Fluorescent sensors based on BODIPY derivatives for aluminium ion recognition: an experimental and theoretical study

Two BODIPY derivative sensors for metal ion recognition containing 10-(4-hydroxyphenyl) (L1) and 10-(3,4-dihydroxyphenyl) (L2) were synthesized in a one-pot reaction of benzaldehyde derivative and 2,4-dimethylpyrrole in the presence of trifluoroacetic acid as catalyst. The binding abilities between these sensors and 50 equivalents of Na(+), K(+), Ag(+), Ca(2+), Fe(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Pb(2+), Al(3+) and Cr(3+) ions were studied using UV-vis and fluorescent spectroscopic methods. Of all the metal ions tested, Al(3+) ion showed the greatest decrease in intensity in the spectra of the sensors, and therefore Al(3+) ion forms the strongest complex. The binding abilities of BODIPY receptors with Na(+), Ag(+), Ca(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+) and Al(3+) ions were also investigated using density functional theory (DFT) calculations at B3LYP/LanL2DZ theoretical level. The calculated results point to the same conclusion. DFT calculations also provided the HOMO-LUMO energy levels, which can explain the spectrum change upon complexation.