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It is shown that corannulene-based strained π-surfaces can be obtained through the use of mechanochemical Suzuki and Scholl reactions. Besides being solvent-free, the mechanochemical synthesis is high-yielding, fast, and scalable. Therefore, gram-scale preparation can be carried out in a facile and sustainable manner. The synthesized nanographene structure carries positive (bowl-like) and negative (saddle-like) Gaussian curvatures and adopts an overall quasi-monkey saddle-type of geometry. In terms of properties, the non-planar surface exhibits a high electron affinity that was measured by cyclic voltammetry, with electrolysis and in situ UV/vis spectroscopy experiments indicating that the one-electron reduced state displays a long lifetime in solution. Overall, these results indicate the future potential of mechanochemistry in accessing synthetically challenging and functional curved π-systems.

To explore the correlation of the acceptor electron affinity and the molecular conformation to the thermally activated delayed fluorescence (TADF) feature, a series of d-π-A molecules were designed and synthesized with triazine (Trz) as the acceptor (A) and carbazole (Cz) or tert-butylcarbazole (BuCz) as the donor (D). On the phenylene bridge between D and A, methyl or trifluoromethyl was incorporated close either to D or to A to tune the molecular conformation and the electron-withdrawing ability of acceptor. Both the twist angles and the singlet and triplet energy difference (ΔEST ) were observed strongly dependent on the type and position of the substituent on the π-bridge. Only those molecules with trifluoromethyl locating close to the D side, namely TrzCz-CF3 and TrzBuCz-CF3 , exhibit TADF feature, verifying that both sufficient electron affinity of the A unit and large dihedral angle between D and the π-bridge are necessary to ensure the occurrence of TADF. The blue organic light-emitting diodes fabricated with TrzCz-CF3 and TrzBuCz-CF3 achieved external quantum efficiencies of 9.40 % and 14.22 % with CIE coordinates of (0.19, 0.23) and (0.18, 0.29) respectively. This study provides practical design strategy for blue TADF materials particularly when planar and less crowded group is used as donor.

A unique approach is used to relate the HOMO-LUMO energy difference to the difference between the ionization potential (IP) and electron affinity (EA) to assist in deducing not only the colors, but also chromophores in elemental nonmetals. Our analysis focuses on compounds with lone pair electrons and σ electrons, namely X2 (X = F, Cl, Br, I), S8 and P4 . For the dihalogens, the [IP - EA] energies are found to be: F2 (12.58 eV), Cl2 (8.98 eV), Br2 (7.90 eV), I2 (6.78 eV). We suggest that the interahalogen X-X bond itself is the chromophore for these dihalogens, in which the light absorbed by the F2 , Cl2 , Br2 , I2 leads to longer wavelengths in the visible by a π → σ* transition. Trace impurities are a likely case of cyclic S8 which contains amounts of selenium leading to a yellow color, where the [IP - EA] energy of S8 is found to be 7.02 eV. Elemental P4 with an [IP - EA] energy of 9.09 eV contains a tetrahedral and σ aromatic structure. In future work, refinement of the analysis will be required for compounds with π electrons and σ electrons, such as polycyclic aromatic hydrocarbons (PAHs).

The first example of a two-state (neutral and reduced), stable electron-accepting material and its radical anion is presented. FV-PDI, generated from cyclocarbonylation and then a carbonyl coupling reaction, shows a largely degenerate LUMO of -4.38 eV based on the delocalization of π-electrons across the whole molecular skeleton through a fulvalene bridge. The stability and electron affinity allow spontaneous electron transfer to afford a stable radical anion. Spectroscopic characterization and structural elucidation showed that the radical anion [FV-PDI].- has remarkable stability and near-infrared absorptions extending to 1200 nm. Single-crystal X-ray diffraction analyses revealed significant changes in the molecular shape and packing arrangement of the formed radical anion. The central C-C bond linking the two PDI halves is lengthened from approximately 1.33 to 1.43 A, and the alternating arrangement of positively and negatively charged units favor the stable charge-transfer complex.

The newly synthesized phosphorus- and arsenic-containing analogues of the thio- and seleno-cyanate anions, PCSe- , AsCS- , and AsCSe- , as well as the known ion NCSe- were investigated in the gas phase by negative-ion photoelectron spectroscopy (NIPES), velocity-map imaging (VMI) spectroscopy, and quantum-chemical computations. The electron affinities (EA), spin-orbit (SO) splittings, and "symmetric"/"asymmetric" stretching frequencies of the neutral radicals ECX. (E=N, P, As; X=S, Se), generated by electron detachment from the corresponding anions, were obtained from the spectra. The calculated EAs, SO splittings, and vibrational frequencies are in excellent agreement with the experimental measurements. These newly obtained values, when combined with those previously determined for the lighter analogues, show interesting trends on descending the pnictogen and chalcogen series. These trends are rationalized based on electronegativity arguments, the electron distributions in the HOMOs, and NBO/NRT analyses.

Superhalogens, owing to their large electron affinity (EA, exceeding those of any halogen atom), play an essential role in physical chemistry as well as new material design. They have applications in hydrogen storage and lithium-ion batteries. Owing to the unique geometries and electronic features of magnesium-based clusters, their potential to form a new class of lithium salts has been investigated here theoretically. The idea is assessed by conducting ab initio computations on Li+ /Mgn F2n+1-2m Om - compounds (n=2, 3; m=0-3) and analyzing their performance as potential Li-ion battery electrolytes. The Mg3 F7 - cluster, with large electron binding energy (EA of 7.93 eV), has been proven to serve as a building block for lithium salts. It is shown that, apart from high electronic stability, the new superhalogen-based electrolytes exhibit a set of desirable properties, including a large band gap, high electrolyte stability window, easy mobility of the Li+ , and favorable insensitivity to water.

