Comparison of diffusivities data of streptocyanine dyes by electrochemical and NMR-DOSY methods

Abstract

Diffusivity data of streptocyanine dyes in acetonitrile were investigated using both transient voltammetric techniques and NMR-DOSY. Results of voltammetric measurements allow determination of the diffusion coefficient D values in the range of 1.2-1.6 x 10-9 m² s-1 for the target dyes. Deuterated acetonitrile solvent was used for NMR-DOSY experiments and diffusivities of streptocyanines are given after calibration of acetonitrile on its tracer diffusion value of D∗ACN of 4.37 x 10-⁹. The results for the two methods appear to be in good agreement allowing use of the convenient NMR-DOSY method to measure diffusivity of streptocyanine dyes at low concentrations and so giving a direct access to the number of exchanged electrons using limiting current electrochemical techniques. This last method affords a great advantage of obtaining diffusion coefficients by non-electrochemical method.