Abstract
The polarized infrared spectra of single crystals for potassium hydrogen maleate (KHM) and its deuterated analogue (KDM) have been measured at room and low (approximately 15 K) temperature. The hydrogen bond and internal vibrations of the maleate ion are discussed. The antisymmetric stretching vibration, ν aOHO, of the strong hydrogen bond gives rise to an intense, broad absorption with its centre of gravity at approximately 820(±50)cm −1, divided into three broad bands at 990, 700 and 545 cm −1 by wide ‘transmission windows’ (at 795 and 605 cm −1). These transmission windows result from the strong anharmonic interaction of ν aOHO with some of the internal modes of the maleate anion. Deuteration results in a surprisingly small change in the ν aOHO absorption. The γOHO vibration obeys C s site symmetry selection rules; thus the hydrogen-bond potential in the KHM crystal is symmetrical with a single minimum. The possibility of coupling between the νCO and νCO vibrations is considered.
Published Version
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