Abstract: Reaction of nitrated Sm₂O₃ with 1,10-phenanthroline in the system of EtOH/H₂O with pH≈4 adjusted by HAc resulted in a novel acetate anions bridged dinuclear Sm(Ⅲ) complex Sm₂(CH₃COO)₄·(NO₃)₂(phen)₂, the complex was characterized by elemental analysis, IR, NMR spectroscopy and
the crystal structure was determined by X-ray diffraction. Besides, the kinetics
of thermal decomposition of the complex was studied by thermal analysis technique under non-isothermal condition. The crystal structure belongs to the triclinic system, space group P1 with a=0.979 6(3) nm, b=0.981 3(4) nm, c=1.127 3(4) nm, α=106.666(5)°, β=113.034(5)°, γ=102.656(5)°, V=0.885 4(5) nm³, Z=1, μ=3.361 mm^-1, D_c=1.915 g/cm³, F(000)=498,
R₁=0.059 6, wR₂=0.144 8. The possible reaction mechanism was suggested
to be a second order chemical reaction. The kinetic equation may be expressed
as dα/dT=A/［βe^-E/RT(1-α)²］. The apparent activation energy and pre-exponential factor of the reaction were 344.84 kJ/mol and lnA=66.52, respectively.

Key words: Sm(Ⅲ) complex, 1,10-Phenanthroline, Crystal structure, Thermal decomposition kinetics