Abstract
Two bis-imidazolium salts 1,8-bis[2’-(N-R-imidazoliumyl)acetylamino]naphthalene chloride (L1H4·Cl2: R = Et; L2H4·Cl2: R = nBu), as well as their four NHC metal complexes [L1H2Ag]Cl (1), [L1Ni] (2), [L2Ni] (3) and [L1H2Hg(HgCl4)] (4) have been synthesized. In each of the cationic moieties of complexes 1 or 4, there is a groove-like 14-membered macrometallocycle, and each macrometallocycle is consisted of one biscarbene ligand L1H2 and one metal ion (silver(I) ion for 1 and mercury(II) ion for 4). Three 6-membered cycles are contained in each molecule of complexes 2 or 3. Additionally, the selective recognition of macrometallocycle 1 for Cu2+ was studied with the methods of fluorescence and ultraviolet spectroscopy, 1H NMR titrations, MS and IR spectra. The experimental results display macrometallocycle 1 can discriminate Cu2+ from other cations effectively.
Highlights
The detection of Cu2+ occupies an important position in host-guest chemistry because it plays a crucial part in chemistry, biology and environmental science[1,2,3]
In the process of searching for suitable chemosensors for Cu2+, we focused on N-heterocyclic carbene (NHC) metal complexes because of their diverse structures, such as macrocycle[25,26,27,28,29], molecular rectangle[30,31,32] and groove[33,34]
Precursors L1H4·Cl2 and L2H4·Cl2 remain stable in the air, and can be dissolved in DMSO, dichloromethane and acetonitrile, but their solubility is poor in benzene, diethyl ether and petroleum ether
Summary
The detection of Cu2+ occupies an important position in host-guest chemistry because it plays a crucial part in chemistry, biology and environmental science[1,2,3]. Ingesting excess or deficient Cu2+ will cause serious illness, such as Alzheimer’s and Wilson’s diseases, haematological manifestations and liver damage[4,5,6,7,8,9,10,11,12]. Excess Cu2+ can destroy the aquatic ecosystem, and disturb the nutrient absorption and transport of some plants[13]. Among the detection of Cu2+, the fluorescent chemosensor is one of significant tools due to its high sensitivity and the simplicity of equipment[14,15,16]. A variety of types of fluorescent chemosensors for Cu2+ have been reported, such as organic small molecules and MOFs17–23. Liu and co-workers reported a sensor based on porous conjugated polymers for Cu2+, and it is high sensitivity and selectivity[24]. Though some chemosensors for Cu2+ have appeared, the design and synthesis of new practical chemosensors are still desirable
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