We have selected a new class of material which shows presence of large conductance switching. The acceptor groups present in the molecules result in low OFF-state current in the devices and hence large ON/OFF ratio of 100,000. The ON-state in the molecules has been due to conjugation restoration via electroreduction. The ON/OFF ratio decreased to 4 in devices based on molecules without any acceptor groups. The devices have undergone 'write-read-erase-read' sequence for hours, showing their applicability in random-access-memory elements. (C) 2003 Elsevier Science B.V. All rights reserved.