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 (<i>k</i>_app) was measured for the electron hopping process via potential-step chronoamperometry. As a result, the <i>k</i>_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

<i>N</i>‑Heterocyclic Carbene-Based Conducting Polymer–Gold Nanoparticle Hybrids and Their Catalytic Application

Hybrid nanocomposites of <i>N</i>-heterocyclic carbene (NHC)-functionalized conducting polymers (CPs) with gold nanoparticles (AuNPs) were prepared by concurrent disproportionation and oxidative coupling. The formation of hybrid nanocomposites, NHC-CP/AuNPs, in the simultaneous process was confirmed by transmission electron microscopy, powder X-ray diffraction, cyclic voltammetry, and ¹³C solid-state NMR analyses. More importantly, the NHC group played a pivotal role in the dispersion of AuNPs. Further, NHC-CP/AuNPs exhibited good catalytic activity for the reduction of 4-nitrophenol

Torsionally Responsive Tropone-Fused Conjugated Polymers

Torsionally responsive molecular systems can change their electronic properties according to the dihedral angles and can be utilized as sensory materials. We have designed and synthesized novel tropone-fused conjugated polymers <b>PBTr</b>, <b>PBTr-T</b>, and <b>PBTr-Tz</b> that showed interesting dihedral-angle-dependent variations in UV–vis absorptions. Tropone-fused thiophene derivatives were prepared from one-step condensation of thiophene-3,4-dialdehyde and aliphatic ketones via a modular, facile, and high-yielding method. Subsequent halogenation and Stille cross-coupling polymerization with a bis­(stannyl)­benzo­dithiophene resulted in a tropone-fused conjugated polymer <b>PBTr</b>. We were also able to prepare thiophene- and thiazole-bridged polymers, <b>PBTr-T</b> and <b>PBTr-Tz</b>, respectively, using similar synthetic methods. Electronic absorptions of the newly synthesized <b>PBTrs</b> were measured in solutions and in films states. Substantial red-shifts occurred in the case of thiophene-bridged <b>PBTr-T</b>, whereas almost no shift was observed for thiazole-bridged <b>PBTr-Tz</b>. We attributed this to the substantial change in the torsional angle between the tropone-fused thiophene moiety and thiophene, which was further supported by density functional theory (DFT) calculations. Similar spectral changes of UV–vis absorptions were observed when a poor solvent (methanol) was introduced to a chloroform solution of <b>PBTr-T</b>. Reverse torsional angle variations were realized with initially planar <b>PBTr-Tz</b> by introducing steric hindrance through protonation on the thiazole rings. We believe that torsionally responsive tropone-fused conjugated polymers are promising as novel platforms for sensory applications