Bonding mechanisms, potential energy curves, accurate structures, energetics, and electron affinities are obtained for all M(CX)1-3 species with M = Li, Na, and X = O, S, Se, Te, and Po, at the coupled-cluster level with triple-ζ quality basis sets. We discuss and rationalize the trends within different molecular groups. For example, we found larger binding energies for M = Li, for CX = CPo, and for the tri-coordinated (n = 3) complexes. All three facts are explained by the fact that the global minimum of the titled complexes originate from the first excited 2 P (2p1 for Li or 3p1 for Na) state of the metal, with each ligand forming a dative bond with the metal. All of the complexes, except Na(CO)3 , have stable anions, and their electron affinity increases as MCX

Benzoaceanthrylene analogs with tetracoordinate boron at the ring junction were synthesized through tandem electrophilic C-H borylation of 2,6-dinaphthylpyridine followed by nucleophilic substitution. Notably, the [5,6]-annulation occurred selectively over [6,6]-annulation with the assistance of nitrogen coordination of the pyridine ring. The X-ray crystallographic analysis revealed the polycyclic skeleton with a distorted tetracoordinate boron atom and a unique packing structure with intermolecular π-π interaction. The photophysical and electrochemical properties of these benzoaceanthrylene analogs were evaluated by UV-vis spectroscopy and differential pulse voltammetry. The electron affinity of the fluorine-substituted derivative is estimated to be 3.49 eV from the ionization potential and optical band gap. Thus, this derivative is expected to be a promising n-type semiconducting material.

Three isostructural donor–acceptor complexes DPTTA‐FXTCNQ (X = 1, 2, 4) are investigated experimentally and theoretically. By tuning the number of F atoms in the acceptor molecules, the resulting complexes display a continuous down shift of the valence band maximum, conducting band minimum, and optical bandgap. The majority carriers convert from hole (DPTTA‐F1TCNQ), balanced hole, and electron (DPTTA‐F2TCNQ) to electron (DPTTA‐F4TCNQ). This result shows that band engineering can be realized easily in the donor–acceptor complex systems by tuning the electron affinity of the acceptor. The bandgaps of these three complexes vary from 0.31 to 0.41 eV; this narrow bandgap feature is crucial for achieving high thermoelectric performance and the unintentional doping in DPTTA‐F4TCNQ leads to the effective suppression of the bipolar cancelling effect on the Seebeck coefficient and the highest power factor.

Three-dimensional accurate potential energy surfaces around the local minima of NO2 - and NO2 were calculated with the SAC/SAC-CI analytical energy gradient method. Therefrom, the ionization photoelectron spectra of NO2 - , the equilibrium geometries and adiabatic electron affinity of NO2 , and the vibrational frequencies including harmonicity and anharmonicity of NO2 - and NO2 were obtained. The calculated electron affinity was in reasonable agreement with the experimental value. The SAC-CI photoelectron spectra of NO2 - at 350 K and 700 K including the rotational effects were calculated using the Franck-Condon approximation. The theoretical spectra reproduced well the fine experimental photoelectron spectra observed by Ervin et al. (J. Phys. Chem. 1988, 92, 5405). The results showed that the ionizations from many vibrational excited states as well as the vibrational ground state are included in the experimental photoelectron spectra especially at 700 K and that the rotational effects are important to reproduce the experimental photoelectron spectra of both temperatures. The SAC/SAC-CI theoretical results supported the analyses of the spectra by Ervin et al., except that we could show some small contributions from the asymmetric-stretching mode of NO2 - . © 2018 Wiley Periodicals, Inc.

Geometrical structures and ground and excited states of silver clusters are theoretically investigated using long-range corrected (LC) density functional theory (DFT) calculations. The discrepancy between HOMO-LUMO gaps and the vertical ionization potential minus vertical electron affinity values, which should be the same values, is explored to reveal the significance of long-range exchange effects on the electronic states of metal clusters. The difference between HOMO-LUMO gaps and HOMO-LUMO excitation energies, which is called "exciton binding energy," is also tested. As a result, it is found that the long-range exchange effects are requisite in DFT calculations to quantitatively investigate the ground and excited states of metal clusters. © 2018 Wiley Periodicals, Inc.

We report herein a gas-phase reactivity study on a para-benzyne cation and its three cyano-substituted, isomeric derivatives performed using a dual-linear quadrupole ion trap mass spectrometer. All four biradicals were found to undergo primary and secondary radical reactions analogous to those observed for the related monoradicals, indicating the presence of two reactive radical sites. The reactivity of all biradicals is substantially lower than that of the related monoradicals, as expected based on the singlet ground states of the biradicals. The cyano-substituted biradicals show substantially greater reactivity than the analogous unsubstituted biradical. The greater reactivity is rationalized by the substantially greater (calculated) electron affinity of the radical sites of the cyano-substituted biradicals, which results in stabilization of their transition states through polar effects. This finding is in contrast to the long-standing thinking that the magnitude of the singlet-triplet splitting controls the reactivity of para-benzynes.

A long-range corrected density functional theory (LC-DFT) was applied to study the geometric structures, relative stabilities, electronic structures, reactivity descriptors and magnetic properties of the bimetallic NiCun-1 and Ni2 Cun-2 (n = 3-13) clusters, obtained by doping one or two Ni atoms to the lowest energy structures of Cun , followed by geometry optimizations. The optimized geometries revealed that the lowest energy structures of the NiCun-1 and Ni2 Cun-2 clusters favor the Ni atom(s) situated at the most highly coordinated position of the host copper clusters. The averaged binding energy, the fragmentation energies and the second-order energy differences signified that the Ni doped clusters can continue to gain an energy during the growth process. The electronic structures revealed that the highest occupied molecular orbital and the lowest unoccupied molecular orbital energies of the LC-DFT are reliable and can be used to predict the vertical ionization potential and the vertical electron affinity of the systems. The reactivity descriptors such as the chemical potential, chemical hardness and electrophilic power, and the reactivity principle such as the minimum polarizability principle are operative for characterizing and rationalizing the electronic structures of these clusters. Moreover, doping of Ni atoms into the copper clusters carry most of the total spin magnetic moment. © 2018 Wiley Periodicals, Inc.

