The photochemical reaction of 2,2'-dipyridyl (DP) with 5-sulfosalicylic acid (SSA) was studied using time-resolved CIDNP in homogeneous and beta-cyclodextrin (beta-CD) aqueous solutions. The degenerate electron exchange rate constant of DP radical anion with diamagnetic precursor was estimated as 1.1 x 10(8) M-1 s(-1) from CIDNP kinetic in homogeneous solution. It was found that DP-beta-CD inclusion complex formation alter the kinetics of DP polarization. For beta-CD solution the drastic decreasing of nuclear relaxation time of DP radical anion was found comparing to the homogeneous solution. (c) 2006 Elsevier B.V. All rights reserved.