EFFECT OF HIGH-PRESSURE ON THE INFRARED-SPECTRA OF THE THIAMINE ENZYME ACTIVE ALDEHYDE INTERMEDIATE 2-(ALPHA-HYDROXYBENZYL)THIAMINE CHLORIDE (HBT) AND THE MERCURY(II) COMPLEX, HG(HBT)CL3

The effects of high external pressures (approximately 30 kbar) on the IR spectra of the protonated form of 2-(alpha-hydroxybenzyl)thiamine chloride (HBT.HCI) and the zwitterionic mercury(II) complex Hg(HBT) Cl3 have been investigated at room temperature. With the exception of the nu(OH) peak of the HBT ligand, all the observed peaks shift towards higher wavenumbers with increasing pressure. The most pressure-sensitive peaks (d-nu/dP > 0.6 cm-1/kbar) are chiefly associated with vibrations of the pyrimidine ring. The S conformation of the pyrimidine and thiazolium rings is apparently retained under high pressure in both HBT and Hg(HBT)Cl3, as is also the case in solution.