Highest Occupied Molecular Orbital Energy Research Articles

Synthesis of linear unsubstituted poly(4,4′‐triphenylamine) via Suzuki‐Miyaura coupling of an asymmetric AB monomer

AbstractPolytriarylamines (PTAAs) are amorphous polymers that can be reversibly oxidized to generate stable radical cations. Despite exhibiting a low charge carrier mobility, PTAAs are widely used as hole‐transporting layers in perovskite solar cells due to their excellent stability under ambient conditions. The highest occupied molecular orbital (HOMO) energy levels of PTAA are generally in the range of −5.1 to −5.2 eV, and therefore slightly too high for an optimal alignment with perovskites. Most linear PTAAs carry two or three methyl substituents per repeating unit. While these prevent crosslinking of chains and thus provide reaction control, the electron‐donating substituents raise the energy level of the HOMO. Unsubstituted PTAA on the other hand is usually obtained crosslinked via oxidative polymerization, while nickel‐catalyzed Grignard polycondensation leads to inclusion of impurities. We report the synthesis of linear unsubstituted PTAA using Suzuki‐Miyaura coupling of a novel asymmetric monomer, 4‐((4‐bromophenyl)(phenyl)amino)phenyl)boronic acid M1. Based on matrix‐assisted laser desorption/ionization‐time of flight (MALDI‐TOF) and 1H NMR analysis, we can conclude that the hydrogen‐terminated linear polymer is obtained. The determined HOMO energy level of −5.47 eV is a favorable match for many perovskite systems.

Simple Double Hetero[5]helicenes Realize Highly Efficient and Narrowband Circularly Polarized Organic Light-Emitting Diodes

Simple Double Hetero[5]helicenes Realize Highly Efficient and Narrowband Circularly Polarized Organic Light-Emitting Diodes

Enhancing the Intermolecular Interactions of Ladder-Type Heteroheptacene-Based Nonfullerene Acceptors for Efficient Polymer Solar Cells by Incorporating Asymmetric Side Chains

Enhancing the Intermolecular Interactions of Ladder-Type Heteroheptacene-Based Nonfullerene Acceptors for Efficient Polymer Solar Cells by Incorporating Asymmetric Side Chains

Computational Design of Rhenium(I) Carbonyl Complexes for Anticancer Photodynamic Therapy.

New Re(I) carbonyl complexes are proposed as candidates for photodynamic therapy after investigating the effects of the pyridocarbazole-type ligand conjugation, addition of substituents to this ligand, and replacement of one CO by phosphines in [Re(pyridocarbazole)(CO)3(pyridine)] complexes by means of the density functional theory (DFT) and time-dependent DFT. We have found, first, that increasing the conjugation in the bidentate ligand reduces the highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) energy gap of the complex, so its absorption wavelength red-shifts. When the enlargement of this ligand is carried out by merging the electron-withdrawing 1H-pyrrole-2,5-dione heterocycle, it enhances even more the stabilization of the LUMO due to its electron-acceptor character. Second, the analysis of the shape and composition of the orbitals involved in the band of interest indicates which substituents of the bidentate ligand and which positions are optimal for reducing the HOMO–LUMO energy gap. The introduction of electron-withdrawing substituents into the pyridine ring of the pyridocarbazole ligand mainly stabilizes the LUMO, whereas the HOMO energy increases primarily when electron-donating substituents are introduced into its indole moiety. Each type of substituents results in a bathochromic shift of the lowest-lying absorption band, which is even larger if they are combined in the same complex. Finally, the removal of the π-backbonding interaction between Re and the CO trans to the monodentate pyridine when it is replaced by phosphines PMe3, 1,4-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane (DAPTA), and 1,4,7-triaza-9-phosphatricyclo[5.3.2.1]tridecane (CAP) causes another extra bathochromic shift due to the destabilization of the HOMO, which is low with DAPTA, moderate with PMe3, but especially large with CAP. Through the combination of the PMe3 or CAP ligands with adequate electron-withdrawing and/or electron-donating substituents at the pyridocarbazole ligand, we have found several complexes with significant absorption at the therapeutic window. In addition, according to our results on the singlet–triplet energy gap, all of them should be able to produce cytotoxic singlet oxygen.

