Metal driven self-assembly of pyridine appended ligands with cis-protected/naked Pd(II) ion:: a comparative study

Discrete self-assemblies prepared by designed pyridine appended ligands with cis-protected Pd(II) ion (5) are described. If ligands 2, 3 and 4 are separately treated with (5), the formation of (i) dynamic equilibrium of macrocyclic M2L2 (6) and M4L4 assemblies (7); (ii) macrocyclic M2L2 product (9); and (iii) macrobicyclic M3L2 (11) occurred, respectively. The assembly so obtained from the combination of a ligand and (5) may be considered as a module or reminiscent of the assembly that is expected from the complexation of same ligand with naked Pd(II). In fact, complexation of the above mentioned ligands with naked Pd(II) resulted in discrete structures. This is in contrast to the possible polymeric structure usually obtained from such types of ligands in combination with naked Cd(II), Ni(II) etc. The result that the ligands 2, 3, and 4 with naked Pd(II) give macrotricyclic M2L4 (8); macropentacyclic M4L8 (10); and M6L8 spherical assembly (12), respectively, establishes interesting strategies. Thus we have shown rational comparison of a particular ligand for either cis-protected or naked Pd(II) ion for first time.