One dinuclear manganese(II) complex [Mn_2(C_(12)H _8N_2)_4(C_8H_5O_4)_2](C_8H_4O_4)·EH_2O has been synthesized with o-phthalic acid and 1,10-phenanthroline. The crystal structure was determined by X-ray diffraction. The crystal belongs to the triclinic system, space group P1 with a = 1.17767(3), b = 1.22292(2), c = 1.35860(3) nm, α = 110.5300(10), β = 97.6140(10), γ = 93.7300(10)°, V = 1.80307(7) nm~3, D_c = 1.404 g/cm~3, Z = 2, F(000) = 784, the final GOOF = 1.047, R = 0.0398 and wR = 0.1038. The crystal structure of the title complex con...