Energy splittings resulting from anisotropy and exchange interactions in the dimer of single-molecule magnets [Mn4O3Cl4(O2CEt)(3)(py)(3)](2)-8MeCN are determined for both an undeuterated and a partially deuterated sample using inelastic neutron scattering. The antiferromagnetic (AF) exchange coupling between the two Mn-4 subunits strongly depends on their separation. The Cl---Cl distance between the two subunits can be modified either by exchanging the solvent of crystallization or by deuteration of the C-H---Cl hydrogen bonds. The exchange of acetonitrile for n-hexane leads to a five times greater shortening of the Cl---Cl separation than does full deuteration of all the hydrogen bonds. As a result, the AF exchange coupling constants between the subunits are 0.0073(4) and 0.0103(9) meV in the samples with acetonitrile and n-hexane solvent molecules, respectively, in the crystal structure. On the other hand, the effect of C-H---Cl deuteration on the AF exchange coupling is not detectable within the experimental accuracy of INS.