Electron Donor Acceptor Groups Research Articles

Синтез новых S-производных 4-амино-1,3,5-триазин-2-тиона и их исследование методами ЯМР 1Н, 13С и хромато-масс-спектрометрии

4-Amino-1,3,5-triazine-2-thione 1 interacts with allyl bromide, 2-methyl-3-chloro-1-propene, 2,3-dibromopropene-1, prenyl bromide in DMFA/K2CO3 and with cinnamyl chloride, butenyl bromide in DMFA/NaOH to form 4-allylsulfanyl- 2, 4-(2-methylpropene-2-yl)sulfanyl- 3, 4-(2-bromopropene-2-yl)sulfanyl- 4, 4-(2-methylbutene-2-yl)sulfanyl- 5, 4-cinnamylsulfanyl- 6 and 4-(butene-1-yl)sulfanyl-1,3,5-triazine-2-amines 7, respectively. The structure of compounds 2–7 was studied by 1H NMR, as well as of compounds 5 and 7, in their case including 13C NMR; allyl sulfide 2, prenyl sulfide 5 and butenyl sulfide 7 were also studied using chromatography mass spectrometry. In the 1H NMR spectra of compounds 2–7, the weakest field signal in the range of 8.22–8.30 p.p.m. is the signal of the aromatic proton of the triazine cycle, manifested as a singlet. The signals of protons of the S-CH2 group are observed in a strong field – at 3.10–4.19 p.p.m. – depending on the presence of electron donor or electron acceptor groups in the alkenyl fragment. The protons of the =CH2 group are present only in the structure of sulfides 2–4 and 7; they form two signals in the 1H NMR spectra: one signal at 4.85–5.58 p.p.m., the second at 5.03–6.10 p.p.m. In the 13C NMR spectra of prenyl sulfide 5 and butenyl sulfide 7, the carbon atoms of the S-alkenyl groups resonate in the region of strong fields. In the region of weak fields, the signals of aromatic carbon atoms of the 1,3,5-triazine cycle are observed: 182.32–157.95 p.p.m. In the mass spectra of compounds 2, 5 and 7, the characteristic peaks are [M 15]+ and [M-33]+ peaks, the formation of which is associated with the fragmentation of molecular ions undergoing cleavage of the methyl radical and the •SH radical, respectively. The haloalkyl derivative of the heterocyclic series – 2-chloro-1-(2,2,4-trimethyl-4-phenyl-3,4-dihydroquinoline-1(2H)-yl) ethanoate – in reaction with compound 1 has led to the introduction of a new pharmacophore fragment into the simm-triazine molecule, which contributes to the expansion of the spectrum of potential biological activity of its derivatives.

Solvent-free one-pot two component synthesis. Tuning of optoelectronic properties of fluorescent phloroglucinol-aryl Schiff base compounds

A series of new aryl-Schiff base derivatives were synthetized from the one-pot approach: two component condensation reaction in absence of solvent, in quantitative yields with a high atom economy under green conditions. All of the derivatives were fully characterized by NMR, vibrational absorption analysis, UV/vis absorption and fluorescence spectroscopy, and high-resolution mass spectrometry. The aryl-Schiff bases predominantly present the enol-imine tautomer in acetone-d6, while both enol-imine and keto-imine tautomer readily concur in dimethyl sulphoxide-d6. The emission of the series could be tailored by substituting electron donor or electron acceptor groups in the aryl-Schiff bases from fluorescent to not fluorescent molecules, respectively. Fluorescent molecules emit blue, cyan and yellow color with quantum yields in the 2.4–6.2 % range and average lifetime of ∼0.2 ns. The large Stokes’ shift for the molecule bearing a methylalcoxy (3248 cm−1) and diethyl amine (5017 cm−1) suggests a possible intramolecular charge transfer process as also corroborated by cyclic voltammetry, and explaining their low fluorescence quantum yield. The aryl-Schiff base substituted with the methylalcoxy (2b) was used as an electron donor material in photovoltaic devices in configuration: ITO/PEDOT:PSS/2b:PC61BM/Fields metal. The device built under atmospheric conditions displayed an intrinsic power conversion efficiency of PCE ∼0.4 %, with a Voc of 420 mV and Jsc 4.28 mA/cm2.

