A Novel Near-IR Effective Pyrene-Based Donor-Acceptor Electrochrome

In this work, a novel donor-acceptor electrochromic monomer (3HTP), containing a pyrene subunit connected to a quinoxaline acceptor bridge, is synthesized. The corresponding polymer, poly-(3HTP), is directly deposited onto an indium tin oxide (ITO)/glass surface via an electrochemical process. Atomic force microscopy (AFM) images reveal that the electrochemically deposited poly-(3HTP) has a smooth surface due to self-assembly of the planar pyrene subunit. Electrochemical and optical properties are investigated via cyclic voltammetry and UV-vis absorption measurements. The polymer film shows a multielectrochromic feature at both anodic and cathodic regimes. Poly-(3HTP) exhibits a strong near-infrared (NIR) absorption at the oxidized state with an optical contrast of 88% (at 1800 nm), a very fast response time of 0.5 s and fast switching times, and long-term stability. Density functional theory calculations reveal that the molecule has a high planarity, and the NIR absorption arises from a strong intramolecular charge transfer from the polymer backbone to the planar pyrene subunit.