Anion tuning of Zn2+ architectures using a Tris-base salicylic ligand

In this study, a hydroxyl-rich Schiff base ligand, H4L, and its resulting complexes with ZnCl2, Zn(CH3COO)2 and Zn(ClO4)2 were explored. Interestingly, depending on the zinc salt and/or the crystallisation method, four unique structures were obtained. A synthesis with ZnCl2 gave 1, a mononuclear structure ((H3L)2Zn), while with Zn(CH3COO)2, a trinuclear system [(H3L)2Zn3(CH3COO)4], 2, was found. Interestingly two multinuclear architectures were observed with Zn(ClO4)2. Firstly, diethyl ether diffusion of a methanolic reaction mixture with minimal atmospheric air volume gave 3, a hexanuclear architecture of the type [(H2L)4(H3L)2Zn6](ClO4)2, while slow evaporation of a similar mixture gave 4, a nonanuclear architecture with the formula [(H2L)6Zn9(CO3)2](ClO4)2. Compound 4 unexpectedly fixed atmospheric CO2 as CO32−, incorporating it into the architecture. As expected, a diethyl ether diffusion with a larger volume of air (∼100 mL) of a similar methanolic reaction mixture gave a mixture of 3 and 4. In addition, bulk samples of all compounds were also investigated by PXRD, and results are in good agreement with the observed single crystal data. Furthermore, complexes 1-4 were characterised using FT-IR and simultaneous thermal analysis (STA), and additionally the photophysical properties of H4L and complexes 1-4 have also been explored.