Shift Current in Molecular Crystals Possessing Charge-Transfer Characteristics

Further research on organic molecule crystals with spontaneous polarization as a possible candidate for the bulk photovoltaic effect is urgently needed to meet the requirements for optoelectric devices. We demonstrate the shift current in a type of molecular crystal that acts at high temperatures and contains organic molecules with electron donor-acceptor groups, such as paranitroaniline derivatives. We find an extremely strong multicomponent shift-current response along the parallel and perpendicular to polar molecules of the crystals using density-functional simulations, which is more than 10 times larger than the previously reported value for shift current over a broad spectral range from visible to ultraviolet spectrum. Even more intriguing, the remarkable dependency of the conduction- and valence-band dispersions on the lattice constant along polarization allows the shift current in these organic molecule structures to be tuned under stress and doping. Our findings not only suggest a class of organic compounds for realizing the highly controllable shift-current response, but also open up a channel for the search for solar materials.

One-pot Sonogashira–Hydroarylation reaction catalyzed by anionic palladium complexes in an aqueous medium

It was found that anionic Pd(II) complexes of type [CA]2[PdCl4] and [CA]2[Pd2Cl6] (CA = imidazolium or pyridinium cation) are effective catalysts for copper-free Sonogashira coupling in an aqueous medium without additional ligands or co-catalysts. Both types of substrates, containing electron donor or electron acceptor groups, formed the corresponding products in good to excellent yield. The most active complex, [bmpy]2[Pd2Cl6] (bmpy = 1-butyl-4-methylpyridinium cation), was employed to the hydroarylation of the Sonogashira product in a one-pot process, using microwave radiation, NaBPh4 as a phenyl source and water as a proton donor. In these reactions the presence of electron donor substituents facilitated a higher conversion of diarylacetylenes to triarylethenes than electron acceptor groups.

Influence of donor-acceptor groups on the electrical and optical properties of C50 fullerene.

In this research, the C50 fullerene was employed as the source of the π electrons and the electron donor-acceptor groups were used to enhance its optical properties. Considerable enhancement in its electronic and optical property of C50 as the result of donor and acceptor group presence was observed. For instance, in UV-Visible absorption spectrum, the number of absorption lines significantly increase which may be the relaxation of the electronic transition selection rules. Considerably, the substituted forms of C50, have numbers of absorption bands in near infrared region. The BH2-C50-NCH3Li and NO-C50-NCH3Li molecules have superior improvement in optical properties. Finally, the donor and acceptor groups influence on non-linear optical properties (NLO) of C50 was explored and the considerable improvement in NLO properties of C50 was observed in which the NLO improvements for BH2-C50-NCH3Li and NO-C50-CH2Li cases is higher than others.

An efficient, green and sustainable potassium hydroxide activated magnetic corn cob biochar for imidacloprid removal

The extensive use of imidacloprid (IMI) has led to its being frequently detected in natural water, also caused the potential damage to the ecosystem. Development of efficient, green and sustainable technique is demanded to eliminate this problem. A novel biochar (KMCBC) derived from agriculture waste of corn cob was first time co-modified by potassium hydroxide (KOH), ferric chloride (FeCl3) and zinc chloride (ZnCl2), which showed the greater adsorption amount (410 mg g−1 at 298 K) for imidacloprid (IMI). Pseudo-second-order kinetic and Langmuir isotherm models fitted well with the experimental data, together with the physicochemical characterization analysis, demonstrating that the adsorption process of IMI by KMCBC might be mainly controlled by micropore filling, π-π electron donor-acceptor and functional groups interactions (H-bonding and complexation). Additionally, the thermodynamics parameters suggested that IMI adsorption in this study was a spontaneous, endothermic and randomly increasing process. Besides, KMCBC owned the easy separation performance and promising environmental safety, also exhibited a high selective adsorption capacity regardless of solution pH (its optimum adsorption performance for IMI was obtained at pH = 5), inorganic ions strength and humic acid (HA) concentrations. The regenerated KMCBC (synergistic ultrasound/ethanol) could sustainably and efficiently adsorb IMI in the reuse cycles. Therefore, this study provided an efficient, green and sustainable adsorbent of KMCBC for IMI removal.

