Towards a New Family of Photoluminescent Organozinc 8- Hydroxyquinolinates with a High Propensity to Form Noncovalent Porous Materials

We report on investigations of reactions of tBu2Zn with 8-hydroxy- quinoline (q-H) and the influence of water on the composition and structure of the final product. A new synthetic approach to photoluminescent zinc complexes with quinolinate ligands was developed that allowed the isolation of a series of structurally diverse and novel alkylzinc 8-hydroxyquinolate complexes: the trinuclear alkylzinc ag- gregate (tBuZn(q))3 (13), the pentanu- clear oxo cluster ((tBu)3Zn5Am4-O)(q)5) (2), and the tetranuclear hydroxo clus- ter (Zn(q)2)2AtBuZn(OH))2 (3). All compounds were characterized in solu- tion by 1 H NMR, IR, UV/Vis, and pho- toluminescence (PL) spectroscopy, and in the solid state by X-ray diffraction, TGA, and PL studies. Density func- tional theory calculations were also car- ried out for these new Zn II complexes to rationalize their luminescence be- havior. A detailed analysis of the supramolecular structures of 2 and 3 shows that the unique shape of the cor- responding single molecules leads to the formation of extended 3D net- works with 1D open channels. Varying the stoichiometry, shape, and supra- molecular structure of the resulting complexes leads to changes in their spectroscopic properties. The close- packed crystal structure of 13 shows a redshifted emission maximum in comparison to the porous crystal struc- ture of 2 and the THF-solvated struc- ture of 3.