We present here the coordination self-assembly of a new heteroleptic (bpyPd) 4 L 1 L 2 2 coordination complex (1) from one novel pyridinium-functionalized bis-2,4,6-tris(pyridin-3-yl)-1,3,5-triazine (bis-3-TPT, L 1 ) macrocyclic ligand, two separate 3-TPT (L 2 ) ligands, and four cis-blocking bpyPd(NO 3 ) 2 (bpy = 2,2′bipyridine). While homoleptic self-assemblies with either L 1 or L 2 gave dynamic mixtures of products, a single thermodynamic heteroleptic complex was obtained driven by the shape complementarity of building blocks. Moreover, the redox-active nature of the heteroleptic assembly facilitates the highly efficient catalytic aerobic photo-oxidation of aromatic secondary alcohols under mild conditions.

We report the syntheses and host–guest chemistry of two interconvertible coordination cages, Pd2L2 and Pd1L1, from a dynamic macrocycle ligand (L) and a cis-blocking (tmen)­Pd­(NO3)2 (tmen = tetramethylethylenediamine) unit (Pd). The water-soluble macrocyclic L, which can bind various polycyclic aromatic hydrocarbon (PAH) guests in its cis-conformation, was constructed via four pyridinium bonds between two 2,4,6-tri­(4-pyridyl)-1,3,5-triazine [TPT] panels and two p-xylene bridges. We selectively formed each cage either by changing the reaction concentration/solvent/temperature or through induced-fit guest encapsulation, while direct assembly of L and Pd resulted in a mixture of Pd2L2 and Pd1L1 in equilibrium. X-ray structures of the free ligand and the host–guest complexes confirmed the induce-fit adaptive changes in the ligand’s conformation and the cage’s cavity. This work demonstrates a useful strategy for designing multistimuli-responsive supramolecular hosts by coordination self-assembly with macrocyclic ligands featuring rich conformational freedom.