A Brief History of Photoactive Interlocked Systems Assembled by Transition Metal Template Synthesis

More than three decades of research efforts have yielded powerful methodologies based on transition metal template-directed syntheses for the assembly of a huge number of interlocked systems, molecular knots, machines and synthesizers. Such template techniques have been applied in the preparation of mechanically linked electron donor–acceptor artificial photosynthetic models. Consequently, synthetic challenging photoactive rotaxanes and catenanes have been reported, in which the chromophores are not covalently linked but are still associated with undergoing sequential energy (EnT) and electron transfer (ET) processes upon photoexcitation. Many interlocked photosynthetic models produce highly energetic, but still long-living charge separated states (CSS). The present work describes in a historical perspective some key advances in the field of photoactive interlocked systems assembled by transition metal template techniques, which illustrate the usefulness of rotaxanes and catenanes as molecular scaffolds to organize electron donor–acceptor groups. The effects of molecular dynamics, molecular topology, as well as the role of the transition metal ion used as template species, on the thermodynamic and kinetic parameters of the photoinduced energy and electron transfer processes in the interlocked systems are also discussed.

Improving the Electrical and Optical Properties of C40 Fullerene Using the Donor–Acceptor Groups

In the present study, the C40 fullerene was selected as the source of the π electrons and the electron-donor–acceptor groups was used to improve the optical and electrical properties of it. For this purpose the fullerene C40 molecule was sandwiched between the electron donor and acceptor groups, and its electronic and optical properties was calculated. The –NHLi, –CH2Li and –NCH3Li groups were used as electron donor groups and the –CN, –NO and –BH2 groups as electron acceptor groups. It was demonstrated that in comparison to its pristine form, the calculated Eg for sandwiched form of fullerene C40 molecules is lower. For instance for the BH2-C40-NCH3Li compound, the bond gap is about 1.3 eV which suggests a greater electrical conductivity of this compound than other compounds. On the other hand the highest Eg value for the CN–C40–CH2Li nanocluster is the value of 1.51 eV (highest obtained Eg). The optical properties of pristine fullerene and fullerene functionalized with electron donor and acceptor groups were investigated which drastic effect of donor and acceptor groups on C40 fullerene was observed. The results of this research may be useful in designing new photosensitizer.

A study on the modification of azole rings to regulate the transition dipole moment, MLCT and T1 structural distortion of 2-pyridyl-azole copper (I) complexes for high phosphorescence performance

Heterocyclic ligands based on 2-pyridyl-azole, have become some of the ideal ligands for metal complexes due to their flexible structure and wide wavelength tunability. In this paper, a series of Cu(N∧N) (P∧P) complexes are studied by density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods. The results indicate that the combination of incorporation of N atoms and substitution of electron donor-acceptor groups can effectively control the type and the proportion of the lowest triplet states (T1) phosphorescent transition. A higher matching degree between the effective spin-orbit coupling (SOC) matrix elements and the transition dipole moments (The Sn state has both effective SOC and large transition dipole moments of Sn→S0 transition) brings about a larger transition dipole moment MTa of T1a→S0 transition, and further results in the fastest radiative decay rate (kr) for complex 2, although the main transition of which is internal-ligand charge transfer (ILCT). In addition, the non-radiative decay rate (knr) of complex 2 is lower than other complexes of series 3 (the reorganization energy produced by in-plane bending vibration of C–H bond in six-membered ring is larger than complex 2), so this complex has the highest quantum yield. Overall, the above analyses illustrate that despite the participation of Cu(I) in transition as an indispensable factor for the radiative transition, the higher component ratio does not necessarily lead to a faster kr. In addition, it is also essential to have a well-matched large transition dipole moments of the singlet states Sn→S0 transition involved in the effective SOC. Consequently, in the development of the 2-pyridyl-azole Cu(I) luminescent materials, the high quantum yield materials can be designed by adjusting the substituent at C3 position and the strength of electron donor-acceptor groups at C5 position to balance the charge transfer transition modes.

