Hydrogen bonding nature during ADP crystallization

The hydrogen bonding nature during ADP crystallization is studied on the basis of anisotropic chemical bonding conditions in ADP crystal combined with in situ IR observation. The variations of hydrogen bonding nature of NH4+ and H2PO4- groups dominate the transformation from the free hydrated ionic state to crystalline state during ADP crystallization. Anisotropic ADP crystal morphology depends on the anisotropic chemical bonding conditions along [100] and [101] directions. ADP crystal morphologies with different (H2PO4-)(n) (n = 1-8) clusters can be calculated on the basis of hydrogen bonding conditions and (H2PO4-)(n) cluster structures at the growth interface. Experimentally, in situ IR spectrum can record the breaking of P-O center dot center dot center dot H-O-H and H-N center dot center dot center dot H-O-H, and the formation of P-O center dot center dot center dot H-O-P and H-N center dot center dot center dot H-O-P hydrogen bonding during ADP crystallization. The present work provides a promising strategy to identify the chemical bonding nature during crystallization processes of molecular crystals from aqueous solution. (C) 2013 Elsevier B.V. All rights reserved.