Photoresponsive Electrodes Modified with DNA Duplexes Possessing a Porphyrin Dimer

We describe here the formation of a porphyrin (Por) dimer using a DNA duplex as a scaffold and photocurrent generation from electrodes modified with a monolayer of Por-DNA conjugates. The solid-phase click reaction between an azide-porphyrin and oligonucleotide labeled with an ethynyl group on CPG supports was utilized for the conjugation of the Por to the DNA. UV/vis absorption and circular dichroism (CD) spectral studies revealed that the Por dimer can be formed via DNA hybridization and the through-space electronic interactions characterized from the exciton-coupled absorption and the bisignate CD can occur between the two Por molecules. Photoelectrochemical experiments were performed for the electrodes functionalized with a monolayer composed of the Por-DNA conjugates. We found that the Por dimer on the electrode, which was designed to resemble the special pair in natural photosynthesis, shows an efficient photocurrent generation in the presence of electron acceptor reagents compared to the Por monomer. Our findings strongly support the idea that the DNA structures could be useful to construct the Por arrays, which is essential for the design of photo- and bio-electronic devices.