The binding mechanism of nitroreductase fluorescent probe: Active pocket deformation and intramolecular hydrogen bonds

Nitroreductase (NTR), a member of the flavoenzyme family, could react with nicotinamide adenine dinucleotide by reducing nitro to amino at hypoxic tumor, which can be monitored by some fluorescent probes in vivo. Here, molecular docking and molecular dynamics simulation techniques were used to explore the molecular mechanisms between NTR and probes. The results showed that formation of hydrogen bond in 1F5V-13 between A@His215 and B@Ser41 with 74.53% occupancy might be the main reason for the decrease of probe fluorescence emission in experiment. Moreover, Probe 16 was rotated by nearly 60 degrees with respect to the position of other probes in protein binding pocket, deforming the protein active pocket, changing the hydrogen bond formation, which leads to the fluorescence performance of 16 with electron donor and electron acceptor groups was superior to other probes in experiment. The deformation of protein active pocket and the formation of intramolecular hydrogen bonds revealed the difference in performance of NTR fluorescent probe at molecular level, which provide theoretical guidance for latter design of fluorescent probes with better performance.

Tuning the Optical Properties of Novel Antitumoral Drugs Based on Cyclometalated Iridium(III) Complexes.

Most of the current efforts in drug discovery are devoted to the design of molecules able to mitigate side effects by concentrating the biological action in the targeted tissue. One promising strategy is photodynamic therapy, which is based on the in situ generation of reactive singlet oxygen upon radiation exposure. However, such an approach requires the use of an efficient photosensitizer. This contribution deals with the optical properties of an Ir(III) complex, [Ir(pbz)2(N^N)] (pbz = 2-phenylbenzimidazole; N^N = methyl 1-butyl-2-pyridyl-benzimidazole-5-carboxylate), which has recently been shown to exhort a strong photoactivity, but still needs further improvements to reach clinical applications. We performed density functional theory calculations at the M06, PBE0, ωB97xD, and CAM-B3LYP levels to predict the impact of introducing electron donor-acceptor groups into the nature of the lowest excited states. The simulations performed demonstrate that the presence of a NH2 at the pbz ligand and a NO2 group at the N^N ligand yield a bathochromic shift of absorption spectrum. We report the most sensitive positions to tune the optical signatures of this family of complexes.

Quantum computational study of non-linear optical properties of some phenanthrene derivatives.

Non-linear optical (NLO) behavior of some phenanthrene-based organic molecules is studied using quantum computational MP2 and B3LYP methods with cc-pVDZ basis set. The design of these molecules is based on possible intramolecular charge transfer between electron donor and electron acceptor groups via an aromatic bridge. The -NO2, -CN, -CF3, -C(CF3)C(CF3)2, -SO3H and -C(CN)C(CN)2 acceptors and the -NH2, -N(CH3)2 and pyrrolidinyl donors have been considered. The HOMO and LUMO energies, polarizabilities and first hyperpolarizabilities are calculated for the optimized structures both in the gas phase and in the conductor-like polarizable continuum model (CPCM) of different solvents. Moreover, the energies of the vertical transitions in the UV-Vis range having large oscillator strengths and their corresponding adiabatic transition energies are calculated using TD-DFT-B3LYP/cc-pVDZ method. Also, UV-Vis and infrared spectra are simulated for these designed molecules. Results show that these phenanthrene derivatives have generally very good NLO behavior. Also, NLO properties are enhanced when (-C(CN)C(CN)2 & -NH2) and (-NO2 & pyrrolidinyl) pairs of (acceptor & donor) groups are used. The approach adopted in the present quantum computational study can be used for similar studies for better description and understanding of the NLO responses of the electron donor-bridge-acceptor systems with π-conjugated bridges.

