The Synthesis And Applications Of Fluorescent Dyes Based On The Benzimidazo[2,1-a]Benz[de]Isoquinoline-7-one-12-carboxyl Ic Acid

In this paper, we have prepared eight fluorescent probes based on the fluorophore of benzimidazo[2,1-a]benz[de]isoquinoline-7-one-12 carboxylic acid though introducing different complex groups on the C-12 position:N-[2-(dimethylamino)ethyl]benzimidazo [2,1-a]benz[de]isoquinoline-7-one-12-carboxylamide (L1), N-[2-(dimethylamino)ethyl]ben-zimidazo[2,1-a]benz[de]isoquinoline-7-one-12-carboxylaminium bromide (L2), N-(4-methyl piperazin-1yl)benzimidazo[2,1 a]benz[de]isoquinoline-7-one-12-carboxylamide (L3),4-[(ben-zimidazo[2,1-a]benz[de]isoquinoline-7-one-12-carbonyl)amino]-1,1-dimethylpiperzinium br-omide (L4), N,N-bis(pyridin-2-ylmethyl) benzimidazo[2,1-a]benz[de]isoquinoline-7-one-12-carboxamide (L5), N-{2-[bis(pyridin-2-ylmethyl)amino]ethyl}benzimidazo[2,1-a]benz[de]-isoquinoline-7-one-12-carboxamide (L6), N'-((1-butyl-2-oxo-1,2-dihydroquinolin-3-yl)me-thylidene)-7-oxo-7H-benzo[de]benzo[4,5]imidazo[2,1-a]isoquinoline-12-carbohydrazide (L7), 7-oxo-N'-((4-oxo-4H-chromen-3-yl)methylene)-7H-benzo[de]benzo[4,5]imidazo[2,1-a]isoqui noline-12-carbohydrazide (L8). The structures of the above probes were validated by'H NMR,13C NMR. and MS spectra, and their optical properties were investigated by UV-vis absorbance and fluorescence emission spectra.The eight fluorescent probes all exhibited excellent optical properties, and they could be used to detect pH changes, anions and cations in aqueous solution. In acetonitrile/water (9:1) solution, L1 could be used as a fluorescent "turn-on" probe towards acidic pH changes (9.2-4.2). In aqueous solution, L2 had a good solubility and could be used as a ratiometric fluorescent probe towards basic pH changes (8.9-11.5). Furthermore, by alter addition of HCl and NaOH, the fluorescence emission spectra of L1 and L2 could be repeated several times without fluorescence decrease. In acetonitrile/water (9:1) buffer solution, probe L3 and L4 showed fluorescence "turn-on" response towards Cu2+ and the response were not interfered from the other competitive metal ions. In the same condition, L5 exhibited excellent selectivity and sensitivity towards Cd2+ and Cu2+ based on different mechanisms. Upon binding with Cu2+, the solution showed fluorescence quenching response and the color changed from yellow-green to non-fluorescence; upon binding with Cd2+, the solution showed fluorescence ratiometric response with color changing from yellow-green to blue under UV light. In addition, the new formed [Cu(L5)] and [Cd(L5)] complexes could be used as new platforms for the selective detection of PPi though fluorescence recovery response. In acetonitrile/water (9:1) buffer solution, L6 had a great selectivity towards Cd2+ based on the fluorescence "turn-on" response. In addition, at pH 3.5, the protonated L6 had good solubility in water and could be used as a fluorescent quenching probe towards Cu2+through electrostatic interaction. The Cu2+ detection was not interfered by the other metal ions. In acetonitrile/water (9/1) buffer solution, L7 could be used as a fluorescent "turn-on" probe towards to Zn2+, and the new formed L7+Zn2+complex had a great selectivity towards NO2-. The studies indicated that L7 could exhibit different level fluorescence due to the control of C=N isomerization. Probe L7 had a very weak fluorescence. Upon binding with Zn2+, a stable complex of L7+Zn2++Cl- was formed, and emission intensity showed a mediate enhancement due to the partial inhibition of C=N isomerization. What is more, upon addition of NO2-, Cl-could be easily displaced by NO2- and give a more stable complex of L7+Zn2++NO2-. As a result, the emission intensity showed a further enhancement due to the completely inhibition of C=N isomerization. The control of isomerization could not only be used to detect NO2-, but also be used as a new detection platform for the detection of other anions. In acetonitrile/water (9:1) buffer solution, L8 showed quite weak fluorescence, and could be used as fluorescence "turn-on" and "tun-off" probe towards Cu2+and Fe3+, respectively. Furthermore, the new formed complex L8+Cu2+could be used as a new platform for selective detection of Fe3+, resulting in a dual detection of Fe3+ by probe L8.