Electron density effect of aromatic carboxylic acids in naphthalenediimide-based coordination polymers: from thermal electron transfer and charge transfer to photoinduced electron transfer.

Various naphthalenediimide (NDI) based electron donor-acceptor coordination polymers (D-A CPs) have been constructed and used to explore charge transfer (CT) and electron transfer (ET) behaviors. Up to now, significant progress has been made in the interface contact and electron donor-acceptor ability matching mechanism, while the electronic density effect of the electron donors on the CT and ET behaviors is still not known. Herein, two NDI-based D-A CPs, [Cd2(H2NDI)(IPA)2(H2O)2] (1) and [Cd2(H2NDI)(IPA-OH)2(H2O)2] (2), are constructed using an NDI-based ligand and two aromatic carboxylic acid ligands (H2NDI = 2,7-bis(3,5-dimethyl) dipyrazol-1,4,5,8-naphthalene tetracarboxydiimide, H2IPA = isophthalic acid; and H2IPA-OH = 5-hydroxyisophthalic acid). UV-vis and EPR spectroscopy and DFT calculations analyses reveal that the occurrence of themal electron transfer (TET) in 1 and 2 results from the HOMO of the IPA and IPA-OH lying higher than the LUMO of the NDI. Meanwhile, compared to 1, the UV-vis absorption spectrum of 2 exhibits a significant red shift, which suggests higher electron density of the donor and more electron transfer pathways are beneficial for the occurrence of intermolecular CT. After UV light irradiation, the comparison of the photochromic behavior of 1 and 2 confirms the negative effect of the stronger CT on photoinduced electron transfer (PET). The present study illustrates the delicate modulating effect of electron density on the CT and ET behaviors in D-A CPs.

Size Effect of Arylenediimide π-Conjugate Systems on the Photoresponsive Behaviors in Eu3+-Based Coordination Polymers.

Various arylenediimides (ADIs) have been applied to construct photoresponsive coordination polymers (CPs), while the size effect of ADI π-conjugate systems on the photoresponsive behaviors in CPs has been overlooked in the past few years. Herein, we emphasize the size effect of ADI π-conjugate systems on photoinduced electron transfer (ET) in CPs, taking two Eu3+-based CPs, [Eu(H2BINDI)(BINDI)0.5(H2O)2]·NH2(CH3)2·8H2O (1) and [Eu2(BIPMDI)(DMF)4(NO3)2]·H2O·2DMF (2) [H4BINDI = N,N'-bis(5-isophthalic acid)naphthalenediimide; H4BIPMDI = N,N'-bis(5-isophthalic acid)pyromellitic diimide; DMF = N,N-dimethylformamide], as a case. Both 1 and 2 display ET-based photochromic behaviors with distinct photoresponsive rates and coloration contrast, which can contribute to the size effect of diimide cores on the interfacial contacts of electron donors/acceptors. Meanwhile, ET between the neighboring larger NDI cores of the H4BINDI ligands can block ligand-to-metal charge transfer and quench luminescence of the Eu3+ metal center in 1. Therefore, this work will provide a theoretical basis for the development and exploration of photoresponsive materials.

Effect of positional isomers on the photochromic behaviors of bipyridyltriazolium chloroantimonate hybrids.

Two chloroantimonate hybrids with isomeric bipyridyltriazoliums and similar packing patterns, {[2-bpt]2[(SbCl5)Cl2]}n (1) and {[4-bpt]2[(SbCl5)Cl2]}n (2) (2-bpt2+ = protonated 3,5-bis(pyridine-2-yl)-1,2,4-triazole, 4-bpt2+ = protonated 3,5-bis(pyridine-4-yl)-1,2,4-triazole), have been designed and synthesized. Distinct intermolecular electronic interactions and photochromic behaviors are attributed to the remarkable modulation of positional isomeric effect on the electron deficiency of the acceptors and donor-acceptor matching relationship. 1 is the first reported photochromic chloroantimonate hybrid.

Synthesis of Aryl Silacarboxylates via Palladium-Catalyzed C-O Bond Formation of Silacarboxylic Acids and Aryl Iodides.

The first palladium-catalyzed C-O bond formation method for the synthesis of silacarboxylates by silacarboxylic acids with a broad range of aryl iodides and iodo-N-heterocycles is reported. Electron-deficient, electron-rich, and sterically hindered aryl iodides were well-tolerated to furnish the corresponding aryl silacarboxylates in moderate to excellent yields. Active functional groups, such as -NH2, -CHO, and allyl-, showed good tolerance, even in the large-scale synthesis. Double and triple esterification were also demonstrated to be effective.

Five monocyclic pyridinium derivative based halo-argentate/cuprate hybrids or iodide salts: influence of composition on photochromic behaviors.

The rational choice of an electron acceptor was proved to be an effective strategy for the development of novel electron transfer (ET) photochromic iodides, but the types and amounts of reported electron acceptors are relatively limited so far, especially for monocyclic aromatic molecules. Herein, using monocyclic pyridinium derivatives (N-protonation-4-carboxypyridinium/N-protonation-4-carbamoylpyridinium/1-methyl-4-(carbomethoxy)pyridinium) as structural directing agents and electron acceptors, five new electron donor-acceptor-based halo-argentate/cuprate hybrids or iodide salts have been synthesized, including [HINA][Ag4I5] (1), [HINAM]I (2), [HINAM]I·0.5(I2) (3), [MCMP][Ag2Br3] (4) and [MCMP][Cu2I3] (5). Noteworthily, compounds 1-3 exhibit interesting photochromic behaviours, while compounds 4 and 5 are non-photochromic. Finally, the possible chromic mechanisms and influencing factors for the title compounds were also discussed.

