Energetic ionic salts based on nitrogen-rich heterocycles: A prospective study

New energetic salts may be synthesized via the quarternization of azido or nitro derivatives of 1,2,4-triazole, and substituted derivatives of tetrazole with nitric acid or perchloric acid or iodomethane followed by metathesis reaction with AgNO₃ or AgClO₄ have been suggested in the literature for synthesis of new energetic ionic salts. The present review focuses briefly on the synthesis aspects and some of the physico-chemical properties of energetic materials of the class have been investigated. The structures of prospective energetic ionic salts include (a) 1-(2-azidoethyl)-1,2,4-triazolium-5-nitrotetrazolate, (b) 1-(2-azidoethyl)-3-azido-1,2,4-triazolium 5-nitrotetrazolate, (c) 1-(2-azidoethyl)-4-amino-1,2,4-triazolium perchlorate, 1-(2-azidoethyl)-1,2,4-triazole and so on. These compounds may find a wide spectrum of futuristic applications in the area of energetic materials. The salts exhibit good thermal stabilities, low vapour pressure, high heat of formation and high densities. Constant volume combustion energies may be determined experimentally using oxygen bomb calorimeter, DSC, ¹H and ¹³C NMR. The standard molar enthalpies of formation will be derived from designed Hess thermochemical cycles.     

Understanding the adsorption of 4H-1,2,4-triazole derivatives on mild steel surface in molar hydrochloric acid

This study examines the use of some 4H-triazole derivatives, namely 3,5-diphenyl-4H-1,2,4-triazole (DHT), 3,5-bis(4-pyridyl)-4H-1,2,4-triazole (4-PHT) and 3,5-bis(4-methyltiophenyl)-4H-1,2,4-triazole (4-MTHT) for corrosion and dissolution protection of mild steel in normal hydrochloric acid solution. The inhibiting efficiency of the different additives is evaluated by means of weight loss and electrochemical techniques such as ac impedance measurements and polarisation curves. The experimental results obtained reveal that 4-MTHT is the best effective inhibitor and the inhibition efficiency is found to be in the following order: 4-MTHT > 4-PHT > DHT. The variation in inhibitive efficiency mainly depends on the type and nature of the substituents present in the inhibitor molecule. Polarisation curves show that theses triazoles are mixed-type inhibitors in 1 M HCl. The inhibition efficiency increases with 4H-triazole derivatives concentration and attains the maximum value of 99.6% in the case of 4-MTHT at 5 × 10⁻⁴ M. The results obtained from weight loss electrochemical studies were in reasonable agreement. The adsorption of 4H-triazole derivatives on the steel surface obeys to the Langmuir isotherm model. The thermodynamic data of adsorption and activation are determined and discussed. The fundamental thermodynamic functions were used to glean important information about the 4H-triazoles inhibitory behaviour. Molecular modeling was used to get better insight, about structural and electronic effects in relation to the inhibition efficiencies.     

Parallel synthesis of 1,2,4-triazole derivatives using microwave and continuous-flow techniques

Abstract  

An efficient and convenient solution-phase synthesis of a 1H-1,2,4-triazole library with potential agrochemical activity is reported employing microwave-assisted organic synthesis (MAOS) and continuous-flow microfluidic synthetic methods starting from commercially available 3,5-dibromo-1H-1,2,4-triazole (1). MAOS was used for the synthesis of 5-amino-3-bromo-1,2,4-triazole analogs 3 and for their 3-aryl derivatives 4 via Suzuki–Miyaura coupling with polymer-supported catalyst. A microfluidic hydrogenation reactor integrated into an automated parallel synthesis platform was built and utilized for the reductive dehalogenation reactions providing 5-aminotriazoles (5).     

Experimental evidence of the vibrational coupling of nearest neighbours in 1D spin crossover polymers of rigid bridging ligands

The nuclear inelastic scattering signatures of the low spin centres of the methanosulphonate, tosylate and perchlorate salts of the spin crossover polymer ([Fe(II)(4-amino-1,2,4-triazole)₃]⁺²) _n have been compared for the pure low-spin phase, for the mixed high-spin and low-spin phases, as well as for Zn(II) diluted samples. Within this series a change in the spectral pattern in the 320–500 cm^?1 region is observed involving the decrease of the intensities of a band at ～320 cm^?1 and those over 400 cm^?1 as the molar fraction of the low-spin centres decreases. On the basis of the DFT calculations (B3LYP/CEP-31G) this effect is interpreted in terms of vibrational coupling of the iron centres of the same spin.     

