Metallocyclic receptors with Re-I/Os-II-based moieties: Molecular photophysics and selective molecular sensing

New metallocyclic Re-I and Os-II complexes with polyphosphant/polyyne space rs, including dimers [{Re(CO)(3)Cl(C2nP2)}(2)] (n = 1, 1; 2, 2) and tetrame rs [{Re(CO)(3)Cl(C2nP2)}4] (n = 1, 3, 2, 4, C2P2 = Ph2P-C equivalent toC-PP h2, C4P2 = Ph2P-C equivalent toC-C equivalent toC-PPh2), as well as the mix ed-metal [{Re(CO)(3)Cl}(2){Os-(bpr)(2)}(2)(C2P2)(4)](PF6)(4) (6, bpy = 2,2' -bipyridine) and its precursor [Os(bpy)(2)(C2P2)(2)](PF6)(2) (5) have been synthesized. Characterization has been carried out using P-31{H-1} NMR, FAB /MS, ESI/MS, IR spectroscopy, elemental analysis (EA), and X-ray single cry stal structure determination. These new metallocyclic complexes are found t o be emissive, with a characteristic Re-I-based emission at 505-525 nm (lif etimes of 3.4-6.8 ns) and an Os-II-based emission at 600-605 nm (lifetimes of 650-675 ns). High quantum yields of 0.25 and 0.17 were observed for 5 an d 6, which were representative of the few most emissive species reported wi th Os-II centers. Efficient energy transfer from the Re-I donor to the Os-I I acceptor was also found, In addition, a host-guest study was performed us ing emissive metallocycle 6, and host-guest binding constants of 775M(-1), 1580M(-1), and 1680M(-1) were obtained for the guests anisole, 1,4-dimethox ybenzene, and 1,3,5-trimethoxybenzene, respectively. The correlation betwee n the guest molecule size, cavity dimension, and the host-guest binding con stant is discussed. Furthermore, the relationship between the Jc-acceptor a bility of the nonchromophoric phosphanes, the energy gap between the ground and excited state, and the nonradiative decay rate constant (k(nr)) is als o explored.