Structures and Luminescent Sensing Properties of Terbium Metal–Organic Frameworks with Methyl-Decorated Phenanthroline Ligand
Two new Tb(III) metal–organic frameworks based on 4,7-dimethylphenanthroline (dmphen) and flexible ligand <i>trans</i>-1,4-cyclohexanedicarboxylate (chdc<sup>2−</sup>) were synthesized and characterized. Their crystallographic formulae are [Tb<sub>2</sub>(dmphen)&...
Saved in:
| Main Authors: | , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2024-11-01
|
| Series: | Crystals |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2073-4352/14/12/1026 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| Summary: | Two new Tb(III) metal–organic frameworks based on 4,7-dimethylphenanthroline (dmphen) and flexible ligand <i>trans</i>-1,4-cyclohexanedicarboxylate (chdc<sup>2−</sup>) were synthesized and characterized. Their crystallographic formulae are [Tb<sub>2</sub>(dmphen)<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub>(chdc)<sub>3</sub>]·2DMF (<b>1</b>; DMF = N,N-dimethylformamide) and [Tb<sub>2</sub>(dmphen)<sub>2</sub>(NO<sub>3</sub>)<sub>2</sub>(chdc)<sub>2</sub>]·2DMF (<b>2</b>). Among some differences in their synthetic conditions, the most important one is apparently the using of terbium(III) nitrate instead of terbium(III) chloride as a metal precursor in the synthesis of <b>2</b>, providing a nitrate coordination to Tb<sup>3+</sup>, and its subsequent notable structural differences to <b>1</b>. Compound <b>1</b> was found to have a layered <i>hcb</i> structure with intralayer windows ca. 10 × 8 Å<sup>2</sup> in size. Its layer-to-layer packing leaves narrow channels running across these windows, with 18% as a total solvent-accessible volume in the coordination structure. Compound <b>2</b> was found to have a layered <i>sql</i> structure with smaller intralayer windows of ca. 8 × 6 Å<sup>2</sup> in size. Methyl substituents on the phen ligands do not affect the topology of the framework but seem to have a substantial effect on the packing density, as well as the pore volume of the resulting MOF. A high 18.4% luminescence quantum yield was found for <b>2</b>. Its emission lifetime of 0.695(12) ms belongs to a typical range for phosphorescent Tb(III)-carboxylate complexes. A quenching of its emission by different nitroaromatic molecules was found. A linear concentration dependence on 3-nitrotoluene and 4-nitro-<i>m</i>-xylene at micromolar concentrations was found during luminescent titration experiments (LOD values ca. 350 nM), suggesting this MOF to be a viable and highly sensitive luminescent sensor for such substrates. |
|---|---|
| ISSN: | 2073-4352 |