Luminescent Donor-Acceptor β-Diketones: Modulation of Emission by Solvent Polarity and Group II Metal Binding

Journal of Fluorescence (Impact Factor: 1.93). 09/2009; 19(5):881-889. DOI: 10.1007/s10895-009-0487-6


A class of aryl trifluoromethyl-containing β-diketones were synthesized via one step Claisen condensation. These π-conjugated
diketones exhibit strong solvatochromism from intramolecular donor-acceptor charge transfer (CT). In addition, fluorescence
quantum yields (ϕf) and lifetimes (τf) were measured in different solvents. Diketones exhibit bathochromic shifts in emission spectra with increasing solvent polarity.
Fluorescence changes upon Group II metal binding were also studied. Despite the relatively simple structure, the anthracene-CF3 diketone, atm, has strong binding affinity for Mg2+. A 70nm blue shift and sixfold increase in intensity were observed upon addition of only one equivalent MgCl2 in ethanol solution. It also shows selectivity for Mg2+ binding even in the presence of excess Ca2+. Association constant (Ka) calculations suggest atm has two orders of magnitude stronger chelation for divalent magnesium than for calcium. These findings
make atm an attractive starting point for molecular probe and light emitting material design.

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