Insights into Corrosion Inhibition Behavior of a 5-Mercapto-1, 2, 4-triazole Derivative for Mild Steel in Hydrochloric Acid Solution: Experimental and DFT Studies

A triazole heterocyclic compound namely 3-(4-ethyl-5-mercapto-1, 2, 4-triazol-3-yl)-1-phenylpropanone (EMTP) was examined for its corrosion protection of mild steel (MS) against 1 M hydrochloric acid medium using gravimetric techniques. EMTP exhibited excellent corrosion protection performance at low and high concentrations towards MS in HCl solution. Comparison of corrosion protection performance of EMTP and its parent triazole and temperature effects of on inhibition efficacy were also studied. EMTP has potential corrosion inhibitor for mild steel in 1.0 M hydrochloric acid solution with the highest protection efficacy of 97% at 303 K. The weight loss findings implied that EMTP protects the metal surface corrosion through the creation of a protective layer at the surface mild steel–corrosive solution interface. The inhibitive efficacy increases with the increase of inhibitor concentration and decreases with increased temperature. The adsorption of EMTP on the surface of MS follows Langmuir’s adsorption isotherm process. DFT method was conducted on EMTP molecule to calculate the quantum chemical parameters and to determine the relationship between the molecular structure of EMTP and protection performance. The molecular parameters, such as energy gap and frontier molecular orbital (highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO)), and the absolute electronegativity (χ) value from inhibitor molecules to unoccupied d-orbital of iron atoms on the mild steel surface were also determined and correlated with protection efficiency. The theoretical findings revealed that the protection performance of EMTP increased with the increase in HOMO energy, and the nitrogen, oxygen and sulfur atoms are most probable positions for bonding through giving electrons to the d-orbital of iron atoms on the mild steel surface.

The Influence of Anion Structure on the Ionic Liquids/Au (100) Interface by Molecular Dynamics Simulations.

The microstructure of electrical double layers (EDLs) of 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF4), 1-butyl-3-methylimidazoliumhexafluorophosphate ([Bmim]PF6), and 1-butyl-3-methylimidazoliumbis (trifluoromethylsulfonyl) imide ([Bmim]TFSI) were studied by quantum chemical calculation and molecular dynamics simulation. For the set of ionic liquids investigated here, we found some interesting universal laws due to differences geometry and electronic structure of anions. We show that the morphology of the three anions on the electrode surface is different due to the different geometric structure. The plane formed by the bottom three atoms of the symmetrically tetrahedral BF4- and the bottom atom of the symmetrically octahedral PF6- face the electrode whether the electrode is charged or not, while the conformation of twisted V-shaped TFSI- changes with different surface charges on the electrode. Meanwhile, we also demonstrate that the energy of highest occupied molecular orbital (EHOMO), the energy of lowest unoccupied molecular orbital (ELUMO) and their energies gap (ΔE) are very interesting due to different electronic structure of anions. Specially, the EHOMO, ELUMO, and ΔE were related to the electronegativity of the central atom in the case of the same symmetry on the neutral surface. The more electronegative the central atom is, the lower EHOMO, ELUMO and higher ΔE values are. However, on the charged surface, the interaction between anion and electrode is opposite to ΔE. Moreover, different arrangements of anion and cation are related to the interaction between particles. The stronger interaction leads a double-row structure and the weak interaction lead worm-like and island patterns on Au (100) surface. In general, we observed that the higher ΔE cause stronger interaction, which lead to different patterns on Au (100) surface. Meanwhile, we also confirmed that the stronger interaction between particles and electrode lead to the thinner effective EDL and a large differential capacitance value. These results provide a new perspective for double-layer structure in atomic and molecular level. This is helpful to deepen the understanding of the interface phenomena and characteristics of [Bmim]BF4, [Bmim]PF6, and [Bmim]TFSI on Au (100) system and provide theoretical basis for the application of these kind of systems.

The Dog That Didn't Bark: A New Interpretation of Hypsoporphyrin Spectra and the Question of Hypsocorroles.

