Diastereoselectively self-sorted low-symmetry binuclear metallomacrocycle and trinuclear metallocage.

A pyridine/aniline appended unsymmetrical bis-monodentate ligand N -(3-aminophenyl)nicotinamide, L un is synthesized via condensation of nicotinic acid with excess m -phenylene diamine. A low-symmetry binuclear complex of the Pd 2 L' 2 L un 2 type and an extremely rare trinuclear complex of the Pd 3 L un 6 type are produced by self-assembly of the ligand L un with cis -protected palladium(II) ( i.e. , PdL') and palladium(II), respectively. Two isomers ( i.e. [(2,0), (2,0)] and [(1,1), (1,1)]-forms) are theoretically possible for the Pd 2 L' 2 L un 2 -type complex whereas nine isomers can be envisaged in the case of the Pd 3 L un 6 -type arrangement. However, one of the isomers of the Pd 2 L' 2 L un 2 -type complex as well as the one for the Pd 3 L un 6 -type complex are experimentally obtained. The exclusive formation of specific isomers could be predicted from the 1D/2D NMR study in the solution state and the DFT calculations in the gas phase/implicit solvent media. The formation of the predicted all-(1,1)-[Pd 2 (en) 2 L un 2 ](NO 3 ) 4 has been confirmed by a single-crystal XRD study. DFT calculations for the isomers of the Pd 3 L un 6 -type arrangement show that a [ cis (2,2), cis (2,2), cis (2,2)] isomer is energetically favourable than the alternatively predicted [ trans (2,2), trans (2,2), trans (2,2)] isomer. Conformational changes within the build of the exclusively formed isomers are proposed on the basis of NMR study.