Long-Lived Multiple Charge Separation by Proton-Coupled Electron Transfer.

Multiple charge separation has been successfully realized by a proton-coupled electron transfer reaction in an organic cocrystal. Benefiting from the adjustable electronic energy level of the electron donor and acceptor through thermal-induced proton migration, distinct optical absorption behaviors combined with color changes to blue or green are observed in these charge-separated states. It is of interest to note that such charge-separated states exhibit a longer lifetime of over a month as a result of the excellent coplanarity and π-π interaction of the electron acceptors. Moreover, the enhanced absorption toward longer wavelengths endows the charge-separated state with near-infrared (808 nm) photothermal conversion for imaging and bacterial inhibition, whereby the conversion performance can be controlled by the degree of proton migration.

Synergy of Electron Transfer and Charge Transfer in the Control of Photodynamic Behavior of Coordination Polymers.

Photodynamic behavior controlled by the synergy of electron transfer and charge transfer has been characterized in two regioisomeric pyridinium-bearing coordination polymers (Cd-Bip and Cd-Bpy) with the help of a smart charge-distribution-related isoreticular strategy. Because it is relatively weak, the charge-transfer interaction between adjacent 2D networks in Cd-Bip can be easily perturbed by photoinduced electron transfer under irradiation with 365 nm light, and then successfully drives the occurrence of photodynamic behavior. In contrast, lower energy 450 nm light is absorbed to a lesser extent, and can only induce a low degree of electron transfer, which is insufficient to actuate operation of this photodynamic behavior in Cd-Bip.

Improved Effect of Metal Coordination on Molecular Oxygen Activation for Selective Aerobic Photooxidation.

A pyridinium-based complex with environment-friendly and earth-abundant ZnII ion was synthesized and explored as a green catalyst applied in activating molecular oxygen for the simple and efficient photooxidation of alcohols into aldehydes under additive-free and mild conditions. The metal coordination was conducive to promoting the electron transfer efficiency and introducing the heavy-atom effect for the increased generation of ⋅O2 - and 1 O2 . Accordingly, improved photocatalytic performance of this complex compared to its precursor, no matter activity or selectivity, was obtained, facilitating the transformation of alcohols into aldehydes in a sustainable way.

Photoinduced-electron-transfer-driven surface modification to regulate adsorption behavior in a pyridinium-decorated metal-organic framework.

Surface modification based on a photo-induced electron transfer (PET) reaction in a pyridinium-decorated MOF material was found to be effective in regulating adsorption capacity. The current system enables the adsorption behavior to be manipulated based on variable affinity toward guest molecules through the redistribution of charge population with the preservation of the original pore structure, which is different from the prevalent approaches depending on photoinduced changes in molecular configurations of the pore backbone.

A multifunctional Ni(ii) coordination polymer: synthesis, crystal structure and applications as a luminescent sensor, electrochemical probe, and photocatalyst.

Herein, a nickel coordination polymer (CP 1), {Ni(1,4-bib)1.5(TPA-Cl2)·H2O}n (1,4-bib = 1,4-bis(1H-imidazol-1-yl)benzene, H2TPA-Cl2 = 2,5-dichloro-terephthalic acid), has been synthesized under solvothermal conditions. The structure of CP 1 is a 3D 3-fold interpenetrating framework with the sqc12 topology. The thermal stability and luminescence properties of CP 1 were investigated. Scanning electron microscopy (SEM) images of this material display that it possesses an irregular block 3D structure. Interestingly, CP 1 can serve as a multifunctional material via its luminescence sensing, electrochemical sensing, and photocatalytic properties. The experimental results indicate that CP 1 is an efficient luminescent sensor for the detection of Fe3+ ions in an aqueous solution. In addition, CP 1 exhibits a sensitive and rapid electrochemical response to nitrite ions in water solution. The photocatalytic activities of CP 1 were evaluated in the degradation of different dye contaminants (MB, RhB, and MO), and the results demonstrate that its photocatalytic efficiency for the degradation of MB is highest (92.1% for MB, 85.7% for RhB, and 86.2% for MO). The effects of different dyes, different powers of UV light, and different amounts of catalyst CP 1 on the photocatalytic efficiency were also explored. Finally, the mechanism of the luminescence quenching effect toward Fe3+ ions, electroreduction of nitrite ions, and photocatalytic degradation of different dyes have been investigated in detail.

Rigid versus semi-rigid bis(imidazole) ligands in the assembly of two Co(ii) coordination polymers: structural variability, electrochemical properties and photocatalytic behavior.

