Electron Acceptor Groups Research Articles

Tuning of organic heterojunction conductivity by the substituents’ electronic effects in phthalocyanines for ambipolar gas sensors

Exploiting organic heterojunction effects in electrical devices are an important strategy to improve the electrical conductivity, which can be utilized into improving the conductometric gas sensors performances. In this endeavor, the present article reports fabrication of organic heterostructures in a bilayer device configuration incorporating octa-substituted nickel phthalocyanines (NiPc) and radical lutetium bis-phthalocyanine (LuPc2) and investigates their sensing properties towards NH3 vapor. NiPc having hexyl sulfanyl, hexyl sulfonyl and p-carboxyphenoxy moieties are synthesized, which electronic effects are electron donating, accepting and moderate accepting, respectively, also validated by cyclic voltammetry. The electronic effects of substituents in NiPc modulate the interfacial electrical conductivity and the type of the organic heterojunction formed. The electron acceptor and donor groups favor the formation of accumulation and accumulation/depletion heterojunctions, which are also correlated to negative and positive response towards NH3, respectively. Among the studied heterojunction devices, the one based on hexyl sulfanyl groups, revealed the highest and the most stable response in 10−90 ppm of NH3 and under variable relative humidity (rh) (10–70 %). Interestingly, the bilayer device having p-carboxyphenoxy substituted NiPc, exhibited ambipolar behavior such that its p-type semiconducting nature is changed into n-type at higher rh values, also demonstrated by change in its negative response into positive towards NH3.

The Influences of Sulfoxide Electron Traps in Transparent Polyimides with Low Retardation, Yellow Index, and CTE

AbstractDue to the development of dynamic flexible organic light‐emitting diode displays, colorless polyimides (CPI) as the supporting or protecting optical films, are facing significant challenges due to the requirements of optical, mechanical, thermal, and chemical properties. Typical CPIs are derived from TFDB (2,2‐bis(trifluoro‐methyl)‐4,4′‐diaminobiphenyl)/6FDA (4,4′‐(hexafluoroisopropylidene)diphthalic anhydride), which still need to be improved in both dimensional stability and optical performance. In this communication, a strong electron acceptor group, the sulfoxide bond, is first introduced into the TFDB block of CPI chains. Based on this introduction, the distribution of the electron cloud in the polymer chain is reconstructed under the strongly pulling electron effect, and the spatial conformation of the polymer chain is also affected by the rigid and twisted sulfoxide group. The influences on CPI's optical properties, especially the refractive index and the retardation, are studied and discussed in detail by experimental results and theoretical calculations. It is shown that the CPI with the sulfoxide group exhibits higher optical transparency, lower yellow index, phase retardation and coefficient of thermal expansion, which is an ideal material for CPI optical films.

Computational Evaluation of Bioactive Compounds from Colocasia affinis Schott as a Novel EGFR Inhibitor for Cancer Treatment.

Introduction:Epidermal growth factor receptor (EGFR) is a transmembrane protein that belongs to the ErbB/HER-family of tyrosine kinase receptors. Somatic mutations and overexpression of EGFR have been reported to play a vital role in cancer cell development and progression, including cell proliferation, differentiation, angiogenesis, apoptosis, and metastatic spread. Hence, EGFR is an important therapeutic target for the treatment of various types of epithelial cancers. Somatic mutations have led to resistance to clinically approved synthetic EGFR inhibitors. Furthermore, synthetic EGFR inhibitors have been associated with several side effects. Thus, there is a need to develop novel EGFR inhibitors with an acceptable biosafety profile and high efficacy.Methods:Herein, we employed structural bioinformatics and theoretical chemistry techniques via molecular docking, molecular mechanics generalized Born surface area (MM-GBSA) calculation, density functional theory analysis (DFT), and pharmacokinetic study to identify novel EGFR inhibitors.Results:The stringent molecular docking and MM-GBSA calculations identified MET 793, LYS 745, PHE 723, ASP 855, ARG 411, and THR 854 as principal amino acid residues for EGFR-ligands interactions. Furthermore, Colocasia affinis Schott compounds exhibited higher binding energy and more stable interactions than the reference compound (gefitinib). DFT analysis also ascertains better bioactivity and chemical reactivity of C. affinis Schott with favorable intramolecular charge transfer between electron-donor and electron acceptor groups. The pharmacokinetic profile of C. affinis Schott bioactive compounds satisfies Lipinski’s rule of five assessment.Conclusion:Collectively, C. affinis Schott compounds demonstrated higher inhibitory potentials against EGFR and better pharmacological properties when compared with gefitinib. C. affinis Schott compounds are therefore suggested as promising therapeutic EGFR inhibitors for cancer treatment.

