Order and Disorder in the Structures of Two Crystal Polymorphs of the Adduct Bis(Quinolinium-2-Carboxylate) DL-Malic Acid
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The structures of two polymorphs of the anhydrous cocrystal adduct of bis(quinolinium-2-carboxylate) DL-malic acid, one triclinic the other monoclinic and disordered, have been determined at 200 K. Crystals of the triclinic polymorph 1 have space group P-1, with Z = 1 in a cell with dimensions a = 4.4854(4), b = 9.8914(7), c = 12.4670(8) Ŭ a = 79.671(5), ߠ= 83.094(6), ? = 88.745(6)Crystals of the monoclinic polymorph 2 have space group P21/c, with Z = 2 in a cell with dimensions a = 13.3640(4), b = 4.4237(12), c = 18.4182(5) Ŭ ߠ= 100.782(3)Both structures comprise centrosymmetric cyclic hydrogen-bonded quinolinic acid zwitterion dimers [graph set R22(10)] and 50% disordered malic acid molecules which lie across crystallographic inversion centres. However, the oxygen atoms of the malic acid carboxylic groups in 2 are 50% rotationally disordered whereas in 1 these are ordered. There are similar primary malic acid carboxyl O-H緷Oquinaldic acid hydrogen-bonding chain interactions in each polymorph, extended into two-dimensional structures but in 1 this involves centrosymmetric cyclic head-to-head malic acid hydroxyl-carboxyl O-H緷O interactions [graph set R22(10)] whereas in 2 the links are through single hydroxy-carboxyl hydrogen bonds. Graphical Abstract The structure determinations of two crystal polymorphs of the 2:1 adduct of quinolinium-2-carboxylate with DL-malic acid has shown one to be triclinic and ordered while in the second monoclinic form the carboxylic acid groups of the malic acid moiety are disordered.
Journal of Chemical Crystallography
© 2010 Springer Netherlands. This is an electronic version of an article published in Journal of Chemical Crystallography, Volume 41, Number 2 (2011), 241-246. Journal of Chemical Crystallography is available online at: http://www.springerlink.com/ with the open URL of your article.
Structural Chemistry and Spectroscopy