Improving the optical properties of [14] and [18] annulenes sandwiched between electron donor-acceptor groups

In the present research, an electron donor-acceptor compound (called push-pull systems) were studied using DFT methods in the vacuum space. We used [14] annulene and [18] annulene as π conjugated system and connected methoxy diphenylamine group as an electron donor and cyanoacrylic acid as an electron acceptor group. It was shown that the donor and acceptor groups narrowed the Eg of structure which is the result of hyperconjugation. Pristine annulenes had intensive light absorption in the ultraviolet region in electromagnetic radiation. After both molecules sandwiched between electron donor-acceptor groups, a significant redshift from the UV region to the visible and IR region was observed. Also in NMR calculation, it was observed the amount of aromaticity has increased after sandwiching. In all IR and Raman spectrum, it was shown the amount and intensity of light absorption increased after placing annulenes in electron donor-acceptor groups. The results of this research may be useful in designing new materials applicable as photosensitizers and photodynamic therapy.

In-silico analysis of substituent effect on the static first order hyperpolarizability of electron donating mono substituted Chalcone derivatives.

Noncentrosymmetric π conjugated systems with suitable electron donor acceptor groups play a crucial role in material NLO activity. The influence of an electron donating mono substituent at the para position of the phenylene ring of chalcone was investigated as a resource for second harmonic generation. The geometrical optimization of 11 electron donating group substituted chalcones were performed using density functional theory at the B3LYP/6-311G(d,p) level and compared with experimental geometrical parameters of five reported chalcones. All the derivatives are transparent to visible radiation as shown by the electronic absorption spectra investigated by the TDDFT-CAM B3LYP/6-311G(d,p) method, and the maximum absorption wavelength was due to the πPhB → π* transition. The first order hyperpolarizability βtot, calculated using the CAM B3LYP/6-311G(d,p) method, increases with the electron donating ability of the substituent, and the largest βtot was observed for dimethylamino substituent. The Hammett substituent constant (σp) shows good linear correlation with β, λmax, and Egap in the ground state. The Brown constant (σp+) was better correlated indicating the polarization of carbonyl group in the excited state. Frontier molecular orbitals also reveal the valence electron excitation. Correlation of σp with various parameters was analyzed to assess the property interrelationship with electronic reorganization in the molecule. The electronic structures of molecular fragments were described in terms of natural bond orbital analysis, which shows intramolecular interactions.

Interaction of Elemental Mercury with a Diverse Series of π-Organic Substrates Probed by Computational Methods: Is Mercury Fixation Possible?

A multitude of electronic structure computational methods has been employed to study the intermolecular adducts formed upon the interaction of elemental mercury, Hg0, with benzene and substituted benzenes of the general formula [Hg(η6-1,3,5-C3H3R3)], where R is either an electron donor substituent, such as −NH2, −OH, −SH, −NH(COCH3), −C≡CH, −S(CH3), −C═CH2, −CH3, −N(CH3)3, and −O(CH3)3 or an electron acceptor substituent, such as −COOH, −NO2, −CHO, −CO(CH3), −CN, −SO2H, −CF3, −C(CO)(NH2), −Cl, −F, and −C(CO)Cl. In addition, a set of neutral and negatively charged octupolar molecules, with alternating electron donor and electron acceptor groups in the 1,3,5 and 2,4,6 positions of the benzene ring, have been included in this study. The estimated interaction energies of Hg0 with these systems range from −2.6 to −13.7 kcal/mol. The interplay of electrostatic, dispersion forces and covalent interaction components constitute the Hg0···π-organic substrate interactions. In the [Hg(η6-1,3,5-C3H3R3)] adducts with e...

