Fluorescent chemosensor for mercury(II) cations in an aqueous solution based on 4-acetylamino-1, 8-naphthalimide derivative containing the N-phenylazadithia-15-crown-5-ether receptor

Abstract

The 4-acetylamino-1,8-naphthalimide derivative containing the N-phenylazadithia-15crown-5-ether fragment in the N-aryl substituent at the imide nitrogen atom of the naphthalimide core was synthesized, and its cation-dependent spectral properties were studied. The resulting compound in the photoexcited state exhibits low-intensity fl uorescence due to the process of electron transfer from the N-aryl group to the naphthalimide residue, which is confi rmed by the data of quantum chemical calculations performed using the PM6 method. The binding of Hg 2+ in an aqueous acetate buff er solution at pH 6.0 is accompanied by the formation of a 1 : 1 metal-ligand complex in which the electron transfer is suppressed leading to fl uorescence enhancement. The observed spectral changes were used for the determination of the stability constant K of the complex (logK = 6.51±0.03). The found limit of Hg 2+ detection using the synthesized sensor (28 nmol L -1 ) is fairly close the maximum permissible concentration for mercury in drinking water. The study of the selectivity of complexation showed that the presence of Cu 2+ , Zn 2+ , Ni 2+ , Pb 2+ , Cd 2+ , Ca 2+ , Mg 2+ , and Fe 2+ cations did not impede the determination of Hg 2+ . The presented results indicate that the synthesized chemosensor is promising as a selective and highly sensitive fl uorescent reagent for Hg 2+ ions in an aqueous solution.

Fluorescent RET-Based Chemosensor Bearing 1,8-Naphthalimide and Styrylpyridine Chromophores for Ratiometric Detection of Hg2+ and Its Bio-Application

“…It has been subsequently found that NI-SP accumulates in lysosomes of human lung adenocarcinoma A549 cells (a cell line used for in vitro fluorescence imaging), where pH is rather acidic (4.5–4.8) [ 45 ]. We have also shown in our recent papers that AC15C5 ether fragment in the compound NI2 [ 40 ], as well as in the naphthalimides with a similar structure but bearing NH 2 [ 31 ] and NHAc [ 32 ] groups instead of OMe at the C-4 atom of the naphthalene core, starts to protonate at a pH below 4.0. Higher pH values thus provide a possibility for the switching of PET upon the interaction of the A15C5 macrocycle nitrogen lone pair with a metal cation.…”

“…Complexation with Ag + was also observed for monochromophoric naphthalimides bearing the A15C5 group. Thus, compound NI2 demonstrated a rather high selectivity for Ag + over Hg 2+ at pH 7.4 [ 40 ], whereas both Hg 2+ and Ag + cations were capable of binding with the A15C5 macrocycle in an acidic medium (pH 6.0, acetate buffer, see the data for the A15C5-containing naphthalimide derivative with a close to NI2 structure [ 32 ]). In the latter case, the initially Hg 2+ -enhanced fluorescence of the naphthalimide unit was quenched in a similar fashion when competing silver cations were added to the solution.…”

“…Naphthalimides are classic fluorescent dyes whose electronic absorption and emission depend on the properties of the molecular structure and surrounding medium [ 19 , 20 , 21 , 22 ]; they have been widely applied as photoactive components in the construction of molecular devices with switchable optical characteristics [ 23 , 24 , 25 , 26 ] including fluorescent chemosensors [ 27 , 28 , 29 , 30 ]. As a receptor, we used azadithia-15-crown-5 (A15C5) ether exhibiting high affinity towards mercury (II) cations in a slightly acidic aqueous solution [ 18 , 31 , 32 ]. It has recently been shown that the presence of the A15C5 group in the N -aryl substituent at imide nitrogen of the 1,8-naphthalimide residue results in OFF→ON fluoroionophores based on the PET signaling mechanism [ 31 , 32 ].…”

“…As a receptor, we used azadithia-15-crown-5 (A15C5) ether exhibiting high affinity towards mercury (II) cations in a slightly acidic aqueous solution [ 18 , 31 , 32 ]. It has recently been shown that the presence of the A15C5 group in the N -aryl substituent at imide nitrogen of the 1,8-naphthalimide residue results in OFF→ON fluoroionophores based on the PET signaling mechanism [ 31 , 32 ]. The same structural feature was realized in the case of the NI - SP probe, thereby providing for the NI fragment to sense cations via the increase in its fluorescence intensity.…”

A Study on Cation-Dependent Resonance Energy Transfer in Crown-Containing Bischromophoric System Based on 4-Methoxyand 4-Styryl-1,8-naphthalimide

“…Photoinduced Electron Transfer). [22][23][24][25][26][27][28][29][30][31][32] В частности, присутствие фрагмента азадитиа-15-краун-5-эфира в структуре 4-метоксинафталимида 15C5-MNI (Cхема 1) обес-печивало селективный флуоресцентный отклик на катионы серебра в нейтральном водном растворе (HEPESбуфер, рН 7.3) за счет образования комплекса состава металл -лиганд 1:1. [31] Добавление других катионов металлов (Hg 2+ , Cu 2+ , Zn 2+ , Fe 2+ , Ni 2+ , Pb 2+ , Cd 2+ , Ca 2+ , Mg 2+ ) к сенсору 15C5-MNI не вызывало спектральных изменений.…”