No abstract

In search of magneto-optic materials, the mononuclear compounds Ln (depma)(NO ) (hmpa) (Ln=Dy, Gd) were synthesized. The anthracene moieties undergo [4+4] dimerization when irradiated at 365 nm without loss of crystallinity. The Dy compound switches from a single-ion to a single-molecule magnet with doubling of the spin reversal barrier energy and from yellow-green to blue-white emission. The dimerization is reversed by heating at 100 °C or partially on light irradiating at 254 nm. The results suggest that lanthanide phosphonates with anthracene are promising smart materials displaying synergistic magneto-optic property.

We report that a new 2D 3d-4f phosphonate [Co(III)La(III)(notpH)(H2O)6]ClO4·5H2O (CoLa-II) can undergo a phase transition above 45 °C and 93% relative humidity, resulting in [H3O][CoLa(notp)(H2O)4]ClO4·3H2O (CoLa-III). The transition is accompanied by the release of the proton from intralayer to interlayer, and thus the proton conductivity of the material is increased by 1 order of magnitude.

A combination of humidity-dependent single crystal to single crystal (SC−SC) structural transformation and single crystal proton conductivity measurements is essential to elucidate the underlying proton transport mechanism in metal−organic framework materials. Herein, we report a new layered Co−Ca phosphonate [Co III Ca II (notpH 2 )(H 2 O) 2 ]ClO 4 •nH 2 O [abbreviated as CoCa•nH 2 O, where notpH 6 = 1,4,7-triazacyclononane-1,4,7-triyl-tris-(methylenephosphonic acid), C 9 H 18 N 3 (PO 3 H 2 ) 3 ]. CoCa•nH 2 O undergoes a reversible relative humidity (RH) dependent SC−SC structural transformation between CoCa•2H 2 O and CoCa• 4H 2 O at room temperature. Accordingly the continuous hydrogen bond network observed in CoCa, leading to a drastic decrease in proton conductivity by ∼5 orders of magnitude. The process is reversible; hence, the proton conductivity is tunable simply through humidity control. The AC impedance measurements using single crystals of CoCa•nH 2 O reveal that the [010] direction of H-bond extension is the preferred proton conduction pathway showing the greatest conductivity of 1.00 × 10 −3 S cm −1 at 25 °C and 95% RH. Although the [20−1] direction, which involves the phosphonate oxygen atoms in the H-bond network shows the lowest conductivity of 4.35 × 10 −8 S cm −1 at 25 °C and 95% RH, the ClO 4 − anions play a key role in not only connecting the lattice water molecules into a continuous hydrogen bond network but also assisting the proton diffusion between the lattice water molecules. This work provides a rare example of a proton conductive MOF with a well-illustrated proton conduction mechanism and is a promising humidity sensor for future applications.

This work presents a mixed-ligand metal−organic framework (m-MOF) integrated with two ligands, one as a luminophore and the other as a coreactant, on one metal node for self-enhanced electrochemiluminescence (ECL). Both 9,10-di(pcarboxyphenyl)anthracene (DPA) and 1,4-diazabicyclo[2.2.2]octane (D-H 2 ) ligands can be oxidized, generating the cation radicals DPA +• and D-H 2 +• , respectively. The latter can be deprotonated to form the neutral radical (D-H • ) and then react with DPA +• to produce excited DPA* for ECL emission without exogenous coreactants. As a result of the incorporation into the MOF framework and the intrareticular charge transfer between the two ligands, the ECL intensity of the m-MOF was increased 26.5-fold compared with that of the mixture of DPA and D-H 2 in aqueous solution. Moreover, with the process of second oxidation of D-H 2 , stepwise ECL emission was observed as a result of local excitation in the DPA unit, which was identified through density functional theory calculations. Overall, the implementation of the mixed-ligand approach, which combines the luminophore and coreactant as linkers in reticular materials, enriches the fundamentals and applications of ECL systems.

The first example of a ratiometric thermometer based on lanthanide phosphonate is reported, which operates down to the cryogenic temperature range with a maximum relative sensitivity of 3.9% K−1.

[DyIII(SCN)3(depma)2(4-hpy)2] (1) shows reversible thermo-induced phase transition associated with thermochromism and dielectric anomaly and photo-induced dimerization with synergistic switching of luminescence, magnetic and dielectric properties.

Three iridium(III)-based metal-organic frameworks (MOFs), namely [Cd{Ir(ppy-COO)}(DMF)(HO)]·6HO·2DMF (1), [Cd{Ir(ppy-COO)}(DMA)(HO)]·0.5HO·2DMA (2), and [Cd{Ir(ppy-COO)}(DEF)(HO)]·8HO·2DEF (3) (ppy-COOH = methyl-3-(pyridin-2-yl)benzoic acid, DMF = N,N-dimethylformamide, DMA = N,N-dimethylacetamide, DEF = N,N-diethylformamide), have been synthesized and characterized. Single-crystal structural determinations reveal that compounds 1-3 are isostructural, showing a three-dimensional framework structure with (3,6) connected rtl topologyin whose trimers of {Cd(COO)} are cross-linked by Ir(ppy-COO). The structures are completely different from those of other Ir(III)-based MOFs. Compound 1 was selected for a detailed study on sensing properties. The excellent luminescence as well as good water stability of 1 makes it a highly selective and sensitive multiresponsive luminescent sensor for Fe and CrO. The detection limits are 67.8 and 145.1 ppb, respectively. Compound 1 can also be used as an optical sensor for selective sensing of adenosine triphosphate (ATP) over adenosine diphosphate (ADP) and adenosine monophosphate (AMP) in aqueous solution. This is the first example of iridium(III)-based MOFs for the optical detection of Fe, CrO, and ATP. More interestingly, the luminescent composite film doped with 1% (w/w) of compound 1, 1@PMMA (PMMA = poly(methyl methacrylate)), can be successfully prepared, which endows efficient sensitivity for Fe and CrO detection and thus provides great potential for future applications.