Effect of organic substituents on the adsorption of carbon dioxide on a metal–organic framework

The adsorption of carbon dioxide on the MOF-5 metal–organic framework and modifications of it obtained by replacing the hydrogen atoms in the organic ligands with electron donor (–CH3,–OCH3) or electron acceptor groups (–CN,–NO2) is investigated using the grand canonical Monte Carlo (GCMC) method and density functional theory (DFT). It is shown that the adsorption of carbon dioxide molecules on the structures of metal–organic frameworks is most likely on Zn4O clusters, and that the adsorption of carbon dioxide is of a physical nature. The presence of substituents–CH3,–OCH3,–CN in metal–organic frameworks increases their capacity to adsorb carbon dioxide, while that of nitro groups (–NO2) has the opposite effect.

Theoretical study of nonlinear optical properties of some azoic dyes

In this paper we presented semi-empirical PM3, ab-initio (HF, MP2) and DFT (B3LYP, B3PW91) calculation of the dipole moment, polarizability, and first hyperpolarizability of some azoics dyes derivatives which have electron donor and electron acceptor groups on either sides. The first hyperpolarizability of these molecules was calculated with PM3 method, HF/6-31G**, HF/6-31+G**, HF/6-31++G**, DFT with B3LYP and B3PW91 functional, and MP2/6-31++G** based on finite field approach using GAUSSIAN03 program. The effects of the intramolecular charge transfer (ICT) from the donor to the acceptor groups on the molecular geometry and atomic charge distribution of these NLO chromophores are derived from its HF, MP2 and DFT calculations. The variation of this property has also been correlated to E (HOMO-LUMO) gap and to the nature of the highest occupied molecular orbital HOMO and the lowest unoccupied molecular orbital HOMO. The study reveals that the azoics dyes derivatives have large hyperpolarizability values; hence they may be used in the development of nonlinear optical materials.

D-π-A conjugated molecules for optoelectronic applications.

Dipolar chromophores consisting of electron donor (D) and electron acceptor (A) groups connected through a conjugated π-bridge have been actively studied and integrated in optoelectronic and electronic devices. Generally, such π-conjugated molecules provide substantial delocalization of π-electrons over the molecules. Here, a brief overview of recent research on D-π-A dipolar chromophores including their syntheses and several promising applications is reported, especially in nonlinear optical devices and organic photovoltaics. Structure/property relationships are discussed in order to exploit the potentials by tuning the π-electron density, polarizability, and HOMO-LUMO band gap of the chromophores. Some of the examples may well set the stage for chip-scale integration of optoelectronics as well as the realization of an important array of new device technologies.

Photophysical study of the Dibenzylideneacetones and 3-Benzylidenethiochroman-4-ones

In this work, a study of the optical properties of Dibenzylideneacetones a-c and 3-Benzylidenethiochroman-4-ones {d-e} is presented. Optical measurements and theoretical approaches are used to establish the contribution of electron donor-acceptor groups in the apparition of fluorescence emission.

Theoretical study of novel porphyrins bearing electron donor–acceptor groups

AbstractThis research project is focused on molecules that comprise a series of asymmetrically A3B‐type meso‐substituted free‐base porphyrins and their related Zn‐metalloporphyrins. A and B were taken as electron‐donor and electron–acceptor groups. Full geometry optimizations without symmetry constrains were performed with B3LYP/6‐31G(d,P) methodology. Time‐dependent density functional theory calculations of the optimized structures indicate that there is a good agreement with the available experimental results. The highest occupied molecular orbital–lowest occupied molecular orbital (LUMO) gaps (ranging between 2.62 and 2.80 eV) are similar to those reported before for other porphyrins (2.29 eV). Also, the LUMO is situated close to the conduction band of titanium oxide, increasing the possibility of a charge transfer process. As porphyrins may act as electron transfer systems, the electron donor–acceptor capacity of these systems is characterized using two parameters; electrodonating (χ−) and electroaccepting (χ+) electronegativity. The main goal of this investigation is to analyze the electronic structure and the donor–acceptor properties of these porphyrins to see if these compounds could be useful for further applications related to the design of solar cells. © 2012 Wiley Periodicals, Inc.