Electro-donating Groups Research Articles

Theoretical study on effect of substituent on aromaticity of tetrazole ring

Tetrazole compounds are a category of energetic materials with great potential. Their stability is inherently related to their aromatics. On the basis of research in DFT at b3lyp/6–311** level on three compounds interested, viz. 5-amino-1 H-tetrazole, 5-carboxyl-1 H-tetrazole, and 2-methyl-5-carboxyl-tetrazole, their aromatic characters are extensively analyzed by virtue of different estimation method. Analyses show that these methods, Nucleus-independent Chemical Shift, iso-chemical shielding surface, adaptive natural density partitioning, π-electrons density, and localized orbital locator of π-electron density are efficient for substituted-tetrazole ring aromaticity estimation. Conclusion denotes that both substituent and substituted position can significantly affect the aromaticity of tetrazole ring of tetrazole compound. Among these given substituents, electro-withdrawing group -COOH significantly increases the aromaticity of the tetrazole rings due to the withdrawing to π-electrons thereof but electro-donating group -NH2 weakens the one of the tetrazole rings due to the donating to π-electrons thereof. But for 2-methyl-5-carboxyl-tetrazole, the aromaticity increasing of -COOH imposed on π-electrons of tetrazole ring thereof is partially balanced by the existence of the electron-donating group -CH3 at asymmetric meta-position of tetrazole ring. Consequently, the aromaticity order is 5-Carboxyl-1 H-tetrazole > 2-methyl-5-Carboxyl-tetrazole > 5-amino-1 H-tetrazole.

2-Phenylpyridine-based phosphorescent Ir(III) complexes for highly efficient greenish-blue organic light-emitting diodes with EQEs up to 33.5%

A group of heteroleptic cyclometalated iridium complexes Ir1–Ir4 were designed with 2-phenylpyridine (ppy) derivatives as cyclometalating ligands and 2-(3-(trifluoromethyl)-1H-pyrazol-5-yl)pyridine (fppz) or 2-(5-(4-(trifluoromethyl)phenyl)-2H-1,2,4-triazol-3-yl)pyridine (Htaz) as ancillary ligands. The incorporation of electro-donating group into ppy ligands to elevate ligands-centered 3π-π* energy level and utilization of fppz or Htaz ancillary ligands combined to tune the intrinsic electronic properties. These complexes showed greenish-blue or green phosphorescence and are characterized by high photoluminescence quantum yields of up to 70% and short lifetimes below 1 μs. The organic light-emitting diodes (OLEDs) with Ir1–Ir4 as doped emitters all exhibited high efficiencies with low efficiency roll-off. Particularly, the Ir3 device exhibited distinguished performances with the maximum current efficiency of 86.9 cd A−1 and an external quantum efficiency (EQE) of 33.5%. Even at high brightness of 1000 cd m−2, the EQE still remained at 24.6%. Evidently the EQE of 33.5% of Ir3 device is one of the highest efficiencies ever reported for greenish-blue phosphorescence OLEDs.

Azaacenes Based Electroactive Materials: Preparation, Structure, Electrochemistry, Spectroscopy and Applications-A Critical Review.

This short critical review is devoted to the synthesis and functionalization of various types of azaacenes, organic semiconducting compounds which can be considered as promising materials for the fabrication of n-channel or ambipolar field effect transistors (FETs), components of active layers in light emitting diodes (LEDs), components of organic memory devices and others. Emphasis is put on the diversity of azaacenes preparation methods and the possibility of tuning their redox and spectroscopic properties by changing the C/N ratio, modifying the nitrogen atoms distribution mode, functionalization with electroaccepting or electrodonating groups and changing their molecular shape. Processability, structural features and degradation pathways of these compounds are also discussed. A unique feature of this review concerns the listed redox potentials of all discussed compounds which were normalized vs. Fc/Fc+. This required, in frequent cases, recalculation of the originally reported data in which these potentials were determined against different types of reference electrodes. The same applied to all reported electron affinities (EAs). EA values calculated using different methods were recalculated by applying the method of Sworakowski and co-workers (Org. Electron. 2016, 33, 300–310) to yield, for the first time, a set of normalized data, which could be directly compared.

