Toppled Molecular-Domino Sets by Self-Assembly of Self-assembly: The π-Polymers

Abstract

A series of designed binuclear palladium(II)-based self-assemblies, [Pd2(en)2(L)2](NO3)4, 1a; [Pd2(tmeda)2(L)2](NO3)4, 2a; [Pd2(bpy)2(L)2](NO3)4, 3a; and [Pd2(phen)2(L)2](NO3)4, 4a, are synthesized. These complexes are obtained in good to excellent yields by equimolar combination of the nonchelating bidentate ligand bis(4-pyridylmethyl)piperazine, L, with the corresponding cis-protected palladium(II) component, that is, Pd(N-N)(NO3)2, under suitable reaction conditions. The cis-protecting N-N units used are ethylenediamine (en), tetramethylethylenediamine (tmeda), 2,2′-bipyridyl (bpy), and 1,10-phenanthroline (phen). The complexes 1a–4a are well-characterized by 1H NMR, H–H COSY, and HSQC, and the molecular compositions have been established by ESI-MS. The molecular structures are confirmed for the complexes [Pd2(tmeda)2(L)2](ClO4)4, 2b; [Pd2(bpy)2(L)2](ClO4)4, 3b; and [Pd2(phen)2(L)2](NO3)4, 4a, by the single-crystal X-ray diffraction technique. In the cases of the complexes 3b and 4a, the crystal packin...