Design, synthesis, photophysics, and anion-binding studies of bis(dicyclohexylphosphino)methane-containing dinuclear gold(I) thiolate complexes with urea receptors

Abstract

A series of bis(dicyclohexylphosphino)methane (dcpm)-containing gold(I) thiolate complexes with urea receptors, 1-3, has been successfully designed and synthesized, and their photophysical and anion-binding properties have been studied. The linker between the thiolate and the urea group, and the electronic environment of the urea moiety, have been found to exert a great influence on the photophysical and anion-binding properties of the complexes. Complex 3 displays an intense long-lived orange-red luminescence at around 620 nm in the solid state and in the glass state at 77 K, which is considerably red shifted from the band seen in a solution of dichloromethane at room temperature, suggesting the presence of Au···Au interactions. Upon introducing an electronwithdrawing NO2 group, complex 1 was found to show high selectivity and sensitivity for F- through a drastic color change from yellow to red. The anionbinding constants of the complexes have been determined from electronic absorption and1H NMR spectroscopy titration studies and the data were found to fit well to a 1:1 binding model for the interactions between the complexes and the anions. Complexes 1 and 2 show the same anion selectivity trend of F- > AcO- > H2PO4 > Cl- ≈ Br- ≈I -, which is consistent with the trend in anion basicity. In addition, complex 1 has been shown to exhibit higher binding affinity for anions compared with those of complexes 2 and 3, probably due to the higher acidity of the urea moiety as a result of the introduction of the NO2 group. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.