Abstract: A mixed-ligand complex Ni(mnt)(bipyO2) with large conjugate system was synthesized by reaction of bipyO2(2,2′-bipyridine-1,1′-dioxide),mnt2－(maleonitriledithiolate) and NiCl2. The determinations of elemental analysis, IR, UV, molar conductivity and TG-DTA showed the complex to have electroneutrality and a square planar structure. It is a thermostable brown solid under temperature 335 ℃. The ultraviolet absorption spectra of the complex in DMSO solution exhibited intensive absorption bands at 255～290 nm(π-π* in bipyO2 and mnt), 310～340 nm(n-π*, metel cation to ligands), 370～420 nm(π-π* in mnt) and 440～520 nm, and the latter was assigned as a large conjugate system interlocking metal ion and ligands π to π* transition. The study of sensitive properties showed the complex to be a good sensitive material of ammonia. The sensor manufactured using the complex has a good sensitivity and selectivity to ammonia. When working voltage is 10 V and NH3 concentration is less than 2.6 mmol•L－1. The output voltage of the sensor varied linearly in response to the change of NH3 concentration (Fig.3). The average recovery rate of the sensor is 100.2％(Table 4). The responsive time is about 20 s, and the return time is about 45 s. The sensor could be used in quantitative analysis of trace ammonia.

Key words: Nickel, Sensor, Complex, Maleonitriledithiolate(mnt), 2,2′-bipyridine-1,1′-dioxide(bipyO₂)