Frontier Orbital Energies Research Articles

A Hypothetical Study on the Structural Properties of Limonene Compounds Using Semi-Empirical (PM3) Method with Arguslab Software

Limonene, in its racemic form (+/-), is a naturally occurring cyclic monoterpene and a primary constituent of citrus peel oil, known for its chemopreventive and antitumor properties. The conformational analysis and geometric optimization of certain limonene compounds were performed using the PM3 semi-empirical quantum mechanical calculations in ArgusLab 4.0.1 software. The compounds' geometries, geometric, and thermodynamic parameters were obtained using their most stable structures. The HOMO-LUMO frontier orbital energies, molecular electrostatic potential (MEP), solvent surface distribution, and UV spectrum values of the optimized compounds were also calculated.

Carboxylic acid-assisted hydration for the preparation of mesoporous magnesium hydroxide/magnesium oxide with ultra-high adsorption performance and selective adsorption: Experiments and DFT investigations

Herein, mesoporous Mg(OH)2 is prepared by one-step hydration method using microcrystalline magnesite as raw material and acetic acid as hydration agent, and the mesoporous MgO is obtained after thermal conversion. The adsorption experiments on three single dye systems (Congo red (CR), methyl orange (MO) and methylene blue (MB)) and three binary mixed dye systems (CR/MO, CR/MB and MO/MB) show that mesoporous MgO possesses superior adsorption selectivity towards anionic dyes. The mesoporous Mg(OH)2 with cardroom-like structure, obvious pore channel and abundant edge and concern shows good adsorption capacity for CR (6591.96 mg/g) and MO (3087.04 mg/g). The mesoporous MgO obtained by calcination has high specific surface area (66 m2/g) and partially inherits the cardroom-like structure of Mg(OH)2, exhibiting remarkable adsorption performance (CR: 10521.89 mg/g; MO: 6694.65 mg/g). CR and MO adsorption on the Mg(OH)2/MgO accords with the Langmuir model and pseudo-second-order kinetic model. The density functional theory (DFT) is employed to evaluate the reactivity of CR/MO, such as molecular frontier orbital energies and energy gap, demonstrating that CR exhibits superior reactivity and adsorptive capacity in comparison to MO. The MgO sample is regenerated by calcination after CR/MO adsorption and the CR removal efficiency of MgO reaches above 85 % after 10 cycles.

Mechanistic Study of Atomic Oxygen Erosion on Polyimide Under Electric Fields: A Molecular Dynamics and Density Functional Theory Approach.

Polyimide (PI) is widely used in aerospace applications due to its superior insulating properties. However, the high concentration of atomic oxygen (AO) in low Earth orbit leads to significant performance degradation in PI, and the underlying mechanism of AO erosion under an electric field remains unclear. This study utilizes molecular dynamics simulations to model AO erosion on PI under various electric field strengths and explores the corresponding degradation mechanisms. The results indicate that the presence of an electric field exacerbates the degradation of PI by AO. AO erosion elevates the polymer's temperature, and the combined effects of thermal and electric stresses increase the polymer's free volume, loosening its structure and accelerating degradation. The quantity of AO-induced erosion products increases with rising electric field strength, causing more large carbon chains to detach from the polymer surface. Density functional theory (DFT) calculations further reveal that the electric field reduces the frontier orbital energy gap in PI molecules, making AO erosion reactions more thermodynamically favorable. This work provides an atomic-level insight into the degradation mechanism of PI under AO erosion in electric fields and offers a theoretical basis for future studies on polymer resistance to AO erosion in space environments.

