Two Dynamic ABW-Type Metal Organic Frameworks Built of Pentacarboxylate and Zn²⁺ as Photoluminescent Probes of Nitroaromatics

Self-assembly reactions of Zn²⁺ and L^5– (H₅L = 2,5-(6-(4-carboxyphenylamino)-1,3,5-triazine-2,4-diyldiimino) diterephthalic acid) lead to the formation of two new ABW-type zeolitic metal–organic frameworks (Z-MOFs): (Me₂NH₂)­[Zn₂L]­·3.5DMF (<b>1</b>) and (Me₂NH₂)­[Zn₂L­(H₂O)]­·2DMF­·8H₂O (<b>2</b>) (DMF = <i>N</i>,<i>N</i>-dimethylformamide). They are the first two Z-MOFs which are built of the same pentacarboxylate ligand and metal ion but have two configurations and channel shapes (distorted honeycomb- and herringbone-shaped channels for <b>1</b> and <b>2</b> respectively). They can demonstrate interesting structural transformations triggered by vacuum heating or soaking in different solvents. While direct transformations between <b>1</b> and <b>2</b> were revealed to be not feasible, <b>2</b> could be first transformed to a crystalline intermediate <b>3</b> and then into <b>1</b>. Furthermore, while transformations between <b>2</b> and <b>3</b> are irreversible, those between <b>1</b> and <b>3</b> are reversible, accompanied by a 26 nm shift of their emission peak positions. In comparison to the ligand, <b>1</b>, <b>2</b>, and <b>3</b> exhibit blue shifts in their luminescent emission peaks and have intensive blue emission in both solid and solution phases. The efficient and selective quenching of their photoluminescence by a series of nitroaromatics (NACs) solutions phase and by nitrobenzene (NB) vapor makes them promising probes for detecting NACs. <b>1</b>–<b>3</b> represent the first series of MOFs as promising photoluminescent probes for detecting dinoseb down to 2.4 ppm. The electron transfer, long-range energy transfer, and/or electrostatic interactions between the frameworks and NACs mainly contribute to the quenching mechanisms

Optimizing Height and Packing Density of Oriented One-Dimensional Photocatalysts for Efficient Water Photoelectrolysis

Dependences of water-photoelectrolysis efficiency on heights and packing densities of vertically arrayed ZnO nanorods (NRs) and ZnO microrods (MRs) were systematically studied for the first time over a wide range of light incidence angles, under the direction of nanooptics simulation. In the photoelectrolysis, dense NRs of 1.8 μm in height afforded the highest photocatalytic efficiencies, and further increases of the height kept lowering down the photocatalytic efficiencies, while sparse MRs taller in height consistently afforded better electrolyte penetration and higher photocurrent densities especially at higher angles of incident light. The experimental results are in line with the nanooptics simulation. This new finding is generally applicable to advancing solar-energy conversions, optics, and optoelectronics using oriented one-dimensional micro/nanocrystallites

1‑D “Platinum Wire” Stacking Structure Built of Platinum(II) Diimine Bis(σ-acetylide) Units with Luminescence in the NIR Region

A square-planar platinum­(II) complex, Pt­(DiBrbpy)­(CCC₆H₄Et-4)₂ (<b>1</b>) (DiBrbpy = 4,4-dibromo-2,2′-bipyridine), and crystals of its three solvated forms, namely, <b>1</b>·DMSO, <b>1</b>·1/2­(CH₃CN), and <b>1</b>·1/8­(CH₂Cl₂), were developed and characterized. <b>1</b>·DMSO and <b>1</b>·1/2­(CH₃CN) contain quasi-dimeric and dimeric structures with luminescence in the visible range, whereas <b>1</b>·1/8­(CH₂Cl₂) exhibits NIR luminescence at 1022 nm due to its intrinsic 1-D “platinum wire” stacking structure with strong Pt–Pt interactions. <b>1</b>·1/8­(CH₂Cl₂) represents the first compound based on platinum­(II) diimine bis­(σ-acetylide) molecular units with the NIR luminescence beyond 1000 nm. <b>1</b> selectively responds to DMSO and CH₃CN by changing its color and luminescence property and the three solvated forms can be reversibly converted to each other upon exposure to corresponding solvent vapors. Their desolvated forms, namely <b>1a</b>, <b>1b</b>, and <b>1c</b>, obtained after heating <b>1</b>·DMSO, <b>1</b>·1/2­(CH₃CN), and <b>1</b>·1/8­(CH₂Cl₂), respectively, can also be restored to the original solvated forms upon exposure to corresponding solvent vapors. <b>1a</b> and <b>1b</b> emit NIR luminescence peaked at 998 and 1018 nm respectively, suggesting indirect synthetic methods as powerful alternatives to achieve NIR luminescence with long wavelength. In contrast, <b>1c</b> exhibits a red luminescence with a broad unstructured emission band centered at 667 nm. All the responses to organic solvent vapors and heating are due to the structural transformations which result in the conversion of the lowest energy excited states between ³MLCT/³LLCT and ³MMLCT in solid-state as supported by time-dependent density functional theory (TD-DFT) calculations