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A facile synthetic method for N-alkylated substituted benzochalcogenadiazoles is described. When treated with Meerwein salt, the 4-nitrobenzochalcogenadiazoles have undergone an N-alkylation to afford the expected salts as a mixture of two N1/N3 isomers in toluene. The regioselectivity of the alkylation reaction was then confirmed by spectroscopic data as well as theoretical calculations.

Nonlinear optical (NLO) effects of organic materials are caused by delocalized electrons and large polarization in molecules. In the present work, theoretical study by using the Density Functional Theory (DFT) at B3LYP/6-311G(d,p) level of theory on three types of pyridine derivates 2,6-dimethoxy-3,5-dinitropyridine (M1), 2-methoxy-3-nitropyridine (M2) and 2-methoxy-5-nitropyridine (M3) is reported. The nuclear magnetic resonance (1H and 13C NMR) chemical shifts of the title compounds were calculated using the Gauge Independent Atomic Orbital (GIAO) method and compared to the observed results. Both infrared absorption and Raman are complementary to provide characteristic fundamental vibrations that are necessary for the identification of the molecular structures. Electronic properties such as frontier molecular orbital (HOMO, LUMO), ionization potential ( IP ad ) and electronic affinity ( EA ad ) were determined to get better insight into the molecular properties. Using the Time-Dependent Density Functional Theory (TD-DFT), electronic absorption spectra have been predicted and closely matching the experimental findings. The natural bonding orbital (NBO) calculations were performed in order to elucidate various second order interactions in between the filled and vacant orbitals which are a measure of the intermolecular as well as the delocalization within the molecule. In addition, we have demonstrated that these molecular systems have large first static hyperpolarizabilities and may have potential applications in the development of NLO materials.

σ-complexation reactions of 2-N-(4′-X-pheny1)-4,6-dinitrobenzotriazole 1-oxides 1a (X = CH3) and 1e (X = CF3) with a series of C-nucleophiles, as reference, have been investigated kinetically in aqueous solution at 20 °C. The reactions are second-order and exhibit electrophilicity parameter E = -10.25 for 1a and E = -11.66 for 1e. Comparison with other derivative benzotriazoles 1a, 1c, 1d, and 1f–i reported in preceding papers is discussed, and it is shown that the E vs. pKa plot is nonlinear. In this context, geometries optimization of electrophiles 1a–i were performed at density functional theory (DFT) with the B3LYP hybrid functional and the 6–31 g(d,p) and 6–31 + g(d,p) basis sets, in acetonitrile, using the Gaussian 09 package, in order to clarify the negative deviations observed for benzotriazoles 1h and 1i. Thus, the origin of the nonlinear E vs. pKa plot was interpreted in terms of strong steric compression of the adjacent ortho-nitro and N-oxide functions. In addition, Parr's electrophilicity indices ω for these series of benzotriazoles 1a–i were calculated from the electronic chemical potential μ and the chemical hardness η and compared to experimental electrophilicity parameters E. More importantly, it has been shown that such theoretical and experimental electrophilicity scales are linearly and directly related to the correlation parameters of r2 > 0.97.

Kinetics of the reactions of 7-Imidazolium-4-nitrobenzofurazan 1a and 7-phenoxy-4-nitrobenzofurazan 1b with secondary amines 2a-c were studied spectrophotometrically in acetonitrile at 20 °C. The second-order rate constants have been used to evaluate the electrophilicity parameters E of 1a and 1b according to the linear free energy relationship log k (20 °C) = s (N + E). The theoretical electrophilic reactivity of the 7-phenoxy-4-nitrobenzofurazan 1a and 7-Imidazolium-4-nitrobenzofurazan 1b and two other nitrobenzofurazans 1c (L = OCH3) and 1d (L = Cl) have been studied by Density Functional Theory (DFT/B3LYP: Becke, 3-parameter, Lee- Yang-Parr) and the 6–311g(d,p) basis set implemented in Gaussian 09W Software. The derived electronic chemical potential (μ) and the corresponding chemical hardness (η) parameters have been used to calculate the global electrophilicity index (ω) of these series of electrophiles defined by the relationship ω = μ2/η. A good correlation between the calculated ω values and their experimentally observed electrophilic reactivities (i.e., Mayr’s electrophilicities E) is found and discussed.