Azobenzene is a widely recognized tool for achieving artificial spatiotemporal control of enzyme activity through the use of light. Photocontrol reversibility is typically based on photostationary sta...

Chiral, photoswitchable dopants composed of triptycene and azobenzene exhibit exceptionally large helical twisting powers that change dramatically upon isomerization when incorporated into the liquid...

Christian Hering-Junghans and Robert Kretschmer, Germany, discuss the ambident reactivity of the bis(gallylene), demonstrated by the reactions with azobenzene and the triphosphirane (PMes)₃

The combination of a visible-light switchable azobenzene A with aliphatic diamines X of variable chain lengths gives access to various macrocyclic isomers. While diamines with even numbers of methyle...

Doping cholesteric liquid crystals (CLCs) with photoresponsive chiral molecules is an effective strategy for devising responsive soft materials, as it allows for the phototuning of the noncovalent interactions in the CLCs, and hence, their helical pitch and optical properties. Here we describe the use of tribenzotriquinacene-based (TBTQ) hydrazone and azobenzene chiral dopants in the modulation of the helical pitch of the LC host, 5CB. The unique C3-symmetry of the TBTQ scaffold enhances the noncovalent interactions with the host and thus the chiral information transfer, resulting in helical twisting power (β) values as high as 147 μm–1. Notably, the TBTQ hydrazone exhibits an unusual deviation from trends observed so far in previous studies, resulting in larger β values for the Z isomer rather than the E one. Moreover, the overall β values for the hydrazone-based dopants are unexpectedly higher than those of the azobenzene dopants. These results indicate that the host/guest interactions are better when the photoswitchable chiral dopant is more rigid, as is the case with the H-bonded Z state of the hydrazone. The large β values and excellent miscibility of the hydrazone-based dopants in 5CB allowed us to design films that reflect visible structural color. The properties of the azobenzene-based dopants precluded their use in such applications. By codoping 5CB with hydrazone and azobenzene derivatives of opposite chirality, we demonstrated reversible handedness inversion upon photoswitching, providing a versatile soft material platform for reconfigurable photonic materials and colorimetric display technologies.

AbstractThe rich chemistry of molecular framework materials enables precise control of physico-chemical properties through structural design of framework t

Azobenzene is one of the best-known molecules that can be switched between two forms by light. However, the question of how the molecule moves in the first few picoseconds (trillionths of a second) after it absorbs light has remained unresolved for nearly 50 years.

Subtle electronic modifications of tailored amphiphilic azobenzene derivatives exhibit distinct cis-state half-lives despite similar activation barriers. The structural functionalization enables the ...

Beilstein Journal of Organic Chemistry

Unified nonadiabatic switching: thermal Z→E isomerization of para-substituted azobenzenes proceeds through a single nonadiabatic rotational pathway. The iconic bell-shaped Hammett plot is a σp artifa...

A new class of photoswitchable NHC ligands, named azImBA, has been developed by integrating azobenzene into a previously unreported imidazobenzoxazol-1-ylidene framework. These rigid photochromic carb...

TRXL experiments were conducted at the XSS beamline of the Pohang Accelerator Laboratory X-ray free-electron laser (PAL-XFEL) facility. Key experimental parameters are summarized in Supplementary Table 1. A laser-pump and X-ray-probe scheme was used to initiate the photoisomerization reaction of azobenzene. Optical laser pulses at a wavelength of 400 nm, generated as the second harmonic of a femtosecond titanium:sapphire laser system, were used as the pump pulses. These pump pulses with an energy of 8.5 µJ were focused onto the sample with a spot size of 55 × 66 µm2 (full-width at half-maximum (FWHM), horizontal × vertical), corresponding to a laser fluence of 1.5 mJ mm−2. The repetition rate of the optical laser was 30 Hz. The X-ray beam, used as the probe, was focused onto the sample with a spot size of 20 µm × 20 µm (FWHM), delivering approximately 1 × 1012 photons per pulse at a repetition rate of 60 Hz, with a centre energy of 15.01 keV. By utilizing the X-ray with twice the repetition rate of the laser, we alternately measured laser-on and laser-off scattering images. The optical laser and X-ray beams were overlapped at a 10° crossing angle at the sample position. The temporal...