on the electron-deficient viologen moiety of viologen carboxylic ligand, leading to the formation of viologen radicals and charge transfer complexes. Moreover, compound 1 exhibits rapid and selective detection of antibiotics like metronidazole (MDZ) and dimetridazole (DTZ) via a competitive absorption-induced luminescence quenching process, featuring high quenching coefficients and low detection limits. Additionally, magnetic property investigations reveal predominant antiferromagnetic coupling between Mn(II) ions within compound 1.