Less is more: on the effect of benzannulation on the solid-state emission of difluoroborates

We investigate the emission properties of four organic dyes containing a strong electron-donating N(CH3)2 group and an NBF2O-bearing heterocyclic moiety acting as the electron-accepting group.

Impact of Intermolecular Interactions Between a Diketopyrrolopyrrole-Based Conjugated Polymer and Bromobenzaldehyde on Field-Effect Transistors

In this study, intermolecular interactions were investigated for increasing the charge carrier mobility of organic field-effect transistors (OFETs) based on a conjugated polymer. A diketopyrrolopyrrole (DPP)-based conjugated polymer widely used in OFETs, i.e., poly[2,5-(2-octyldodecyl)-3,6-diketopyrrolopyrrole-alt-5,5-(2,5-di(thien-2-yl)thieno[3,2-b]thiophene)] (PDPP-DTT), was assembled using 2-bromobenzaldehyde (2-BBA) and used as an active layer for OFETs. Morphological characterization and analysis for non-covalent intermolecular interactions suggested that the halogen bonding between the bromide of 2-BBA and electron-donor group of PDPP-DTT and the association between the electron-acceptor group in 2-BBA and sulfur of PDPP-DTT improved the hole transfer in the PDPP-DTT-based OFETs. The intermolecular interactions resulting from the addition of 2-BBA contributed to the two-fold enhancement of the hole mobility, two-order increase in magnitude of the current on/off ratio, and 50% decrease in the threshold voltage of the OFETs based on PDPP-DPP.

Donor-acceptor-acceptor-type near-infrared fluorophores that contain dithienophosphole oxide and boryl groups: effect of the boryl group on the nonradiative decay.

The use of donor–π–acceptor (D–π–A) skeletons is an effective strategy for the design of fluorophores with red-shifted emission. In particular, the use of amino and boryl moieties as the electron-donating and -accepting groups, respectively, can produce dyes that exhibit high fluorescence and solvatochromism. Herein, we introduce a dithienophosphole P-oxide scaffold as an acceptor–spacer to produce a boryl- and amino-substituted donor–acceptor–acceptor (D–A–A) π-system. The thus obtained fluorophores exhibit emission in the near-infrared (NIR) region, while maintaining high fluorescence quantum yields even in polar solvents (e.g. λem = 704 nm and ΦF = 0.69 in CH3CN). A comparison of these compounds with their formyl- or cyano-substituted counterparts demonstrated the importance of the boryl group for generating intense emission. The differences among these electron-accepting substituents were examined in detail using theoretical calculations, which revealed the crucial role of the boryl group in lowering the nonradiative decay rate constant by decreasing the non-adiabatic coupling in the internal conversion process. The D–A–A framework was further fine-tuned to improve the photostability. One of these D–A–A dyes was successfully used in bioimaging to visualize the blood vessels of Japanese medaka larvae and mouse brain.

Meta-Terphenyl linked donor-π-acceptor dyads: intramolecular charge transfer controlled by electron acceptor group tuning.

A series of meta-terphenyl linked donor–π–acceptor (D–π–A) dyads were prepared to understand the electronic effects of a meta-terphenyl linker according to the electron-accepting ability change. The energy band gaps of the dyads were controlled by tuning the accepting ability, which resulted in emission colors ranging from blue-green to red. In the Lippert–Mataga plots, intramolecular charge transfer (ICT) behavior was observed, which showed gradually increased ICT characteristics as the accepting ability was increased. On the other hand, in the absorption spectra, a red shift of the ICT transition was observed differently from the electron-accepting ability tendency. Thus, the experimental results show that the ICT is determined by steric hindrance rather than the acceptor ability in the ground state due to the lack of π-conjugation of the terphenyl linker by the electron node in the meta-position, whereas ICT in the excited state is controlled by electron-accepting ability.

Novel DPP derivatives functionalized with auxiliary electron-acceptor groups and characterized by narrow bandgap and ambipolar charge transport properties

Four novel diketopyrrolopyrrole (DPP) derivatives have been synthesized and characterized: the dyes are based on a DPP electron acceptor core symmetrically functionalized with donor bi-furyl moieties and end capped with four different auxiliary electron-acceptor groups. Because of the alternation along the molecular backbone of electron acceptor and donor groups, all the dyes are characterized by optical absorption maxima approaching or exceeding 700 nm. In the solid state, this optical behavior determines for all the dyes a very low optical bandgap ranging from 1.57 eV to 1.29 eV, while electrochemical characterization shows a clear dependence of the LUMO energies on the strength of the auxiliary electron-acceptor groups. All the dyes are characterized by stable LUMO energies suitable for their application as n-type semiconductors. Organic field-effect transistors based on the reported compounds display actually n-type behavior and, in three cases, a very interesting and balanced ambipolar charge transport behavior was moreover observed.

