Structures and vibrations of the dimers and trimers of hydrazine/water

Energetics, geometrical structures and vibrations of complexes of the type N2H4(H2O)n with n=1,2 have been determined at the MP2 and CCSD(T) levels of theory. One dimer and five trimer conformations are found as minima on the PES. By calculating the barriers of three rearrangement reactions, it could be shown that for the trimers only the global minimum contributes to the IR spectrum. Harmonic frequencies were calculated using the MP2/6-311++G(3df,2p) method, while anharmonic corrections were obtained employing the MP2/6-31+G(2d,p) method by means of second-order perturbation theory. At least 16 conformations of the type (N2H4)2·H2O are expected; two of the most stable ones were also calculated at the MP2/6-311++G(3df,2p) level.