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

Thermodynamically favored heteroleptic coordination of Pt(II) ions with one aza- and another oxo-coordinating ligand yield tricomponent supramolecular coordination complexes (SCCs), which possess much greater structural complexity and functional diversity than traditional bicomponent SCCs containing only one of the ligands. Through X-ray crystallography, 1H, 31P, and 2D NMR spectroscopies, mass spectrometry, and computational studies, herein, we demonstrated that heteroleptic coordination of tetrapyridyl porphyrins (MTPP, M = Zn or H2) and various dicarboxylate ligands (XDC) having different lengths and rigidity with cis-(Et3P)2PtII corners yielded bow-tie (⋈)-shaped tricomponent [{cis-(Et3P)2Pt}4(MTPP)(XDC)2]4+ complexes featuring a MTPP core and two parallel XDC linkers held together by four heteroligated PtII(N,O) corners and ruled out the MTPP-based tetragonal prism formation. Irrespective of the rigidity and length of the XDC linkers within a certain range (~7–11 Å), they intramolecularly bridged two adjacent pyridyl tips of an MTPP ligand via PtII(N,O) corners, which led to the formation of bow-tie complexes instead of prisms. This happened because the angles of projection between the adjacent pyridyl rings of MTPP cores adapted to accommodate the bridging XDC linkers having different lengths, and the bow-tie formation was entropically favored over tetragonal prisms. This work not only unveiled novel bow-tie-shaped coordination complexes, but also accurately defined the actual structures and compositions of MTPP-based tricomponent SCCs. Furthermore, a representative bow-tie complex containing an electron-rich ZnTPP core selectively formed a charge-transfer (CT) complex with highly electron deficient 1,4,5,8,9,12-hexaazatriphenylene-2,3,6,7,10,11-heaxacarbonitrile (HATHCN) but not with π-donors like pyrene.