Mustard carbonates: the effect of the leaving group

The substitution of a chlorine atom with a carbonate moiety in mustard compounds has led to a new class of molecules, namely mustard carbonates that retain the reactivity of the well-know toxic iprites, but are safe for the operator and the environment [1]. In this work, we report the further development in mustard carbonates chemistry.The influence of the leaving group on the anchimeric effect of sulfur mustard carbonates has been investigated both in autoclave and neat conditions. Results have led to enhanced selectivity of the anchimerically driven alkylation, as well as, to the improved and more accessible reaction conditions [2]. On the basis of the best results obtained the greener and efficient one-pot method of anchimericlly aided alkylation through syntesis of 2-(methylthio)ethyl ethyl carbonate in situ has been developed. Besides, a new family of half-mustard carbonate anisotropic electrophiles has been synthesized and their reactivity with aromatic nucleophiles has been investigated. The selectivity between two possible products deriving from the nucleophilic attack on the anysotropic mustard carbonates has been shown to depend on the intensity of the electron-withdrawig effect (combination of –I and –M effects) of substituent on an aromatic nucleophile in the para-position. This is remarkable example of how Green Chemistry can domesticate toxic compounds and open the way for their potential application in both preparative and industrial chemistry

Mustard carbonate analogues: influence of the leaving group

The substitution of a chlorine atom with a carbonate moiety in mustard compounds has led to a new class of molecules, namely mustard carbonates that retain the reactivity of the well-know toxic iprites, but are safe for the operator and the environment [1]. Herein we report the influence of the leaving group on the neighboring effect of sulfur half mustard carbonates (HMCs) usually less reactive than nitrogen ones [2]. Several new 2-(methylthio)ethyl alkyl carbonates have been synthesized and their reactivity has been investigated in both autoclave and neat conditions. The results reactions between the HMCs and phenol performed in autoclave (180 °C, no base, in acetonitrile media) showed that the efficiency of the anchimeric effect is directly dependent on the steric hindrance of the HMC leaving group. The least steric hindered 2-(methylthio)ethyl methyl carbonate gave the methyl (2-phenoxyethyl)sulfane in higher yield, whereas the most steric hindered 2-(methylthio)ethyl t-butyl carbonate did not reacted at all. The influence of the leaving group on the anchimeric effect has been also investigated in neat conditions at 150 °C in the presence of catalytic amount of K2CO3. In this case, due to the absence of the solvent and the presence of the base the reaction is more complicated by transesterification reactions and formation of unwanted products. Interestingly 2-(methylthio)ethyl ethyl carbonate showed to be the most efficient carbonate among the ones studied. This resulted might be ascribed to its ability to free the cyclic intermediate from its molecular cage as intimate ion pair more readily than the other HMCs. Finally, several nucleophiles have been then tested in neat reaction conditions using 2-(methylthio)ethyl ethyl carbonate and a catalytic amount of base. In all cases studied it was observed an almost quantitative anchimeric aided alkylation over SN2 reaction, i.e., formation of ethyl aryl ethers. The best results achieved have led to an enhanced product selectivity, more accessible reaction conditions and a better insight on the reaction mechanism of mustard carbonates

Fluctuations of Quantum Entanglement

It is emphasized that quantum entanglement determined in terms of the von Neumann entropy operator is a stochastic quantity and, therefore, can fluctuate. The rms fluctuations of the entanglement entropy of two-qubit systems in both pure and mixed states have been obtained. It has been found that entanglement fluctuations in the maximally entangled states are absent. Regions where the entanglement fluctuations are larger than the entanglement itself (strong fluctuation regions) have been revealed. It has been found that the magnitude of the relative entanglement fluctuations is divergent at the points of the transition of systems from an entangled state to a separable state. It has been shown that entanglement fluctuations vanish in the separable states.Comment: 5 pages, 4 figure

Quantum Entanglement in Nitrosyl Iron Complexes

Recent magnetic susceptibility measurements for polycrystalline samples of binuclear nitrosyl iron complexes [Fe_2(C_3H_3N_2S)_2(NO)_4] (I) and [Fe_2(SC_3H_5N_2)_2(NO)_4] (II), suggest that quantum-mechanical entanglement of the spin degrees of freedom exists in these compounds. Entanglement E exists below the temperature T_E that we have estimated for complexes I and II to be 80-90 and 110-120 K, respectively. Using an expression of entanglement in terms of magnetic susceptibility for a Heisenberg dimer, we find the temperature dependence of the entanglement for complex II. Having arisen at the temperature T_E, the entanglement increases monotonically with decreasing temperature and reaches 90-95% in this complex at T=25 K, when the subordinate effects are still small.Comment: 8 page

Spectacular enhancement of the thermal and photochemical stability of mapbi3 perovskite films using functionalized tetraazaadamantane as a molecular modifier

Perovskite solar cells represent a highly promising third-generation photovoltaic tech-nology. However, their practical implementation is hindered by low device operational stability, mostly related to facile degradation of the absorber materials under exposure to light and elevated temperatures. Improving the intrinsic stability of complex lead halides is a big scientific challenge, which might be addressed using various “molecular modifiers”. These modifiers are usually rep-resented by some additives undergoing strong interactions with the perovskite absorber material, resulting in enhanced solar cell efficiency and/or operational stability. Herein, we present a deriva-tive of 1,4,6,10-tetraazaadamantane, NAdCl, as a promising molecular modifier for lead halide perovskites. NAdCl spectacularly improved both the thermal and photochemical stability of methy-lammonium lead iodide (MAPbI3 ) films and, most importantly, prevented the formation of metallic lead Pb0 as a photolysis product. NAdCl improves the electronic quality of perovskite films by healing the traps for charge carriers. Furthermore, it strongly interacts with the perovskite framework and most likely stabilizes undercoordinated Pb2+ ions, which are responsible for Pb0 formation under light exposure. The obtained results feature 1,4,6,10-tetraazaadamantane derivatives as highly promising molecular modifiers that might help to improve the operational lifetime of perovskite solar cells and facilitate the practical implementation of this photovoltaic technology. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.This work was supported by Russian Science Foundation (project No. 19-73-30020). The XPS measurements were supported by the Ministry of Education and Science of the Russian Federation (project FEUZ-2020-0060), Theme ‘Electron’, no. AAAA-A18-118020190098-5 and Russian Foundation for Basic Research (project No. 21-52-52002)

Field induced single ion magnet based on a quasi octahedral Co ii complex with mixed sulfur oxygen coordination environment

Synthesis and characterization of structure and magnetic properties of the quasi octahedral complex pipH2 [Co TDA 2] 2H2O I , pipH22 piperazine dication, TDA2 amp; 8722; thiodiacetic anion are described. X ray diffraction studies reveal the first coordination sphere of the Co II ion, consisting of two chelating tridentate TDA ligands with a mixed sulfur oxygen strongly elongated octahedral coordination environment. SQUID magnetometry, frequency domain Fourier transform FD FT THz EPR spectroscopy, and high level ab initio SA CASSCF NEVPT2 quantum chemical calculations reveal a strong easy plane type magnetic anisotropy D amp; 8776; 54 cm amp; 8722;1 of complex I. The complex shows field induced slow relaxation of magnetization at an applied DC field of 1000 O