Improving the optical properties of [5] circulene with different electron donors and acceptor substitutions (push-pull system).

In this research, the circulene molecule was selected, and the electron donor and acceptor groups were attached to improve its optical properties. Large negative values of enthalpies, Gibbs free energies, and exothermic energies of formation for these molecules, especially for the CN-CIR-NHLi molecule, show that their formation is highly reasonable. It was illustrated that the Eg of the circulene molecule was lowered in the electron donor and acceptor groups' presence, while the CN-CIR-NHLi and CF3-CIR-NHLi molecules have the lowest values of Eg. It was observed that the optical properties of circulene molecules were improved in electron donor and acceptor groups' presence. Between these groups, the -CN and -CF3 as electron acceptors and -NHLi substituents, as electron donor groups, yield higher enhancements on the optical properties of circulene, which is in agreement with the results obtained for Eg values. Graphical abstract.

The Influence of Asymmetric Charge Transfer on IR Spectra of Excited Quadrupole Molecules

The influence of symmetry breaking caused by charge transfer in excited quadrupole molecules of the D-π-A-π-D or A-π-D-π-A type, where A and D are the electron-acceptor and electron-donor groups, respectively, on spectra of characteristic vibrations is investigated. Types of possible changes in IR spectra with increase in molecule’s asymmetry are classified within the earlier developed theory of symmetry breaking and its manifestation in nonstationary IR spectra. Physical interpretation of the revealed trends is presented, and the latter are compared with currently available experimental data.

Synthesis opto-electronic characterization and NLO evaluation of 6-methyl 5-nitro Uracil crystal using XRD, spectroscopic and theoretical tools

The organic composite crystal for 6-methyl 5-nitro Uracil was grown using slow-evaporation method and the crystal quality was checked by observing the peaks in XRD pattern. The molecular structure of 6-methyl 5-nitro Uracil was used to find crystal parameters for determining NLO activity. The appropriate electronic geometrical structure was keenly noted and the transitional energy exchange was studied and thereby fine-tuning of crystal performance was made by adopting suitable electron-accepting and with-drawing substitutional groups. The crystal parameters; a≠b≠c confirmed the orthorhombic lattice pattern. The space group was found as P21/a and Transparency range was observed as 409–1256 nm. The laser measurements were made and laser Damage threshold was estimated at 10 ns[1.08–3 GW/cm2]. The scattering characteristics of bond networks over the molecule were observed by studying vibrational characteristics of elemental bonds. The hybrid calculations on DFT methods were made using B3LYP/6-311++(D,P) basis set. The chemical shift was observed and retracing chemical potential was identified from the parametric oscillation. The frontier molecular interactions between ground and excited orbital lobe overlapping segments were noted and type of interaction system was identified. The electronic and protonic transfer energy was measured and the origination point of equivalent chemical potential was acknowledged. The NBMO profile was keenly grafted and the transitional energy was measured at every consumed electronic energy band. The vibrational circular dichroic image for all vibrational regions was sketched and the rate of transmission and absorption ratio was verified from peak intensity.

Theoretical insights on the luminescent mechanism of an efficient aggregation‐induced nondoped delayed fluorescence emitter using QM/MM method

AbstractThermally activated delayed fluorescence (TADF) materials with an aggregation‐induced emission (AIE) mechanism have great potential for use in organic light‐emitting diodes (OLEDs). In this study, the luminescent mechanism of a novel efficient aggregation‐induced, nondoped, delayed fluorescence emitter 2‐(10H‐phenoxazin‐10‐yl)‐10‐phenyl‐10H‐phenothiazine‐5,5‐dioxide (PXZ2PTO) is theoretically studied based on first‐principles calculations. The polarizable continuum model and quantum mechanics and molecular mechanics method are used to simulate the surrounding environments for molecules in the toluene solution and the solid phase, respectively. Our results show that PXZ2PTO exhibits the superior AIE property. The nonradiative decay rate in the solid phase is two orders of magnitude lower than that in toluene, caused by the suppressed geometry changes during excitations and decay channels. Meanwhile, studies of intermolecular interactions using the dimer model indicate that PXZ2PTO possesses a special highly stereoscopic structure in the solid phase, and the electron acceptor group is almost perpendicular to the electron donor group, inducing a strong steric hindrance effect between adjacent molecules and leading to enhanced intramolecular interaction. Furthermore, the excited‐state dynamics studies show that the intersystem and reverse intersystem crossing rates of PXZ2PTO are comparable to the radiative decay rate, which indicates that PXZ2PTO is an excellent potential TADF emitter with full exciton usage. Our theoretical research gives a reasonable explanation of the experimental results and provides valuable information for designing highly efficient AIE‐TADF emitters in practical OLEDs.

