A new indium selenide, namely (bdaH)InSe2 (1) (bda = 1,4-butanediamine) has been solvothermally synthesized and structurally characterized. It belongs to the non-centrosymmetric space group Fdd2. Its structure features an infinite one-dimensional anionic chain of [InSe2](n)(n-) with monoprotonated [bdaH](+) as charge compensating cation. The organic [bdaH](+) cations are joined into a supramolecular one-dimensional chain via N-H center dot center dot center dot N hydrogen bonding, which further interacts with the inorganic chain via N-H center dot center dot center dot Se and C-H center dot center dot center dot Se hydrogen bonding, forming a supramolecular three-dimensional network. Based on such a well-defined structure, the thermal stability, optical, conductivity, and dielectric properties were systematically investigated, showing that dielectric constant, as well as conductivity, had a hump at about 95 degrees C, which could be attributed to water molecules in the crystal boundary. (C) 2011 Elsevier Ltd. All rights reserved.