Asymmetric sulfenylation of 3-CF 3 -Oxindoles through organocatalysis with a quinidine derivative

An asymmetric sulfenylation of 3-CF3-oxindoles catalyzed by a quinidine derivative was described. 3-CF3-oxindoles with electro-donating groups led to corresponding products in good yield and with good enantioselectivity while 3-CF3-oxindoles bearing electro-withdrawing groups were not competent substrates due to its significant decomposition at the optimal reaction conditions. As for the sulfenylation reagents based on thiophenol, both electro-donating groups and electro-withdrawing groups were well tolerated.

THEORETICAL STUDY OF THE CHEMICAL REACTIVITY OF ACTIVATED CARBON

We used conceptual DFT to study global and local reactivity of both nonfunctionalized and functionalized activated carbons, with groups -OH,-CHO, -NH2, -COOH, and -CONH2. Electron-withdrawing groups were observed to increase the reactive surface, while electro-donating groups increase stability as reactivity of the activated carbon decreases. Descriptor groups were used to study the reactivity of structural fragments of activated carbons. The electrophilic and nucleophilic sites indicate that the carbon surface has an amphiphilic behavior that allows it to be used as an adsorbent material for a variety of molecules.

Copper(II)-Catalyzed Asymmetric Henry Reaction of o-Alkynylbenzaldehydes Followed by Gold(I)-Mediated Cycloisomerization: An Enantioselective Route to Chiral 1H-Isochromenes and 1,3-Dihydroisobenzofurans

By combining the copper(II)-catalyzed asymmetric Henry reaction of o-alkynylbenzaldehydes with subsequent gold(I)-catalyzed cycloisomerization, optically active 1H-isochromenes and 1,3-dihydroisobenzofurans were successfully synthesized in good overall yields with good to excellent enantioselectivities (up to 98%). Various substrates were investigated, and a correlation between the regioselectivity and electronic nature of the substrates was studied. The substrates with electro-donating groups at the alkynyl moiety preferred a 6-endo-dig manner to generated 1H-isochromenes 3 as main products (up to >30:1) while the ones with electron-withdrawing groups were inclined to undergo 5-exo-dig cyclization to form 1,3-dihydroisobenzofurans 4 (up to 1:5).

Palladium-Catalyzed Stereoconvergent Formylation of (E/Z)-β-Bromo-β-fluorostyrenes: Straightforward Access to (Z)-α-Fluorocinnamic Aldehydes and (Z)-β-Fluorocinnamic Alcohols

We report here the stereoconvergent formylation of (E/Z)-β-bromo-β-fluorostyrene mixtures with carbon monoxide and sodium formate catalyzed by palladium. Optimization of reaction conditions leads to the corresponding pure (Z)-α-fluorocinnamaldehydes in good yields. The reaction was extended to styrenes bearing electro-attracting or electro-donating groups. The obtained α-fluoroaldehydes were smoothly reduced to the corresponding (Z)-β-fluorocinnamic alcohol by NaBH(4). The reaction could be performed on functionalized substrates as demonstrated by the access to the glucoside of β-fluoroconiferyl alcohol, (Z)-β-fluoroconiferin, a strong inhibitor of lignin polymerization.

QSAR analysis of 2-benzoxazolyl hydrazone derivatives for anticancer activity and its possible target prediction

QSAR studies on a series of 2-benzoxazolyl hydrazone derivatives against various cancer cell lines were carried out to interpret the physicochemical properties responsible for the antitumor activity. The integy moments of the molecules (vsurf_ID8 and vsurf_IW6) reveals that the active site surface or the biological membrane where these compounds bind or penetrate must have a very specific and localized hydrophobic region. These integy moments reduce the interaction energy between the molecule and the water, which improve the antitumor activity. The potential energy descriptors indicate that the flexibility of the freely rotatable bonds is important for the interaction with the chemotherapeutic target and/or barriers to reach the target. Comparing the results obtained from this study and other QSAR studies addressed to similar compounds, we concluded that the benzoxazolyl derivatives may bind to the same target. The present analysis has shown that the antitumor activity can be improved with the presence of specific hydrophobic substituents and electro-donating groups nearby the hydrazone moiety. Moreover, the formation of an intramolecular hydrogen bond has a high impact on the pharmacological activity of these compounds. The information gathered from these studies provides useful information about the binding site of these compounds.

