화학공학소재연구정보센터
Journal of Physical Chemistry A, Vol.112, No.5, 833-838, 2008
Ion-pair interaction in pyridinium carboxylate solutions
Ion-pair interactions between pyridinium cations and various carboxylate anions are explored using noisy light based coherent anti-Stokes Raman scattering (I((2))CARS). Binary mixtures of pyridine and various carboxylic acids (including halo-acetie acids, straight-chain carboxylic acids, and pivalic acid) are prepared. A Bronsted type acid-base reaction occurs in these mixtures to create pyridinium and carboxylate ions. Both pyridine, itself, and pyridinium have strong I((2))CARS signals originating from their ring breathing modes. The vibrational frequency of the ring breathing mode for pyridine is blue-shifted by hydrogen bonding, and that same mode for pyridinium is red-shifted by ion-pair interaction. Frequency shift data for the ring breathing mode of pyridine and pyridinium are presented. These data are discussed in terms of a simplistic model for the electronic behavior of these compounds.