Fluorescence quenching of methoxycalixarenes (MOCX) by chloroalkanes (CA) has been investigated in acetonitrile solutions. Observed quenching is attributed to photoinduced dissociative electron transfer (DET) interaction, which is supported by the characterization of the Cl- ions and by the radical scavenging experiments. Comparing the Cl-yields with different DET systems, it is inferred that both concerted and stepwise DET mechanisms operate simultaneously in MOCX-CA systems. A correlation of the quenching constants with the free-energy changes following a Suitable DET theory supports the above inference. (C) 2003 Elsevier Science B.V. All rights reserved.