This work is a comparative study of magnetic field effect (MFE) on photoinduced electron transfer between N-ethylcarbazole (ECZ)-dimethylterephthalate (DMT) pair and ECZ-1,4-dicyanobenzene (DCB) pair. Our aim was to see how a change in the steric bulk of the acceptor is manifested in the magnetic field behaviour of a system. The steric effect in DMT is responsible for maximization of MFE at a higher dielectric constant, e; sustaining spin correlation to a larger extent so that the MFE vs. 8 plot is broad and enhancing free ion formation so that the MFE is lower for ECZ-DMT compared to ECZ-DCB. (c) 2005 Elsevier B.V. All rights reserved.