Fitzgerald L J, Gerkin R E
Chemistry Department, Ohio State University, Columbus 43210.
Acta Crystallogr C. 1994 Feb 15;50 ( Pt 2):185-8. doi: 10.1107/s0108270193006092.
In the title structure, the 1,4,5,8-naphthalenetetra-carboxylate anion possesses 2/m symmetry with the twofold axis coincident with the central C--C bond of the naphthalene rings. The ten atoms comprising the naphthalene core have a mean deviation of 0.033 A from the best least-squares plane describing these atoms, with the carboxyl C atom 0.395 (2) A removed from the plane. The dihedral angle between the carboxylate plane and the least-squares plane of the naphthalene rings is 46.2 (3) degrees. The O--C--O angle of the carboxylate group, 121.13(12) degrees, is smaller than normally expected, presumably due to the bidentate interaction with the Ca ion. The Ca ion is coordinated by eight O atoms: six carboxylate O atoms and two water O atoms. Because the Ca ion resides on a twofold axis there are only four independent Ca--O distances, which are in the range 2.368 (1)-2.681 (1)A. In this structure, the organic anions are separated by Ca ions and water molecules such that there are no short-range organic-organic interactions. One of the water molecules separating the organic anions is not involved in coordination with Ca, and is disordered.
在标题结构中，1,4,5,8-萘四羧酸根阴离子具有2/m对称性，二重轴与萘环的中心C-C键重合。构成萘核的十个原子与描述这些原子的最佳最小二乘平面的平均偏差为0.033 Å，羧基C原子与该平面相距0.395(2) Å。羧酸根平面与萘环的最小二乘平面之间的二面角为46.2(3)度。羧酸根基团的O-C-O角为121.13(12)度，比正常预期的要小，这可能是由于与Ca离子的双齿相互作用。Ca离子由八个O原子配位：六个羧酸根O原子和两个水分子O原子。由于Ca离子位于二重轴上，因此只有四个独立的Ca-O距离，范围为2.368(1)-2.681(1) Å。在该结构中，有机阴离子被Ca离子和水分子隔开，因此不存在短程有机-有机相互作用。分隔有机阴离子的一个水分子不参与与Ca的配位，且呈无序状态。
