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Influence of Cation Size on the Co‐crystallisation of Benzoic Acid with Different Benzoates
Author(s) -
Butterhof Christian,
Milius Wolfgang,
Breu Josef
Publication year - 2013
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.201200464
Subject(s) - benzoic acid , denticity , chemistry , dissolution , crystal structure , ionic bonding , ionic compound , crystallography , crystal engineering , benzoates , crystallization , salt (chemistry) , coordination complex , cryptand , counterion , carboxylic acid , ion , supramolecular chemistry , organic chemistry , metal
In the pharmaceutical industry many new active pharmaceutical ingredients (APIs) are marketed as carboxylic salts because of enhanced solubility and dissolution rates. These salts are, however, often hard to crystallise and/or exhibit a low degree of crystallinity. The reason may be the largely differing sizes of cation and anion. One way out of the resulting “coordination dilemma“ is the formation of co‐crystals of the salt with its neutral acid which delivers additional coordination sites for the cation. In this line, the crystal structure of a new co‐crystal of benzoic acid (HBz) and lithium benzoate (LiBz) with composition 1HBz · 1LiBz was determined and was compared to published ionic co‐crystals of other alkali salts with respect to the structure determining criteria: coordination number of the cation, ratio of HBz:Bz – , mode of coordination of the carboxylic groups (mono‐ or bidentate), and connectivity (edge‐ or corner‐sharing) between neighbouring polyhedra. The new crystal structure is closely related to form A of 2HBz · 1NaBz. Both crystal structures contain dimers with shared edges which are further connected by bridging bidentate ligands to tapes.