Electronic effects of heterocyclic ring systems as evaluated with the aid of13C and15N NMR chemical shifts and NBO analysis

Green synthesis and corrosion inhibition study of 2-amino-N′-((thiophen-2-yl)methylene)benzohydrazide

2-Amino-N′-((thiophen-2-yl)methylene)benzohydrazide (ATMBH) was synthesized by a conventional method, as well as by microwave (MW) irradiation.

Preparation of dihydroquinazoline carbohydrazone Fe(ii) complexes for spin crossover

Mononuclear spin-crossover complexes of dihydroquinazoline derivatives were synthesized to enable the spin crossover phenomenon via the variation of the solvent, anion and substituent.

An experimental study of the electronic absorption and fluorescence spectral properties of new p-substituted-N-phenylpyrroles and their electrosynthesized polymers

Electronic absorption and fluorescence spectral properties of new p-substituted-N-phenylpyrroles (N-PhPys), including HOPhPy, MeOPhPy, ThPhPy, PhDPy, DPhDPy, PyPhThThPhPy, and their available, electrosynthesized polymers were investigated. Electronic absorption spectra, fluorescence excitation and emission spectra, fluorescence quantum yields (ΦF) and lifetimes (τF), and other photophysical parameters of these N-PhPy derivatives and their polymers were measured in DMF, DMSO diluted solutions and/or solid state at room temperature. The electronic absorption spectra of N-PhPy derivatives and their polymers included one to several bands, located in the 270-395 nm region, according to the p-phenyl substituent electron-donating effect and conjugated heteroaromatic system length. The fluorescence excitation spectra were characterized by one broad main peak, with, in most cases, one (or more) poorly resolved shoulder (s), appearing in the 270-405 nm region, and their emission spectra were generally constituted of several bands located in the 330-480 nm region. No significant shift of the absorption, fluorescence excitation and emission spectra wavelengths was found upon going from the monomers to the corresponding polymers. ΦF values were high, varying between 0.11 and 0.63, according to the nature of substituents(s) and to the conjugated system extension. Fluorescence decays were mono-exponential for the monomers and poly-exponential for PyPhThThPhPy and for polymers. τF values were relatively short (0.35-5.17 ns), and markedly decreased with the electron-donor character of the phenyl group p-substituent and the conjugated system extension.

The alternating of substituent effect on the ¹³C NMR shifts of all bridge carbons in cinnamyl aniline derivatives

Bridge carbon (13)C NMR shifts of a wide set of substituted cinnamyl anilines p-XC(6)H(4)CHCHCHNC(6)H(4)Y-p (XNO(2), Cl, H, Me, MeO, or NMe(2); YNO(2), CN, CO(2)Et, Cl, F, H, Me, MeO or NMe(2)) had been used as a probe to study the change of substituent effect in the conjugated system. The goal of this work was to study the difference among the substituent effect on SCS of all bridge carbons, and find the alternating of substituent effect in this model compounds. In this study, it was found that the change of the inductive effect and the conjugative effect on different bridge carbons is related to the bond number (m) from the substituent to the corresponding carbon, and the adjusted parameters σ(F(rel))(∗) and σ(R(ver))(∗) can be suitable to scale the difference of the inductive effect and the conjugative effect on bridge carbons. Moreover, because of the difference of substituent effect on bridge carbons, the substituent cross-interaction item Δσ(2)(Δσ(2) = (σ(F(rel))(∗)(X) + σ(R(ver))(∗)(X) - σ(F(rel))(∗)(Y) - σ(R(ver))(∗)(Y))(2)) was not suitable simply to scale the interaction between substituents X and Y for all bridge carbons, so the Δσ(2) was recommended to be divided into two parts: Δσ(F(rel))(2) (Δσ(F(rel))(2) = σ(F(rel))(∗)(X) - σ(F(rel))(∗)(Y))(2)) and Δσ(R(ver))(2) (Δσ(R(ver))(2) = (σ(R(ver))(∗)(X) - σ(R(ver))(∗)(Y))(2)). With σ(F(rel))(∗), σ(R(ver))(∗), Δσ(F(rel))(2), Δσ(R(ver))(2), and δ(C,parent), the obtained correlation equation can be used to correlate with the 159 sorts of SCS of the different bridge carbon in cinnamyl aniline derivatives. The correlation coefficient is 0.9993, and the standard deviation is only 0.53 ppm. The multi-parameter correlation equation can be recommended to predict well the corresponding bridge carbons SCS of disubstituted cinnamyl anilines.