Six- and four-coordinated zinc(II) complexes exhibit strong blue fluorescent properties

A Review: Blue Fluorescent Zinc (II) Complexes for OLEDs-A Last Five-Year Recap

Blue emissions in organic light-emitting diodes (OLEDs) are essential for their application in solid-state lighting and full-colour flat panel displays. On the other hand, high-power blue emitters are still uncommon, especially those that can achieve the Commission Internationale de l'Eclairage (CIE, X, Y) coordinates of (0.14, 0.08) in the National Television System Committee (NTSC) blue standard and have high external quantum efficiencies (EQE) of more than 5% because their molecular design presents an enormous challenge. Therefore, creating effective, stable, pure, and deep blue fluorescent materials is vital. Here, it is addressed how useful blue fluorescent Zn (II) complexes are for making organic light-emitting diodes (OLEDs). Utilizing Zn (II) complexes is appealing because of their favourable luminous characteristics, acceptance and mobility, and affordability. This mini-review article aims to provide an overview of Zn (II) complexes that emit blue fluorescent light and have been reported since 2018, while highlighting the unique qualities that make them appropriate OLED materials.

A dual emission metal-organic framework for rapid ratiometric fluorescence detection of CO3 2- in seawater

A dual emission metal-organic framework (IRMOF-10-Eu) was prepared and used as a ratiometric fluorescent sensor for CO₃ ^2- detection. IRMOF-10-Eu had good stability and excellent luminescence in aqueous solution. IRMOF-10-Eu showed dual fluorescence emission from the ligand and Eu³⁺ with single excitation. Upon treatment with CO₃ ^2-, the fluorescence ratio (I ₆₂₄/I ₃₅₈) of the probe displayed significant change. The relative fluorescence intensity ratio (I ₆₂₄/I ₃₅₈) and CO₃ ^2- concentration had a linear relationship in 50-300 μM range with a low detection limit of 9.58 μM. And the luminescence probe of CO₃ ^2- showed a fast detection time. The possible mechanism was investigated. CO₃ ^2- changed the structure of IRMOF-10-Eu and interrupted the energy transfer process. Thus, the fluorescence emission intensity of the ligand was increased and Eu³⁺ was decreased with the addition of CO₃ ^2-. IRMOF-10-Eu was used to detect CO₃ ^2- in seawater, which showed good prospect in practical application. Subsequently, a highly selective and sensitive probe, IRMOF-10-Eu, may pave an efficient way for CO₃ ^2- detection in seawater.

Supramolecular Polymers of two Novel 4-Substituted-1,2,4-Triazolate Complexes: [Cd(pCltrz)2(NCS)2(H2O)2] and [Cu(4-atrz)4(Cl)0.5(H2O)0.5]·(ClO4)1.5 (pCltrz: 4-(p-chlorophenyl)-1,2,4-triazole; 4-atrz: 4-amino-1,2,4-triazole)

The synthesis and structural characterisation of two novel complexes of 4-substituted-1,2,4-triazoles, namely [Cd(pCltrz)2(NCS)2(H2O)2] (1) and [Cu(4-atrz)4(Cl)0.5(H2O)0.5]·(ClO4)1.5(2), are described. Elemental analysis, IR spectra and X-ray crystal structure analysis were carried out to determine the compositions and crystal structures of two compounds. The cadmium atom in 1 has a distorted octahedral coordination and forms one-dimensional chains via hydrogen bonding contacts. 2 has a distorted pyramid environment at the copper atom and a unique double-layer supramolecular structure connected via hydrogen bonds.

Fluorescence sensing of nitro-aromatics by Zn(ii) and Cd(ii) based coordination polymers having the 5-[bis(4-carboxybenzyl)-amino]isophthalic acid ligand

Three new d¹⁰ based MOFs using 5-[bis(3-carboxybenzyl)-amino]isophthalic acid were synthesized and their sensing behavior towards nitroaromatics was evaluated.

Synthesis, characterization, crystal structures and thermal and photoluminescence studies of dimethylpyrazine-carboxylate mixed ligand silver(i) coordination polymers with various multinuclear silver units

Seven new silver(i) coordination compounds based on dimethylpyrazine have been synthesized and characterized.