Effect of Fe3+ doping on the electronic structure and surface hydration properties of quartz

In this study, the effects of Fe3+ doping on the crystal structure and surface properties of quartz were analyzed using density functional theory (DFT) calculations and molecular dynamics (MD) simulations. The crystal structure, surface model, and adsorption model of the water molecule layer for Fe3+-doped α-quartz were established. The DFT calculations reveal that Fe3+ doping affects the α-quartz lattice parameters and surface active sites. The adsorption energy near the sites occupied by Fe3+ is −66.20 kJ/mol, which is considerably lower than that of the undoped system (−42.35 kJ/mol). This makes it easier for water molecules to be adsorbed on the Fe3+-doped α-quartz (001) surface. The frontier orbital energy, electron density difference, charge density, and Mulliken bond population analyses indicate that the presence of Fe3+ improves the ability of the (001) surface of α-quartz to attract and bind water molecules. This improvement is mainly due to the formation of hydrogen bonds between the surface hydroxyl groups and water molecules on the surface of Fe3+-doped quartz and the equilibrium of the electrostatic interaction between the cation and water molecules. MD simulations show that a hydration layer with a thickness of approximately 8 Å is formed on the surface of Fe3+-doped α-quartz. Compared with the undoped system, the hydration film on the surface of the doped system is thicker, indicating that the incorporation of Fe3+ impurities in the lattice enhances the surface hydration characteristics of quartz. These results offer theoretical guidance for achieving efficient separation and thorough purification of quartz.

Intraplanar heterostructure-mediated activation of peroxydisulfate for singular-electron-transfer degradation of organic pollutants

Activating peroxydisulfate (PDS) through electron transfer pathways (ETP) is promising for degrading organic pollutants in aquatic environments. However, enhancing the activation selectivity remains a challenge. Herein, this study developed an intraplanar heterojunction with C-ring grafted g-C3N4 (CCN) as the catalyst, enabling PDS activation through a singular ETP. The CCN/PDS system achieved complete degradation and efficient mineralization (87.15 %) of bisphenol F (BPF), significantly reducing its ecological toxicity. Both experimental and theoretical investigations revealed that the intraplanar heterojunction could modulate the orbital occupation in g-C3N4/PDS, enhancing PDS adsorption and activation selectivity. Driven by the differences in the frontier orbital energy, the CCN/PDS system achieved a singular ETP without active species formation. The CCN/PDS system efficiently degraded BPF in complex water environments, showing performance stability across a wide pH range and against various coexisting ions. In a continuous-flow automatic catalytic device, the CCN/PDS system maintained a constant 100 % BPF degradation for 600 min. This study advances the understanding of PDS activation via singular ETP and introduces a new approach to water purification.

Theoretical investigation of isomeric structures of B2O3. Kinetic and thermodynamic study of the transformation of boric oxide to metaboric acid HBO2. Complexation of HBO2: from dimer to hexamer

In this study, Density Functional Theory was adopted. Isomeric structures of boric oxide B 2 O 3 were investigated at B3LYP/6-311G++(d,p), M052X, M062X, M08HX, M11/6-311G++(d,p) levels of theory. For validation of stable states, optimisation was performed using the correlated coupled cluster with single, double, and perturbative triple excitations (CCSD(T)) method in conjunction with the augmented correlation-consistent polarisation valence Double Zeta (aug-cc-pVDZ) (AVDZ) basis sets. Intrinsic Reaction Coordinates (IRCs) calculations were carried out to give kinetics of reactions B 2 O 3 +H 2 O ⇌ 2HBO 2 , B 2 O 3 +HCl ⇌ HBO 2 + OBCl. Complexation of HBO 2 was considered using B3LYP-D3, B97-D, MN15 and wB97X-D dispersion-corrected functionals. Counterpoise-corrected complexation energies as well as frontier orbital HOMO-LUMO energy gaps of (HBO 2 ) n (n = 2, 3, 4, 5, 6) clusters were derived in order to study their stability owed to hydrogen bonds.

Glaser-Hay-Coupled Random Copolymers Containing Boron Difluoride Formazanate Dyes.

