Luminescent Star-Shaped Zinc(II) and Platinum(II) Complexes Based on Star-Shaped 2,2′-Dipyridylamino-Derived Ligands

Abstract

New ZnII and PtII complexes of the star-shaped ligands 2,4,6-tris(2,2′-dipyridylamino)-1,3,5-triazine (tdat), 1,3,5-tris(2,2′-dipyridylamino)benzene (tdab), 2,4,6-tris[p-(2,2′-dipyridylamino)phenyl]-1,3,5-triazine (tdapt) and 1,3,5-tris[p-(2,2′-dipyridylamino)phenyl]benzene (tdapb) have been synthesized and characterized. 1:1, 1:2 and 1:3 (ligand vs. the number of Zn atoms) ZnII complexes of the tdat ligand have been identified. The 1:1 and 1:2 ZnII complexes of tdat are dynamic in solution. For the tdab, tdapt and tdapb ligands, only 1:3 complexes of PtII and ZnII have been isolated. Single-crystal X-ray diffraction analyses have been carried out for some of these new complexes, which revealed that there is a distinct difference in the arrangement of star-shaped ligands in the complexes of ZnII and those of PtII. The PtII complexes of tdat and tdab adopt an unusual “bowl” shape and stack in a “head-to-tail” fashion in the crystal lattice. In contrast, the corresponding ZnII complexes do not have a “bowl” shape. The difference between the ZnII complexes and the PtII complexes can be attributed to the different coordination geometry preferred by the two metal ions. The ZnII complex of tdapb displays several crystal motifs, two of which contain benzene molecules in the crystal lattices. All complexes are luminescent in the blue region, attributable to ligand-based π ⇄ π* transitions. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)