Rationale The anion mass spectral lifetimes for several aromatic hydrocarbons reported in the subject article were related to significantly different electron affinities. The different values are rationalized using negative ion mass spectral data. Methods Electron affinities for polycyclic aromatic hydrocarbons are reported from the temperature dependence of unpublished electron capture detector data. These are compared with published values and the largest values are assigned to the ground state. Results The ground state adiabatic electron affinities: (eV) pentacene, 1.41 (3); tetracene, 1.058 (5); benz(a)pyrene, 0.82 (4); benz(a) anthracene, 0.69 (2) anthracene, 0.68 (2); and pyrene, 0.59 (1) are used to assign excited state adiabatic electron affinities: (eV) tetracene: 0.88 (4); anthracene 0.53 (1); pyrene, 0.41 (1); benz(a)anthracene, 0.39 (10); chrysene, 0.32 (1); and phenanthrene, 0.12 (2) and ground state adiabatic electron affinities: (eV) dibenz(a,j)anthracene, 0.69 (3); dibenz(a,h)anthracene, 0.68 (3); benz(e)pyrene, 0.60 (3); and picene, 0.59 (3) from experimental data. The lifetime of benz(a)pyrene is predicted to be larger than 150 μs and for benzo(c)phenanthrene and picene about 40 μs, from ground state adiabatic electron affinities. Conclusions The assignments of adiabatic electron affinities of aromatic hydrocarbons determined from electron capture detector and mass spectrometric data to ground and excited states are supported by constant electronegativities. A set of consistent ground state adiabatic electron affinities for 15 polycyclic aromatic hydrocarbons is related to lifetimes from the subject article.

Two series of aromatic compounds with perfluoroalkyl (RF ) groups of increasing length, 1,3,5,7-naphthalene(RF )4 and 1,3,5,7,9-corannulene(RF )5 , have been prepared and their electronic properties studied by low-temperature photoelectron spectroscopy (PES) (for gas-phase electron affinity measurements). These and many related compounds were also studied by DFT calculations. The data demonstrate unambiguously that the electron-withdrawing ability of RF substituents increases significantly and uniformly from CF3 to C2 F5 to n-C3 F7 to n-C4 F9 .

Increasing the doping level of semiconducting polymer using strong dopants is essential for achieving good electrical conductivity. As for p‐dopant, raising the electron affinity of a neutral compound through the dense introduction of electron‐withdrawing group has always been the predominant strategy to achieve strong dopant. However, this simple and intuitive strategy faces extendibility, accessibility, and stability issues for further development. Herein, the use of dicationic state of tetraaryl benzidine (TAB2+) in conjunction with bis(trifluoromethylsulfonyl)imide anion (TFSI−) as a strong and atmospherically stable p‐dopant (TAB–2TFSI), for which the concept is hinted from a rapid and spontaneous dimerization of radical cation dopant, is demonstrated. TAB–2TFSI possesses a large redox potential such that it would have deteriorated when in contact with H2O. However, no trace of degradation after 1 year of storage under atmospheric conditions is observed. When doping the state‐of‐the‐art semiconducting polymer with TAB–2TFSI, a high doping level together with significantly enhanced crystallinity is achieved which led to an electrical conductivity as high as 656 S cm−1. The concept of utilizing charged molecule as a dopant is highly versatile and will potentially accelerate the development of a strong yet stable dopant., The use of charged molecules as a strong and atmospherically stable p‐dopant is demonstrated. Despite showing a strong doping ability above −5.7 eV, the newly reported dopant shows no trace of deterioration upon storage under ambient conditions over a year. A highly ordered cocrystal structure is formed with polythiophene, leading to an electrical conductivity as high as 650 S cm−1.

The applications of any ultrathin semiconductor device are inseparable from high-quality metal-semiconductor contacts with designed Schottky barriers. Building van der Waals (vdWs) contacts of 2D semiconductors represents an advanced strategy of lowering the Schottky barrier height by reducing interface states, but will finally fail at the theoretical minimum barrier due to the inevitable energy difference between the semiconductor electron affinity and the metal work function. Here, an effective molecule optimization strategy is reported to upgrade the general vdWs contacts, achieving near-zero Schottky barriers and creating high-performance electronic devices. The molecule treatment can induce the defect healing effect in p-type semiconductors and further enhance the hole density, leading to an effectively thinned Schottky barrier width and improved carrier interface transmission efficiency. With an ultrathin Schottky barrier width of ≈2.17 nm and outstanding contact resistance of ≈9 kΩ µm in the optimized Au/WSe2 contacts, an ultrahigh field-effect mobility of ≈148 cm2 V-1 s-1 in chemical vapor deposition grown WSe2 flakes is achieved. Unlike conventional chemical treatments, this molecule upgradation strategy leaves no residue and displays a high-temperature stability at >200 °C. Furthermore, the Schottky barrier optimization is generalized to other metal-semiconductor contacts, including 1T-PtSe2 /WSe2 , 1T'-MoTe2 /WSe2 , 2H-NbS2 /WSe2 , and Au/PdSe2 , defining a simple, universal, and scalable method to minimize contact resistance.

Black phosphorus (BP) shows great potential in electronic and optoelectronic devices owing to its semiconducting properties, such as thickness-dependent direct bandgap and ambipolar transport characteristics. However, the poor stability of BP in air seriously limits its practical applications. To develop effective schemes to protect BP, it is crucial to reveal the degradation mechanism under various environments. To date, it is generally accepted that BP degrades in air via light-induced oxidation. Herein, we report a new degradation channel via water-catalyzed oxidation of BP in the dark. When oxygen co-adsorbs with highly polarized water molecules on BP surface, the polarization effect of water can significantly lower the energy levels of oxygen (i.e. enhanced electron affinity), thereby facilitating the electron transfer from BP to oxygen to trigger the BP oxidation even in the dark environment. This new degradation mechanism lays important foundation for the development of proper protecting schemes in black phosphorus-based devices.