𝜋-Conjugated polymers, including those based on acetylenic repeating units, are an exciting class of materials that offer narrow optical band gaps and tunable frontier orbital energies that lead to their use in organic electronics. This work expands the knowledge of structure-property relationships of acetylenic polymers through the synthesis and characterization of a series of Glaser-Hay-coupled model compounds and random copolymers comprised of BF2 formazanate, fluorene, and/or bis(alkoxy)benzene units. The model compounds and copolymers synthesized exhibit redox activity associated with the reversible reduction of the BF2 formazanate units and the irreversible reduction of the fluorene and bis(alkoxy)benzene units. The copolymers exhibit absorption profiles characteristic or intermediate of their respective models and homopolymers, leading to broad absorption of UV-vis light. The alkyne linkages of the model compounds and copolymers are reacted with [Co2(CO)8] to convert the alkyne functional groups into cobalt carbonyl clusters. This transformation leads to blue-shifted absorption profiles due to a decrease in π-conjugation, demonstrating the ability to tune the properties of these materials through post-polymerization functionalization. The redox activity and broad absorption bands of the polymers reported make them excellent candidates for use in photovoltaics and other light-harvesting applications.

The interaction between beta-ionone and 2-hydroxypropyl-beta-cyclodextrin during the formation of the inclusion complex

As an aroma material, beta-ionone also has a range of pharmacological activities. To solve its problems such as low bioavailability, water-immiscibility, thermo-instability, and volatility, beta-ionone was successfully encapsulated in 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CD) in our previous work. However, the structure of the product, the interaction between beta-ionone and HP-beta-CD, and the mechanism of action were not clear. In this paper, in order to gain a more profound understanding of the structure and chemical behavior of beta-ionone-HP-beta-CD inclusion complex, the interaction between beta-ionone and HP-beta-CD was investigated by molecular simulation. The optimized structures, binding energy, deformation energy, charge transfer, frontier orbital energy gap, chemical hardness, chemical potential, and electrophilicity index were obtained. In the complex, beta-ionone denotes electrons to HP-beta-CD and carries a positive charge. The negative chemical potential of inclusion complex indicates that complex process is spontaneous. The complex shows a relatively higher reactivity and electrophilicity than beta-ionone and HP-beta-CD.

Resonance Effects from Substituents on L-Type Ligands Mediate Synthetic Control of Gold Nanocluster Frontier Orbital Energies.

The ligands of metal nanoclusters can be used to control their properties and reactivity, but a framework guiding their use remains elusive. Hammett studies of Au8(PPh3)72+ and Au9(PPh3)83+ nanoclusters with para- and meta-methyl and -methoxy groups indicate that resonance effects, not inductive effects, yield quantitative shifts of the HOMO-LUMO transitions involving orbitals local to the cluster core. Individual ligand exchanges reveal that these shifts are caused by only four of seven ligands, inconsistent with inductive effects. Quantum chemical calculations predict no trend in Au atom charges with respect to Hammett parameter but do predict bond length trends expected for a resonance structure that includes the Au atoms. Computed orbitals show contributions from specific para-OMe oxygen lone pairs to the HOMO, indicating delocalization from the core to specific ligands. These results suggest that resonance structures could be drawn including Au and ligands, guiding efforts to modulate nanocluster electronic structure and energy transfer.

N‐Type Molecular Thermoelectrics Based on Solution‐Doped Indenofluorene‐Dimalononitrile: Simultaneous Enhancement of Doping Level and Molecular Order

AbstractThe development of n‐type organic thermoelectric materials, especially π‐conjugated small molecules, lags far behind their p‐type counterparts, due primarily to the scarcity of efficient electron‐transporting molecules and the typically low electron affinities of n‐type conjugated molecules that leads to inefficient n‐doping. Herein, the n‐doping of two functionalized (carbonyl vs dicyanovinylene) indenofluorene‐based conjugated small molecules, 2,8‐bis(5‐(2‐octyldodecyl)thien‐2‐yl)indeno[1,2‐b]fluorene‐6,12‐dione (TIFDKT) and 2,2′‐(2,8‐bis(3‐alkylthiophen‐2‐yl)indeno[1,2‐b]fluorene‐6,12‐diylidene)dimalononitrile (TIFDMT) are demonstrated, with n‐type dopant N‐DMBI. While TIFDKT shows decent miscibility with N‐DMBI, it can be hardly n‐doped owing to its insufficiently low LUMO. On the other hand, TIFDMT, despite a poorer miscibility with N‐DMBI, can be efficiently n‐doped, reaching a respectable electrical conductivity of 0.16 S cm−1. Electron paramagnetic resonance measurements confirm the efficient n‐doping of TIFDMT. Based on density functional theory (DFT) calculations, the LUMO frontier orbital energy of TIFDMT is much lower, and its wave function is more delocalized compared to TIFDKT. Additionally, the polarons are more delocalized in the n‐doped TIFDMT. Remarkably, as indicated by the grazing‐incidence wide‐angle X‐ray scattering (GIWAXS), the molecular order for TIFDMT thin‐film is enhanced by n‐doping, leading to more favorable packing with edge‐on orientation and shorter π‐π stacking distances (from 3.61 to 3.36 Å). This induces more efficient charge transport in the doped state. Upon optimization, a decent thermoelectric power factor of 0.25 µWm−1K−2 is achieved for n‐doped TIFDMT. This work reveals the effect of carbonyl vs dicyanovinylene on the n‐doping efficiency, microstructure evolution upon doping and thermoelectric performance, offering a stepping stone for the future design of efficient n‐type thermoelectric molecules.

