Interpenetration-Enabled Photochromism and Fluorescence Photomodulation in a Metal–Organic Framework with the Thiazolothiazole Extended Viologen Fluorophore

Abstract

A novel metal−organic framework (MOF), formulated as [Cd 2 (TTVTC)Cl 2 (H 2 O) 3 ]•2H 2 O (1), was synthesized from a tetracarboxylate ligand ([TTVTC] 2− ) functionalized with the thiazolothiazole extended viologen (TTV 2+ ) fluorophore. The MOF features three-dimensional (10,3)-d frameworks with 6-fold interpenetration. The MOF exhibits reversible photochromism, due to photoinduced electron transfer from carboxylate to TTV 2+ . The photoactivity benefits from the electron donor−acceptor contacts enabled by mutual interpenetration of the frameworks. This is the first demonstration of photochromism in TTV 2+ derivatives. In addition, the fluorescence arising from the TTV 2+ fluorophore can be reversibly modulated during the photochromic process. The work demonstrates the great potential of extended viologen based ligands in the construction of MOFs with dual photomodulable optical properties, which could find future applications in photoelectronics.

Metal‐Organic Frameworks with Novel Catenane‐like Interlocking: Metal‐Determined Photoresponse and Uranyl Sensing

“…The pristine sample is ESR silent. However, Xe‐light illumination leads to a sharp signal with g =2.0034 (Figure 2b), which is very close to that expected for free electron [4e,7a,11a,15] . The results clearly indicate photogeneration of free radicals.…”

A Photo‐Responsive Charge‐Assisted Hydrogen‐Bonded Organic Network with Ultra‐Stable Viologen Radicals

“…And it is believed that the distance from donor atom to acceptor atom above 4 Å is not favorable for photoinduced ET. [ 34,40‐41 ] A photochromic phenomenon was clearly observed by naked eyes, there must be efficient pathways between electron donor and acceptor as for photoinduced ET. After carefully analyzing the structure of 1 , there are several possible pathways for photoinduced ET.…”

A Series of Polyoxometalate‐Viologen Photochromic Materials for UV Probing, Amine Detecting and Inkless and Erasable Printing

“…These two characteristic absorption peaks belong to viologen radicals. [27] This result indicates that the color change of compound 1 is induced by the photoinduced generation of the viologen radical in the bmypd ligand. Furthermore, the intensity of the absorption peaks increase as the illumination time goes on (Figure S7).…”

“…It can be seen from the solid-state UV spectra that for M-1, M-2 and M-3, after irradiated by a Xe lamp, there are new absorption bands appeared at 400-800 nm attributed to the characteristic peaks of viologen radicals. [27][28] Moreover, the intensity of the absorption peaks increased with the irradiation time increasing (Figure S19). The above characteristics show that the devices M-1, M-2 and M-3 have great potential in the field of ultraviolet detection.…”