Pt(II)-Coordinated Tricomponent Self-Assemblies of Tetrapyridyl Porphyrin and Dicarboxylate Ligands: Are They 3D Prisms or 2D Bow Ties?

Abstract

Thermodynamically favored heteroleptic coordination of Pt(II) ions with one aza- and another oxo-coordinating ligand yield tricomponent supramolecular coordination complexes (SCCs) that possess much greater structural complexity and functional diversity than traditional bicomponent SCCs containing only one ligand. Herein, we demonstrate that heteroleptic coordination of tetrapyridyl-porphyrins (MTPP, M = Zn or H2) and various dicarboxylate ligands (XDC) having different lengths and rigidity with cis-(Et3P)2PtII corners actually yields bow-tie (⋈)-shaped [{cis-(Et3P)2Pt}4(MTPP)(XDC)2]4+ complexes featuring a MTPP core and two parallel XDC linkers connected by four heteroligated PtII(N,O) corners. Although previous reports had claimed that the tricomponent self-assembly method produced tetragonal prisms having two cofacial MTPP and four XDC linkers connected by eight PtII(N,O) corners, our studies demonstrated that in reality, no such prism was formed, because instead of connecting two cofacial MTPP ligands, the XDC linkers actually bridged two adjacent pyridyl termini of an MTPP ligand via shared PtII(N,O) corners, forming bow-tie complexes.