Nearly a half-century after Gouterman classified the UV–vis–NIR spectra of porphyrin derivatives as normal, hyper, or hypso, we propose a heretofore unsuspected “mechanism” underlying hypso spectra. Hypsoporphyrins, which exhibit blueshifted optical spectra relative to normal porphyrins (such as Zn porphyrins), typically involve dn transition metal ions, where n > 6. The spectral blueshifts have been traditionally ascribed to elevated porphyrin eg LUMO (lowest unoccupied molecular orbital) energy levels as a result of antibonding interactions with metal dπ orbitals. Herein, we have found instead that the blueshifts reflect a lowering of the a2u HOMO (highest occupied molecular orbital) energy levels. Electronegative metals such as Pd and Pt transfer smaller quantities of electron density to the porphyrin nitrogens, compared to a more electropositive metal such as Zn. With large amplitudes at the porphyrin nitrogens, the a2u HOMOs of Pd(II) and Pt(II) porphyrins accordingly exhibit lower orbital energies than those of Zn(II) porphyrins, thus explaining the hypso effect. Hypso spectra are also observed for corroles: compared with six-coordinate Al(III) corroles, which may be thought of exhibiting normal spectra, Au(III) corroles, for instance, exhibit blueshifted or hypso spectra.

Electronic and Optical Properties of Polythiophene Molecules and Derivatives

The electronic and optical properties of polythiophene (PT) for polymer light-emitting diodes (PLEDs) were calculated using density functional theory (DFT) and time-dependent DFT. We calculated the electronic and optical properties of thiophene and PT polymers with degrees of polymerization (DP) from 2 to 30 monomers (T1–T30) and their derivatives. The associated highest occupied molecular orbital (HOMO) energy, lowest unoccupied molecular orbital (LUMO) energy, band gaps, electron orbitals, and molecular structures were determined. As the DP increased, the LUMO energy gradually decreased, and the HOMO energy gradually increased. The band gap of PT approached 2 eV as the DP of the PT polymer increased from 1 to 30. The calculations and exchange–correlation functional were verified against values in the literature and experimental data from cyclic voltammetry (redox potential) and ultraviolet-visible, photoluminescence, and ultraviolet photoelectron spectra. The color of PT PLEDs can be adjusted by controlling the DP of the polymer and the substituents.

Electrocatalytic Detection of Epinephrine at Polyaniline-Biosynthesized Nickel Oxide Modified Electrode. Supported By Computational Study

The design of a simple, cost effective and reliable assay with fast response time for epinephrine (EP) is unceasing due to its dual function as a neurotransmitter and a fight-flight hormone released amid critical stress. In contribution, Polyaniline (PANI) and nickel oxide (NiO) nanoparticle was integrated unto glassy carbon electrode (GCE) in the design of a sensor for EP. PANI and NiO were synthesized through chemical oxidation polymerization and Callistemon viminalis leaf extracts, accordingly. The choice of electrode materials was based on the high surface area resulting from the synergistic catalytic properties of PANI and NiO, ease and cost of preparation. Fourier transform infrared spectroscopy, ultraviolet visible spectroscopy, x-ray diffraction and scanning electron microscopy results revealed successful synthesis of PANI, NiO and the composite (PANI/NiO). Electron transport properties of the bare and modified electrodes (GCE/PANI, GCE/NiO and GCE/PANI/NiO) as well as their electrocatalytic activity towards EP, was investigated using cyclic voltammetry and electrochemical impedance spectroscopy. Voltammetric and impedimetric response was enhanced at the PANI/NiO electrode compared with other electrode investigated. This was ascribed to improved synergistic Electrocatalytic effect of nanocomposite. Under optimized experimental conditions (pH and deposition time), the limit of detection measured was 8.2 μM and 6.1×10-3 μA/μM sensitivity over a linear EP concentrations ranging from 0 - 534 μM in 0.1 M phosphate buffer solution using square wave voltammetry. Good recovery of 102-105% was obtained for EP determination in adrenaline injection solution. The developed sensor demonstrated a good reproducibility, stability and selectivity to EP in the presence of ascorbic acid and uric acid.In addition, computational study of the LUMO (lowest unoccupied molecular orbitals)-HOMO (highest occupied molecular orbital) energy band gap of 5.48 eV calculated for EP at density functional theory level supports charge transfer and stability of EP at the nanocomposite modified electrode. Keywords. Electrocatalytic, Epinephrine, Detection, modified electrode, Polyaniline, Nickel oxide, Computational, Voltammetric, Impedimetric. Figure 1

