The donor/acceptor (D/A) substituted π-conjugated organic molecules possess extremely fast nonlinear optical (NLO) response time that is purely electronic in origin. This makes them promising candidates for optoelectronic applications. In the present study, we utilized four hybrid density functionals (B3LYP, B97-2, PBE0, BMK), Hartree–Fock, and second order Møller–Plesset correlation energy correction, truncated at second-order (MP2) methods with different basis sets to estimate molecular first hyperpolarizability (β) of D/A-substituted benzenes and stilbenes (D=OMe, OH, NMe2, NH2; A=NO2, CN). The results of density functional theory (DFT) calculations are compared to those of MP2 method and to the experimental data. We addressed the following questions: (1) the accurate techniques to compare calculated results to each other and to experiment, (2) the choice of the basis set, (3) the effect of molecular planarity, and (4) the choice of the method. Comparison of the absolute values of hyperpolarizabilities obtained computationally and experimentally is complicated by the ambiguities in conventions and reference values used by different experimental groups. A much more tangible way is to compare the ratios of β’s for two (or more) given molecules of interest that were calculated at the same level of theory and measured at the same laboratory using the same conventions and reference values. Coincidentally, it is the relative hyperpolarizabilities rather than absolute ones that are of importance in the rational molecular design of effective NLO materials. This design includes prediction of the most promising candidates from particular homologous series, which are to be synthesized and used for further investigation. In order to accomplish this goal, semiquantitative level of accuracy is usually sufficient. Augmentation of the basis set with polarization and diffuse functions changes β by 20%; however, further extension of the basis set does not have significant effect. Thus, we recommend 6-31+G* basis set. We also show that the use of planar geometry constraints for the molecules, which can somewhat deviate from planarity in the gas phase, leads to sufficient accuracy (with an error less than 10%) of predicted values. For all the molecules studied, MP2 values are in better agreement with experiment, while DFT hybrid methods overestimate β values. BMK functional gives the best agreement with experiment, with systematic overestimation close to the factor of 1.4. We propose to use the scaled BMK results for prediction of molecular hyperpolarizability at semiquantitative level of accuracy.

The azasydnone unit is a promising explosophoric block for future generations of highly thermostable and dense energetic materials.

Nickel oxyhydroxide, NiOOH, anode has been shown to be an effective tool for the oxidation of aminofurazans to azofurazans in ca. 1% aqueous alkali at room temperature. The electrochemical reaction is simple and convenient, eliminating the use of expensive and toxic organic or inorganic oxidants. The green economic preparation of desired azo compounds is very clean, producing only H₂ as a result of cathodic reduction.

Although desirable from an energetic materials chemistry perspective, nitroazoles bearing oxygen-rich explosophoric units at a nitrogen atom of the ring are a highly challenging target using current literature approaches. In this paper, we report the first simple two-step protocol to efficiently prepare unprecedented N-(2-fluoro-2,2,-dinitroethyl) derivatives of imidazoles, pyrazoles, triazoles, and tetrazoles. Michael addition of NH-azoles to 1,1-dinitroethene, generated from 1,1,1-trinitroethane, followed by fluorination provides the N-dinitrofluoroethylated nitrogen heterocycles in moderate to good overall yields. The syntheses employ azoles with electron-withdrawing groups, predominantly, the nitro group, and can be extended to other structurally attractive electron-deficient NH-heterocycles.