Hexanuclear zinc(II) carboxylate complexes from the use of pyridine-2,6-dimethanol: Synthetic, structural and photoluminescence studies

Abstract

The employment of pyridine-2,6-dimethanol (pdmH2) in zinc(II) carboxylate chemistry is reported. The syntheses, crystal structures, and spectroscopic characterization are described for the structurally similar cluster compounds [Zn6(OH)2(O2CR) 8(pdmH)2] (R = Ph (1)

But (2)), obtained in very good yields by the reactions between Zn(O2CR) 2·2H2O (R = Ph, But) and pdmH 2 in a 3:1 molar ratio in MeOH or MeCN solvent media, respectively. The [Zn6(μ3-OH)2(μ3-OR) 2]8+ core of both clusters can be conveniently described as four edge-sharing triangles (RO- = pdmH-). The three crystallographically unique metal ions in both 1 and 2 are found in three different coordination environments (4-, 5- and 6-coordinate), within the same molecule, a very rare case in hexanuclear Zn(II) cluster chemistry. The benzoate-analogue ZnII6 (1) displays photoluminescence with a maximum at 404 nm, upon maximum excitation at 337 nm, whereas the pivalate-analogue ZnII6 (2) shows a non-emissive character

the origin of the photoluminescence is discussed.