A visible-light activatable photoacid has been studied, which upon irradiation, changes from a weak acid, with a pK(a) of 7.8, to a strong acid, which achieves nearly complete proton dissociation. This process is reversible and the half-life of the proton-dissociation state is ~70s. The long lifetime of the proton-dissociation state is due to a sequential intramolecular photochromic reaction. Using this photoacid, a pH change of 2.2 units has been achieved. In addition, we demonstrated that the photoinduced proton concentration can catalyze an esterification reaction, and greatly alter the volume of a pH-sensitive polymer. This work shows that acid-catalyzed and pH-sensitive processes can be photochemically controlled by using this type of photoacid.

Three Fe(II) bis(terpyridine)-based complexes with thiophene (Fe(L1)), bithiophene (Fe(L2)), and 3,4-ethylenedioxythiophene (Fe(L3)) side chains were designed and synthesized for the purpose of providing two terminal active sites for electrochemical polymerization. The corresponding metallopolymers (poly-Fe(Ln), n = 2 or 3) were synthesized on indium tin oxide (ITO)-coated glass substrates via oxidative electropolymerization of the thiophene-substituted monomers and characterized using electrochemistry, X-ray photoelectron spectroscopy, UV-vis spectroscopy, and atomic force microscopy. The film poly-Fe(L2) was further studied for electrochromic (EC) color-switching properties and fabricated into a solid-state EC device. Poly-Fe(L2) films exhibit an intense MLCT absorption band at 596 nm (ε = 4.7 × 10 M cm) in the UV-vis spectra without any applied voltage. Upon application of low potentials (between 1.1 and 0.4 V vs Fc/Fc), the obtained electropolymerized film exhibited great contrast with a change of transmittance percentage (ΔT%) of 40% and a high coloration efficiency of 3823 cm C with a switching time of 1 s. The film demonstrates commonplace stability and reversibility with a 10% loss in peak current intensity after 200 cyclic voltammetry cycles and almost no loss in change of transmittance (ΔT%) after 900 potential switches between 1.1 and 0.4 V (vs Fc/Fc) with a time interval of 0.75 s. The electropolymerization of Fe(L2) provides convenient and controllable film fabrication. Electrochromic behavior was also achieved in a solid-state device composed of a poly-Fe(L2) film and a polymer-supported electrolyte sandwiched between two ITO-coated glass electrodes.

A novel negative photochromic compound has been designed and synthesized. The structure of the compound consists of a tricyanofuran (TCF) moiety and a quinoline moiety, bridged by a double bond. Upon irradiation with visible light, the neutral thermostable form of the compound quickly transforms to a cyclic zwitterionic form with over 90% conversion efficiency.

Four new disubstituted and monosubstituted nitro- and amino- bis(pyrazol-1-yl)pyridine (bppy) ligands, substituted at the pyrazole 4-position (1, 2, 5, 6) have been synthesized, along with two luminescent Eu(iii) tris-β-diketonate derivatives of the amino substituted ligands (7, 8). The compounds have been studied using UV-Vis absorbance spectroscopy and cyclic voltammetry which has allowed for characterization of the electronic environments of these ligands. The calculated HOMO-LUMO gap values (1: 3.54 eV; 2: 3.53 eV; 5: 3.01 eV; 6: 3.66 eV) differ from that of bppy (3.86 eV) and the range is indicative that tuning of the ligand electronic environment is possible. Additionally, fluorescence spectroscopy studies were employed to determine ligand T energy levels of the amine-bearing ligands 2 and 6, yielding values of T of 25 381 cm and 26 201 cm, respectively. These ligands were employed in the synthesis of Eu(iii) complexes 7 and 8, for which the absolute and intrinsic quantum yields, lifetimes and ligand sensitization efficiencies were determined.

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