Halogen-dependent photoinduced electron transfer and chromism of three protonated nicotinohydrazide halozincates.

Three isostructural halozincates, [HNH][ZnX4]·H2O (HNH2+ = protonated nicotinohydrazide, X = I (1), Br (2), Cl (3)), have been synthesized and exhibit halogen-dependent photoinduced electron transfer and chromic properties. Due to the different electron-donating nature of halogen atoms, only iodozincate hybrid 1 can easily undergo photoinduced electron transfer and eye-detectable photochromic behavior, revealing a unique matching rule between a moderate electron acceptor and halozincates.

Stoichiometry-controlled structural and functional variation in two photochromic iodoargentates with a fast and wide range response.

By using 1-methyl-4-(carbomethoxy)pyridinium (MCMP+) as counterions, two iodoargentate hybrids, 1D [MCMP][AgI2] (1) and 3D [MCMP][Ag3I4] (2) have been synthesized and they exhibit rare electron transfer photochromism with a fast response rate, a wide response range and a long-lived charge-separated state in iodometallate systems. Noteworthily, the marked differences in the structure and photochromic performance of 1 and 2 are largely ascribed to the different aggregating behavior of electron-deficient MCMP+ counterions (C-HO hydrogen bonded trimer in 1 and π-π/C-Hπ chain in 2).

Ultrasensitive Photochromic Iodocuprate(I) Hybrid.

By employing in situ methylnicotinohydrazide dication (MNH(2+)) as an electron acceptor, we have constructed an iodocuprate(I) hybrid {[MNH][Cu2I3]2}n (1), which exhibits charge transfer (CT) thermochromism due to the intense absorption of CT and electron transfer (ET) photochromism with high photocoloration contrast and fast response to UV irradiation due to the synergetic effect of valence change of copper ions.

A competitive strategy based on cucurbit[7]uril supramolecular interaction for simple and sensitive detection of dibucaine.

In this work, the competitive interaction between dibucaine and three fluorescent probes (i.e., berberine, palmatine, and coptisine) for occupancy of the cucurbit[7]uril (CB[7]) cavity was studied by fluorescence spectra, UV-visible absorption spectra, (1)H NMR spectra, and theoretical calculations in acidic aqueous solution. Based on the fluorescence enhancement of berberine, palmatine, and coptisine upon binding with CB[7], respectively, a series of fluorescence detection methods for dibucaine were proposed. At the optimized conditions, the fluorescence intensity of berberine-CB[7], palmatine-CB[7], and coptisine-CB[7] complexes showed negative correlation to the concentration of dibucaine, which led to a series of simple and sensitive fluorescence methods for the determination of dibucaine for the first time. Linear ranges obtained in the detection of the dibucaine were 0.018-3.34 µmol L(-1), 0.032-4.47 µmol L(-1), and 0.079-4.42 µmol L(-1) with detection limits of 6.0 nmol L(-1), 12.0 nmol L(-1), and 25.0 nmol L(-1), respectively. Moreover, the proposed method was successfully applied for the determination of the drug in biological fluids. The competitive mode based on CB[7] superstructure provided a promising assay strategy for fluorescence detection in various potential applications.

Anionic surfactant micelle-mediated extraction coupled with dispersive magnetic microextraction for the determination of phthalate esters.

A novel and easy two-step microextraction technique combining anionic surfactant coacervation phase (CAP) extraction and dispersive microsolid-phase extraction (D-µ-SPE) was developed for the high-performance liquid chromatography-ultraviolet detection to determination of phthalate esters (PEs) in water samples. The method started with the phase separation of sodium dodecylbenzenesulfonic acid (SDBSA) obtained by adding NaCl, whereas the target analytes were extracted in the CAP. The CAP was then retrieved using diatomaceous earth-supported magnetite nanoparticles. The effects of solution acidity, SDBSA, and electrolyte concentration, extraction time, magnetic material quantity, and elution solvent volume were discussed. Under optimal extraction conditions, the extraction recoveries ranged from 48.6 to 84.8%, and relative standard deviations ranged from 3.9 to 5.7% (n = 10). The detection limits ranged from 0.5 to 5.0 ng mL(-1) for the five PEs. The proposed method was used to determine the five PEs in the water samples and recoveries between 85.7 and 105.5%.

Supramolecular interaction of two tryptophans with p-sulfonated calix[4,6,8]arene.

The complex characteristics of p-sulfonated calix[n]arene (SCnA) and two tryptophans N-[(tert-butoxy) carbonyl]-tryptophan (trp-A) and N-carbobenzoxy-tryptophane (trp-B) were examined through various techniques. Spectrofluorimetry was performed at different temperatures to determine the stability constants and evaluate the thermodynamic parameters of the two complexes. The effect of pH on complex formation was estimated. According to the fluorescence data, the assumption about the steric hindrance of the tert-butyl group of trp-A and the phenyl group of trp-B was put forward. (1)H NMR was also performed to determine the binding interaction mechanism. Results showed that the indole benzene rings of the two tryptophans partly penetrated into the cavity of p-sulfonated calix[n]arene. The shift in Ha, Hb and Hc, Hd positions became more significant as the number of phenolic units of the calixarene ring increased. Molecular modeling of the complexes elucidated the assumption about the steric hindrance of the tert-butyl group of trp-A and the phenyl group of trp-B. These observations of molecular modeling computation are consistent with previous fluorescence data and (1)H NMR results.