Synthesis and anticonvulsant activity evaluation of 8-alkoxy-5-(4H-1,2,4-triazol-4-yl)quinoline derivatives

Two series of 8-alkoxy-5-(4H-1,2,4-triazol-4-yl)quinolines and 8-alkoxy-5-(2H-1,2,4-triazol-3-one-4-yl)quinolines were synthesized. The anticonvulsant activity of these compounds was evaluated with maximal electroshock seizure test and rotarod test. Among the synthesized compounds, 8-octoxy-5-(4H-1,2,4-triazol-4-yl)quinoline (4g) was the most active compound with ED(50) of 8.80 mg/kg, TD(50) of 176.03 mg/kg and protective index of 20.0. Its neurotoxicity was lower than all other synthesized compounds and also markedly lower than that of the reference drug carbamazepine. In addition, the potency of compound 4g against seizures induced by pentylenetetrazole, 3-mercaptopropionic acid, and bicuculline suggested its broad spectrum activity, and the mechanisms of action including inhibition of voltage-gated ion channels and modulation of GABAergic activity might involve in its anticonvulsant activity.

Synthesis, controlled release properties, and increased antifungal activities of novel cis- and trans-racemate complexes of propiconazole

Twenty novel metal complexes M(1)(cis-L)(2)Y(2), M(1)(trans-L)(2)Y(2,) M(2)(cis-L)(4)Y(2), and M(2)(trans-L)(4)Y(2) (M(1) = Zn(II), Co(II), Cu(II); M(2) = Mn(II), Ni(II); Y = OAc, Cl, ClO(4), and NO(3)) were synthesized by reacting bivalent transitional metal salt MY(2).nH(2)O (n = 0-6) with ligands cis-racemate of propiconazole (cis-L) and trans-racemate of propiconazole (trans-L), respectively. All of these synthesized complexes were identified by atomic absorption spectrometry, elemental analysis, and IR and UV spectra. The cumulative release studies of some selected complexes in static water were performed; all determined complexes were found to exhibit attractive controlled release properties, yet the ligand release rates of cis-L complexes were slower than those of trans-L complexes. Meanwhile, it was found that the release rate of ligand cis-L from representative complex Zn(cis-L)(2)Cl(2) was affected obviously by different conditions, such as temperature, pH, and PVA film coating. The antifungal activities of the ligands and their complexes against five selected plant pathogenic fungi were evaluated; the results demonstrated that the toxicity of cis-L was 3.39-5.95 times greater than that of trans-L, and all of the synthesized complexes showed superior activities of 1.19-6.36 times to those of their ligands, especially Zn complexes having toxicities 2.62-6.36 times greater than those of their ligands. Moreover, the cis-L complexes had more sensitive activities than their relevant trans-L complexes; for example, Zn(cis-L)(2)Cl(2) appeared to be 5.00-8.67 times stronger than Zn(trans-L)(2)Cl(2) complex. In addition, the mechanism of increased antifungal activities of the title complexes in comparison with their ligands was discussed preliminarily.

Study of fluorescence properties of several 4-acyl pyrazolone derivatives and their Zn (II) complexes

Fluorescence properties of four 4-acyl pyrazolone derivatives (H(2)L(1)=N-(1,3-diphenyl-4-propylene-5-pyrazolone)-salicylidene hydrazone (1), H(2)L(2)=N-(1,3-diphenyl-4-ethylene-5-pyrazolone)-salicylidene hydrazone (2), H(2)L(3)=N-(1,3-diphenyl-4-benzylidene-5-pyrazolone)-salicylidene hydrazone (3), H(2)L(4)=N-(1,3-diphenyl-4-phenylethylene-5-pyrazolone)-salicylidene hydrazone (4), and their Zn (II) complexes: (Zn(H(2)L(1))(2) (5), Zn(H(2)L(2))(2).3CH(3)OH (6), Zn(H(2)L(3))(2).2CH(3)OH (7), and Zn(4)(H(2)L(4))(4) (8)) were studied at room temperature. It was revealed that these compounds show different fluorescence properties both in the solid state and in solution. Density functional theory (DFT) calculations on ligands 1-4 were also performed to further understand their emission properties. The calculation results indicate that the energy gaps between the highest occupied molecular orbitals (HOMOs) and the lowest unoccupied molecular orbitals (LUMOs) of these ligands are in the following order 1>2>3, which is consistent with the redshift of the emission spectra.