have developed a unique series of photochromic paracyclophane (PC)-bridged and naphthalene-bridged imidazole dimers, with a PC or naphthyl moiety that coupled two triarylimidazole groups, which showed fast photochromism both in solution and solid states, leading to a myriad of actual and anticipated applications in areas such as optical data processing and light modulators. On the basis of earlier studies, Abe et al. Such photochromic materials have found applications in waveguides, optical data storage, and ophthalmic plastic lenses. The mechanism of chromism in solution is the interconversion of dimer and colored triphenylimidazyl radicals. In the early 1960s, Hayashi and Maeda first demonstrated that hexaphenylbiimidazole (dimer of 2,4,5-triphenylimidazyl radical) exhibited unique photo-, thermo-, and piezochromic properties.
Since then, many triarylimidazole derivatives have been synthesized and studied with regard to their ultraviolet, fluorescent, and chemiluminescent properties, in which their luminescent properties have been utilized to develop assays for the determination of trace amounts of inorganic and organic compounds in biological materials. The mechanism is thought to involve attack by oxygen to form a hydroperoxide, followed by conversion to a dioxetane intermediate, and cleavage of the peroxide bond resulting in light emission. The chemiluminescence of 2,4,5-triphenylimidazole was first reported by Radziszewski in 1877, who found that this compound emitted a yellow light when it reacted with oxygen in the presence of strong base.
The chemical flexibility of this class of compounds allows the preparation of a large variety of related structures and, consequently, the tailoring of the chemiluminescent, photochromic, redox, temperature-dependent UV–Vis absorbance, and biological properties. Triarylimidazoles and their derivatives have attracted considerable attention in recent years because of their unique properties and applications in diverse fields. In addition, the poly(DVT) showed the characteristic of temperature-dependent absorbance in the near-ultraviolet (UV) spectral region, of which a linear dependence of UV absorbance on temperature was confirmed for the polymer both in solution and in solid states. The molecular weight of the resulting polymer increased linearly with monomer conversion, while a low polydispersity was maintained throughout. Kinetic studies demonstrated that the polymerization process of DVT followed pseudo-first-order kinetics with respect to the monomer concentrations. Subsequently, poly(DVT) was prepared by the reversible addition-fragmentation chain transfer (RAFT) polymerization of DVT in dimethyl sulfoxide using S-dodecyl- S′-( α, α′-dimethyl- α″-acetic acid)-trithiocarbonate (DMP) as the RAFT agent and 2,2 ′-azobis(isobutyronitrile) (AIBN) as the initiator. A novel monomer consisting of a 4-vinyl-1,2,3-triazole unit directly linked to a triphenylimidazole unit, 1-(4-(4,5-diphenyl-1 H-imidazol-2-yl)phenyl)-4-vinyl-1 H-1,2,3-triazole (DVT), has been successfully synthesized using click chemistry followed by elimination reaction.