Synthesis, Characterization and Assessment of Antioxidant and Melanogenic Inhibitory Properties of Edaravone Derivatives.

A series of edaravone derivatives and the corresponding Cu(II) complexes were synthesized and characterized using spectroscopic and analytical techniques such as IR, UV, NMR and elemental analysis. Antioxidant activities of all compounds were examined using free radical scavenging methods such as hydrogen peroxide scavenging activity (HPSA), 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2-2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS) assays. All of the tested compounds exhibited good antioxidant activity. Further, the frontier orbital energy levels, as well as various chemical properties, were determined using the density functional theory (DFT) calculations. The MEP maps of all of the derivatives were plotted to identify the nucleophilic and electrophilic reactive sites. Further, binding energies of all of the organic compounds with the protein tyrosinase was investigated to determine their potential anti-melanogenic applications. The selected ligand, L6 was subjected to molecular dynamics simulation analysis to determine the stability of the ligand-protein complex. The MD simulation was performed (150 ns) to estimate the stability of the tyrosinase-L6 complex. Other key parameters, such as, RMSD, RMSF, Rg, hydrogen bonds, SASA and MMPBSA were also analyzed to understand the interaction of L6 with the tyrosinase protein.

Pyrazine bound, zinc 5,10,15,20-tetrakis(4-chlorophenyl)porphyrin: Synthesis, crystal structure and computational studies

This work describes the synthesis, characterization, crystal structure, and computational analyses of the zinc porphyrin [ZnT(4-Cl)PP], 1 and its pyrazine bound analogue, [ZnT(4-Cl)PP(pyz)], 2, (where T(4-Cl)PP stands for 5,10,15,20-tetrakis-(4-chlorophenyl)porphyrin and pyz represents pyrazine). Both compounds were structurally characterized by UV–visible spectroscopy, infrared spectroscopy, 1HNMR spectroscopy, 13CNMR spectroscopy and single crystal XRD. The crystal structure of the 2 consists of a zinc porphyrin with an axial pyrazine ligand forming a penta-coordinated complex with Zn1-N5(pyz) distance 2.228(3) Å. To investigate the key insights into their photophysical properties, fluorescence emission spectral analysis of the synthesized compounds has been studied. Theoretical calculations like optimization of geometry, the energy of frontier orbitals, Hirshfeld surface analysis and simulation of electronic spectra were performed which supports the experimental results.

Oxidation of Weakly Interacting Diradicals: An Approach for Strong and Tunable Near-Infrared-Absorbing Dyes Based on Small Chromophores.

Near-infrared (NIR)-absorbing dyes are valuable for various applications, such as bioimaging and electronic devices. This work introduces a novel approach for designing NIR dyes, oxidation of weakly coupled diradicals. Our approach features a weak exchange interaction in diradicals, which potentially leads to bonding/antibonding molecular orbitals with a small energy gap. We found that removing one of two singly occupied molecular orbital electrons of the diradicals results in an exceptionally narrow frontier orbital energy gap. We examined a series of Blatter radical dimers, and the most weakly coupled diradical prepared in this work (ΔEST ∼ 0.12 eV) with a molecular weight of 590 Da exhibited a strong NIR absorption band reaching 2200 nm upon one-electron oxidation. The optical band gaps of the radical cations strongly correlate to the exchange interaction in the precursor neutral species, offering prediction and fine-tuning of the optical band gap in the NIR region.