Narrow-energy gap conjugated polymers based on benzobisthiadiazole and thiadiazoloquinoxaline: DFT and TDDFT study.

Herein, the HOMO-LUMO energy gaps (Eg) and UV spectra of benzo[1,2-c:4,5-c']bis([1,2,5]thiadiazole (BBT) and [1,2,5]thiadiazolo[3,4-g]quinoxaline (TQ)-based donor-acceptor-donor type-conjugated polymers were computed by using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) at B3LYP/6-31G(d,p) level. The donor groups consist of thiophene (TH), 3,4-ethylenedioxythiophene (EDOT), and 3,4-propylene dioxythiophene (ProDOT) units and the bisthiadiazole and thiadiazoloquinoxaline were chosen as electron acceptor groups. To examine the effects of the alkyl side chain on the molecular structure and Eg of the polymer, methyl groups were added at the 3,4-, 2,3-, and 3,3-positions of TH, EDOT, and ProDOT donor groups, respectively. Our calculated HOMO-LUMO energy gaps are in the range of 0.05 to 1.37eV. The calculation results show that the energy gaps are in line with the available experimental values. The novel BBT and TQ derivatives with improved optical and electronic properties may find use in electronic applications. Graphical abstract.

First theoretical framework of Z-shaped acceptor materials with fused-chrysene core for high performance organic solar cells.

Chrysene core containing fused ring acceptor materials have remarkable efficiency for high performance organic solar cells. Therefore, present study has been carried out with the aim to design chrysene based novel Z-shaped electron acceptor molecules (Z1-Z6) from famous Z-shaped photovoltaic material FCIC (R) for organic photovoltaic applications. End-capped engineering at two electron-accepting end groups 1,1-dicyanomethylene-3-indanone of FCIC is made with highly efficient end-capped acceptor moieties and impact of end-capped modifications on structure-property relationship, photovoltaic and electronic properties of newly designed molecules (Z1-Z6) has been studied in detail through DFT and TDDFT calculations. The efficiencies of the designed molecules are evaluated through energy gaps, exciton binding energy along with transition density matrix (TDM) analysis, reorganizational energy of electron and hole, absorption maxima and open circuit voltage of investigated molecules. The designed molecules exhibit red-shift and intense absorption in near-infrared region (683-749nm) of UV-Vis-NIR absorption spectrum with narrowing of HOMO-LUMO energy gap from 2.31eV in R to 1.95 in eV in Z5. Moreover, reduction in reorganization energy of electron from 0.0071 (R) to 0.0049 (Z5), and enhancement in open circuit voltage from 1.08V in R to 1.20V in Z5 are also observed. Twisted Z-shape of designed molecules prevents self-aggregation that facilitates miscibility of donor and acceptor. Low values of binding energy, excitation energy, and reorganizational energy (electron and hole) suggest that novel designed molecules offer high charge mobilities as compared to FCIC. Our findings indicate that these novel designed molecules can display better photovoltaic parameters and are suitable candidates if used in organic solar cells.

Complete Prevention of Contact Electrification by Molecular Engineering

Electrostatic charges are easily generated on surfaces during contact electrification. With sizes several orders of magnitude smaller than that of surface topography, these invisible charges have emerged as a new dimension in mediating the functions of surfaces such as energy conversion, liquid transport, reactivity, and adsorbability. However, charges accumulation can also pose many undesirable consequences. Despite notable progress, existing approaches in engineering antistatic surfaces suffer from limitations such as the need of modifying bulk materials or delicate control of patterning on surfaces that rely on the neutralization of generated charges. Herein, we report a general toolbox for designing antistatic coatings by leveraging on chemically heterogeneous components with electron-donating and electron-accepting functional groups to molecularly engineer the surface potential to achieve an electrostatic homogeneity and completely prevent charge generation. Our approach is general, which allows the facile fabrication of antistatic coatings on various materials, even flexible and curved, with good re-writability and transparency.