Electron irradiation effects on 4-amino-5-mercapto-3-[1-(4-isobutylphenyl)ethyl]-1,2,4-triazole single crystal

In this paper, we report the electron irradiation effects on the properties of an organic NLO single crystal of 4-amino-5-mercapto-3-[1-(4-isobutylphenyl)ethyl]-1,2,4-triazole. The crystal was irradiated with electron beam of different doses and was characterized by powder XRD, UV-Vis, FTIR, DSC, microhardness and SHG measurements. In XRD, the peaks are shifted due to irradiation. The SHG efficiency has been found to enhance rapidly with irradiation. The investigation of the influence of electron irradiation on the surface morphology of the grown crystal reveals the formation of craters on the surface. The laser damage threshold remains constant as the dose rate increases whereas refractive index increases after irradiation.     

A phase-matchable nonlinear optical crystal 4-amino-5-mercapto-3-[1-(4-isobutylphenyl)ethyl]-1,2,4-triazole: Synthesis,crystal growth and characterization

In this paper, we report the synthesis, growth and characterization of a new organic NLO single crystal of 4-amino-5-mercapto-3-[1-(4-isobutylphenyl)ethyl]-1,2,4-triazole (AMIT). The title compound is synthesized and single crystals were grown by the slow evaporation technique at room temperature. The grown crystal was characterized by powder XRD, FTIR, UV-Vis. and microhardness studies. The thermal analysis of the crystal was carried out by TGA, DTAand DSC. FromDSC, the melting point of the crystal is found to be 168°C. The scanning electron microscopy (SEM) provides information about the surface morphology of the crystal. The SHG efficiency has been estimated as 0.3 times that of KDP using Kurtz powder method and is found to be a phase-matchable NLO crystal.     

Nuclear inelastic scattering study of a dinuclear iron(II) complex showing a direct spin transition

The results of the nuclear inelastic scattering (NIS)/nuclear resonance vibrational spectroscopy (NRVS) for the powder spectra of dimeric [Fe ₂L₅(NCS) ₄] (L = N-salicylidene-4-amino-1,2,4-triazole) complex are presented. This system is spin crossover (SCO) material tagged with a fluorophore that can sense or “feel” the SCO signal ripping through the molecular network and thereby providing an opportunity to register the SCO transition. The spectra have been measured for the low-spin and high-spin phases of the complex. The high-spin isomer reveals one broad band above 200 cm ^?1, while the low-spin one displays two intense bands in the range from 390 to 430 cm ^?1, accompanied by a number of weaker bands below this area and one at ca. 490 cm ^?1. A normal coordinate analysis based on density functional calculations yields the assignment of the spin marker bands to particular molecular modes. In addition the vibrational contribution to the spin transition has been estimated     

6-巯基-5-三唑并[4,3-b]-s-四嗪(MTT）的密度泛函理论研究

采用密度泛函理论（Density functional theory,DFT）,在B3LYP/6-31g(d) (C,H,N,S),Ag原子采用LanL2d赝势基组水平上对甲醛（HCHO）与4-氨基-5肼基-3-巯基-1,2,4-三唑(4-amino-5-hydrazino-3-mercapto-1,2,4-triazole,AHMT)衍生化反应生的成产物6-巯基-5-三唑并[4,3-b]-s-四嗪（6-mercapto-5-triazolo[4,3-b]-s-tetrazine,MTT）及其银配合物进行结构优化,优化结果表明MTT的结构是一个近平面结构。通过对频率计算,获得MTT分子及其银配合物的拉曼光谱,对400-1800 cm-1波段内的拉曼光谱特征峰进行了指认。同时讨论了MTT分子的表面静电势,分析可能发生化学反应的位点。并采用含时密度泛函理论（Time Dependent density functional theory,TDDFT）对MTT分子与Ag3配合物的激发态进行了计算分析,并使用电荷转移光谱对Ag配合物与MTT之间电荷转移关系进行了研究。该研究对MTT分子的光谱测定和电子性质提供了理论基础。     

新型三唑硫酮席夫碱的微波合成与结构表征

微波辐射条件下,以氨基均三唑硫醇与查尔酮为原料,通过亲核取代反应,制备了3-（4-氨基-5-巯基-3-对甲苯基均三唑-1-氮代）-1,3-二苯-1-丙酮（3）,（3）与系列芳香醛经缩合反应,合成了4种三唑硫酮席夫碱（4a-4d）.探讨了各实验因素对收率的影响,得到了优化的工艺条件：n（芳香醛）∶n（氨基三唑硫酮）=1∶1.1微波功率500W,催化剂冰醋酸2mL,反应时间4-7min,溶剂DMF,收率为65％-77％.利用IR、MS、1H NMR对目标产物进行了结构表征.     

