For the HBs present in the monomer and dimer clusters, the following order of BE strength is observed: DD<Monomer<SDSA<A+SDSA. The weakest of these interactions is the DD since it forms a hydrogen bond with the organic probe through a water acting as a double HB donor. As Figure to the organic probe is also donating an HB to a neighbouring molecule of water: accepting electronic density from both molecules and reducing the HB donating capabilities of the central water in DD. For SDSA and A+SDSA, the water molecule donating an HB to the probe is also acting as an HB acceptor of another water molecule. This is the well-known "cooperative" effect in hydrogen bonding: The water bound to the probe is electron deficient because it is donating electron density to a neighbouring water molecule, making the former water better able to accept electron density from the probe. This effect is also at play in the A+SDSA motif, which interactions are further enhanced by the secondary A interactions.