New Light on an Old Story: Breaking Kasha’s Rule in Phosphorescence Mechanism of Organic Boron Compounds and Molecule Design

In this work, the phosphorescence mechanism of (E)-3-(((4-nitrophenyl)imino)methyl)-2H-thiochroman-4-olate-BF2 compound (S-BF2) is investigated theoretically. The phosphorescence of S-BF2 has been reassigned to the second triplet state (T2) by the density matrix renormalization group (DMRG) method combined with the multi-configurational pair density functional theory (MCPDFT) to approach the limit of theoretical accuracy. The calculated radiative and non-radiative rate constants support the breakdown of Kasha’s rule further. Our conclusion contradicts previous reports that phosphorescence comes from the first triplet state (T1). Based on the revised phosphorescence mechanism, we have purposefully designed some novel compounds in theory to enhance the phosphorescence efficiency from T2 by replacing substitute groups in S-BF2. Overall, both S-BF2 and newly designed high-efficiency molecules exhibit anti-Kasha T2 phosphorescence instead of the conventional T1 emission. This work provides a useful guidance for future design of high-efficiency green-emitting phosphors.

Synthesis and Characterization of New Boron Compounds Using Reaction of Diazonium Tetraphenylborate with Enaminoamides

A family of oxazaborines, diazaborinones, triazaborines, and triazaborinones was prepared by reaction of polarized ethylenes, such as β-enaminoamides, with 4-methylbenzenediazonium tetraphenylborates. The reaction conditions (stirring in CH2Cl2 at room temperature (Method A) or stirring with CH3COONa in CH2Cl2 at room temperature (Method B) or refluxing in the CH2Cl2/toluene mixture (Method C)) controlled the formation and relative content of these compounds in the reaction mixtures from one to three products. Substituted oxazaborines gradually rearranged into diazaborinones at 250 °C. The prepared compounds were characterized by 1H NMR, 13C NMR, IR, and UV–Vis spectroscopy, HRMS, or microanalysis. The structure of individual compounds was confirmed by 11B NMR, 15N NMR, 1D NOESY, and X-ray analysis. The mechanism of reaction of enaminoamides with 4-methylbenzenediazonium tetraphenylborate was proposed.

Domates Tohumlarında Pseudomonas syringae pv. tomato’ya Karşı Farklı Bor Bileşiklerinin Etkililikleri

Pseudomonas syringae pv. tomato, the bacterial agent for tomato speck disease, can cause serious epidemics with high leaf moisture, mild temperatures, and cultural practices allowing bacterial dissemination among host plants. Boron is an essential micro-nutrient for plant growth and health in agricultural production. In this study, the effectiveness of 14 different Boron compounds at 5 different doses (1, 5, 10, 20 and 40 mM) against P. s. pv. tomato at a concentration of 108 CFU ml-1 in vitro was evaluated and the most successful 4 different Boron compounds (Ammonium tetrafluoroborate, Sodium tetrafluoroborate, Zinc borate and Disodium octaborate tetrahydrate) were coated with 5 mM doses infected cv. H2274 tomato seeds to determine bacterial populations and seed emergence rates in the seeds. Among the 14 different Boron compounds used in the experiments, Disodium octaborate tetrahydrate was the most successful active ingredient 92% ratio in inhibiting P. s. pv. tomato populations in tomato seeds, while 39% success was achieved with sodium tetrafluoroborate applications. According to the results of the research, it is thought that some Boron compounds can be an economical, effective and environmentally friendly chemical in reducing P. s. pv. tomato in tomato seeds within the scope of good agricultural practices.

Modification of Glass/Polyester Laminates with Flame Retardants

This paper presents a review of flame retardants used for glass/polyester laminates. It concerns flame retardants withdrawn from use such as compounds containing halogen atoms and flame retardants currently used in the industry, such as inorganic hydroxides, phosphorus and nitrogen-containing compounds, antimony, and boron compounds, as well as tin–zinc compounds. Attention is also drawn to the use of nanoclays and the production of nanocomposites, intumescent flame retardant systems, and mats, as well as polyhedral oligomeric silsesquioxanes. The paper discusses the action mechanism of particular flame retardants and presents their advantages and disadvantages.

Validation of the method for evaluating the efficacy of food baits against pharaoh ant colonies

The validation of the method for testing the effectiveness of food baits against colonies of the Pharaoh ant using experiments with commercially produced and laboratory-prepared sugar baits containing insecticides from different chemical groups was carried out. We studied baits based on boron compounds (boric acid and sodium tetraborate), neonicotinoids (thiamethoxam, imidacloprid, and acetamiprid), oxadiazines (indoxacarb), phenylpyrazoles (fipronil), carbamates (methomyl), pyrroles (chlorfenapyr) amidinohydrazones (hydramethylnon), avermectins (abamectin), and insect growth regulators (pyriproxyfen). The proposed algorithm for conducting experiments covers the whole variety of active ingredients of insecticides used in baits. The verification of several dozen products intended for the elimination of colonies of the Pharaoh ant has shown that most of the products are suitable for the requirements for efficacy indices. Keywords: Pharaoh ant, insecticidal baits.

The radiation properties of burning clouds of metal dust. 3. Modification of the emission spectrum

In this work we studied the emission spectra of the combustion products of low-volume dust clouds (V = 5 L) from aluminum (ASD-4), as well as clouds from mixed compositions of aluminum with inorganic powdery oxidizing agents (NaNO3, NaCl, Na2CO3·10H2O, Sr(NO3)2, Ba(NO3)2, KNO3, CuSO4, CuSO4·10H2O) and combustible (B, AlB2, Cu). This article discusses the possibilities of purposeful modification of the emission spectrum of the base composition using various inert and optically active dispersed additives that shift the maximum of the emission spectrum of the fuel composition to the region of longer waves or cause a local change in the emission spectrum in the corresponding spectral regions. In the course of the experiments, it was revealed that the introduction of additives into the basic composition of dispersed fuel does not significantly change the dynamic characteristics of the suspension. However, the additives lead to a decrease in temperature (by about 100–200°K in the presence of an additive up to 25% by weight) and to a corresponding shift in the maximum of the radiation spectrum. The possibility of a significant local modification of the spectrum in the yellow region with the help of inorganic additives to the fuel of sodium salts with a low decomposition temperature (additives Na2CO3·10H2O) was shown experimentally. Boron additives and boron compounds (B, AlB2) leads to a significant increase in the luminosity of the flame in the green region of the spectrum with a maximum radiation in the range Δλ = 530 ÷ 580 nm. The article presents the lighting characteristics (luminous intensity, light sum) of large clouds (V ≥ 10 m3) of mixed compositions based on PAP-2 aluminum powder. It was found that the introduction of inorganic additives to the base fuel does not lead to a noticeable change in the lighting characteristics, but somewhat increases the time of the cloud glow both in the visible and infrared parts of the spectrum.