Computational Methods and Molecular Modelling for Some Predicted Tautomers of Pyrimidine Compounds

Introduction: Several molecular modelling techniques and quantum chemical methods have been performed to correlate the chemical structures of the compounds with their physical molecular properties. Methods: Using theoretical parameters help to characterize the molecular structure of the investigated ligands and to study their equlibria mechanism. Molecular modelling data such as the bond length, bond order, bond angles and dihedral angles values were estimated for some pyrimidine compounds, where the data suggested the presence of tautomerism and a dynamic equilibria are deduced between all the detected tautomers in the solid state. Results: Four main tautomers were predicted for barbital and thiobarbituric acid, while three tautomers were for thiouracil. Quantum chemical parameters such as the highest occupied molecular orbital energy (EHOMO), the lowest unoccupied molecular orbital energy (ELUMO), energy gap (ΔE), dipole moment (μ), sum of the total negative charge (STNC), electronegativity (χ), chemical potential (Pi), global hardness (η) and softness (σ) were calculated. Conclusion: These studies display a good correlation between the theoretical and experimental data.

Molecular electrostatic potential and pattern recognition models to design potentially active pentamidine derivatives against Trypanosoma brucei rhodesiense

Molecular electrostatic potential (MEP) and pattern recognition (PR) were used to draw potentially active pentamidine derivatives against Trypanosome brucei rhodesiense (T. b. rhodesiense). PR models: Principal Component Analysis, PCA model; Hierarchical Cluster Analysis, HCA model; K-Nearest Neighbor, KNN model; Soft Independent Modeling of Class Analogy, SIMCA model; and Stepwise Discriminant Analysis, SDA model, were built by reducing the dimensionality of a data matrix to twenty-eight pentamidine derivatives and allowed the compounds to be classified into two classes: more active and less active, according to their degrees of activity against T. b. rhodesiense. The study outlined that the properties HOMO (highest occupied molecular orbital) energy, VOL (molecular volume), and ASA_P (water accessible surface area of all polar (½qi½³0. 2) atoms) are the most relevant for the construction of the models. The key structural features required for biological activity investigated through MEP were used as guidelines in the design of thirteen new compounds, which were evaluated by PR models as more active or less active against T. b. rhodesiense. The application of PR models indicated nine promising compounds (29, 30, 31, 32, 33, 36, 37, 39, and 40) for synthesis and biological assays.

Harnessing the Inductive Effect To Design New Donor–Acceptor–Acceptor′-Configured Small-Molecule Donors for Vacuum-Processed Organic Photovoltaics

Three new donor–acceptor–acceptor′ (D–A–A′)-configured molecules, DTCFiBT, DTCFoBT, and DTCF2BT, with F-substituted benzothiadiazole (BT) as the A group, and two molecules, DTCPiTD and DTCPoTD, adopting pyridal[2,1,3]-thiadiazole (PTD) as the A group, were synthesized and characterized. The effects of the F-substitution number and the orientation of mono F-substituted BT and PTD relative to the D group on the physical properties and intermolecular interactions were examined, together with theoretical calculations to establish the structure–property relationship. In comparison to the parent molecule DTCPB, the inductive effects of F-substituted BTs lower both highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of DTCFiBT, DTCFoBT, and DTCF2BT and, thus, similar optical energy gaps (Egopt), while DTCPiTD and DTCPoTD exhibit much lower LUMO energy levels and reduced Egopt, ascribing to the electron-deficient character of PTD. The strong dipolar features of the D–A–A′-configured structure resulting in the antiparallel dimeric packing with different intermolecular interactions in their crystal structures were observed by X-ray analyses. Small-molecule organic solar cells (SMOSCs) with a bulk heterojunction active layer comprising new D–A–A′ donors and C70 were fabricated and characterized. The deeper LUMO levels and reduced Egopt benefit the DTCPiTD- and DTCPoTD-based devices to have higher short current density (JSC), while the DTCFiBT-, DTCFoBT-, and DTCF2BT-based devices benefited from the lower HOMO energy levels that lead to the higher open circuit voltage (VOC). Transient photoluminescence, atomic force microscopy, and incident-light-intensity-dependent device characteristics were examined to reveal the recombination issue for the inferior DTCFoBT-based device. Among these new donors, the DTCFiBT-based device shows the best performance, with VOC of 0.94, JSC of 11.3 mA/cm2, fill factor (FF) of 0.65, and power conversion efficiency of 6.8%, which are attributed to the high VOC as a result of the deeper HOMO level and the superior FF as a result of good exciton separation and charge carrier transport.

