Construction of Ag/1,2,4-Triazole/Polyoxometalates Hybrid Family Varying from Diverse Supramolecular Assemblies to 3-D Rod-Packing Framework

Eight members of the Ag/1,2,4-triazole/polyoxometalates (POMs) hybrid supramolecular family, namely, [Ag4(dmtrz)4][Mo8O26] (dmtrz = 3,5-dimethyl-1,2,4-triazole, 1), [Ag6(3atrz)6][PMo12O40]2·H2O (3atrz = 3-amino-1,2,4-triazole, 2),
[Ag2(3atrz)2]2[HPMoVI10MoV2O40] (3), [Ag2(dmtrz)2]2[HPMoVI10MoV2O40] (4), [Ag2(trz)2]2[Mo8O26] (trz = 1,2,4-triazole,
5), [Ag2(3atrz)2][Ag2(3atrz)2(Mo8O26)] (6), [Ag4(4atrz)2Cl][Ag(Mo8O26)] (4atrz = 4-amino-1,2,4-triazole, 7), and [Ag5(trz)4]2[Ag2(Mo8O26)]·4H2O (8), were synthesized through hydrothermal reactions of 1,2,4-triazole or its derivatives
with appropriate silver salts and molybdates. Crystal structure analysis reveals that the POM-dependent Ag−1,2,4-triazolate units in these hybrid compounds form a novel tetranuclear cluster (1), a unique double calix[3]arene-shaped hexamer (2), zigzag chains (5 and 6), helix chains (3, 4, and 8), and an interesting looped chain (7). A
series of hydrogen bonding-based supramolecular assemblies varying among the 0-D + 0-D (1 and 2), 0-D + 1-D
(3 and 4), 1-D + 1-D (5 and 7), and 1-D + 2-D (6) modes between the organomatic cations and POM anions were
observed in these structures. Moreover, the inorganic chain [Ag(Mo8O26)]n3n- in 7 constructed by the building block
[Mo8O26]4- linked only via single Ag+ ion is unprecedented. Compound 8 is the first high-dimensional framework
constructed from the [Ag2(Mo8O26)]n2n- rod-shaped subunits. These hybrid supramolecular compounds present
interesting photochemical properties. The spectroscopic experiments show that they not only are potential
semiconductor materials but also have interesting photoluminescence phenomena, including O → Mo [LMCT] and
intraligand [π − π*] emissions generated by internal heavy metal effect.