Binuclear and starburst organoplatinum(II) complexes of 2,2′-dipyridylamino derivative ligands:: Structures, fluxionality, and luminescence

New binuclear and starburst trinuclear organoplatinum complexes based on 2,2'-dipyridylamino (dpa) derivative ligands, Pt2Ph4(bab), bab = 1,4-bis(2,2'-dipyridylamino)-benzene, 1, Pt2Ph4(babp),babp=4,4'-bis(2,2'-dipyridylamino)biphenyl,2,Pt3Ph6(tab), tab = 1,3,5-tris(2,2'-dipyridylamino)benzene, 3, Pt(3)h(6)(tat), tat = 2,4,6-tris(2,2'-dipyridylamino)-1,3,5-triazine, 4, Pt3Ph6(tapb), tapb = 1,3,5-tris[p-(2,2'-dipyridylamino)phenyl]-benzene, 5, Pt3Ph6(tapt), tapt = 2,4,6-tris[p-(2,2'-dipyridylamino)phenyl]-1,3,5-triazine, 6, Pt3Ph6(tabpb), tabpb 1,3,5-trisf4'-[4"-(2,2'-dipyridylamino)]biphenyl}benzene, 7, and Pt3Ph6(tabpt), tabpt 1,3,5-trist4'-[4"-(2,2'-dipyridylamino)]biphenyl}benzene, 8, were synthesized by the reaction of [PtPh2(SMe2)](n) with the corresponding chelate ligand. The structures of complexes 1-5 and 8 were determined by single-crystal X-ray diffraction. All eight complexes have phosphorescent emissions in the blue/green region at 77 K, attributed to ligand-centered pi --> pi* transitions. Ligand-based fluorescent emission was also detected for complexes 5, 6, and 8. Complexes 1-8 display versatile structures in the solid state. Complex 4 was found to be fluxional in solution. The key factors that influence the structures of the complexes in solution and the solid state are the degree of conjugation of the amino nitrogen lone pair electrons of the dpa unit with the central aromatic linker and intramolecular nonbonding interactions.