It is proposed to characterize the new three-dimensional polymer of single molecule magnets, {K4[mu-Co(H2O)4]2[Co4(citr)4].8H2O}n, citr = citrate, C6H4O7, by single crystal neutron diffraction in order to elucidate the mechanism of H/D exchange that occurs when this crystalline substance is exposed to D2O vapor. The channels in this structure contain H2O and K+, arranged in such a way that removal or displacement of entire H2O molecules could not be achieved without significant disruption of the K+ cation structure and charge balance. Neutron diffraction analyses will reveal the exact sites of selective H/D exchange, if it occurs, and permit a conclusion to be drawn as to whether a proton-wire mechanism is operative as an alternative to full H2O/D2O substitution.