Bis(2-thienyl)diketopyrrolopyrrole with two Zn(II)-cyclens (ZnCyc-DPP) was designed and synthesized to evaluate the selective binding of Zn(II)-cyclen with thymine base in single-strand DNA as a tool for the construction of a highly ordered multichromophore system on DNAs. Through UV/Vis titrations, gel filtration chromatography, and circular dichroism spectroscopy, ZnCyc-DPP formed J-type DPP aggregates with oligo-dTn DNAs. The DPP aggregates absorbed on a gold electrode exhibited good photocurrent responses. The present results show that binding Zn(II)-cyclen-chromophore conjugates and thymine bases together is a powerful tool for preparing DNA-templated multichromophoric systems with specific functions.

Multichromophore arrays of bis(2-thienyl)diketopyrrolopyrrole (DPP) and naphthalenediimide (NDI) with two Zn(II) -cyclens were constructed using thymidine DNA as a scaffold through the binding of the Zn(II) -cyclens with thymine bases. We demonstrate photocurrent generation in a donor-acceptor heterojunction configuration consisting of the DPP (donor) and NDI (acceptor) arrays co-immobilized on an Au electrode. The co-immobilized electrode exhibited good photocurrent responses because of the efficient charge separation between the DPP and NDI arrays. In contrast, an immobilized electrode consisting of randomly assembled DPP-NDI arrays generated no photocurrent response because DPP formed ground-state charge-transfer complexes with NDI in the randomly assembled arrays. Therefore, our approach to generate donor-acceptor heterojunctions based on DNA-multichromophore arrays is a useful method to efficiently generate photocurrent.

Bis(2-thienyl)-diketopyrrolopyrrole having two Zn IIcylcens (DPPCy) was synthesized. DPP-aggregates were constructed by self-organization of DPPCy and dT n -DNAs. In the presence of Lascorbic acid as an electron sacrifice reagent, the DPP aggregates immobilized on a gold electrode exhibit good anodic photocurrent responses as well as cathodic photocurrent responses in the presence of methyl viologen. The anodic photocurrent responses depend on the DNA lengths because of the formation of uniform DPPaggregates corresponding to the DNA lengths. The present results show that photocurrent responses of the DPP-aggregates can be controlled by DNA lengths and electron sacrifice reagents.