New monomers containing 4-cyanophenyl (–PhCN) groups attached to a thieno[3,2-b]thiophene (TT) or dithieno[3,2-b:2′,3′-d]thiophene (DTT) structure were synthesized and characterized as 4-(2,5-dibromothieno[3,2-b]thiophen-3-yl)benzonitrile (Br–TT–PhCN) or 4,4′-(2,6-dibromodithieno[3,2-b:2′,3′-d]thiophene-3,5-diyl)dibenzonitrile (Br–DTT–PhCN). The Suzuki coupling of 9,9-dioctylfluorene-2,7-diboronic acid bis(1,3-propanediol)ester and the Br–TT–PhCN or Br–DTT–PhCN monomer was utilized for the syntheses of novel copolymers poly{9,9-dioctylfluorene-2,7-diyl-alt-3-(4′-cyanophenyl)thieno[3,2-b]thiophene-2,5-diyl} (PFTT–PhCN) and poly{9,9-dioctylfluorene-2,7-diyl-alt-3,5-bis(4′-cyanophenyl)dithieno[3,2-b:2′,3′-d]thiophene-2,6-diyl} (PFDTT–PhCN), respectively. The photophysical, electrochemical, and electroluminescent (EL) properties of these novel copolymers were studied. Their photoluminescence (PL) exhibited the same emission maximum for both copolymers in solution. Red-shifted PL emissions were observed in the thin films. The PL emission maximum of PFTT–PhCN was more significantly redshifted than that of PFDTT–PhCN, indicating more pronounced excimer or aggregate formation in PFTT–PhCN. The ionization potential (HOMO level) and electron affinity (LUMO level) values were 5.54 and 2.81 eV, respectively, for PFTT–PhCN and were 5.57 and 2.92 eV, respectively, for PFDTT–PhCN. Polymer light-emitting diodes (LEDs) with copolymer active layers were fabricated and studied. Anomalous behavior and memory effects were observed from the current–voltage characteristics of the LEDs for both copolymers. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 2629–2638

Two donor–acceptor conjugated polymers with azaisoindigo as acceptor units and bithiophene and terthiophene as donor units have been synthesized by Stille polymerization. These two polymers have been successfully applied in field-effect transistors and polymer solar cells. By changing the donor component of the conjugated polymer backbone from bithiophene to terthiophene, the density of thiophene in the backbone is increased, manifesting as a decrease in both ionization potential and in electron affinity. Therefore, the charge transport in field-effect transistors switches from ambipolar to predominantly hole transport behavior. PAIIDTT exhibits hole mobility up to 0.40 cm2/Vs and electron mobility of 0.02 cm2/Vs, whereas PAIIDTTT exhibits hole mobility of 0.62 cm2/Vs. Polymer solar cells were fabricated based on these two polymers as donors with PC61BM and PC71BM as acceptor where PAIIDTT shows a modest efficiency of 2.57% with a very low energy loss of 0.55 eV, while PAIIDTTT shows a higher efficiency of 6.16% with a higher energy loss of 0.74 eV. Our results suggest that azaisoindgo is a useful building block for the development of efficient polymer solar cells with further improvement possibility by tuning the alternative units on the polymer backbone. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 2691–2699.

Accurate determination of ionization potentials (IPs), electron affinities (EAs), fundamental gaps (FGs), and HOMO, LUMO energy levels of organic molecules play an important role in modeling and predicting the efficiencies of organic photovoltaics, OLEDs etc. In this work, we investigate the effects of Hartree Fock (HF) Exchange, correlation energy, and long range corrections in predicting IP and EA in Hybrid Functionals. We observe increase in percentage of HF exchange results in increase of IPs and decrease in EAs. Contrary to the general expectations inclusion of both HF exchange and correlation energy (from the second order perturbation theory MP2) leads to poor prediction. Range separated Hybrid Functionals are found to be more reliable among various DFT Functionals investigated. DFT Functionals predict accurate IPs whereas post HF methods predict accurate EAs. © 2017 Wiley Periodicals, Inc.

Experimentally characterized endohedral metallofullerenes are of current interest in expanding the range of viable fullerenic structures and their applications. Smaller metallofullerenes, such as M@C28 , show that several d- and f-block elements can be efficiently confined in relatively small carbon cages. This article explores the potential capabilities of the smallest fullerene cage, that is, C20 , to encapsulate p-block elements from group 14, that is, E = Si, Ge, Sn, and Pb. Our interest relates to the bonding features and optical properties related to E@C20 . The results indicate both s- and p-type concentric bonds, in contrast to the well explored endohedral structures encapsulating f-block elements. Our results suggest the E@C20 series to be a new family of viable endohedral fullerenes. In addition spectroscopic properties related to electron affinity, optical, and vibrational were modeled to gain further information useful for characterization. Characteristic optical patterns were studied predicting a distinctive first peak located between 400 and 250 nm, which is red-shifted going to the heavier encapsulated Group 14 atoms. Electron affinity properties expose different patterns useful to differentiate the hollow C20 fullerene to the proposed p-block endohedral counterparts. © 2017 Wiley Periodicals, Inc.

Optimized syntheses of 6,13-dimesityl-6,13-dihydro-6,13-diborapentacene (DBP) and a related compound (DBI) featuring two biphenylene-2,3-diyl units in place of naphthalene-2,3-diyl moieties are reported. Striking differences between the optoelectronic properties of DBP and DBI have been experimentally observed, and explained by quantum chemical calculations. DBP is a member of the oligoacene family, DBI is a linear [N]phenylene derivative. The yellow DBP shows blue photoluminescence, the deep red DBI is nonfluorescent. Both compounds give rise to two reversible redox transitions at E1/2 =-2.03 V, -2.75 V (DBP) and -1.52 V, -2.30 V (DBI; THF, vs. FcH/FcH+ ). The higher electron affinity of DBI agrees with a lower calculated LUMO energy level [-0.57 eV for DBI with respect to DBP @HF//SCS-MP2/def2-TZVP] and a higher Lewis acidity of its boron centers, which is reflected in the trend of adduct formation with small Lewis bases (MeCN, F- ). The thermochemistry underlying this trend, as well as the mechanism of fluorescence quenching in DBI, are revealed by state-of-the-art quantum chemical calculations. It is suggested that the nonradiative deactivation occurs via a low-lying, doubly excited state.