Synthesis and characteristic of a new arylimido derivative of hexamolybdate with remote strong electro-donating group (Bu 4N) 2[Mo 6O 18NC 6H 4N(CH 3) 2− p

A new monofunctionized arylimido derivative of hexamolybdate, (Bu 4N) 2[Mo 6O 18NC 6H 4N(CH 3) 2− p], is synthesized by α-octamolybdate and hydrochloride salt of N, N-dimethyl-1,4-dianiline with DCC as a dehydrating agent. The derivative’s crystal data has been obtained and the IR, UV–Vis, 1H NMR spectra and cyclic voltammetry properties have also been studied.

The cathodic cleavage of aromatic sulphones. When the fragmentation process is followed by an aromatic substitution by means of electrogenerated sulphinate as nucleophile

Anion radicals from aromatic sulphones also substituted by cleavable electrodonating groups may possess an astonishing stability. However, t-butyl aryl sulphones of those series behave quite differently. A very fast and unexpected scission of the aromatic carbon—sulphur bond occurs and is followed by an attack of the sulphonate ion towards the substrate— via an aromatic substitution—with the formation of a symmetrical disulphone.

The electrochemistry of mononuclear and dinuclear complexes of transition and inner transition metal ions with compartmental ligands

Electrochemical studies on binuclear complexes can serve to get light on the function of metalloenzymes incorporating two metal ions in close proximity at the active site. Int his connection, compartmental ligands offer the opportunity to synthetize metal complexes with adjacent coordination sites differing in the donor set [1]. In previous papers [2, 3] were reported the electrochemical behaviour of mononuclear and dinuclear complexes of copper(II), nickel(II) and dioxouranium(VI) with th Schiff base ligand H 4aapen, derived from o-acetoacetylphenol and 1, 2-diaminoethane. ▪ We report now the electrochemical properties of copper(II), nickel(II) and dioxouranium(VI) complexes of the Schiff base ligand H 4fsalacen, derived from 3-formylsalicylic acid and 1, 2-diaminoethane [4]. ▪ Mononuclear Complexes The following mononuclear complexes have been taken into consideration(See next column). ▪ ▪ The cyclic voltammetric behaviour of all the complexes, both at platinum and mercury microelectrodes in DMSO solution, shows the occurrence of a cathodic process which involves a quasireversible one electron charge transfer, uncomplicated in the case of the nickel(II) and the dioxouranium(VI) complexes, while followed by a subsequent chemical reaction (the decomposition of the anion) in the case of the copper(II) complex. In any case the use of appropriate scan rates allows us the computation of the formal potentials for the reduction of the central metal ions (Table I). As an example in Fig. 1 the cyclic voltammetric response of H 2fsalacen UO 2is reported. Dinuclear Complexes Both homodinuclear and heterodinuclear complexes have been studied. ( See next page) t001 Formal Reduction Potential (V vs. ferrocenium/ferrocene) of fsalacen Complexes as a Function of the Coordination Site. Metal (M) or Metal ions in the fsalacen complex [M (N 2O 2) fsalacen]/[M (N 2O 2) fsalacen] − [M (O 2O 2) fsaleacen]/[M (O 2O 2) fsalacen] Ni(II) −1.59 UO 2(VI) −1.14 Cu(II) −0.92 Ni(II) N 2 O 2 Ni(II) O 2 O 2 −1.80 −2.05 Cu(II) N 2 O 2 Cu(II) O 2 O 2 −1.10 −1.67 a Cu(II) N 2 O 2 Ni(II) O 2 O 2 −1.42 −2.17 Ni(II) N 2 O 2 Cu(II) O 2 O 2 −2.05 −1.05 Cu(II) N 2 O 2 UO 2(VI) O 2 O 2 − −1.22 Ni(II) N 2 O 2 UO 2(VI) O 2 O 2 −1.69 −1.44 a Peak potential value at v = 0.2 s −1 ▪ The electrochemical behaviour of dinuclear complexes essentially parallels that of the corresponding mononuclear species as to the electrode mechanism; on the contrary shifts of reduction potentials occur, due to the metal-metal interaction [5]. In Fig. 2 the cyclic voltammetric behaviour of fsalacenNi N 2 O 2 UO 2 O 2 O 2 is reported as atypical example. ▪ Table I summarizes the reduction potentials of all the complexes studied. A comparison with reduction potentials of the corresponding aapen complexes indicates that fsalacen compounds are generally more easily reducible. The easiest addition of electrons to fsalacen complexes to respect with aapen complex can be explained in terms of electronic effects; in fact electron-withdrawing groups, ▪, are present in the side chains of the molecule of fsalacen ligand whereas electro-donating groups, CH 3 are present in the molecule of aapen ligand.