(Invited) Order, Disorder, and Energy Loss in Organic Photovoltaics

We will discuss our recent work to better understand the role of charge transfer (CT) states in organic solar cell function. For one, we have been exploring organic semiconductor-based thin films that feature crystalline grains of up to 1 mm in extent, termed microcrystalline films. We have found that CT states incorporating these long-range-ordered films can be highly delocalized, contributing to noticeably lower energy losses. In another system, we are studying donor-acceptor pairs that feature very high optical gaps (>3 eV) but relatively small frontier orbital energy offset (<1 eV). Such interfaces present multiple CT states that reveal new insight about photocurrent generation and nonradiative recombination at donor-acceptor interfaces. Finally, we have developed a framework to discriminate between dynamic and static disorder contributions. Both are shown to contribute, and the relative contribution depends on materials choice and temperature.

Progress on the Development of Boron Subphthalocyanines (BsubPcs) and Subnaphthalocyanines (BsubNcs) Including Hybrids and Their Sustainability

Our group focuses on molecular design, synthetic methods and in-depth characterization of boron subphthalocyanines (BsubPcs) and subnaphthalocyanines (BsubNcs)[1] to apply them to organic electronics.[2] BsubPcs, BsubNcs and their hybrids called Bsub(Pc3-p-Ncp) are macrocycles with central boron atom and are p-conjugated macrocycles. Our focal point balances between the basic and applied chemistry, chemical engineering and their in-depth physical properties (electrochemistry included). Once materials are developed, we merge them into organic electronics for application into organic light emitting diodes (OLEDs) and organic photovoltaics (OPVs)/organic solar cells (OSCs).For this presentation, all points above will be factored in and I will focus on our progress on the development of hybrids, and mixed alloys and none mixed alloys of BsubNcs,.Regarding hybrids, they are a mixture of BsubPcs and BsubNcs, we named as X-RnBsub(Pc3-p-Ncp) – ‘p’ being the numbers of the substitutions; they were formed via reaction of BCl3 and a statistical distribution of phthalonitrile and 2,3-dicyanonaphthalene; X the axial substituent, Rn the number of peripheral substitutions, Pcp the number of 6 p-conjugated bonds, Ncp the number of 10 p-conjugated bonds (Figure).[3] We found that X-RnBsub(Pc1-Nc2) have low photostability, therefore, we developed a ‘statistical’ synthetic methodology to target X-RnBsub(Pc2-Nc1)s, and therefore could be purified to enable physical characterization. Their absorption spectra are as wide if BsubPc+BsubNc was mixed together, therefore, has potential to harvest a larger scope of photons for OPVs or to achieved FRET transfer from a host to emit via OLED. We also confirmed their electrochemical oxidation and reduction stability and their photoluminescence.More recently, we developed a new methodology called ‘steric hinderance’ to have even a higher yield of the X-RnBsub(Pc3-p-Ncp) hybrids, and the achievement was also based on computational modelling. I will also outline this approach.In the past as we have shown that BsubNcs end up being a mixed alloyed composition with random bay-position halogenation that is formed during the reaction of BCl3 with 2,3-dicyanonaphthalene at temperature.[4] The random bay-position halogenation has been shown to be impactful in a positive way within OPV devices, negative within OLED devices and also has electrochemical variations. Ongoing, given it is random halogenation, and some of the positive outcomes, this justifies considering additional mixed alloyed compositions.We have recently been able to develop a separation method for the mixed alloyed BsubNc compositions and acquired data to show the impact of the percentage/number of bay-position halogens, chlorine and bromine included, on the electrochemical potentials and the photoluminescence.[5] We have also applied a computational model to look at the relative impact of the random bay-position halogenation on the electronics.[6] We have found that the frequency of halogenation has a larger impact on the predicted HOMO/LUMO energy levels than does the random halogen positioning around the bay-positions of the BsubNcs. As this computational data is therefore comparable to the acquired electrochemical data.I will also present a new synthetic methodology to avoid the random bay-position halogenation of the associated BsubNcs. We also have recently within these semesters developed alternative chemistry to more tune the mixed alloys of the BsubNcs. This will also be a part of the presentation.We have also recently developed an AI-ML method to further accelerate the BsubNc development. The focal point of this approach was to have bay-position substitutions to then not have any random bay-position halogenation of the BsubNcs. So, these current and upcoming outcomes will also be a part of the presentations.For this presentation, I will also be outlining the sustainability of these great macrocyclic compounds. Claessens, C. G.; et al, Subphthalocyanines, Subporphyrazines, and Subporphyrins: Singular Nonplanar Aromatic Systems. Chem. Rev. 2014, 114 (4), 2192-2277.Morse, G. E.; et al, Boron Subphthalocyanines as Organic Electronic Materials. ACS Appl. Mater. & Interfaces 2012, 4 (10), 5055-5068.Farac, N.F.; et al, Cs-Symmetric, Peripherally Fluorinated Boron Subphthalocyanine–Subnaphthalocyanine Hybrids: Shedding New Light on Their Fundamental Photophysical Properties and Their Functionality as Optoelectronic Materials. J. Phys. Chem. C 2023, 127 (1), 702–727.Dang, J. D.; et al, The mixed alloyed chemical composition of chloro-(chloro)n-boron subnaphthalocyanines dictates their physical properties and performance in organic photovoltaic devices. J Mater. Chem. A 2016, 4 (24), 9566-9577.Holst, D.P.; et al, Enhanced analytical and physical characterization of mixtures of random bay-position chlorinated boron subnaphthalocyanines enabled by an established partial separation method (a part 2). New J. Chem. 2021, 45, 21082-21091.Holst, D.P.; et al, Updated Calibrated Model for the Prediction of Molecular Frontier Orbital Energies and Its Application to Boron Subphthalocyanines. J. Chem. Inf. Model. 2022, 62 (4), 829–840. Figure 1

