A Naphthalenediimide-Based Metal–Organic Framework and Thin Film Exhibiting Photochromic and Electrochromic Properties

Abstract

A multifunctional metal-organic framework, NBU-3, has been explored as a 2D three-connected network based on a naphthalenediimide-based ligand. The NBU-3 crystals display photochromic properties, and NBU-3 thin films on FTO substrates exhibit electrochromic properties. NBU-3 is the first example of MOF materials containing both photochromic and electrochromic properties, which can be desirable for thin film devices.

Anion-Controlled Architecture and Photochromism of Naphthalene Diimide-Based Coordination Polymers

“…After irradiation, the photochromic products of 1 and 3 show new characteristic bands around 520 nm and 645 nm. These characteristic spectral bands are similar to that observed for NDI radical, suggesting that the color changes of 1 and 3 may arise from the photo-induced generation of radicals in DPNDI molecules [29,30,41].…”

“…To confirm the generation of the radicals, the electron spin resonance (ESR) spectra of 1-3 were measured before and after irradiation ( Figure 5). Compounds 1 and 3 exhibit no ESR signal before irradiation, but strong ESR signals at 2.0026 and 2.0019 for compounds 1 and 3 are observed after irradiation, which are similar to those found in NDI-based coordination polymers [29,30,32,40]. This indicates that DPNDI ligand is indeed reduced to generate DPNDI − free radicals after two compounds are irradiated.…”

“…645 nm. These characteristic spectral bands are similar to that observed for NDI radical, suggesting that the color changes of 1 and 3 may arise from the photo-induced generation of radicals in DPNDI molecules [29,30,41]. To confirm the generation of the radicals, the electron spin resonance (ESR) spectra of 1-3 were measured before and after irradiation ( Figure 5).…”

“…Naphthalene diimide (NDI) possess π-conjugated planes, high redox activity, and strong π-acidity, which are excellent candidates of organic ligands for the construction of photochromic coordination polymers due to the controllability of the substituent groups on the diimide nitrogens and the reversibility of the electron transfer [25][26][27]. Many groups have been used as NDI derivatives as catalysts through anion-π catalysis, and as organic ligands to construct coordination polymers [26,[28][29][30][31][32][33]. In order to investigate the detailed effect of different anions on the structures and photochromic properties, and as coordination polymers constructed by the neutral ligands have close relationship with the counter anions [34], we chose a neutral ligand N,N-di(4-pyridyl)-1,4,5,8-naphthalene diimide (DPNDI) as an organic ligand.…”

Excitonically Coupled States in Crystalline Coordination Networks

“…[6] The latter is of high interestw ith regardt ot he incorporation of optically active guests in the chromophorich ost lattice.F urthermore, a number of approaches have been developed to grow well-defined thin films on optically transparent, conductive substrates, an importantp rerequisite for optoelectronica pplications. [9] In recent years, af ew reports on NDI-based MOFs already demonstratedt heir potential as electro/photochromic materials, specifically exploiting the redox-active features. There have been seminalw orks on the cooperative properties in self-assembled organic structures of these particularly interesting dyes for photoinduced energy and electront ransfers,a nd in organic electronics.…”