The thermodynamic properties of the molecular complexes between water and a series of diatomic molecules of atmospheric interest have been explored using the classic large-amplitude motions/quantum harmonic vibrations (CLAM/QHV) model taking into explicit account the rovibrational dynamics of non-rigid molecules. For this purpose, the complete 5D intermolecular potential energy hypersurfaces of the complexes H2OO2, H2OF2, H2OCl2, H2OOH have been explored using the fast scanning technique accounting the molecular PES symmetry as implemented in the ADANIMEHS program. The energies of the unique PES points (the points having an unique structure) have been calculated using a variety of quantum chemical methods up to CCSD(T)/6-311++G(2d,2p). The effect of the intramolecular structural relaxation of monomers on resulting thermodynamic properties has been investigated. The evaluation of the thermodynamic functions and equilibrium constants of the complex formation have been performed using the ADANIMEHS code implementing the CLAM/QHV model. On this basis, the calculated equilibrium constants and thermodynamic functions as well as their temperature dependencies are discussed in comparison with available results obtained with other theoretical models and approaches.