Enhancing the Circularly Polarized Luminescence of Europium Coordination Polymers by Doping a Chromophore Ligand into Superhelices.

Lanthanide-based molecular materials showing efficient circularly polarized luminescence (CPL) activity with a high quantum yield are attractive due to their potential applications in data storage, optical sensors, and 3D displays. Herein we present an innovative method to achieve enhanced CPL activity and a high quantum yield by doping a chromophore ligand into a coordination polymer superhelix. A series of homochiral europium(III) phosphonates with a helical morphology were prepared with the molecular formula S-, R-[Eu(cyampH)3-3n(nempH)3n]·3H2O (S/R-Eu-n, n = 0-5%). The doping of chromophore ligand S- or R-nempH2 into superhelices of S/R-Eu-0% not only turned on the CPL activity with the dissymmetry factor |glum| on the order of 10-3 but also increased the quantum yield by about 14-fold. This work may shed light on the development of efficient CPL-active lanthanide-based coordination polymers for applications.

Macroscopic handedness inversion of terbium coordination polymers achieved by doping homochiral ligand analogues.

Inspired by natural biological systems, chiral or handedness inversion by altering external and internal conditions to influence intermolecular interactions is an attractive topic for regulating chiral self-assembled materials. For coordination polymers, the regulation of their helical handedness remains little reported compared to polymers and supramolecules. In this work, we choose the chiral ligands R-pempH2 (pempH2 = (1-phenylethylamino)methylphosphonic acid) and R-XpempH2 (X = F, Cl, Br) as the second ligand, which can introduce C-H⋯π and C-H⋯X interactions, doped into the reaction system of the Tb(R-cyampH)3·3H2O (cyampH2 = (1-cyclohexylethylamino)methylphosphonic acid) coordination polymer, which itself can form a right-handed superhelix by van der Waals forces, and a series of superhelices R-1H-x, R-2F-x, R-3Cl-x, and R-4Br-x with different doping ratios x were obtained, whose handedness is related to the second ligand and its doping ratio, indicating the decisive role of interchain interactions of different strengths in the helical handedness. This study could provide a new pathway for the design and self-assembly of chiral materials with controllable handedness and help the further understanding of the mechanism of self-assembly of coordination polymers forming macroscopic helical systems.

X-Ray Triggered Coordination-Bond Breakage in Dysprosium-Organic Framework and its Impact on Magnetic Properties.

Photosensitive lanthanide-based single-molecule magnets (Ln-SMM) are very attractive for their potential applications in information storage, switching, and sensors. However, the light-driven structural transformation in Ln-SMMs hardly changes the coordination number of the lanthanide ion. Herein, for the first time it is reported that X-ray (λ=0.71073 Å) irradiation can break the coordination bond of Dy-OH2 in the three-dimensional (3D) metal-organic framework Dy2 (amp2 H2 )3 (H2 O)6 ⋅ 4H2 O (MDAF-5), in which the {Dy2 (OPO)2 } dimers are cross-linked by dianthracene-phosphonate ligands. The structural transformation proceeds in a single-crystal-to-single-crystal (SC-SC) fashion, forming the new phase Dy2 (amp2 H2 )3 (H2 O)4 ⋅ 4H2 O (MDAF-5-X). The phase transition is accompanied by a significant change in magnetic properties due to the alteration in coordination geometry of the DyIII ion from a distorted pentagonal bipyramid in MDAF-5 to a distorted octahedron in MDAF-5-X.

Photoresponsive proton conduction in Zr-based metal-organic frameworks using the photothermal effect.

A highly stable and porous MOF [Zr2(H4TPPP)(OH/F)2]·xH2O (1) containing a metal-free porphyrin-phosphonate ligand is reported. It shows high proton conductivity of 1.2 × 10-3 S·cm-1 at 25 °C and 95% RH, a photothermal effect over a wide spectral range from UV-vis to NIR, and photo-enhanced and switchable proton conductivity.

Metal phosphonates incorporating metalloligands: assembly, structures and properties.

