Enhancement of photoinduced electron transfer in self-assembled polymer films using mixed metal-terpyridine complexes

The design and synthesis of photoactive polymeric systems are important in regard to solar energy harvesting and utilization. In this report, we synthesized photoactive polymeric thin films via iterative self-assembly using reversible metal-terpyridine (M-tpy) interactions. The growth rate of thin film deposition depends on the metal ion of choice. Ru(II)(tpy)₂-incorporated poly(vinyl alcohol) also functionalized with tpy was subjected to iterative self-assembly on glass substrates. UV-vis spectroscopy and surface profilometer investigations show that the polymeric thin films with Cu(II) grew 2 times faster than those with Zn(II), attributed to the strong M-tpy interaction. Interestingly, photocurrent generated in the polymeric thin films with Zn(II) was much higher than those of other films. The apparent diffusion rate constant (k_app) was measured for the electron hopping process via potential-step chronoamperometry. As a result, the k_app for the polymeric thin films with Zn(II) was almost 2 times larger than those with other metal ions. The choice of metal ions appears crucial in the mixed metal-tpy complex systems not only for the film growth but also for the efficient photoinduced electron transfer.