Hydrogen bonding continued intermolecular

In selected cases, the effect of solvation on the crystalline structure formed is, however, considerably more pronounced. For example, the observed packing in the crystal of 2,4,6-tris( 1,3-propylenediamine-N,N -)cyclotriphosphazene (4) dihydrate (Fig. 6) is due to strong intermolecular hydrogen bonds between molecules of water and suitable couples of N-H groups on the host moiety M). The HzO species form also continuous H-bonded layers of solvation around the cyclophosphazene derivatives, thus stabilizing the crystal lattice. 

Hydrogen-bonded Systems.—The hydrogen bond may be looked upon as the weakest chemical bond, or as the strongest intermolecular interaction, but however it be classified, it continues to attract the theoretician the number of SCF calculations continues to increase rapidly. 

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