Counterintuitive Solid-State Syntheses of Indium-Thiolate-Phen Cations as Efficient and Selective Fluorescent Biosensors for HIV-1ds-DNA and Sudan Ebolavirus RNA Sequences

摘要

Coordination compounds [In(Tab)2(Phen)2](PF6)3 (2), [In(Tab)2 (Phen)2·In(Tab)4(Phen)](OAc)6 (3) and [In(Tab)4(Phen)](OAc)3 (4) (Tab=4-(Trimethylammonio)benzenethiolate; Phen=1,10-Phenanthroline) are formed via a counterintuitive solid-state synthesis involving the mix of In(OAc)3, TabHPF6 and Phen in various stoichiometries. The Tab-to-Phen ratios of 2-4 are opposite to the TabHPF6-to-Phen ratios of the starting materials. By comparison, the corresponding solution-state reactions provide 4 exclusively at high concentrations, and otherwise the Phen-free [In(Tab)4](OAc)3 (1). Reaction of In(OAc)3, TabHPF6 and a bulkier Dpphen (Dpphen=4,7-Diphenyl-1,10-phenanthroline) ligand in the solid state give [In(Tab)2(Dpphen)2](PF6)3 (5) exclusively, regardless of the reaction stoichiometry. Compounds 2, 4 and 5 associate with two fluorophore carboxyfluorescein (FAM) probe labelled DNA fragments (P-DNAs) through electrostatic, π-stacking and/or hydrogen-bonding interactions, forming P-DNA@2, P-DNA@4 and P-DNA@5 hybrids that quench the fluorescence of FAM via a photo-induced electron transfer process. These hybrids are further used as efficient and selective “turn-on” fluorescent sensors for HIV-1 ds-DNA and Sudan Ebolavirus RNA sequences with detection limits in the pM–nM range.