The hydrothermal reactions of 1,2,4,5-cyclohexanetetracarboxylic acid (H4L) with CoCl2·2H2O and rigid or semi-rigid bis(imidazole) ligands were able to generate two Co(ii) coordination polymers (CPs), {[Co5(L)2(1,4-bimb)(µ3-OH)2(H2O)8]·2H2O}n (1), {[Co(L)0.5(1,4-bib)]·H2O}n (2) (1,4-bimb = 1,4-bis(imidazol-1-ylmethyl)benzene, 1,4-bib = 1,4-bis(1H-imidazol-1-yl)benzene). CPs 1 and 2 were structurally characterized by elemental analysis, IR spectroscopy, X-ray powder diffraction and single crystal X-ray diffraction. CP 1 features a 3D 3,3,4,4,5-connected framework with an unprecedented {42·8·102·12}{43·6·86}2{43}2{46}2{62·8}2 topology, which represents the first example of CPs with such a topology. CP 2 possesses a three-fold interpenetration 3D framework with mog topology. The distinct structures of the two CPs may result from diverse coordination modes of the (L)4- ligands and different structural characteristics of rigid or semi-rigid N-donor ligands. The thermal stabilities, photoluminescence properties and electrochemical behavior in the solid state for CPs 1 and 2 have been investigated. The photophysical studies indicated that CPs 1 and 2 are potential semiconductive materials. Moreover, both CPs 1 and 2 show high photocatalytic efficiency for the degradation of methylene blue (MB) under UV light irradiation and exhibit good stability and recyclability. A possible photocatalytic mechanism is speculated by introducing t-butyl alcohol (TBA) as a widely used ˙OH scavenger.

Photoluminescence, electrochemical behavior and photocatalytic activities of cobalt(II) coordination polymer nanostructures synthesized by sonochemical process.

Nanostructures of a new Co(II) coordination polymer (CP), [Co(Hbibp)(nbta)]n (1), (bibp=4,4'-bis(1-imidazolyl)biphenyl, H3nbta=5-nitro-1,2,3-benzenetricarboxylic acid) was synthesized by a sonochemical method. The nano-sized CP 1 was characterized by elemental analysis, IR spectroscopy, X-ray powder diffraction and scanning electron microscopy (SEM). Structural analysis show that CP 1 exhibits a 1D chain structure with a 3-connected SP 1-periodic net (4,4)(0,2) topology, which can be further extended into a 2D supramolecular layer by the NH⋯O hydrogen bond interactions. The thermal stability for CP 1 as bulk and nanoparticles were investigated. The photoluminescence properties and electrochemical behavior for nano-sized CP 1 have also been explored. Moreover, nano-sized CP 1 shows high photocatalytic activities for the degradation of MB under UV irradiation and the photodegradation process is mainly caused by OH radicals. Effects of the sonication time and ultrasonic power on the morphology and size of nanoparticles were studied.

Two copper(i) cyanide coordination polymers modified by semi-rigid bis(benzimidazole) ligands: syntheses, crystal structures, and electrochemical and photocatalytic properties.

Two Cu(i) cyanide coordination polymers (CPs), namely, [Cu2(L1)(CN)2]n (1) and [Cu2(L2)(CN)2]n (2) (L1 = 4,4'-bis(2-methylbenzimidazol-1-ylmethyl)biphenyl, L2 = 4,4'-bis(5,6-dimethylbenzimidazol-1-ylmethyl)biphenyl) were synthesized and structurally characterized by single crystal X-ray diffraction, IR spectroscopy, X-ray powder diffraction and elemental analysis. The cyanide ligands in these CPs are generated in situ from the C-C bond cleavage of acetonitrile under solvothermal conditions, which is environmentally friendly and used conveniently. CP 1 features a three-fold interpenetration 3D framework consisting of Cu10(CN)6(L1)4 rings, which represents the first investigation on introducing bis(benzimidazole) ligands into copper(i) cyanide CPs with ThSi2 topology, while CP 2 exhibits a two-dimensional (6,3) layered structure containing Cu6(CN)4(L2)2 rings. The thermal stabilities, and photoluminescence and electrochemical behavior in the solid state of CPs 1 and 2 have been investigated in detail. Moreover, both CP 1 and CP 2 manifest promising photocatalytic activities (photodegradation efficiency using CP 1 is 90.8% and using CP 2 is 87.2%) for the degradation of methylene blue (MB) under UV light irradiation. A possible photocatalytic mechanism is suggested by introducing t-butyl alcohol (TBA) as a widely used ˙OH scavenger.