{Mn(DHBQ)(H2O)(2)} (H(2)DHBQ = 2,5-dihydroxy-1,4-benzoquinone) was investigated by X-ray diffraction, thermogravimetry, sorption isotherm of water, and proton conductivity measurements. It showed a one-dimensional coordination-polymer structure with axial coordination waters, which is the first report on the crystal structure of a one-dimensional coordination polymer with the DHBQ ligand. It also exhibited reversible structural change associated with desorption/sorption of the waters. The proton conductivities of the anhydride and dihydrate states were measured. The dihydrate showed a high proton conductivity of 4 x 10(-5) S cm(-1), while the anhydride was below the lower limit of the measurable range (< 10(-13) S cm(-1)).