  Here we propose a mechanism by which spin polarization can be generated
dynamically in chiral molecular systems undergoing photo-induced electron
transfer. The proposed mechanism explains how spin polarization emerges in
systems where charge transport is dominated by incoherent hopping, mediated by
spin orbit and electronic exchange couplings through an intermediate charge
transfer state. We derive a simple expression for the spin polarization that
predicts a non-monotonic temperature dependence consistent with recent
experiments. We validate this theory using approximate quantum master equations
and the numerically exact hierarchical equations of motion. The proposed
mechanism of chirality induced spin selectivity should apply to many chiral
systems, and the ideas presented here have implications for the study of spin
transport at temperatures relevant to biology, and provide simple principles
for the molecular control of spins in fluctuating environments.