Magnetic interactions and electronic structure of $$\hbox {Pt}_{2}\hbox {Mn}_{1-x}\hbox {Y}_{x} \hbox {Ga (Y = Cr and Fe)}$$ system: An ab-initio calculation

Structural, optical, electrical conductivity and dielectric relaxation properties of bulk 4-amino-3-mercapto-6-(2-(2-thienyl)vinyl)-1,2,4-triazin-5(4H)-one donor (AMT) are studied. The structure of AMT in its powder form was analysed by X-ray diffraction (XRD), infrared spectroscopy (FT-IR) and atomic force microscopy (AFM). AC measurements (impedance, capacitance and phase angle) are done over the temperature range 303–373 K and in the frequency range from 42 Hz to 5 MHz. Analytical approaches for the experimental results of the σ _AC(ω, T) and the temperature behaviour of the frequency exponent show that the correlated barrier hopping (CBH) model is a good model to explain the AC electrical conductivity of bulk AMT organic semiconductor material. Application of the dielectric modulus formulism gives a simple method for evaluating the activation energy of the dielectric relaxation. The activation energy from the DC conductivity and the relaxation time are quite similar suggesting a hopping mechanism for AMT. The optical band gap of AMT is investigated using spectrophotometric measurement of transmittance at normal incidence of light in the wavelength range 300–1100 nm.     

Mössbauer spectroscopy monitoring the spin transition of a FeII 1D chain with a fluorinated 4-R-1,2,4-triazole

The spin transition properties of [Fe(fletrz)₃](BF₄)₂?2H₂O are described. Fletrz (4-(2’-fluoroethyl)-4H-1,2,4-triazole) is a novel fluorine substituted 1,2,4-triazole ligand which forms 1D chain upon self-assembly with Fe^II ions. This coordination polymer exhibits reversible abrupt thermochromic spin transition that has been probed by SQUID magnetometry, variable temperature ⁵⁷Fe Mossbauer spectroscopy (77–300 K) and differential scanning calorimetry (100–300 K).     

希夫碱配合物M3L3(NO3)6(H3O)2的合成与光谱性质

以4-氨基-1,2,4-三氮唑与对二甲氨基苯甲醛为原料, 在冰醋酸催化下合成了配体4-氨基-1,2,4-三氮唑缩对二甲氨基苯甲醛（L）。 然后利用L与过渡金属硝酸盐［M(NO3)2·xH2O(M=Cu,　Co,　Zn,　Cd; x=3～6)］在无水乙醇中反应, 制得固态配合物M3L6(NO3)6(H2O)2。 通过元素分析、 红外光谱、 紫外光谱、 荧光光谱等手段对合成的配体及配合物进行了表征。 实验结果表明, 该物质是一种多晶粉末状的发光材料,　在紫外光的激发下,　在乙醇溶液体系中的荧光发射峰在416 nm处,　为蓝色荧光, 色纯度高,　荧光量子效率高, 而配合物M3L6(NO3)6(H2O)2的荧光发射峰则红移至445 nm左右, 同时荧光强度显著增强。　M3L6(NO3)6(H2O)2中与M(Ⅱ)发生配位作用的基团是配体中三氮唑环上的氮原子。     

3-氨基-5-巯基-1,2,4-三唑与Ag(I)配位作用的密度泛函理论研究

采用密度泛函理论B3LYP方法研究3-氨基-5-巯基-1,2,4-三唑与Ag(I)的配位特点.计算结果显示,ad-L配体配位能力显著高于中性配体L,其中SN配位模式稳定化能高于中性配体约443.8kJ/mol,且N2模式稳定化能高于中性配体约336.8 kJ/mol;而p-L配体相互作用能和稳定化能均为负值.自然键轨道(NBO)分析显示配体与Ag(I)间存在较强轨道作用.静电势分析发现,L配体最负静电势出现在N1、N2原子周围,因此N1、N2位点更易与Ag(I)配位; ad-L配体静电势为负,因此与Ag(I)作用增强,而质子化的配体p-L静电势为正,因此不易与Ag(I)配位.     

Relaxation behavior of glassy selenium

The dynamics of the glass transition of amorphous selenium was investigated by using differential scanning calorimeter. The heat capacity data were analyzed applying the phenomenological Tool–Narayanaswamy–Moynihan (TNM) model in order to describe the relaxation behavior of a-Se. The TNM parameters were evaluated by fitting the enthalpic cycles and also one isothermal experiment. Furthermore, peak-shift method and several other methods of evaluating the TNM parameters were applied to confirm the results of curve fitting. The results are compared with the other published enthalpy and viscosity data, volume and enthalpy relaxation are compared on account of our previous mercury dilatometry measurements. We found out that the pre-exponential factor A and the apparent activation energy Δh^* of structural relaxation are similar for volume and enthalpy relaxation and Δh^* is very close to the activation energy of viscous flow.     

