Role of peripheral phenanthroline groups in the self-assembly of self-assembled molecular triangles

Self-assembled molecular triangles [Pd-3(phen)(3)(imidazolate)(3)](NO3)(3), la and [Pd-3(phen)(3)(imidazolate)(3)](PF6)(3), 1b are prepared by the combination of imidazole with Pd(phen)(NO3)(2) and Pd(phen) (PF6)(2), respectively. Imidazole was deprotonated during the complexation reactions and the imidazolate so formed acted as a bis-monodentate bridging ligand to form the bowl-shaped trinuclear architectures of 1a/b. Relative orientation of the imidazolate moieties can be best described as syn,anti,anti as observed in the crystal structure of 1b. However, in solution state, slow conformational changes are assumed on the basis of (HNMR)-H-1 spectral data. The molecular triangles are crafted with three peripheral phen units capable of pi-pi stacking interactions. Well-fashioned intermolecular pi-pi interactions are observed in the solid-state, wherein further self-assembly of already self-assembled triangle is observed.