Covalent Organic Framework Impregnated with Silver and Copper Nanoparticles: An Advanced Approach for Catalytic Degradation of Organic Pollutants in Wastewater.

In this study, we introduce an economically viable and scalable process for developing a novel covalent organic framework (COF), which is a cross-linked polymer. The resulting material, TzTFB-COF, is successfully functionalized with silver and copper nanoparticles, which show high adequacy in the degradation of nitroaromatic compounds (NACs). For the synthesis of TzTFB-COF, s-tetrazine diamine (Tz) and 1,3,5-triformylbenzene (TFB) are chosen as building blocks, which exhibit a high density of nitrogen-containing sites. TzTFB-COF shows good chemical and thermal stability (>300 °C). For functionalization of TzTFB-COF with silver and copper nanoparticles, a solution infiltration technique is used. The composite materials, i.e., Ag@TzTFB-COF and Cu@TzTFB-COF, have been characterized using various spectroscopic and analytical techniques, which show high activity, high selectivity, and excellent chemical and thermal stability up to 350 °C. The silver and copper contents of Ag@TzTFB-COF and Cu@TzTFB-COF are determined to be 9.6 and 12.4 wt % by inductively coupled plasma optical emission spectrometer (ICP-OES). The catalytic efficiency of the synthesized Ag@TzTFB-COF and Cu@TzTFB-COF materials is assessed in the context of catalyzing the hydrogenation of NACs. Experimental results reveal a remarkable catalytic performance when conducted in an aqueous medium, and notably, the materials demonstrate substantial potential for reusability across multiple catalytic cycles. The determined parameters for the catalytic hydrogenation reaction, i.e., the rate constants and Gibbs free energies, are found to be 0.0185 s-1 and 9.878 kJ/mol for Ag@TzTFB-COF and 0.0219 s-1 and 9.615 kJ/mol for Cu@TzTFB-COF. Thus, the catalytic reaction exhibits characteristics of endothermic, endergonic, and nonspontaneous nature.

New application of novel tetrazine derivatives as potent VEGFR-2 kinase inhibitors and anti-cancer agents.

Background: A novel series of s-tetrazine derivatives was designed as a new scaffold and synthesized efficiently as VEGFR-2 inhibitors for the first time. Methodology & results: The inhibitory activities of the new compounds were tested by MTT assay and enzyme assay, respectively. Western blot assay, cell apoptosis assay and cell migration assay were carried out to study the action mechanism of them. All the synthesized compounds showed evident VEGFR-2 inhibitory activities (IC50 in the range of 88.53-257.55 nM). Compounds 23h, 25d, 26e and 27c showed excellent anti-proliferative activities against the four tested cell lines and were better than sorafenib basically. Conclusion: Compounds with good activities based on this novel scaffold can be screened successfully.

Synthesis and Luminescent Properties of s-Tetrazine Derivatives Conjugated with the 4H-1,2,4-Triazole Ring.

New derivatives obtained by the combination of unique 1,2,4,5-tetrazine and 4H-1,2,4-triazole rings have great application potential in many fields. Therefore, two synthetic few-step methodologies, which make use of commercially available 4-cyanobenzoic acid (method A) and ethyl diazoacetate (method B), were applied to produce two groups of the aforementioned heterocyclic conjugates. In both cases, the target compounds were obtained in various combinations, by introducing electron-donating or electron-withdrawing substituents into the terminal rings, together with aromatic or aliphatic substituents on the triazole nitrogen atom. Synthesis of such designed systems made it possible to analyze the influence of individual elements of the structure on the reaction course, as well as the absorption and emission properties. The structure of all products was confirmed by conventional spectroscopic methods, and their luminescent properties were also determined.

Novel Conjugated s-Tetrazine Derivatives Bearing a 4H-1,2,4-Triazole Scaffold: Synthesis and Luminescent Properties.

A series of new symmetrical s-tetrazine derivatives, coupled via a 1,4-phenylene linkage with a 4H-1,2,4-triazole ring, were obtained. The combination of these two rings in an extensively coupled system has significant potential applications, mainly in optoelectronics. The methodology used turned out to be useful regardless of the type of five-membered ring or the nature of the individual substituents. All the products were identified by spectroscopic methods, and the target compounds were tested for luminescent properties. This study showed that all the synthesized highly-conjugated triazoles exhibited luminescence; in particular, one derivative, 3,6-bis(4-(5-(4-methoxyphenyl)-4-phenyl-4H-1,2,4-triazol-3-yl)phenyl)-1,2,4,5-tetrazine (13b), showed strong fluorescence emission and ahigh quantum yield close to 1.

Redox Potential Tuning of s-Tetrazine by Substitution of Electron-Withdrawing/Donating Groups for Organic Electrode Materials.

Herein, we tune the redox potential of 3,6-diphenyl-1,2,4,5-tetrazine (DPT) by introducing various electron-donating/withdrawing groups (methoxy, t-butyl, H, F, and trifluoromethyl) into its two peripheral benzene rings for use as electrode material in a Li-ion cell. By both the theoretical DFT calculations and the practical cyclic voltammetry (CV) measurements, it is shown that the redox potentials (E1/2) of the 1,2,4,5-tetrazines (s-tetrazines) have a strong correlation with the Hammett constant of the substituents. In Li-ion coin cells, the discharge voltages of the s-tetrazine electrodes are successfully tuned depending on the electron-donating/withdrawing capabilities of the substituents. Furthermore, it is found that the heterogeneous electron transfer rate (k0) of the s-tetrazine molecules and Li-ion diffusivity (DLi) in the s-tetrazine electrodes are much faster than conventional electrode active materials.