Trapping of metastable high-spin species and weak cooperativity in a mononuclear Fe(II) spin-crossover system

The magnetic and structural properties of three gradual spin transition monomeric compounds based on the cation [Fe(Hpt)₃]²⁺ (Hpt=3-(pyrid-2-yl)-1,2,4-triazole) are presented. The non-cooperative character of the spin-crossover in [Fe(Hpt)₃](BF₄)₂·2H₂O (I) is evaluated in light of its calorimetric properties, which yielded the thermodynamic values Δ_trsH=5.81 kJ mol⁻¹ and Δ_trsS=39.5 J mol⁻¹ K⁻¹. The light-induced excited spin-state trapping effect is performed on [Fe(Hpt)₃](BF₄)₂·2H₂O (I) and [Fe(Hpt)₃](SO₄)_0.4(BF₄)_1.2·3H₂O (II), and the subsequent HS→LS relaxations are studied. Their merely first-order kinetics are affected by disorder in the structure of both complexes, which appears in the presence of a distribution of activation energies. HS species can also be frozen-in in I by rapid cooling. Continuous irradiation is shown to induce only apparent light-induced thermal hysteresis effect in I and II, stemming from slow kinetics of relaxation with respect to the kinetics of measurement.     

Mean work functions effective for negative-ionic, electronic and positive-ionic emissions from polycrystalline surfaces

To elucidate the thermionic property of polycrystalline surfaces, a further study is made on the mean work functions (φ⁻, φ^e and φ⁺) effective for negative-ionic, electronic and positive-ionic emissions. Comparison between theoretical analyses and experimental data yields the conclusions as follows. (1) The equation of φ⁻ = φ^e holds always with both mono- and polycrystalline surfaces. (2) The relation of φ⁻ = φ^e < φ⁺ applies to polycrystalline surfaces because they bear the thermionic contrast (Δφ^* ≡ φ⁺ − φ^e > 0). (3) The value of Δφ^* ranges from ∼0.4 to 0.9 eV depending upon the surface species of polycrystalline metals (e.g., W, Re and Pt), whilst Δφ^* = 0 for monocrystalline surfaces. (4) When the degree of monocrystallization (δ_m) is less than ∼50%, the theoretical value of Δφ^* is virtually independent of δ_m and agrees well with experimental data, nearly the same within ±0.1 eV among the so-called “polycrystalline” surfaces of W. (5) As δ_m increases beyond ∼80 up to 100%, Δφ^* decreases rapidly down to 0 eV, showing again a good agreement between theory and experiment. (6) Our theoretical model is valid in evaluating the effective mean work functions, irrespective of the range of δ_m.     

Autodiffusion en volume dans la phase plastique de l'acide pivalique (acide 2.2 dimethyl propanoique)—I: Mesure des coefficients de diffusion et de l'effet isotopique

Self-diffusion studies have been performed in the orientationally disordered or the so-called plastic phase of pivalic acid. Single crystals of high purity (99.9999%) containing 10⁹?10¹⁰ dislocations m^?2 have been used. Thin layers of pivalic acid labelled with ¹⁴C or tritium were deposited on sample surfaces. Concentrationpenetration curves were established by serial sectioning. Lattice self-diffusion coefficients D, were measured from 281 to 304.75K. At 281K, the value of D is independent of time. From 281 to 301K, D is given by: D(m²S^?1) = (4.9 ± 0.3)10^?4 exp [? (59± 1) kJ mole^?1/RT].The activation enthalpy of the lattice self-diffusion is roughly equal to the heat of sublimation (L_s = 57 kJ mole^?i) and in good agreement with values obtained from NMR. The mass factorf ΔK, where f is the correlation factor and ΔK is a correction factor, has been measured using isotope effect studies. Between 281 and 301K the value obtained is fΔK* 0.1^+0.2_?0.1     

Spectrophotometric determination of some amino heterocyclic donors through charge transfer complex formation with chloranilic acid in acetonitrile