Monolayer transition-metal dichalcogenides (TMDCs) have recently emerged as promising candidates for advanced photonic and valleytronic applications due to their unique optoelectronic properties. However, the low luminescence efficiency of monolayer TMDCs has significantly hampered their use in these fields. Here it is reported that the photoluminescence efficiency of monolayer WS2 can be remarkably enhanced up to fourfold through the fluorination, surpassing the reported performance of molecular and/or electrical doping methods. Its degree is easily controlled by changing the fluorine plasma duration time and can also be reversibly tuned via additional hydrogen plasma treatment, allowing for its versatile tailoring for interfacial band alignment and customized engineering. The striking photoluminescence improvement occurs via a substantial transition of trions to excitons as a result of the strong electron affinity of fluorine dopants, and the fluorination enables unprecedented detection of n-type NH3 gas in WS2 due to changed excitonic dynamics showing excellent sensitivity (at least down to 1.25 ppm). This work provides valuable strategies and insights into exciton physics in monolayer TMDCs, opening up avenues toward highly-efficient 2D light emitters, photovoltaics, nanosensors, and optical interconnects.

Reactions involved in the autoxidation of ascorbate have been investigated with quantum chemical first-principles and ab initio methods. Reaction energies and Gibbs energies of the reactions were calculated at the density functional theory level applying the gradient-corrected BP86 and the hybrid B3LYP functionals together with def2-TZVP basis sets. Results of single-point CC2, CCSD, and CCSD(T) calculations were used for calibration of the density functional theory data and show excellent agreement with the B3LYP values. Based on the Gibbs energy ascorbic acid AscH2 is found to be the energetically lowest species in aqueous solution, whereas the monoanion ascorbate AscH - is the most abundant one near pH = 7. Asc 2- was found to be the preferred reducing agent for autoxidation and oxidation processes. The results also support a metal-catalyzed synthesis of the reactive oxygen species H2 O2 according to a redox cycling mechanism proposed in literature. © 2016 Wiley Periodicals, Inc.

Many high charge carrier mobility (μ) active layers within organic field-effect transistor (OFET) configurations exhibit non-linear current–voltage characteristics that may drift with time under applied bias and, when applying conventional equations for ideal FETs, may give inconsistent μ values. This study demonstrates that the introduction of electron deficient fullerene acceptors into thin films comprised of the high-mobility semiconducting polymer PCDTPT suppresses an undesirable “double-slope” in the current–voltage characteristics, improves operational stability, and changes ambipolar transport to unipolar transport. Examination of other high μ polymers shows general applicability. This study also shows that one can further reduce instability by tuning the relative electron affinity of the polymer and fullerene by creating blends containing different fullerene derivatives and semiconductor polymers. One can obtain hole μ values up to 5.6 cm2 V–1 s–1 that are remarkably stable over multiple bias-sweeping cycles. The results provide a simple, solution-processable route to dictate transport properties and improve semiconductor durability in systems that display similar non-idealities.

RATIONALE Superoxide is the most significant homonuclear diatomic anion in biochemistry. Theory predicts 12 doublet (X, A-K) and 12 quartet (a-l) electronic states split by spin orbital coupling into 54 states dissociating to the (3) P(O) + (2) P(O(-) ) limit. Dissociation energies for the 27 bonding states with positive electron affinities have been determined from mass spectrometric data. However, the 27 antibonding states with negative electron affinities have not been experimentally characterized. METHODS The electron affinity of the hydrogen atom per electron, the Hylleraas, is the fundamental measure of electron correlation. It has been used to assign and evaluate experimental electron affinities of atoms and diatomic molecules. The 27 negative electron affinities of oxygen are estimated from the 27 positive values and the Hylleraas. These values are used to determine frequencies and internuclear separations by fitting theoretical electron impact distributions to the gas-phase mass spectrometric atomic oxygen anion distribution peaking at about 6.5 eV. RESULTS The dissociation energies, internuclear distances and frequencies giving the first complete set of Morse potential energy curves for the 54 superoxide states dissociating to the lowest limit are reported from mass spectrometric data. The potentials are compared to theoretical and empirical literature curves. CONCLUSIONS The existence of the 27 bonding and 27 antibonding spin orbital coupling superoxide states dissociating to (3) P(O) + (2) P(O(-) ) is established from mass analyzed thermal, photon, and electron ionization data. There are electron affinities from 0 to 0.15 eV, and onsets and peaks for dissociative electron attachment that cannot be explained by the 54 states. These support the existence of the 36 superoxide spin states dissociating to [(1) D(O) + (2) P(O(-) )] and [(1) S(O) + (2) P(O(-) )] predicted by quantum mechanics. Copyright © 2016 John Wiley & Sons, Ltd.

Field-effect transistor memories usually require one additional charge storage layer between the gate contact and organic semiconductor channel. To avoid such complication, new donor–acceptor rod–coil diblock copolymers (P3HT44-b-Pison) of poly(3-hexylthiophene) (P3HT)-block-poly(pendent isoindigo) (Piso) are designed, which exhibit high performance transistor memory characteristics without additional charge storage layer. The P3HT and Piso blocks are acted as the charge transporting and storage elements, respectively. The prepared P3HT44-b-Pison can be self-assembled into fibrillar-like nanostructures after the thermal annealing process, confirmed by atomic force microscopy and grazing-incidence X-ray diffraction. The lowest-unoccupied molecular orbital levels of the studied polymers are significantly lowered as the block length of Piso increases, leading to a stronger electron affinity as well as charge storage capability. The field-effect transistors (FETs) fabricated from P3HT44-b-Pison possess p-type mobilities up to 4.56 × 10−2 cm2 V−1 s−1, similar to that of the regioregular P3HT. More interestingly, the FET memory devices fabricated from P3HT44-b-Pison exhibit a memory window ranging from 26 to 79 V by manipulating the block length of Piso, and showed stable long-term data endurance. The results suggest that the FET characteristics and data storage capability can be effectively tuned simultaneously through donor/acceptor ratio and thin film morphology in the block copolymer system.

