STRUCTURE AND FTIR SPECTRA OF 3 2 COMPLEXES OF TRIMETHYLAMINE N-OXIDEAND 4-DIMETHYLAMINE-2,6-DIMETHYLPYRIDINE N-OXIDE WITH PERCHLORIC-ACID/

Trimethylamine N-oxide and 4-dimethylamine-2,6-dimethylpyridine N-oxid e form three types of crystalline complexes with perchloric acid, with the base-to-acid ratio 1:1, 2:1 and 3:2, which are easily distinguish ed by their IR absorption. The asymmetric unit of the P (1) over bar u nit cell contains two (Me(3)NO)(3) .(HClO4)(2) formula units. Each of the formula units assembles into a (Me(3)NO)(3)2H(+) dication and two independent ClO4- anions which show no H-bond interactions with the ca tionic components. The oxygen atom of a central trimethylamine N-oxide molecule accepts hydrogen bonds from two protonated trimethylamine N- oxide cations with O ... O distances in the range 2.537(5) - 2.562(7) Angstrom. The O ... H-O bonds are linear and formed along direction of the two electron lone-pairs on the oxygen atom. In acetonitrile solut ions the 3:2 complexes exist as mixtures of the 1 : 1 and 2: 1 complex es.