calculation [3] , The interactions between magnesium-bound water molecules and carboxylate groups can facilitate the catalytic activity of enzymes by changing the pK* of the water molecule and controlling the orientation of required functional groups. A detailed knowledge of the coordination of magnesium could provide a guideline for drug designs of certain metalloproteins. To our knowledge, no crystal structures of metal ion complexes of the carboxylate of the anthracene adduct have been

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... ed. The bond lengths of CI-Ol and CI-02 are 1.309(2) A and 1.215(2) A, respectively, while the bond lengths of C2-03 and C2-04 are 1.265(2) A and 1.251(2) A, respectively, indicating that the ligand is in the form of the monocarboxylate group while the other group is protonated. Thus, Mg(II) cation is attached to two carboxylate groups from different molecules. In addition to the electrostatic interactions, the crystal structure is stabilized by a network of hydrogen bonds and van der Waals interactions. Intermolecular hydrogen bonds are formed between the carboxylic and the adjacent carboxylate groups. The intermolecular distance between the stacked aromatic rings is approximately 4.1 A indicating n-n interaction. The Mg(II) cation is bound to six water molecules at the inner coordination and four water molecules at outer coordination. The bond lengths between the magnesium cation and oxygen atoms of inner water molecules are in the range of2.030(1)A-2.117(1)A. The outer water molecules are 4.174 A and 4.543 A apart from the Mg ion. The distances between Mg and each oxygen atom of the carboxylic and the carboxylate group (Ol, 02, 03, and 04) are 6.248 A, 4.135 A, 5.239 A, and 3.909 A, respectively. The Mg ion is closer to the carboxylate group with C2 (4.751 A) than to the carboxylic group with CI (5.334 A). The carboxylate group is twisted with the dihedral angle 03-C2-C4-C3 of 61.1 ° while the carboxylic group is twisted with the dihedral angle 02-C1-C3-C4 of 19.6°. The aromatic rings are bent inclining to each other with the angle of 108.2°. The unit cell of the title compound consists of alternative layers between hydrophobic (aromatic moiety of anthracene adducts) and hydrophilic groups (Mg(II) cation). Table 1. Data collection and handling.