Metal phosphonates are an important class of metal-organic hybrid materials that exhibit versatile structures, intriguing functions and high water and thermal stability. Despite a large number of metal phosphonates achieved over the past few decades, those incorporating metalloligands are rather limited. The metalloligand approach can provide a unique opportunity in constructing homo- or mixed-metal coordination polymers with rationally immobilized functional moieties for various applications in gas storage and separation, heterogeneous catalysis, sensing and multifunctional materials. In this feature article, we shall introduce the current status of a special subclass of metal phosphonates, namely, metal-metalloligand phosphonates (MMPs), including synthetic strategies, crystal structures, and properties of those based on paddlewheel diruthenium, metallo-polyazamacrocycle, metalloporphyrin and metallo-tris-bipyridine ligands. Future challenges in this field are discussed.

Cyclometalated Iridium(III) Complexes Incorporating Aromatic Phosphonate Ligands: Syntheses, Structures, and Tunable Optical Properties.

The incorporation of phosphonate ligands into the cyclometalated iridium(III) complexes can not only tune their electronic and optical properties but also provide the possibility of anchoring these molecules on the semiconductor surfaces for further applications. Herein, we report the first examples of mononuclear cyclometallated iridium(III) complexes incorporating phosphonate ligands, namely, [Ir(ppy)2(HL1)]·0.5H2O (1), [Ir(ppy)2(HL2)]·0.5H2O (2), [Ir(dfppy)2(HL1)] (3), and [Ir(dfppy)2(HL2)]·3.5H2O (4) (ppy = 2-phenylpyridine, dfppy = 2-(2,4-difluorophenyl)pyridine, H2L1 = 2-pyridylphosphonic acid, H2L2 = 2-quinolinephosphonic acid). Luminescent spectra are studied both in solution and in the solid state, and significantly red-shifted broad emission bands are observed in complexes 2 and 4. The experimental and density functional theory (DFT) time-dependent-DFT calculation results indicate that the expansion of the aromatic conjugation length in the ancillary phosphonate ligands decreases the lowest unoccupied molecular orbital energy levels of the systems, originating from the triplet state associated with the ancillary ligand such as 3MLCT, 3LC, and 3LLCT charge-transfer transitions.

Synthesis of sevoflurane loaded reduced graphene oxide nanoparticles system for neuroprotective effects for preconditioning against focal cerebral ischaemia.

In this study, sevoflurane (SF) loaded, Fas ligand conjugated reduced graphene oxide (rGO) system is fabricated as a therapeutic agent to target brain ischaemic region. The fluorescence investigation of mice brain denoted that the encapsulated SF in rGOs adsorbed with Fas ligand antibody could be significantly distributed to the ipsilateral side of the ischaemic brain. In addition, the immune-histochemical assay presented that the specific nanoparticles especially deposited in the ischaemic part of the tested mice model. Furthermore, SF encapsulated rGO system exhibited noticeable progress in the brain damage along with neurological deficit post ischaemia with limited dosages in contrast to regular SF. Additionally, Rhodamine labelled nanoparticles were used to find whether Fas ligand antibody has the ability to lead the SF-encapsulated nano rGO to enter the ischaemic part of brain as well as carry out neuro-protection. Overall, these experimental findings suggested that rGOs conjugated Fas ligand system could be treated as an ideal brain targeting drug for cerebral ischemia.

Lipophilic M(α,α'-OC5H11)8phthalocyanines (M = H2 and Ni(II)): synthesis, electronic structure, and their utility for highly efficient carbonyl reductions.

A lipophilic and electron-rich phthalocyanine (α,α'-n-OC5H11)8-H2Pc and its nickel(ii) complex (α,α'-n-OC5H11)8-Ni(ii)Pc have been synthesized and characterized. Detailed analyses of the electronic structure were carried out by spectroscopy, electrochemistry, spectroelectrochemistry, and TD-DFT calculations. A series of experiments demonstrate that the (α,α'-n-OC5H11)8-Ni(ii)Pc complex can be used as a catalyst for highly efficient carbonyl reductions.