Recognition Preference of Rhodamine-Thiospirolactams for Mercury(II) in Aqueous Solution

Abstract

This work presents the design, syntheses, photophysical properties and Hg(2+)-binding of the red-emitting rhodamine derivatives RS1, RS2, and RS3 with different coordination ability and different spatial effects that derived from rhodamine thiohydrazone chromophores and respective carboxaldehydes (benzaldehyde, pyridine-2-carboxaldehyde, ferrocenecarboxaldehyde). Chemosensors RS2 and RS3 afford turn-on fluorescence enhancement and display high brightness in water with the EC(50) for Hg(2+) of 0.5 ppb. The fluorescence intensities are nearly proportional to the amount of Hg(2+) at ppb level, when employing 100 nM probes in water. The fluorescence responses of these two chemosensors are Hg(II) specific, and the probes are selective for Hg(II) over alkali, alkaline earth metals, divalent first-row transition metal ions, and Group 12 congeners Zn(II) and Cd(II), as well as heavy metals Pb(II) and Ag(I). X-ray crystal structure analyses exhibit the thioether derivative of the spirolactone in these compounds. Hg(II)-specific binding in water would make the opening of the spirolactam ring and consequently causes the appearance of strong absorption at visible range, and the obvious and characteristic color change from colorless to pink. Compared to the thioamides, the improved selectivity for Hg(2+) is attributed to the poorer coordination affinity of the thioether over other interference metal ions.

Effects of Single and Double Bonds in Linkers on Colorimetric and Fluorescent Sensing Properties of Polyving Akohol Grafting Rhodamine Hydrazides

“…Rhodamine B, rhodamine 6G, maleic anhydride (MAH) and succinic anhydride (SAH) were purchased from Sigma-Aldrich Trading Co. Ltd. (Shanghai, China); Hydrazine hydrate, thionyl chloride and dimethyl sulfoxide (DMSO) were purchased from Sinopharm Chemical Reagent Co. Ltd. (Shanghai, China) and used without further purification; Anhydrous methanol and ethanol, acetic ether, dichloromethane, petroleum ether, N,Ndimethylformamide (DMF) and pyridine were obtained from commercial suppliers. Rhodamine B hydrazide (RBH) and rhodamine 6G hydrazide (R6GH) were prepared according to the literature method [32][33][34][35].…”

A Cu2+ chemodosimeter based on amplified fluorescence in the red region

“…The introduction of rhodamine skeletal to construct probes of the ''off-on'' type was a reliable method due to the well-known spirolactam (fluorescence ''off'') to ring-opened amide (fluorescence ''on'') equilibrium of rhodamine derivatives [17,[26][27][28][29][30][31][32][33][34]. The spirolactam moiety of rhodamine skeletal served as a signal switcher, which was observed to turn on when the cation was bound.…”

“…Particularly, the lack of additional binding sites, except for these two atoms, made the probe show no or little coordination to any other metal ions but allow only the most preferred cupric ion to bind to the chelating unit. Recently, the spirolactam forms for the derivatives of rhodamine B or G skeletals have been utilized for the detection of other metal ions such as Hg 2 + [25][26][27][28], Cu 2 + [29], Fe 3 + [30], Cr 3 + [31,32], Pb 2 + [33,34], etc. in aqueous solutions via ring-opening processes of spirolactam amides or hydrazides.…”

Ultrasensitive and selective spectrofluorimetric determination of Hg(II) using a dimercaptothiadiazole fluorophore

“…To date, only a few papers were reported for the determination of Hg(II) in the range of microgram to nanogram level by fluorimetric method [3,[16][17][18][19][20][21][22][23][24]. It has been reported that, triazinethione derivative [16], rhodamine-hydrazone derivative [17], rhodamine-thiospirolactams [18], rhodamine 6G-derivative [19], rhodamine B selenolactone [20], p-dimethylaminobenzaldehyde thiosemicarbazone [21] and 6-mercaptopurine [22], [E-4,4 0 -di(N-(2-pyridyl)amino) stilbene] [23], metal nanoparticles [24][25][26] can be used for the determination.…”