Enhancing Magnetic Communication between Metal Centres: The Role of s-Tetrazine Based Radicals as Ligands.

Although 1,2,4,5-tetrazines or s-tetrazines have been known in the literature for more than a century, their coordination chemistry has become increasingly popular in recent years due to their unique redox activity, multiple binding sites and their various applications. The electron-poor character of the ring and stabilization of the radical anion through all four nitrogen atoms in their metal complexes provide new aspects in molecular magnetism towards the synthesis of new high performing Single Molecule Magnets (SMMs). The scope of this review is to examine the role of s-tetrazine radical ligands in transition metal and lanthanide based SMMs and provide a critical overview of the progress thus far in this field. As well, general synthetic routes and new insights for the preparation of s-tetrazines are discussed, along with their redox activity and applications in various fields. Concluding remarks along with the limitations and perspectives of these ligands are discussed.

Single-Junction Polymer Solar Cells with 16.35% Efficiency Enabled by a Platinum(II) Complexation Strategy.

A new strategy of platinum(II) complexation is developed to regulate the crystallinity and molecular packing of polynitrogen heterocyclic polymers, optimize the morphology of the active blends, and improve the efficiency of the resulting nonfullerene polymer solar cells (NF-PSCs). The newly designed s-tetrazine (s-TZ)-containing copolymer of PSFTZ (4,8-bis(5-((2-butyloctyl)thio)-4-fluorothiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene-alt-3,6-bis(4-octylthiophen-2-yl)-1,2,4,5-tetrazine) has a strong aggregation property, which results in serious phase separation and large domains when blending with Y6 ((2,2'-((2Z,2'Z)-((12,13-bis(2-ethylhexyl)-3,9-diundecyl-12,13-dihydro-[1,2,5]thiadiazolo[3,4-e]thieno[2″,3″:4',5']thieno[2',3':4,5]pyrrolo[3,2-g]thieno[2',3':4,5]thieno[3,2-b]indole-2,10-diyl)bis(methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile)), and produces a power-conversion efficiency (PCE) of 13.03%. By adding small amount of Pt(Ph)2 (DMSO)2 (Ph, phenyl and DMSO, dimethyl sulfoxide), platinum(II) complexation would occur between Pt(Ph)2 (DMSO)2 and PSFTZ. The bulky benzene ring on the platinum(II) complex increases the steric hindrance along the polymer main chain, inhibits the polymer aggregation strength, regulates the phase separation, optimizes the morphology, and thus improves the efficiency to 16.35% in the resulting devices. 16.35% is the highest efficiency for single-junction PSCs reported so far.

s-Tetrazines as a New Electrode-Active Material for Secondary Batteries.

Because of the limitations of conventional metal-oxide-based electrodes, studies on organic redox-active materials as alternative electrodes for secondary batteries are emerging. However, reported organic electrode materials are still limited to a few kinds of organic redox groups. Therefore, the development of new redox-active groups for high-performance electrode materials is indispensable. Here, we evaluate s-tetrazine derivatives as a new electrode material in Li-ion batteries and study their charge/discharge mechanisms by ex situ XPS measurements. The porous carbon CMK-3 was introduced to encapsulate the s-tetrazines, which allowed 100 % utilization of the theoretical capacity and stable cycle performance of the s-tetrazines by preventing dissolution of the molecules into the electrolytes. This new class of redox-active group can pave the way for the next-generation of energy storage systems.

Synthesis, crystal structure and thermal properties of an unsymmetrical 1,2,4,5-tetrazine energetic derivative.

A new unsymmetrical s-tetrazine derivative, namely 4-({2-[6-(3,5-dimethyl-1H-pyrazol-1-yl)-1,2,4,5-tetrazin-3-yl]hydrazin-1-ylidene}methyl)phenol (DPHM), C14H14N8O, was synthesized based on 3-(3,5-dimethylpyrazol-1-yl)-6-hydrazinyl-s-tetrazine (DPHT). The structure was characterized by elemental analysis and single-crystal X-ray diffraction. Crystal structure determination shows that DPHM crystallizes in the monoclinic P21/c space group with high coplanarity and a zigzag layered structure. In addition, its thermal behaviour was investigated by DSC and TG-DTG methods. The thermal safety of DPHM was evaluated by self-accelerating decomposition temperature (TSADT), critical temperature of thermal explosion (Tb), entropy of activation (ΔS=), enthalpy of activation (ΔH=) and free energy of activation (ΔG=). Meanwhile, the kinetic parameters and specific heat capacity of DPHM were also determined. The results show that DPHM has better stability and detonation properties than 3-(2-benzylidenehydrazin-1-yl)-6-(3,5-dimethylpyrazol-1-yl)-s-tetrazine (DAHBTz), due to the introduction of a hydroxy group, which increases the number of hydrogen-bond interactions and improves the stability and density of DPHM. This study demonstrates that the performance of an explosive can be optimized through structural modification.

An efficient and mild oxidant for the synthesis of s-tetrazines.

PhI(OAc)2 serves as a mild and effective oxidant for the synthesis of s-tetrazine derivatives- molecules of emerging significance to the field of bioorthogonal chemistry. This reagent serves as a complementary oxidant to harsher nitrous reagents. Use of PhI(OAc)2 improves the synthesis of 5-amino-di(pyridin-2-yl)-s-tetrazine, a molecule that has been broadly used for cellular imaging and nuclear medicine. The generality of PhI(OAc)2 as the oxidant for tetrazine synthesis is demonstrated for nine tetrazines in 75-98% yield.