Isatin-derived non-fullerene acceptors for efficient organic solar cells

Geometries optimization, electronic structure, electronic absorption spectra, charge transport rate, morphology, and photovoltaic properties of indacenodithiophene as donor core unit tie with isatin derive different end-capped electron acceptor groups have been performed using Density Functional Theory (DFT) and time dependent density functional theory (TD-DFT). Isatin unit connected with 2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile in M1, 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile in M2, 2-thioxothiazolidin-4-one in M3, 2-(4-fluorothiophen-2-yl)acetonitrile in M4 and geometries, opto-electronic properties have been computed at TD-DFT MPW1PW91/6-31G level of theory and compared with reference molecule R. Among all novel structures, M2 has lowest value of energy band gap (1.99 eV) and has maximum absorption (λmax = 824.0 nm) in chloroform by TD-MPW1PW91/6-31G (d,p) using IEFPCM model. The red shift in M2 was due presence of strong electron withdrawing acceptor moiety and more extended conjugation as compared to other structures. Indeed, electron withdrawing functionality i.e fluorine and cyno moieties in M2 structure stabilized its LUMO orbital and hence improved its opto-electronic properties. Transition density matrix (TDM) maps results revealed obvious influence of end-capped acceptor group on the exciton. M2 has lower probability of coupling of electron and hole owing easy exciton dissociation as compared to other designed molecules. Theoretically calculated reorganization energy indicates that M1 has the highest hole transfer rate due to the lowest value of λh (0.0068 eV). Similarly, M4 has the highest electron mobility due to lowest value of λe (0.0053 eV). In short, choice of appropriate electron withdrawing end capped acceptor groups is very important for improving the performance of organic solar cells.

Modeling the IR Spectra of Excited Quadrupole Molecules with Broken Symmetry in Polar Solvents

An approach is developed that allows estimation of excited quadrupole molecule parameters responsible for changes in vibration frequencies in states with symmetry breaking by charge transfer from time-resolved IR spectra. The approach is tested on a molecule like A-π-D-π-A composed of an electron-accepting group A coupled with electron-donating group D by means of π-conjugated bonds, a D pyrrolopyrrole core, and two cyanophenyl acceptors. The expression derived for the IR spectrum of a molecule with symmetry breaking is shown to perfectly describe experimental data. The numerical values of the parameters of asymmetry in a series of solvents with different polarities and the solvent-independent parameters of the molecule itself are determined.

DFT Study of New Donor-π-Acceptor Materials Based on Thieno[2,3-b] Indole Candidate for Organic Solar Cells Application

In present search, we report theoretical analysis by using DFT (TD-DFT)-B3LYP with 6-31G (d, p) level on the geometries, optoelectronic and absorption characteristics of novel a series of the donor-π-acceptor dyes. Their π-conjugated bridge is based on the thiophene, benzene, pyridine, and pyrazine, the thieno [2,3-b] indole was used as an electron donor (D) and the acid 2-cyanoacrylic was used as an electron acceptor (A) group. The theoretical information of the electronic structures such as energy levels (HOMO and LUMO) and energy gap of the molecules is based on study the dyes in organic solar cells. Consequently the energy levels, energy gap, photovoltaic properties, quantum chemical and absorption parameters of all the dyes have been computed and reported. The calculations show that the dyes under study can theoretically be good photosensitizers in DSSCs. Also, the results show that the LUMO levels of all dyes design lie over the conduction band (Ecb) of the semiconductors TiO2 (or PC70BM) likewise the HOMO levels lie under the decrease potential vitality of the (electrolytes) comparing to ability of electron transfer from the molecular dye excited state to TiO2 (or PC70BM) and chargeerenewal after photo-oxidation process, separately.

Lasing Properties Activation by Constitutional Isomerism of an Electron-Accepting Group

Materials engineering plays a pivotal role considering its manifold applications, i.e., in medicine as individualized drug carriers or in advanced technologies such as optoelectronic devices and ot...

Effect of relative position of donor and acceptor groups on linear and non-linear optical properties of quinoline system

Quinoline ring although extensively used in designing materials with non-linear optical (NLO) properties, the study of the effect of relative position of various electron-donor and electron-acceptor groups on these properties is still missing. Herein, we present a theoretical analysis of variation of various properties such as polarizability (α), static-hyperpolarizability (β), and one-, two-, and three-photon absorption processes with the relative positions of donor and acceptor groups in substituted quinoline ring using time-dependent density functional response theory. The observed variations in two- and three-photon transition strengths have also been analysed using few-state models.