The selectivity for sulfur removal from oils is an important topic. In this work, the selectivity for different sulfur removal methods has been studied by conceptual density functional theory (CDFT) at the B3LYP/6-311++G(3df,2p) level of theory. In principle, the selectivity is directly related to the mechanisms of sulfur removal. It cannot be precisely elucidated until the mechanisms are totally known. However, current work shows that relationships can be constructed between CDFT and the selectivity. That is, for hydrodesulfurization, good descriptors will be ionization energy, hardness, and bond lengths of SC; for adsorptive desulfurization, the hardness is a good descriptor; for oxidative desulfurization, good descriptors are electron density and Fukui function. And for extractive desulfurization (nonmetal-based ionic liquids), electron affinity and electrophilicity may be good descriptors. In addition, structures and frontier orbitals of various sulfides have also been discussed. It is hoped that these relationships between CDFT and selectivity can give useful information to develop highly efficient sulfur removal methods for specific sulfides, like 4,6-dimethyldibenzothiophene, and 4-methyldibenzothiophene. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2087–2100, 2016

Fine-tuning of the charge carrier polarity in organic transistors is an important step toward high-performance organic complementary circuits and related devices. Here, three new semiconducting polymers, namely, pDPF-DTF2, pDPSe-DTF2, and pDPPy-DTF2, are designed and synthesized using furan, selenophene, and pyridine flanking group-based diketopyrrolopyrrole cores, respectively. Upon evaluating their electrical properties in transistor devices, the best performance has been achieved for pDPSe-DTF2 with the highest and average hole mobility of 1.51 and 1.22 cm2 V−1 s−1, respectively. Most intriguingly, a clear charge-carrier-polarity change is observed when the devices are measured under vacuum. The pDPF-DTF2 polymer exhibits a balanced ambipolar performance with the µh/µe ratio of 1.9, whereas pDPSe-DTF2 exhibits p-type dominated charge carrier transport properties with the µh/µe ratio of 26.7. Such a charge carrier transport change is due to the strong electron-donating nature of the selenophene. Furthermore, pDPPy-DTF2 with electron-withdrawing pyridine flanking units demonstrates unipolar n-type charge transport properties with an electron mobility as high as 0.20 cm2 V−1 s−1. Overall, this study demonstrates a simple yet effective approach to switch the charge carrier polarity in transistors by varying the electron affinity of flanking groups of the diketopyrrolopyrrole unit.

The chemical properties of the 4,5,8-tridehydroisoquinolinium ion (doublet ground state) and related mono- and biradicals were examined in the gas phase in a dual-cell Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometer. The triradical abstracted three hydrogen atoms in a consecutive manner from tetrahydrofuran (THF) and cyclohexane molecules; this demonstrates the presence of three reactive radical sites in this molecule. The high (calculated) electron affinity (EA=6.06 eV) at the radical sites makes the triradical more reactive than two related monoradicals, the 5- and 8-dehydroisoquinolinium ions (EA=4.87 and 5.06 eV, respectively), the reactivity of which is controlled predominantly by polar effects. Calculated triradical stabilization energies predict that the most reactive radical site in the triradical is not position C4, as expected based on the high EA of this radical site, but instead position C5. The latter radical site actually destabilizes the 4,8-biradical moiety, which is singlet coupled. Indeed, experimental reactivity studies show that the radical site at C5 reacts first. This explains why the triradical is not more reactive than the 4-dehydroisoquinolinium ion because the C5 site is the intrinsically least reactive of the three radical sites due to its low EA. Although both EA and spin-spin coupling play major roles in controlling the overall reactivity of the triradical, spin-spin coupling determines the relative reactivity of the three radical sites.

Interfaces formed by two different organic semiconductors often exhibit a large conductivity, originating from transfer of charge between the constituent materials. The precise mechanisms driving charge transfer and determining its magnitude remain vastly unexplored, and are not understood microscopically. To start addressing this issue, we have performed a systematic study of highly reproducible single-crystal interfaces based on rubrene (tetraphenylnaphthacene) and Fx-TCNQ (fluorinated tetracyanoquinodimethane), a family of molecules whose electron affinity can be tuned by increasing the fluorine content. The combined analysis of transport and scanning Kelvin probe measurements reveals that the interfacial charge-carrier density, resistivity, and activation energy correlate with the electron affinity of Fx-TCNQ crystals, with a higher affinity resulting in larger charge transfer. Although the transport properties can be described consistently and quantitatively using a mobility-edge model, we find that a quantitative analysis of charge transfer in terms of single-particle band diagrams reveals a discrepancy ≈100 meV in the interfacial energy level alignment. We attribute the discrepancy to phenomena known to affect the energetics of organic semiconductors, which are neglected by a single-particle description—such as molecular relaxation and bandgap renormalization due to screening. The systematic behavior of the Fx-TCNQ/rubrene interfaces opens the possibility to investigate these phenomena experimentally, under controlled conditions.

The K shell absorption jump ratios, jump factors, effective atomic numbers, and electron densities were derived from the measured total mass attenuation coefficient using an energy dispersive X-ray fluorescence spectrometer for Gd2O3, Gd2(CO3)3H2O, Gd2(C2O4)3H2O, and Gd2(SO4)3 compounds. The total mass attenuation coefficients were measured in the X-ray energy range from 39.52 to 57.14 keV in a transmission geometry utilizing the Kα2, Kα1, Kβ1, and Kβ2 X-rays from different secondary source targets excited by the 59.54-keV photons from an Am-241 annular source and detected by a Si(Li) detector with a resolution of 160 eV at 5.9 keV. The energy gap, ionization energy, electron affinity, and global electrophilicity parameters of oxide, sulfate, oxalate, and carbonate ions were calculated using density functional theory (B3LYP). The experimental results are discussed based on these parameters. Copyright © 2015 John Wiley & Sons, Ltd.

