Synthesis, Characterization, and Properties of Half-Sandwich Iridium/Rhodium-Based Metallarectangles

Tetranuclear half-sandwich iridium or rhodium complexes were obtained in good yields from the reactions of the binuclear half-sandwich metal precursors [Cp*2M2(μ-CA)]­Cl2 (1a, M = Ir; 1b, M = Rh; CA = chloranilate) or [Cp*2M2(μ-DHNA)]­Cl2 (2a, M = Ir; 2b, M = Rh; H2DHNA = 6,11-dihydroxynaphthacene-5,12-dione) with diPyNI (diPyNI = N,N-bis­(4-pyridyl)-1,4,5,8-naphthalene­tetra­carboxydiimide) in the presence of AgOTf (OTf = CF3SO3) in CH3OH, respectively. The new metallarectangles have been characterized by elemental analysis, FT-IR, 1H NMR, electrospray mass spectrometry (ESI-MS), and UV/vis absorption spectroscopy. The interactions of these metallarectangles with aromatic molecules, especially pyrene, in solution have been studied by various NMR techniques (1D, DOSY, and ROESY) and UV–vis absorption. DOSY measurements suggest that the interactions between metallarectangle 4a and pyrene are outside of the cavity. The strong π···π interactions between pyrene and the naphthalene­tetra­carboxydiimide ring of metallarectangle 4a were further supported by single-crystal X-ray diffraction data; pyrene molecules are found outside the cavity of the metallarectangle.