Nematic and smectic bithiophenes for UV sensing mechanism: Comparative calculations on different homologues

Four liquid crystalline molecules in the homologus series of 5,5′-Bis-(alkylpyridinyl)-2,2′-bithiophenes (nPBTP with n = 7, 8, 10, 12) have been investigated for UV sensing mechanism. Optimization of these compounds has been carried out through hybrid functional B3LYP along with 6-31 + G (d) basis set based on the crystallographic parameters as input. The UV absorption spectra of the molecules have been calculated and the configuration interaction singles (CIS) approach has been employed to study the electronic transitions features along with excited states calculation with the help of semiempirical Hamiltonian ZINDO. The INDO/S + CI method has been implemented for the same for comparison of the results. Various spectral parameters associated have been reported. The HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) energies estimations, and the transition energies, the electron excitation nature concerning on the structural variations in the molecules are clarified. The results obtained suggest model UV sensing mechanism for full colour display applications. A comparison has been made between nematic and smectic systems.

Molecular modeling and antioxidant evaluation of new di-2-thienyl ketones festooned with thiazole or pyridine moiety

• Synthesis of new functionalized dithienyl ketones linked thiazole and/or pyridine. • The DFT study was conducted to determine the HOMO-LUMO energies and Fukui's indices. • The local relative electrophilicity and nucleophilicity descriptors were calculated. • Antioxidant activity of the synthesized dithienyl ketone derivatives was explored. • The computational docking processes were examined toward (PDB Code: 2AS1). Different novel derivatives of 5-(5-bromothiophen-2-oyl)-2-(phenylamino)thiophen-3-yl) ethylidene-hydrazinylthiazole and 2-(5-bromothiophen-2-oyl)thieno[2,3-b]pyridine were prepared by utilizing the synthesized (5-bromothien-2-yl) (4-acetyl-3-methyl-5-phenylaminothien-2-yl) ketone (3) as a precursor. The electronic and chemical reactivity of the derivatives toward nucleophilic, electrophilic, and radical attacks were evaluated based on quantum chemical calculations; the highest occupied molecular orbital (HOMO)-lowest occupied molecular orbital (LUMO) energies and Fukui indices were determined using the density functional theory (DFT) at Becke, 3-parameter, Lee–Yang–Parr (B3LYP) level. Compound 6 possessed the lowest HOMO energy value (E H ), LUMO energy value (E L ), and energy gap (ΔE H-L ). Significant inhibition percentage was observed while evaluating the antioxidant activities of the synthesized di-2-thienyl ketones 3–8 using vitamin C as a reference drug. The highest antioxidant activity with an IC 50 value of 39.85 and 34.37 µM was observed for the di-2-thienyl ketones 5 and 6 incorporating thiazole ring. Meanwhile, the rest of the di-2-thienyl ketone derivatives displayed reasonable IC 50 values from 51.60 to 68.88 µM. This experimental data was supported by molecular docking analysis of the interactions between di-2-thienyl ketone compounds and cytochrome c peroxidase (PDB Code: 2AS1) applied through Molecular Operating Environment (MOE) v10.2015.10.

Incorporation of a Guaiacol‐Based Small Molecule Guest Donor Enables Efficient Nonfullerene Acceptor‐Based Ternary Organic Solar Cells

To improve the power conversion efficiency (PCE) of the organic solar cells (OSCs), it is necessary to widen the absorption profile of the active layer. It is possible by using a ternary active layer consisting of either two donors (D) and one acceptor (A) or two acceptors and one donor having complementary absorption and appropriate frontier energy levels for efficient exciton generation and their dissociation into free charge carriers and subsequent charge/energy transfer. Herein, a large bandgap guaiacol‐based small molecule (SMD) is used as guest donor in ternary OSCs to improve the PCE and suppress the energy loss. SMD exhibits a lager bandgap and deeper highest occupied molecular orbital (HOMO) energy level compared with conjugated polymer donor (P). Therefore, the HOMO energy level is effectively down‐shifted when P is mixed with SMD, which is beneficial for attaining high open circuit voltage (VOC). OSCs based on the optimized ternary blend P:SMD:Y6 (0.8:0.2:1.2, w/w) after solvent vapor annealing attained a higher VOC of 0.85 V and low energy loss of 0.51 eV compared with the binary device P:Y6 (1:1.2, w/w) with VOC of 0.81 V and energy loss of 0.55 eV, delivering an overall PCE of 15.37%.

