Light‐Induced Electron Transfer Toward On/Off Room Temperature Phosphorescence in Two Photochromic Coordination Polymers

Abstract

Photoswitchable room temperature phosphorescence (RTP) materials are of great interest due to their potential applications in optical devices and switches. Herein, two Zn‐based coordination polymers (CPs) (H3‐TPB)·[Zn6(H‐HEDP)(HEDP)3(H2O)2]·5H2O (complex 1; HEDP = hydroxyethylidene diphosphonate; TPB = 1,3,5‐tris(4‐pyridyl)benzene) and (H‐TPB)·[Zn3(H‐HEDP)(HEDP)(H2O)]·2H2O (complex 2) with distinguishable photochromism and tunable RTP are synthesized involving photoactive TPB molecules with different packing modes. Complex 1 exhibits bidirectionally on/off RTP regulation via on‐switch with excitation of 250−330 nm light and off‐switch with 350−380 nm, and the “turn‐on” behavior can be attributed to the advance of Förster resonance energy transfer‐assisted intersystem crossing (ISC) process while “turn‐off” process due to the transformation from H3‐TPB cations to H3‐TPB· radicals. Complex 2 exhibits photoswitchable RTP accompanied with reversible photochromism by leveraging the self‐absorption and RTP emission. Two demos based on the above compounds are further applied to demonstrate the application in information recording and encryption fields. This work supplies a strategy toward the design of switchable RTP systems using electron transfer photochromism, shedding light on broadening the frontiers of photoresponsive materials.

Photochromic Ln-Phosphonates Assembled by an Imidazole Derivative: Construction, Crystal Structures, and Light-Enhanced Proton Conductivity

“…The measured proton conductivity of 1 at 70 °C is 1.71 × 10 –4 S·cm –1 (Table S10), which is about 3 times that with an initial low-temperature state, indicating the existence of an efficient proton transfer pathway in compound 1 . The conductivity values of compound 1 are similar to those of previously reported metal phosphonate compounds. , To further investigate the conduction mechanism of solid 1 , the activation energy ( E a ) was obtained according to the Arrhenius equation σ ( T ) = σ 0 exp­( E a / kT ), in which k (J·K –1 ) represents the Boltzmann constant and T (K) is the temperature. , The corresponding value with 0.2182 eV (Figure b) accords with the typical Grotthuss mechanism ( E a < 0.4 eV), implying proton hopping in the H-bonding network.…”

“…The conductivity values of compound 1 are similar to those of previously reported metal phosphonate compounds. 46,47 To further investigate the conduction mechanism of solid 1, the activation energy (E a ) was obtained according to the Arrhenius equation σ(T) = σ 0 exp(E a /kT), in which k (J•K −1 ) represents the Boltzmann constant and T (K) is the temperature. 14,53 The corresponding value with 0.2182 eV (Figure 4b) accords with the typical Grotthuss mechanism (E a < 0.4 eV), implying proton hopping in the H-bonding network.…”

“…Hybrid photochromic CPs with sensitive light response provide a strategy for manipulating the proton conduction behavior and are expected to be strong candidates for the construction of new materials. − In the process of light stimulation, a charge separation state with an ultralong lifetime could be generated, which in turn might cause changes in conductivity. − Therefore, a simple and feasible regulation of the proton conductive properties can be achieved by hybrid complexes with photochromic properties. In this regard, metal phosphoric/phosphonate CPs can be widely used in photochromism and proton conduction, benefitting from the diverse coordination modes (Scheme ) and excellent stability. − The O centers in phosphoric/phosphonate CPs could serve as electron donors to construct photochromic materials. Moreover, the electron-rich O atoms can further form hydrogen-bond networks with other components, providing abundant transport paths toward proton conduction behaviors .…”

Regulating the crystal and electronic structures and optical properties of hybrid bromoplumbates with alkylated N, S- or P-containing aromatic cations

“…Photoluminescence (PL) properties of hybrid materials have attracted increasing attentions because of their application potential in solid state lighting, anti-counterfeiting, etc. 12,28–32 The PL emissions of hybrid materials are always required to be regulated to cater for different requirements. 33–39 Several approaches are effective to tune the PL emissions, which includes altering the emission center, 40,41 functionalization, 42,43 variation of excitation light 44,45 and lattice defect engineering.…”

Direct White-Light Emitting From a Single Metal–Organic Framework with Dual Phosphorescence Peaks

“…It has been suggested that the rigid matrix and strong coordination interactions between metal ions/clusters and photoactive ligands can tightly fix the molecules, confining their motions/vibrations and promoting the generation of triplet excitons for efficient room temperature phosphorescence (RTP) emission . More importantly, their topological diversity, abundant host–guest systems, and hybrids with various materials (such as quantum dots, polymers, metal nanoparticles) endow MOFs as a highly versatile and tunable platform for exploring of multifunctional RTP materials . Despite promising results recently achieved on RTP materials, − the design principle and construction method for the guidance of MOFs based RTP still remain unclear.…”