The initial molecular structure of 2,2′-bis(4-trifluoromethylphenyl)- 5,5′-bithiazole has been optimized in the ground state using density functional theory (DFT). The distribution patterns of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) have also been evaluated. To shed light on the charge transfer properties, we have calculated the reorganization energy of electron λe, the reorganization energy of hole λh, adiabatic electron affinity (EAa), vertical electron affinity (EAv), adiabatic ionization potential (IPa), and vertical ionization potential (IPv) using DFT. Based on the evaluation of hole reorganization energy, λh, and electron reorganization energy, λe, it has been predicted that 2,2′-bis(4-trifluoromethylphenyl)-5,5′-bithiazole would be a better electron transport material. Finally, the effect of electric field on the HOMO, LUMO, and HOMO–LUMO gap were observed to check its suitability for the use as a conducting channel in organic field-effect transistors. © 2015 Wiley Periodicals, Inc.

We developed an efficient solvent- and catalyst-free direct polytrifluoromethylation of solid perylene-3,4,9,10-tetracarboxylic dianhydride that produced a new family of (poly)perfluoroalkyl bay- and ortho-substituted PDIs with two different imide substituents. Direct hydrogen substitution with CN group led to the synthesis of a cyanated perfluoroalkyl PDI derivative for the first time. Absorption, steady-state and time-resolved emission, X-ray diffraction, electrochemical, and gas-phase electron affinity data allowed for systematic studies of substitution effects at bay, ortho, and imide positions in the new PDIs. Solid-state packing showed remarkable variations in the intermolecular interactions that are important for charge transport and photophysical properties. Moreover, analysis of the electrochemical data for 143 electron poor PDIs, including newly reported compounds, revealed some general trends and peculiar effects from substituting electron-withdrawing groups at all three positions.

This work presented quantum chemical studies of the polymerized cellulose building blocks based on Kohn–Sham density functional theory. The relative energy, electronic property, and reactivity of the polymerized cellulose fragments with various sizes were investigated. According to the cohesive energy, the cellulose polymers with longer chains were energetically more favorable. The hydration energies were all positive and exhibited a nearly linear enhancement as the elongation of polymerized cellulose fragments. The electronic properties of the cellulose chains with various sizes were discussed based on the frontier molecular orbital theory. Besides, the reactivity of the polymerized cellulose building blocks was also investigated based on ionization potential, electron affinity energy, and the Fukui function. Copyright © 2015 John Wiley & Sons, Ltd.

The long sought-after, intrinsically short-lived molecule ethylenedione (OCCO) was observed and investigated by anion photoelectron spectroscopy. The adiabatic electron affinity of its quasi-bound (3)Σ(g)(-) state is 1.936(8) eV. The vibrational progression with a 417(15) cm(-1) frequency observed within the triplet band corresponds to a trans-bending mode. Several dissociative singlet states are also observed, corresponding to two components of the (1)Δg state and the (1)Σ(g)(+) state. The experimental results are in agreement with theoretical predictions and constitute the first spectroscopic observation and characterization of this elusive compound.

Crossed McMurry reactions of bifuran- or bithiophenedicarbaldehydes with bipyrroledicarbaldehydes have been studied for the first time. Only those porphycenic macrocycles derived from homocoupled McMurry products were formed. The results are explained by using both density functional theory and electron propagator computations to model the electron affinity of the dialdehyde starting materials. It was predicted that bifuran\bithiophene cross-coupling would indeed occur, and this was demonstrated by the first synthesis of a novel dioxa,dithio hetero-porphycenoid annulene. This approach will allow the prior identification of viable substrates for related crossed McMurry reactions.

Organic electron donors are of importance for a number of applications. However, the factors that are essential for a directed design of compounds with desired reduction power are not clear. Here, we analyze these factors in detail. The intrinsic reduction power, which neglects the environment, has to be separated from extrinsic (e.g., solvent) effects. This power could be quantified by the gas-phase ionization energy. The experimentally obtained redox potentials in solution and the calculated ionization energies in a solvent (modeled with the conductor-like screening model (COSMO)) include both intrinsic and extrinsic factors. An increase in the conjugated π-system of organic electron donors leads to an increase in the intrinsic reduction power, but also decreases the solvent stabilization. Hence, intrinsic and extrinsic effects compete against each other; generally the extrinsic effects dominate. We suggest a simple relationship between the redox potential in solution and the gas-phase ionization energy and the volume of an organic electron donor. We finally arrive at formulas that allow for an estimate of the (gas-phase) ionization energy of an electron donor or the (gas-phase) electron affinity of an electron acceptor from the measured redox potentials in solution. The formulas could be used for neutral organic molecules with no or only small static dipole moment and relatively uniform charge distribution after oxidation/reduction.

The experimental electron affinity (EA) of CO(X 1 R 1 )i s21.5 eV, signifying the metastability of the CO 2 (X 2 P) anion. The electronic structure and bonding of CO 2 ,B F 2 , and BCl 2 vis-�their neutral counterparts have been studied by conventional coupled-cluster (CCSD(T)) and multireference (MRCI) methods. Our results are in agreement with experiment for the CO/CO 2 system, indicating as well the metastable nature of the BF 2 (X 2 P) and BCl 2 (X 2 P) anions, their MRCI EAs being 20.8 6 0.1 and 20.3 6 0.1 eV, respectively. Our work clearly shows the usefulness of stationary state ab initio methods to the elucidation of metastable species. V C 2015 Wiley Periodicals

