Four new metal-organic frameworks with the formulae [Sm(phen)(NO)(chdc)]·2solv, where solv = ,-dimethylformamide (DMF; 1), ,-dimethylacetamide (DMA; 2), ,-diethylformamide (DEF; 3), -formylpiperidine (NFP; 4), phen = 1,10-phenanthroline and chdc = -1,4-cyclohexanedicarboxylate were synthesized and structurally characterized. These compounds are based on similar binuclear samarium(III)-carboxylate blocks, bound by flexible chdc linkers into layered -type coordination networks. The amide solvents drive different intralayer block orientations between 1 and 2-4 and different layer-to-layer packings in all the described compounds. A pronounced dependence of the emission color upon the excitation wavelength variation was determined for 1-4, while the relative impacts of Sm and phen emission on overall luminescence were found to depend strongly on these packings, and their reasonable correlation to the distances between the closest π-π-stacked phen moieties in the structures was revealed. Phase transitions between compounds 1-4 were studied by means of powder X-ray diffraction. Additionally, bimetallic near-white luminophores were obtained for phases 3 and 4 by doping their synthetic systems with a minor (∼5%) Tb additive. In general, this study shows a possibility of tuning the luminescence properties of porous metal-organic frameworks by minor structural differences induced by solvent-driven dynamics with no apparent quenching or other direct impact on the optical properties of the included solvent.
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http://dx.doi.org/10.1039/d4dt02613f | DOI Listing |
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