Coordination polymers: a promising candidate for photo-responsive electronic device application

Structure-directing effect of terephthalate in bridging Zn(II)- and Cd(II)-based coordination polymers towards application in the detection of trace quantities of Pd2+ in aqueous media and their electrical conductivities

Energy crisis and environmental pollution are two central themes of contemporary research towards achieving sustainable development goals (SDGs). Material chemistry is the chief discipline that can resolve glitches in these areas through the appropriate design of chemical compounds with multifunctional properties. In this regard, two stable coordination polymers (CPs) were synthesised in this work using Zn(II) (3d10) and Cd(II) (d10) metal nodes with 1,4-benzenedicarboxylate (bdc2-) as the bridging ligand and monodentate pyridyl-N coordinated 9H-fluoren-2-yl-pyridin-4-ylmethylene-amine (flpy) as the fluorogenic partner. The structures of the polymers [Zn2(bdc)4(flpy)2]n (CP1) and [Cd(bdc)2(flpy)2(H2O)]n·(flpy) (CP2) were confirmed via single-crystal X-ray diffraction measurements. In CP1, the paddle-wheel coordination unit [Zn2(bdc)4] was propagated to constitute a 2D polymer, while in CP2, the capped octahedron motif CdN2O5 generated a 1D chain. Both CP1 and CP2 were strongly emissive, and the emission could be quenched selectively by Pd2+ in aqueous solutions in the presence of as many as twenty other metal ions. Pd(II) is the most toxic in its three oxidation states of 0, II, and IV, and the limit of detection of Pd2+(aq) was 79.1 nM (CP1) and 89.2 nM (CP2), which were much below the toxicity limit of Pd2+ recommended by WHO (the tolerance limit of Pd2+ in water is 3.97-46.98 μM). Based on the Tauc plots of the ITO/(CP1 or CP2)/Al thin films, the bandgaps were determined as 3.63 eV for CP1 (theoretical value = 3.28 eV) and 3.55 eV for CP2 (theoretical value = 3.21 eV). Moreover, the electrical conductivity values of the Schottky semiconducting devices fabricated using these polymers at ambient conditions were 1.285 × 10-4 (CP1) and 2.399 × 10-4 S m-1 (CP2). Therefore, the application of these two CPs can accomplish sustainability goals for future generations.

Syntheses, Structures, and Photocatalytic and Sonocatalytic Degradations of Methyl Blue of Cu(II) and Mn(II) Coordination Polymers Based on Tri(triazole) and Dicarboxylate Ligands

Cu(II) and Mn(II) coordination polymers [Cu(ttpa)(sub)]n (Cuttpa or 1) and {[Mn2(ttpa)2(nip)2(H2O)2]·3H2O}n (Mnttpa or 2) (ttpa = tris(4-(1,2,4-triazol-1-yl)phenyl)amine, H2sub = suberic acid, nip = 5-nitroisophthalicate) were hydrothermally prepared and the structures were characterized. Cuttpa exhibited a 2D (4,4) network based on [Cu2(COO)4] dimers with upper and lower dangled ttpa ligands and a 2D → 3D polythreaded network. Mnttpa showed a 2D (4,4) network with dangled uncoordinated triazole rings from ttpa ligands and nitro groups from nip2- ligands and a 2D → 3D polythreaded network. Eg data of Cuttpa and Mnttpa were 1.88 eV and 2.11 eV. Cuttpa and Mnttpa exhibited good catalytic activity for the decomposition of methyl blue (MB) under visible light and supersound irradiation. The decomposition mechanism using Cuttpa was explored. The holes (h+) and •OH hydroxyl radicals played the main roles, and the •O2- superoxide radicals played certain auxiliary roles in the decomposition of MB within the Cuttpa catalyst.

Photoresponsive metal-organic framework materials for advance applications

The interaction between light and materials produces a range of phenomena within molecular systems, leading to advanced applications in the field of materials science. In this regard, metal-organic framework (MOF) materials have become superior candidates to others because of their easy tailor-made synthetic methods via incorporation of photoactive moieties into their structural assembly. Photoresponsive MOFs exhibit a massive variety of exciting properties, including photochromism, photomagnetism, photoluminescence, photon up or down conversion, photoconductivity, nonlinear optical properties, photosalient effects and photoinduced switching of conformations. These photoresponsive properties of MOFs regulate different potential applications, such as on-demand gas sorption and separation, optical sensing, fabrication of photoactuators and photosensing electronic devices, dye degradation, catalysis, cargo delivery, ink-free erasable printing, bio-imaging and drug delivery in biological systems. Therefore, judicious crystal engineering along with an understanding of their structure-property relationship will lead to the fabrication of desired photosensitive MOFs. Herein, we attempted to incorporate categorical descriptions based on advanced applications of photoresponsive MOFs considering a wide range of recent publications.

Application of a distinctly bent, trinuclear, end-to-end azide bridged, mixed valence cobalt(iii/ii/iii) complex in the fabrication of photosensitive Schottky barrier diodes

A mixed-valence trinuclear cobalt(iii)-cobalt(ii)-cobalt(iii) complex, [(μ-1,3-N3)Co3L(N3)3]·MeOH has been synthesized using a tetradentate N2O2 donor 'reduced Schiff base' ligand, H2L {1,3-bis(2-hydroxybenzylamino)2,2-dimethylpropane} and azide as anionic co-ligand. The complex has been characterised by elemental analysis, IR, UV-vis spectroscopy and single-crystal X-ray diffraction studies etc. The cobalt(iii)-cobalt(ii)-cobalt(iii) skeleton in the complex is non-linear and non-centrosymmetric. The redox behavior of the complex was studied by using Cyclic Voltammetry (CV). The complex is found to be a semiconductor material as confirmed by determining the band gap of this complex by experimental as well as theoretical studies. The band gap in the solid state has been determined experimentally. The conductivity of the synthesized complex based device improves considerably in illumination conditions from the non-illuminated conditions. The complex has also been used to fabricate Schottky barrier diodes.

Heterometallic MIL-125(Ti-Al) frameworks for electrochemical determination of ascorbic acid, dopamine and uric acid

The detection of ascorbic acid (AA), dopamine (DA), and uric acid (UA) is not only of great significance in the areas of biomedicine and neurochemistry but also helpful in disease diagnosis and pathology research. Due to their diverse structures, designability, and large specific surface areas, metal-organic frameworks (MOFs) have recently caught considerable attention in the electrochemical field. Herein, a family of heterometallic MOFs with amino modification, MIL-125(Ti-Al)-xNH2 (x = 0%, 25%, 50%, 75%, and 100%), were synthesized and employed as electrochemical sensors for the detection of AA, DA, and UA. Among them, MIL-125(Ti-Al)-75%NH2 exhibited the most promising electrochemical behavior with 40% doping of carbon black in 0.1 M PBS (pH = 7.10), which displayed individual detection performance with wide linear detection ranges (1.0-6.5 mM for AA, 5-100 μM for DA and 5-120 μM for UA) and low limits of detection (0.215 mM for AA, 0.086 μM for DA, and 0.876 μM for UA, S/N = 3). Furthermore, the as-prepared MIL-125(Ti-Al)-75%NH2/GCE provided a promising platform for future application in real sample analysis, owing to its excellent anti-interference performance and good stability.