Viologen-Based Photochromic Coordination Polymers for Inkless and Erasable Prints.

Four coordination polymers, namely, [Zn(HL1)(L2)0.5]·H2O (1), [Cd(HL1)(L2)0.5]·H2O (2), [Zn(L1)(L3)0.5]·H2O (3), and [Cd(L1)(L3)0.5] (4) (H3L1 = (3,5-dicarboxyl-phenyl)-(4-(2'-carboxyl-phenyl)-benzyl)ether, H2L2Cl2 = 1,1'-bis(4-carboxy-benzyl)-4,4'-bipyridinium dichloride, and L3Cl2 = 1,1'-dimethyl-4,4'-bipyridylium dichloride), have been synthesized hydrothermally. The structures of compounds 1-4 have been determined by single-crystal X-ray diffraction analyses, and further characterized by elemental analyses, infrared (IR) spectra, powder X-ray diffraction (PXRD) analyses, and thermogravimetric analyses. Compounds 1 and 2 display three-dimensional 2-fold interpenetrating frameworks, whereas compounds 3 and 4 exhibit two-dimensional layer structures. These compounds display photochromic behaviors from pale yellow to green under UV light, visible light, or sunlight. The photochromic mechanisms of these compounds have been studied by IR spectra, PXRD analyses, UV-vis absorption spectra, electron paramagnetic resonance spectra, density functional theory calculations, and X-ray photoelectron spectroscopy. The capabilities of compounds 1 and 2 as inkless and erasable printing media have also been tested. Moreover, the photomodulated fluorescence of these compounds has also been investigated.

Series of inorganic-organic hybrid materials constructed from octamolybdates and metal-organic frameworks: syntheses, structures, and physical properties.

Series of inorganic-organic hybrid materials based on octamolybdates, silver ions, and multidentate N-donor ligands, namely, [Ag(2)(2,3'-tmbpt)(ß-Mo(8)O(26))(0.5)] (1), [Ag(2)(2,4'-tmbpt)(2)(α-Mo(8)O(26))(0.5)(H(2)O)(0.5)]·2H(2)O (2), [Ag(3)(3,3'-tmbpt)(2)(α-H(2)Mo(8)O(26))(0.5)(ß-Mo(8)O(26))(0.5)]·3.5H(2)O (3), [Ag(2)(3,3'-tmbpt)(ε-Mo(8)O(26))(0.5)]·1.75H(2)O (4), [Ag(2)(3,4'-tmbpt)(2)(ß-Mo(8)O(26))(0.5)]·0.5H(2)O (5), and [Ag(3,4'-Htmbpt)(ß-Mo(8)O(26))(0.5)] (6), where 2,3'-tmbpt = 1-((1H-1,2,4-triazol-1-yl)methyl)-3-(3-pyridyl)-5-(2-pyridyl)-1,2,4-triazole), 2,4'-tmbpt = 1-((1H-1,2,4-triazol-1-yl)methyl)-3-(4-pyridyl)-5-(2-pyridyl)-1,2,4-triazole), 3,3'-tmbpt = 1-((1H-1,2,4-triazol-1-yl)methyl)-3,5-bis(3-pyridyl)-1,2,4-triazole, and 3,4'-tmbpt = 1-((1H-1,2,4-triazol-1-yl)methyl)-3-(4-pyridyl)-5-(3-pyridyl)-1,2,4-triazole) have been synthesized under hydrothermal conditions. Compound 1 displays a rare 3D (3,4,8)-connected net with (4·8(2))(4(2)·8(4))(4(3)·8(20)·10(5)) topology. Compound 2 shows a rare 3D (4,6)-connected self-catenated framework with (6(4)·8(2))(4(2)·6(3)·8(2))(4(2)·6(8)·8(4)·10) topology. Compound 3 is a scarce 3D framework based on two different kinds of [Mo(8)O(26)](4-) isomers. Compound 4 exhibits a 3D framework constructed by silver-organic sheets and the rare [ε-Mo(8)O(26)](4-) anions. Compound 5 shows an interesting 1D → 2D polythreaded structure. Compound 6 displays a 2D layer structure, which is further linked by the N-H···O hydrogen bonds to form a 3D supramolecular architecture. Their structures have been further characterized by infrared spectra (IR), elemental analyses, powder X-ray diffraction (PXRD), electrochemistry and photoluminesce. Moreover, the photocatalytic activities for degradation of organic pollutant have been investigated for compounds 3-6.

