LANGEVIN MODE STUDY OF SOLVENT VISCIDITY INFLUENCE ON THE PROPERTIES OF 18-CROWN-6

Both conformers (C-i, D-3d) of 18-crown-6 have been studied by Langevi n mode method under four viscidities of solvent: 0.0, 3.0X10(-4), 6.0X 10(-4) Pa . s (about the viscidity of methol at room temperature), 9.0 X10(-4) Pa . s (about the viscidity of water at room temperature). For viscidity of 9.0X10(-4) Pa . s, both Oseen method and Rotne-Prage met hod were used in the calculation. The results showed that the viscidit ies of solvent greatly influenced on the properties of 18-crown-6, esp ecially the distribution df the vibrational frequency and the libratio nal angle of the bond vector. The effects of nondiagonal elements of t he frictional matrix must be considered by using Oseen or Rotne-Prage method when the viscidity of solvent is large. At the same time, the r esults also show that Langevin mode method is a very effectivce model for interpreting molecular motion in solution.