Thionation‐Induced Enhancement of Optical and Electronic Properties in NDI Molecule for Molecular Electronic Applications: A Computational Study Using DFT/TD‐DFT and QTAIM Theory

AbstractThe study investigates the impact of thionation on N,N'‐di(dodecyl)‐4,5,8,9‐naphthalene diimide (NDI) through computational methods such as density functional theory (DFT/TD‐DFT), quantum theory of atoms in molecules (QTAIM), and Landauer theory (LT). Thionation, involving the replacement of diamide oxygens with sulfurs in NDI, significantly enhances quantum‐electronic/thermoelectric properties. Computational analyzes of energy of frontier orbitals HOMO/LUMO, dipole moment, polarizability, first superpolarizability, UV spectrum, and cohesive energy show the superior performance of the thione structure (M2) compared to the pristine structure (M1). Thionation decreased the energy gap from 01.3 eV (in M1 structure) to 1.87 eV (in M2 structure). The absorption wavelength in the pristine structure (M1) is calculated to be 507 nm, which increased to 1067 nm after thionation (M2). Cohesive energy values for each of M1 and M2 structures are calculated as 12.76 and 12.89 Kcal mol−1, respectively, which indicates the improvement of stability after thionation. After connecting M1 and M2 to gold electrodes (Au‐M1‐Au and Au‐M2‐Au) and applying electric fields, the Au‐M2‐Au structure shows a lower energy gap, lower thermoelectric activity and higher conductivity at field intensities with higher than 140 × 10−4 (a.u.), indicating its use as a field‐effect molecular device (such as molecular wire or molecular switch).

Symmetrical Design of Biphenazine Derivative Anode for Proton Ion Batteries with High Voltage and Long-Term Cycle Stability.