A series of host-guest coordination polymers containing viologens: syntheses, crystal structures, thermo/photochromism and factors influencing their thermo/photochromic behaviors.

Responsive molecular chromic materials have shown potential applications in molecular optical switches and sensor devices as they undergo reversible colour changes upon application of external stimuli. Herein, six host-guest coordination polymers 1-6 and one organic supramolecular compound 7 containing viologens have been synthesized under hydrothermal conditions. Compound 1 shows thermochromic behavior with a colour change from green to blue upon heating at 150 °C in air. Compounds 3, 4 and 7 display photochromic behaviors with a colour change from pale yellow to green under UV light, visible light or sunlight. The relationship between their structures and chromic behaviors has been discussed. Thermo/photochromic mechanisms have been investigated by infrared spectroscopy, powder X-ray diffraction analysis, UV-vis absorption spectroscopy, electron paramagnetic resonance spectroscopy, and X-ray photoelectron spectroscopy. The results demonstrate the generation of viologen radicals caused by thermo/photo-induced electron transfer. It is found that compound 4 can be used as an inkless and erasable printing medium. In addition, compounds 3, 4, and 7 can be used as anti-counterfeiting materials for QR codes. Our findings demonstrate the possibility of applying thermo/photochromic coordination polymers in molecular devices.

Solid-state single-crystal-to-single-crystal transformation from a 2D layer to a 3D framework mediated by lattice iodine release.

We describe an exceedingly rare example of solid-state single-crystal-to-single-crystal transformation from a 2D layer to a known 3D framework via lattice iodine release, which involves the formation of a new Cu-O ligand bond and a change in the metal coordination geometry.

Inorganic-organic hybrid compounds based on octamolybdates and multidentate N-donor ligand: syntheses, structures, photoluminescence and photocatalysis.

Six inorganic-organic hybrid compounds, namely, [Cu(2)(2,4'-tmbpt)(2)(ß-Mo(8)O(26))(H(2)O)(2)]·7H(2)O (1), [Cu(2,4'-tmbpt)(γ-Mo(8)O(26))(0.5)(H(2)O)]·H(2)O (2), [Co(2,4'-Htmbpt)(2)(γ-Mo(8)O(26))(H(2)O)(2)] (3), [Zn(2,4'-Htmbpt)(2)(γ-Mo(8)O(26))(H(2)O)(2)] (4), [Ni(2,4'-tmbpt)(α-Mo(8)O(26))(0.5)(H(2)O)]·2.5H(2)O (5) and [Ag(2,4'-Htmbpt)(ß-Mo(8)O(26))(0.5)] (6), have been synthesized under hydrothermal conditions (2,4'-tmbpt = 1-((1H-1,2,4-triazol-1-yl)methyl)-3-(2-pyridyl)-5-(4-pyridyl)-1,2,4-triazole). The structures of compounds 1-6 have been determined by single-crystal X-ray diffraction analyses and characterized by infrared spectra (IR), elemental analyses, powder X-ray diffraction (PXRD) analyses and thermogravimetric analyses (TGA). Compound 1 shows a 3D (3,4)-connected framework constructed by the 2D Cu(II)-organic fragments and [ß-Mo(8)O(26)](4-) anions. Compound 2 exhibits a 2D layer structure based on Cu(II)-organic chains and [γ-Mo(8)O(26)] chains. The layers are extended into a 3D supramolecular framework by hydrogen-bonding interactions. Compounds 3 and 4 are isostructural, and display 1D chain structures. The chains are further interlinked by hydrogen-bonding interactions to form 3D supramolecular architectures. Compound 5 shows a 3D framework based on the 2D Ni(II)-organic fragments and [α-Mo(8)O(26)](4-) anions. In compound 6, the 1D chains constructed by the Ag(I) ions, 2,4'-Htmbpt ligands and [ß-Mo(8)O(26)](4-) anions are extended by hydrogen-bonding interactions into a 2D supramolecular layer. Each layer threads into the adjacent layers, yielding a 2D → 3D interdigitated structure. Moreover, the photoluminescent properties of 4 and 6, the optical band gaps of 1-6, and the photocatalytic properties of 1-6 have also been investigated.