Photochromism of a 3D Cd^II Complex with Two Captured Ligand Isomers Generated In Situ from the Same Precursor

Abstract

Photochromic compounds have gained intense interest owing to their novel photochemical and photophysical reactions as well as their various potential applications such as in sunglasses and optical memories.[1] An appreciable number of photochromic families have been reported to date; [2] however, those based on an electron-transfer (redox) chemical process, especially for metal-organic compounds, are rare.[3] We present herein a hydrothermally synthesized 3D complex [Cd 2 (ic)(mc)(4,4'-bipy) 3 ] n ·4n H 2 O (1Y; ic= itaconate, mc = mesaconate) which exhibits reversible radicalbased redox photochromic behavior. This compound also merits attention for its unusual five-connected Archimedeantype topological structure and unexpected "capture" of isomeric ic and mc ligands that are generated in situ from trans-propene-1,2,3-tricarboxylic acid (H 3 L, Scheme 1).Yellow prismatic crystals of 1Y accompanied by a few colorless block crystals of [Cd 3 L 2 (H 2 O) 6 ] n (2; Figure S1 in the Supporting Information) were obtained by the hydrothermal reaction of CdCO 3 , 4,4'-bipy, H 3 L, and deionized water in a molar ratio of 1:1:1:1111 at 120 8C for 12 h. Powder X-ray diffraction (PXRD) verified the purity of a mechanically separated sample of 1Y ( Figure S2 in the Supporting Information). Thermal analysis and PXRD data show that compound 1Y still keeps its metal-organic framework at 200 8C after the elimination of lattice water molecules ( Figure S2 and S3 in the Supporting Information).A single-crystal X-ray diffraction study of 1Y revealed a 3D structure based on a network of seven-coordinated Cd II centers linked by three kinds of bridging ligands. As shown in Figure 1, the central Cd1 atom is located in a pentagonalbipyramidal coordination environment with N41 and N42 atoms of crystallographically independent 4,4'-bipy ligands acting as the two pyramidal apexes. An important feature of 1Y is the simultaneous "capture" of isomeric ic and mc ligands that originate from the in situ pyrolysis of H 3 L. [4]

Differentiable Detection of Volatile Amines with a Viologen-Derived Metal–Organic Material

“…32 In consistent with the XPS results, a closer inspection into the crystal structure gives evidence for the electron transfer from nitrate, carboxylate, and chloride to pyridinium. It has been recognized that weak intermolecular interactions between viologen and electron donors (D), such as N V •••D, 33,34 40,41 are necessary for PET. As shown in Figure S4, each nitrate in 1 forms five hydrogen bonds with C−H groups from viologen groups (H•••O distances, 2.28−2.62 Å).…”

Photochromic and Nonphotochromic Luminescent Supramolecular Isomers Based on Carboxylate-Functionalized Bipyridinium Ligand: (4,4)-Net versus Interpenetrated (6,3)-Net

“…Photochromic materials not only exhibit color change but also are often accompanied by the variation of some physicochemical behaviors in response to UV or vis photoirradiation. − These features make them suitable for many technological applications in fields of smart windows, rewritable copy papers, information storage, sensors, high density optical memories, solar energy conversion, the mimicry of natural photosynthetic reaction processes, display, protection, decoration, photography, photomechanics and photoswitches, and so on. − Typical examples of photochromic molecules include azobenzene, spiropyran, Schiff base, furylfulgide, and diarylethene. , Viologens, disubstituted bipyridinium derivatives, are usually used as electron acceptors to construct redox photochromic materials and charge transfer molecular systems. − In these systems, the luminescence behavior of bipyridinium derivative can be adjusted by molecular modification, but the incorporation of fluorophores on viologens is little reported . While due to insufficient stability of purely organic viologens, , increasing attention has been devoted for developing the photochromic inorganic–organic hybrids, metal complexes and metal–organic frameworks based on viologens, which have numerous potential applications in photochemical and optoelectronic material field. , It is important to note that some metal complexes based on viologens do not show photochromism, while their isostructural compounds do.…”

Visible colorimetric dosimetry of UV and ionizing radiations by a dual-module photochromic nanocluster

“…The photochromism can be explained by a variety of mechanisms, including phase transitions 47 , generation of radical species 48 , electron-transfer (redox) chemical process 49 , tautomeric shift 50 , photoinduced charge transfer, etc 51 – 54 . To gain insight into the photocoloration mechanism of Th-SINAP-100, the PXRD patterns and FTIR spectra before and after irradiation were collected, showing no obvious variations of structure and chemical constituent (Fig.…”