The present study is directed toward a development of simple, rapid and accurate spectrophotometric method for determination of some amino heterocyclic donors. The Charge transfer (CT) interactions between 3-aminopyrazole (AP), 3,5-dimethyl-pyrazole (DMP), 3-amino-5-methyl-pyrazole (AMP), 2-amino-4-methyl-thiazole (AMT), 2-amino-5-methyl-1,3,4-thiadiazole (AMTD) and 2-amino-5,6-dimethyl-1,2,4-triazine (ADMT) with chloranilic acid (CLA) as π-acceptor have been investigated spectrophotometrically in acetonitrile. Factors controlling the CT-reactions were also studied and optimized. Under the optimum conditions, linear relationships with good correlation coefficients were identified with high accuracy and precision. Job's method of continuous variation, spectrophotometric and conductometric titrations were used to identify the composition of the formed CT-complexes. Benesi-Hildebrand (BH) equation has been used to calculate the formation constants of the charge transfer reactions K_CT and the molar extinction coefficients ε. Free energy change (ΔG^o), oscillator strength (f), transition dipole moment (µ), ionization potential (I_P) and charge transfer energy of the formed CT-complexes (E_CT) were also determined and evaluated.     

Influence of the dimension of a polycrystalline film and the optical anisotropy of crystallites on the effective dielectric constant of the film

The dimension D of a polycrystalline film and the optical anisotropy m = ε_z/ε_x of uniaxial crystallites with the principal components ε_x = ε_y and ε_z of the tensor of the dielectric constant have been shown to produce a strong influence on the effective dielectric constant ε_D^* and the effective refractive index n_D^* = (ε_D^*)^1/2 of the film in the optical transparency region, as well as on the boundaries of the intervals B_Dl ≤ ε_D^* ≤ B_Du. The intervals Δ₂(m) = B_2l–B_2u and Δ₃(m) = B_3l–B_3u are separated by a gap for m in the range 1 < m < 2, whereas the theoretical dependence ε₂^*(m) is separated by a gap from the interval Δ₃(m) for m in the range 1 < m < 4. This is confirmed by a comparison of the experimental (n_oP) and theoretical (n_D^*) ordinary refractive indices for uniaxial polycrystalline films of the conjugated polymer poly(p-phenylene vinylene) (PPV) with uniaxial crystallites and appropriate values of m. In the visible transparency region of the PPV films with a change in m(λ) in the range 2 < m(λ) < 3 due to the dependence of the components ε_x,z(λ) on the light wavelength λ, the refractive indices n_oP²(λ) = ε_oP(λ) are consistent with the theoretical values of ε₂^*(λ) and lie outside the interval Δ₃(m). For m(λ) > 3 near the electronic absorption band of the crystallites, the values of ε_oP(λ) lie in the region of the overlap of the intervals Δ₂(m) and Δ₃(m). The boundaries mc of the range 1 < m < m_c are determined, for which the interval Δ₂(m) is separated by a gap from the dependences ε₃^*(m) corresponding to the effective medium theory with spherical crystallites and hierarchical models of a polycrystal, as well as from the proposed new dependence ε₃^*(m).     

Quantitative relation between the thermionic contrast of metal surfaces and their degree of monocrystallization

For better understanding the peculiarities of work function, a simple model is devised to calculate the effective work functions (?⁺ and ?^e) for positive-ionic and electronic emissions from polycrystalline surfaces, which have a work function range from the maximum (?_max) to the minimum (?_min). Analysis of the theoretical results thus obtained and also of experimental data published to date enables us to find the quantitative relation between the thermionic contrast (Δ?^* ≡ ?⁺ − ?^e) and the degree of monocrystallization (δ_m), thereby yielding the three formulae of (1) Δ?^* = c for 0 < δ_m ? 1/2 (polycrystal), (2) Δ?^* = 4 cδ_m (1 − δ_m) for l/2 ? δ_m ? 1 (polycrystal), and (3) Δ?^* = 0 for δ_m = 1 (monocrystal). For a given surface consisting of a number of patchy faces (i), δ_m corresponds to the largest among its fractional surface areas (F_i) having different values of local work function (?_i). In a typical case of tungsten, the constant of c is evaluated theoretically to be 0.53 ± 0.09 eV, which well agrees with 0.59 ± 0.06 eV determined experimentally by many workers and also which satisfies the essential condition of Δ?^* ≦ c < ?_max − ?_min ≈ 0.8-1.0 eV. Our theoretical model is quite simple, but it is very useful for (1) evaluating both ?⁺ and ?^e with an uncertainty of less than ±0.1 eV, (2) finding the quantitative relation between Δ?^* and δ_m for actual surfaces of both poly- and monocrystals, and also (3) getting a substantial clue as to the problem how the effective work functions are governed by the surface characteristics of both F_i and ?_i.