The trimer complex was synthesized by reacting MnCl 2 with 2,2 bipyridine 1,1 dioxide(bipyO 2) in DMF. The elemental analysis, IR, UV and molar conductivity results indicated the composition of the complex was [Mn 3(bipyO 2) 4Cl 4]Cl 2 .The complex dissolves in water, but does not in organic solvents such as C 2H 5OH, C 2H 5OC 2H 5, CHCl 3, CH 3COCH 3, C 7H 8, DMF and THF. The complex exhibited good sensitivity and selectivity to ammonia of high concentration. It could be used to detect and control NH 3 in the concentration range of 1 0×10 -4 ～5 0×10 -4 mol/L.
