Impact of deformation energy on the hydrogen bonding interactions in gas phase 3-X catechol⋯H2O complexes (X = H, F, Cl, Br): The effect of approach of a water molecule

- Binding energies are correlated with deformation energy.
- NBO analysis and SAPT based energy decomposition analysis are carried out.
- Binding energies of the hydrogen bonded complexes are correlated with CTP.

The conformations and nature of hydrogen bonding interactions for 3-X catechol⋯H2O (X = H, F, Cl, Br) has been investigated by ab initio MP2, CCSD(T), and density functional B3LYP, wB97XD and M06-2X methods. The changes in interaction energies due to deformation of the structures has been studied in detail. The intra- and intermolecular hydrogen bonding interactions due to the different direction of approach of water molecule have been discussed. A detailed natural bond orbital (NBO) analysis and the symmetry-adapted perturbation theory (SAPT) based energy decomposition analysis has been carried out to elucidate interaction strength and properties in these hydrogen bonded systems. The charge transfer percentage (CTP) has been derived which will be universally useful for correlating binding energy, deformation energy and the geometrical parameters such as angles, bond lengths, etc. for other systems as well.

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