Abstract: The design and synthesis of chemosensors for Cu²⁺ constitute a very active area of research as a result of the demand for more sensitive and selective chemosensors for in vitro and in vivo purposes. The synthetic Cu²⁺ selective fluoroionophores so far reported suffer from low sensitivity and, in general, higher concentrations of interfering metal ions disturb the selectivity towards Cu²⁺. Four 1,5-diaryl-3-(2-hydroxyl-4,6-dimethoxylphenyl)-2-pyrazoline(4a—4d) were synthesized and fluorescent sensors for Cu²⁺ ion were investigated. The structures of all the products were determined by IR, ¹H NMR, MS and elemental analysis. Their UV and fluorescence spectra were measured. The influences of eight metal ions such as Cu²⁺, Zn²⁺, Co²⁺, Ni²⁺, Na⁺, K⁺, Ca²⁺ and Mg²⁺ on their fluorescence properties were studied. Spectroscopic studies revealed that the compounds 4a—4d had rather strong affinity toward Cu²⁺. The specificity of the probes 4a—4d toward Cu²⁺ were determined. Nearly no fluorescence intensity changes were observed in emission spectra with Zn²⁺, Co²⁺, Ni²⁺, Na⁺, K⁺, Ca²⁺ and Mg²⁺. However, under identical conditions, the results show fluorescence quenching with Cu²⁺. So we have developed four new fluorescent sensor 4a—4d. They show high sensitivity and selectivity toward Cu²⁺ in DMSO.

Key words: 1,5-Diaryl-3-(2-hydroxy-4,6-dimethoxy-phenyl)-2-pyrazoline, Cu2+, Fluorescence probe