The coordinated tunning optical, electrical and thermal properties of spiro-configured phenyl acridophopsphine oxide and sulfide for host materials

Two spiro-configured phenyl acridophopsphine-based oxide and sulfide host materials, named 5-phenyl-5H-spiro[acridophosphine- 10,9′-fluorene]-5-oxide (PSAFO) and 5-phenyl-5H-spiro [acridopho-sphine-10,9′-fluorene]5-sulfide (PSAFS), were synthesized by convenient method. The lowest unoccupied molecular orbital (LUMO) energy level and electron mobility could be decreased and improved as the S-atom replaced O-atom, respectively. Then, the electron injecting/transporting ability of PSAFS is expected to be enhanced. Moreover, the S-atom would provide PSAFS with better electron-donating capability and heavier molecular weight compared with that of PSAFO. Thus, a higher HOMO (the highest occupied molecular orbital) energy level and thermal stability can be achieved due to the shallower onset of oxidation potential and increased molecular weight. Consequently, a narrower energy gap between HOMO and LUMO of PSAFS would be obtained, and its thermal stability could be improved, which is beneficial to constructing high performance device. Although the frontier molecular orbitals and thermal stability were finely controlled by molecular modification, the high triplet (T 1 ) energy level was still retained due to the limited π-conjugation. With the high T 1 , HOMO and LUMO energy levels of 2.83/2.82, −6.19/-5.66 and −2.12/-2.19 eV, PSAFO and PSAFS based blue TADF OLEDs with low driving voltages of 2.9/3.1 V and maximum EQEs of 12.4/13.8% are successfully realized. • The first spiro-configured phenyl acridophopsphine-based oxidized compounds as hosts for TADF OLEDs. • A facile method was employed to tune the optical, electrical and thermal properties of the hosts collaboratively. • The spiro-configured phenyl acridophopsphine-based oxidized compounds could successfully suppress the concentration quenching of the guest demonstrated by the blue TADF OLEDs with high performance at the high doping ratio of 30%.

Thiophene-Based Double Helices: Radical Cations with SOMO-HOMO Energy Level Inversion.

We report relatively persistent, open-shell thiophene-based double helices, radical cations 1•+ -TMS12 and 2•+ -TMS8 . Closed-shell neutral double helices, 1-TMS12 and 2-TMS8 , have nearly identical first oxidation potentials, E +/0 ≈ +1.33 V, corresponding to reversible oxidation to their radical cations. The radical cations are generated, using tungsten hexachloride in dichloromethane (DCM) as an oxidant, E +/0 ≈ +1.56 V. EPR spectra consist of a relatively sharp singlet peak with an unusually low g-value of 2.001-2.002, thus suggesting exclusive delocalization of spin density over π-conjugated system consisting of carbon atoms only. DFT computations confirm these findings, as only negligible fraction of spin density is found on sulfur and silicon atoms and the spin density is delocalized over a single tetrathiophene moiety. For radical cation, 1•+ -TMS12 , energy level of the singly occupied molecular orbital (SOMO) lies below the four highest occupied molecular orbitals (HOMOs), thus indicating the SOMO-HOMO inversion (SHI) and therefore, violating the Aufbau principle. 1•+ -TMS12 has a half-life of the order of only 5 min at room temperature. EPR peak intensity of 2•+ -TMS8 , which does not show SHI, is practically unchanged over at least 2 h.

