Construction of Cd(ii)-based metal–organic frameworks incorporating SiF62− as fluorescence sensors for arginine

Abstract

Recently, the detection of amino acids has attracted considerable attention in the field of nutrition analysis, health monitoring, and medical diagnosis due to their significance for organisms. In this work, two novel Cd(II)-based metal–organic frameworks (MOFs) with the formulas [Cd(bib)₂(SiF₆)]_n (1) and {[Cd(bib)₂(SiF₆)]·DMF·3H₂O}_n (2, bib = 1-(4-imidazol-1-ylphenyl)imidazole) were synthesized and exhibited fluorescence sensing capacity for arginine. In spite of having the same framework composition, complexes 1 and 2 showed great differences in their structure originating in the variations between the coordination modes of SiF₆²⁻ with Cd²⁺ and the extension direction of the Cd-bib coordination complexes. Structural analysis manifested that complex 1 featured a 3D coordination framework constructed from 2D Cd-bib coordination layers bridged by SiF₆²⁻ anions, while complex 2 possessed 3-fold interpenetrated Cd-bib coordination networks connected by SiF₆²⁻ anions. Furthermore, fluorescence sensing experiments exhibited that both complexes 1 and 2 could be used as fluorescence probes for arginine and the emission intensities of complexes 1 and 2 could be enhanced up to 10.3 and 12.0 times that of the initial emission intensities upon the addition of Arg, respectively.