Molecular systems possessing internal hydrogen bonds draw close scientific attention, as understanding of the properties of this type of interaction is of crucial importance. Good candidates for the studies of internal hydrogen bonding are the small and medium size molecules, because it is possible to easily handle them during experiments and perform high level quantum chemistry calculations in reasonable amounts of time. The molecules possessing a pseudo ring structure where hydrogen bond “closes” this ring form a peculiar class of molecules where properties of hydrogen bond (H-bond) are strongly dependent on the delocalized π type electronic structure of the molecule. Such type of hydrogen bonding is often called Resonance Assisted Hydrogen Bonding (RAHB).[1,2] The smallest members of these molecular families are malonaldehyde and acetylacetone (acac), with symmetric substituents linked to the pseudo ring and widely investigated in previous matrix works,3–8 and the asymmetric acetylacetaldehyde. This type of molecules can exist in two tautomeric forms, namely enol and keto, the enol form being the most stable one due to the strong internal hydrogen bond. These molecules in enolic configuration possess double well potential function for the proton transfer from one oxygen to the other.