Bullock, Sam, Felton, Cara E., Fennessy, Rebecca V., Harding, Lindsay P., Andrews, Michael, Pope, Simon J. A., Rice, Craig R. and Riis-Johannessen, Thomas (2009) Coumarin-based luminescent ligand that forms helicates with dicationic metal ions. Dalton Transactions, 47. pp. 10570-10573. ISSN 14779226

The potentially hexadentate ligand L, which contains two terminal coumarin fluorophores, forms dinuclear double-stranded helicates with dicationic metal ions, giving species of the generic form [M2L2]4+. In solution the free ligand was fluorescent with emission attributed to the coumarin fluorophores (em = 437 nm). The luminescent properties of the corresponding dimetallic helicates complexes were examined and revealed that the Zn2+ complex demonstrates enhanced emission when compared to the parent ligand, whereas Co2+, Cu2+, Cd2+ and Hg2+ induce varying degrees of fluorescence quenching. In particular, comparative luminescence measurements at 77 K and room temperature showed that the quenching mechanism for [Cu2L2]4+ can be attributed to a photoinduced electron transfer. ESI-MS selectivity studies showed that in the presence of a mixture of metal dications no preference for any one metal ion was observed.

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