Syntheses, Structures, and Porous/Luminescent Properties of Silver 3-Alkyl-1,2,4-Triazolate Frameworks with Rare 3-Connected Topologies

Self-assembly of silver(I) ion with 3-alkyl-1,2,4-triazoles in different solvents yielded four new metal azolate frameworks (MAFs), namely, [Ag(mtz)] (1, Hmtz = 3-methyl-1,2,4-triazole), [Ag(etz)] (2, Hetz = 3-ethyl-1,2,4-triazole), [Ag-4(etz)(4)]center dot H2O (3 center dot H2O), and [Ag-4(ptz)(4)] (4, Hptz = 3-propyl-1,2,4-triazole). Single-crystal X-ray diffraction revealed that Ag(I) ions and triazolates in these MAFs are all three-coordinated to give rare 3-connected framework topologies. Although 1 and 2 possess the same uniform (10,3)-d (utp) topology, variation of the alkyl groups renders substantially different coordination structures. On the other hand, 3 center dot H2O and 4, also bearing different alkyl substituents, are isomorphours, and can be simplified as the same uninodal sqc5603 topology (point and vertex symbols are 8(2).10 and 8.8(2).12, respectively). Due to the relatively short alkyl length, the coordination framework of 3 center dot H2O contains one-dimensional narrow channels. According to thermogravimetry and single-crystal X-ray diffraction, 3 center dot H2O can be dehydrated without framework collapse. Although guest-free 3 does not adsorb N-2 at 77 K, 3 center dot H2O can undergo guest exchange, and 3 can adsorb solvent vapor, to give CH2Cl2- and CH3CN- included crystals. Comparing the single-crystal structures of 3 center dot H2O, 3, 3 center dot CH2Cl2, and 3 center dot CH3CN reveals the framework flexibility of 3. These materials also show interesting structure- and guest-dependent photoluminescent properties.