Alkaline-earth and aminonicotinate based coordination polymers with combined fluorescence/long-lasting phosphorescence and metal ion sensing response

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2019, Vol.7 (23), p.6997-712
• Main Authors: Pajuelo-Corral, Oier, Rodríguez-Diéguez, Antonio, Beobide, Garikoitz, Pérez-Yáñez, Sonia, García, Jose A, San Sebastian, Eider, Seco, Jose M, Cepeda, Javier
• Format: Article
• Language: English
• Subjects: Afterglows; Barium; Calcium; Chemical compounds; Coordination polymers; Crystallography; Dehydration; Density functional theory; Fluorescence; Mathematical analysis; Metal ions; Microchannels; Open architectures; Optical properties; Organic chemistry; Phosphorescence; Photoluminescence; Pollutants; Polymers; Reflectance; Solvents; Transition metals; Viability; X-ray diffraction
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/c9tc01300h

Six novel coordination polymers (CPs) based on alkaline-earth (AE) metal ions and two sorts of aminonicotinate ligands, namely [M(μ-2ani)(μ 3 -2ani)(μ-DMF)] n [M II = Sr ( 1 ) and Ba ( 2 )], {[M(μ-6ani) 2 (H 2 O) 2 ]·3H 2 O} n [M II = Ca ( 3 ) and Sr ( 4 )], {[Ca(μ-6ani) 2 (H 2 O) 2 ]} n ( 5 ) and {[Ba(6ani) 2 (H 2 O) 3 ]·7H 2 O} n ( 6 ) [where 2ani = 2-aminonicotinate and 6ani = 6-aminonicotinate] have been synthesized and well characterized. All compounds are firstly built up with AE-carboxylate infinite rods that provide compact 2D-layered structures in 1 and 2 but open architectures containing microchannels in an AE-6ani system. Interestingly, the architecture of 3 behaves as a flexible platform which undergoes spontaneous dehydration to yield compound 5 . Structural transition occurring from 3 to 5 has been supported by periodic density functional theory (DFT) calculations and X-ray diffraction data. In this regard, compound 6 contains a high amount of solvent molecules which suggests the existence of pores in its structure. A deep study of the optical properties including a detailed experimental characterization and DFT based computational calculations of these compounds supports a fascinating photoluminescence performance which entails a bright blue emission accompanied by persistent green afterglows at low temperature, especially for compound 5 as reflected by its lifetime ( τ 1.4 s). In addition to its strong room temperature emission properties, we took advantage of the open yet stable structure of compound 4 , to check its viability as a new material sensitive to the presence of solvents and/or transition metal ions, via significant quenching of the luminescence of 4 . Remarkably, 4 is shown to be a particularly efficient sensor for some water soluble pollutants. Alkaline-earth and aminonicotinate based CPs exhibit green long lasting phosphorescence and bright blue fluorescence responsive to metal ions.