Ion–solvent chemistry in lithium battery electrolytes: From mono-solvent to multi-solvent complexes

The building of safe and high energy-density lithium batteries is strongly dependent on the electrochemical performance of working electrolytes, in which ion–solvent interactions play a vital role. Herein, the ion–solvent chemistry is developed from mono-solvent to multi-solvent complexes to probe the solvation structure and the redox stability of practical electrolytes. The decrease in energies of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of solvents in lithium-ion solvation shells becomes less significant as the number of coordinated solvents increases, but both the HOMO and LUMO energies of the coordinated solvents remain lower than those of free solvents. A positive and approximately linear relationship was found between the decrease in the HOMO/LUMO energy and the average binding energy between Li+ and the coordinated solvents. A binary-solvent complex model further highlight the significant importance of the electrolyte solvation environment in regulating electrolyte stability, and it is essential to consider electrolyte stability from the perspective of ion–solvent complexes. These fresh insights into the energy chemistry of multi-solvent complexes provide critical references for electrolyte design and cell optimization.

Polyyne-metal complexes for use in molecular wire applications: A DFT insight

Metal complexes of the form C5H5N -[CN]-X-[CC]n- C5H5N, where X = Ag, Au, Co, Cu and n = 1,2,3 are studied by Density Functional Theory (DFT) methods to analyze their structural and conducting properties. Relative singlet and triplet energies, Bond length alternation (BLA), transport barrier, molecular orbitals, absorption spectrum, charge transfer with metal surface, charge modified geometry and reorganization energies of these metal complexes are analyzed. It is found that BLA values did not vary significantly in pyridine terminated metal complexes compared to pyridine terminated polyynes, however significant increase in HOMO (highest occupied molecular orbital) energies were noted, which also resulted in lower transport barriers. HOMO-LUMO (lowest unoccupied molecular orbital) energy gaps are also reduced notably to 2.52–3.11 eV which is much lesser than previously reported polyyne chains. Larger reduction in BLA was observed for positively charged polyyne-metal complexes compared to negatively charged ones.

Effect of fluorine atoms on optoelectronic, aggregation and dielectric constants of 2,1,3-benzothiadiazole-based alternating conjugated polymers

Three 2,1,3-benzothiadiazole-based conjugated copolymers named PBDT-0F-BTs, PBDT-2F-BTs and PBDT-6F-FBTs, which were derived from 4,8-bis(4,5-dioctylthiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene and (3,4′-bis(2-hexyl- decyl)-2,2′-dithiophene-5-yl) substituted 2,1,3-benzothiadiazole and/or 5,6-difluoro- 2,1,3-benzothiadiazole derivatives with 2,2′-dithiophene and/or 3,3′-difluoro- 2,2′-dithiophene as π-linkers, were prepared and characterized. The copolymers PBDT-0F-BTs, PBDT-2F-BTs and PBDT-6F-FBTs exhibited the highest occupied molecular orbital (HOMO) and lowest unoccupied orbital (LUMO) energy levels of −5.38 eV/−3.57 eV, −5.45 eV/−3.65 eV and −5.55 eV/−3.78 eV, with the light response from 300 nm to 720–750 nm, alongside with the similar aggregation, except that the charge transporting mobilities were successively increased, and the dielectric constants were gradually improved from 3.3 to 4.8 to 5.9 at 1 KHz, while the fluorine atoms in the each repeat unit of polymers were varied from 0 to 2 and then up to 6, respectively. Beyond that, it has also been found that the power conversion efficiencies and exciton dissociation probability (P(E,T)) of the bulk heterojunction organic photovoltaic cells (BHJ-OPVs) from the blend films of polymers paired with Y6 (2,2'-((2Z,2'Z)-((12,13-bis(2-ethylhexyl)-3,9-diundecyl12,13-dihydro[1,2,5]thia- diazolo[3,4-e]thieno[2'',3'':4',5']thieno[2',3':4,5]pyrrolo[3,2-g]thieno[2',3':4,5]thieno[3,2-b]indole-2,10-diyl)bis(methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-ind-ene-2,1-diylidene))dimalononitrile), were varied from 7.83% and 85.9%, to 9.22% and 90.2% and then up to 12.34% and 91.4%. The results indicated that the continuous insertion of the fluorine atoms into the repeat units of the conjugated polymers would result in the consecutively deepening the HOMO energy levels, increase dielectric constants and charge mobilities, thus devote to the enhancement of the P(E,T) and the performance of the BHJ-OPVs.