Photocontrolled electron transfer reaction is important not only for understanding the complicated biological processes such as photosynthesis and respiration but also for the design and studies of molecular electronics. This paper presents the synthesis and spectral and electrochemical studies of a new dyad I containing an electroactive unit (tetrathiafulvalene, TTF) and a photochromic unit (spiropyran, SP). Spectral studies showed that the redox states of the TTF unit of dyad 1 in the presence of ferric ions were dependent on the photoswitching process of the spiropyran unit upon UV light irradiation. Electrochemical investigations indicated that the oxidation potential of ferrous ion was largely reduced after coordination with MC (the open form of SP). As a result, the electron-transfer reaction from MC.Fe2+ to TTF+., which act as electron donor and acceptor, respectively, is thermodynamically favorable. Therefore, the electron-transfer reaction between the TTF unit and ferric ion can be photocontrolled in the presence of the SP unit. The present result shows the possibility to design new electron donor-acceptor supramolecules containing spiropyran units to photoregulate the electron-transfer reaction.