The reduction and oxidation properties of four nitrocompounds (trinitrotoluene [TNT], 2,4-dinitrotoluene, 2,4-dinitroanisole, and 5-nitro-2,4-dihydro-3H-1,2,4-triazol-3-one [NTO]) dissolved in water as compared with the same properties for compounds adsorbed on a silica surface were studied. To consider the influence of adsorption, cluster models were developed at the M05/tzvp level. A hydroxylated silica (001) surface was chosen to represent a key component of soil. The PCM(Pauling) and SMD solvation models were used to model water bulk influence. The following properties were analyzed: electron affinity, ionization potential, reduction Gibbs free energy, oxidation Gibbs free energy, and reduction and oxidation potentials. It was found that adsorption and solvation decrease gas phase electron affinity, ionization potential, and Gibbs free energy of reduction and oxidation, and thus, promote redox transformation of nitrocompounds. However, in case of solvation, the changes are more significant than for adsorption. This means that nitrocompounds dissolved in water are easier to transform by reduction or oxidation than adsorbed ones. Among the considered compounds, TNT was found to be the most reactive in an electron attachment process and the least reactive for an electron detachment transformation. During ionization, a deprotonation of adsorbed NTO was found to occur.

We have clarified and observed the high electron affinity of pinB-BMes2 (1; Mes = mesityl, pin = pinacolato). By using electrochemistry, it was shown that 1 has a higher electron affinity than those of B2pin2 and Mes3B. One-electron reduction of 1 gave the corresponding radical anion. The ESR spectroscopy and DFT calculation revealed the unsymmetrical distribution of electron density over the B-B bond. UV/Vis spectroscopy showed that the SOMO-related absorption supports the deep purple color of the radical anion. DFT studies on the torsion angle dependency of the LUMO levels and relative energies revealed the reason why 1 has high electron affinity as a result of the substituent effect of the Bpin group.

Naturally occurring biomolecules have increasingly found applications in organic electronics as a low cost, performance-enhancing, environmentally safe alternative. Previous devices, which incorporated DNA in organic light emitting diodes (OLEDs), resulted in significant improvements in performance. In this work, nucleobases (NBs), constituents of DNA and RNA polymers, are investigated for integration into OLEDs. NB small molecules form excellent thin films by low-temperature evaporation, enabling seamless integration into vacuum deposited OLED fabrication. Thin film properties of adenine (A), guanine (G), cytosine (C), thymine (T), and uracil (U) are investigated. Next, their incorporation as electron-blocking (EBL) and hole-blocking layers (HBL) in phosphorescent OLEDs is explored. NBs affect OLED performance through charge transport control, following their electron affinity trend: G A C T U . G and A have lower electron affinity (1.8 2.2 eV), blocking electrons but allowing hole transport. C , T , and U have higher electron affinities (2.6 3.0 eV), transporting electrons and blocking hole transport. A-EBL-based OLEDs achieve current and external quantum efficiencies of 52 cd A 1 and 14.3%, a ca. 50% performance increase over the baseline device with conventional EBL. The combination of enhanced performance, wide diversity of material properties, simplicity of use, and reduced cost indicate the promise of nucleobases for future OLED development.

Broad spectral coverage over the solar spectrum is necessary for photovoltaic technologies and is a focus for organic solar cells. We report a series of small-molecule, nonfullerene electron acceptors containing the [(benzo[c][1,2,5]thiadiazol-4-yl)methylene]malononitrile unit as a high electron affinity component. The optoelectronic properties of these molecules were fine-tuned with the objective of attaining strong absorption at longer wavelengths by changing the low-ionization-potential moiety. The electron-accepting function of these materials was investigated with poly(3-n-hexylthiophene) (P3HT) as a standard electron donor. Significant photocurrent generation in the near infrared region, with an external quantum yield reaching as high as 22 % at 700 nm and an onset >800 nm was achieved. The results support efficient hole transfer to P3HT taking place after light absorption by the acceptor molecules. A Channel II-dominated power conversion efficiency of up to 1.5 % was, thus, achieved.

Organic photovoltaics are under intense development and significant focus has been placed on tuning the donor ionization potential and acceptor electron affinity to optimize open circuit voltage. Here, it is shown that for a series of regioregular-poly(3-hexylthiophene): fullerene bulk heterojunction (BHJ) organic photovoltaic devices with pinned electrodes, integer charge transfer states present in the dark and created as a consequence of Fermi level equilibrium at BHJ have a profound effect on open circuit voltage. The integer charge transfer state formation causes vacuum level misalignment that yields a roughly constant effective donor ionization potential to acceptor electron affinity energy difference at the donor-acceptor interface, even though there is a large variation in electron affinity for the fullerene series. The large variation in open circuit voltage for the corresponding device series instead is found to be a consequence of trap-assisted recombination via integer charge transfer states. Based on the results, novel design rules for optimizing open circuit voltage and performance of organic bulk heterojunction solar cells are proposed. Funding Agencies|Swedish Energy Agency [34142-1]; European Commission [287594]; Academy of Finland [137093]; Swedish Research Council Linnaeus grant LiLi-NFM; Waldemar von Frenckell Foundation; Swedish Cultural Foundation in Finland; Advanced Functional Materials Center at Linkoping University

The redox properties of DNA play an influential role in several important processes such as DNA mutation and the interaction of DNA with drugs. Structural changes in DNA nucleobases from its canonical form to its tautomeric forms can alter these properties and may lead to DNA mutation due to altered base-pairing properties. Experimental results for the standard value of DNA redox properties vary due to choice of methodology and solvent. Theoretical determination of these properties is helpful in pinpointing standard values but still vary depending on methodology and chosen experimental benchmark. However, it is of importance to identify the overall trend of electron mobility within DNA while providing reliable standard values for redox reactions. In this work, we present the results of theoretical calculations for redox properties. Using the thermodynamic cycle, we can approximate reliable values. We report the electron affinities, ionization potentials, and redox potential for the canonical DNA nucleobases and their rare tautomers. For each of these properties, we evaluate its overall trend to gain a greater understanding of the role that electron attachment and electron mobility have within the DNA strand. All calculations are computed at the M06-2X/6–31++G(d,p) level of theory. © 2014 Wiley Periodicals, Inc.