Photochromism of a Naphthalene-Bridged Imidazole Dimer Constrained to the “Anti” Conformation

Abstract

Anti-1,8-bisTPI-naphthalene in which two imidazole rings are constrained to an anti-conformation leading to the first-formed 1,4'-isomer of the bridged imidazole dimer has been synthesized. The color of the radicals is different from that of the previously reported bridged-imidazolyl radicals because the intramolecular interaction between the radicals becomes weak due to the anti-conformation. This molecular design would be a profitable strategy to control the color of the radicals of the bridged imidazole dimer for application in ophthalmic lenses.

Nanosecond photochromic molecular switching of a biphenyl-bridged imidazole dimer revealed by wide range transient absorption spectroscopy

“…The ns transient absorption experiment shows that the colored species of bisDMDPI-BP has a weak and broad background at 4700 nm, where the absorption band due to the radical-radical interaction was observed in the previously studied bridged imidazole dimers. 20,21,26 Our previous work demonstrated that the absorption band due to the radical-radical interaction decreases, becomes broad, and shifts to longer wavelengths with decreasing radical-radical interactions. 21 Since bisDMDPI-BP has little transient absorption at 4700 nm as compared to that of reported bridged imidazole dimers, 20,21 it indicates that the radical-radical interaction of the colored species of bisDMDPI-BP is weak because of the large dihedral angle of the bridging biphenyl.…”

“…BisDMDPI-BP is the 2,2 0 -isomer, in which the C-C bond is formed between the 2-position of an imidazole ring and the 2 0 -position of the other imidazole ring, 24 while almost all reported bridged imidazole dimers are the 1,2 0 -or the 1,4 0 -isomers, in which a C-N bond is formed between the two imidazole rings. 18,20,21,26 While there are several reports on the 2,2 0 -isomers of hexaarylbiimidazole (HABI) derivatives, 27,28 they are sensitive to temperature and pressure, and easily converted to the photochromic 1,2 0 -isomers via the imidazolyl radical formed by thermochromism or piezochromism. Therefore, the stable 2,2 0 -isomer of bisDMDPI-BP offers a unique opportunity to reveal the photochromism of a representative 2,2 0 -isomer.…”

Pentaarylbiimidazole, PABI: an easily synthesized fast photochromic molecule with superior durability

“…[1][2][3][4][5] Inspired by the photochromism of HABI, we have developed the bridged imidazole dimers to accelerate the thermal back reaction. [6][7][8][9][10][11][12][13][14][15][16][17] The bridged imidazole dimers show instantaneous coloration upon UV light irradiation and rapid fading in the dark. The half-lives of the colored species of the naphthalene-bridged imidazole dimer and the [2.2]paracyclophane-bridged imidazole dimer are 830 and 33 ms at 25 1C in benzene, respectively.…”

“…The half-lives of the colored species of the naphthalene-bridged imidazole dimer and the [2.2]paracyclophane-bridged imidazole dimer are 830 and 33 ms at 25 1C in benzene, respectively. 8,16,17 Such fast photochromic molecules could serve as excellent probes and triggers to reveal and control phenomena which occur in the time scales within a few tens of ms.The fast photochromic molecules have potential for applications such as a holographic display and fluorescence switching. [18][19][20] We have broadened the photochromic properties such as the halflife and the color of the colored species by rational design of the bridged imidazole dimers.…”

Synthesis and Fluorescent Properties of Novel Mono- and Di-Substituted 1,8-Naphthalimide Derivatives at the <em>C</em>-4 Position

“…The naphthalene moiety is an ideal fluorophore, and its derivatives have been widely applied as fluorescent dyes, metal sensors, optical sensors and organic light-emitting materials because of their high absorption coefficients, high fluorescence and quantum yields, large Stokes shifts, good photostability and easy modification [6][7][8][9]. In recent years, naphthalimide-based probes have been developed to detect H + , Hg 2+ , Zn 2+ , Cu 2+ , Ag + , Cd 2+ , Pd 2+ , Cr 3+ , Al 3+ , Fe 3+ , and F -via chromogenic and fluorogenic analyses [10][11][12][13][14][15][16].…”