Organic anodes have emerged as a promising energy storage medium in proton ion batteries (PrIBs) due to their ability to reversibly accommodate non-metallic proton ions. Nevertheless, the currently available organic electrodes often encounter dissolution issues, leading to a decrease in long-cycle stability. In addition, the inherent potential of the organic anode is generally relatively high, resulting in low cell voltage of assembled PrIBs (<1.0V). To address these challenges, a novel long-period stable, low redox potential biphenylzine derivative, [2,2'-biphenazine]-7,7'-tetraol (BPZT) is explored, from the perspective of molecular symmetry and solubility, in conjunction with the effect of the molecular frontier orbital energy levels on its redox potential. Specifically, BPZT exhibited a low potential of 0.29V (vs SHE) and is virtually insoluble in 2m H2SO4 electrolyte during cycling. When paired with MnO2@GF or PbO2 cathodes, the resulting PrIBs achieve cell voltages of 1.07V or 1.44V, respectively, and maintain a high capacity retention of 90% over 20000 cycles. Additionally, these full batteries can operate stably at a high mass loading of 10mgBPZTcm-2, highlighting their potential toward long-term energy storage applications.

Quamtum Mechanical Study on Structural and Electronic Properties of Tert-Butyl Based Bridged Dithiophene Oxide Derivatives

Computational modeling is vital to designing and creating organic semiconductors used in solar cells, organic field-effect transistors, and other areas. This work studied the structural and electronic features of a group of substituted tert-butyl bridged dithiophene oxide derivatives using Density Functional Theory (DFT) calculations. Geometry improvements were carried out using the B3LYP hybrid functional and the 6-31G(d,p) basis set in Gaussian 09. Molecular shapes, bond lengths, bond angles, and dihedral angles were studied to find out how substitution patterns change the packing and conformation of molecules. Energy levels, distribution, and makeup of frontier molecular orbitals were found. This calculation also included finding other electronic qualities, such as electronic charges, dipole moments, and polarizabilities. Findings show that tert-butyl substitution makes the molecular backbone stiffer and limits its ability to twist compared to similar molecules that have not been replaced. The chemical geometry stays mostly the same when electron-withdrawing or electron-donating substituents are added to the tert- butyl groups. Nevertheless, the strength and location of substituents have a significant impact on frontier orbital energies. The HOMO-LUMO gap grew significantly when the nitro or cyano groups firmly pulled electrons away from derivatives. For successful charge transport, electron density plots show that the HOMO and LUMO are mainly located on the thiophene and substituent moieties, respectively. Molecular dipole moments are also strongly affected by the electronic features of substituents. This research shows how to change the optoelectronic properties of tert-butyl-based dithiophene oxide derivatives and how their structure-property relationships can be improved. The results help makes new organic semiconductors that work better in various electronic and optoelectronic uses.

Toward the Next Generation of Density Functionals: Escaping the Zero-Sum Game by Using the Exact-Exchange Energy Density.

ConspectusKohn-Sham density functional theory (KS DFT) is arguably the most widely applied electronic-structure method with tens of thousands of publications each year in a wide variety of fields. Its importance and usefulness can thus hardly be overstated. The central quantity that determines the accuracy of KS DFT calculations is the exchange-correlation functional. Its exact form is unknown, or better "unknowable", and therefore the derivation of ever more accurate yet efficiently applicable approximate functionals is the "holy grail" in the field. In this context, the simultaneous minimization of so-called delocalization errors and static correlation errors is the greatest challenge that needs to be overcome as we move toward more accurate yet computationally efficient methods. In many cases, an improvement on one of these two aspects (also often termed fractional-charge and fractional-spin errors, respectively) generates a deterioration in the other one. Here we report on recent notable progress in escaping this so-called "zero-sum-game" by constructing new functionals based on the exact-exchange energy density. In particular, local hybrid and range-separated local hybrid functionals are discussed that incorporate additional terms that deal with static correlation as well as with delocalization errors. Taking hints from other coordinate-space models of nondynamical and strong electron correlations (the B13 and KP16/B13 models), position-dependent functions that cover these aspects in real space have been devised and incorporated into the local-mixing functions determining the position-dependence of exact-exchange admixture of local hybrids as well as into the treatment of range separation in range-separated local hybrids. While initial functionals followed closely the B13 and KP16/B13 frameworks, meanwhile simpler real-space functions based on ratios of semilocal and exact-exchange energy densities have been found, providing a basis for relatively simple and numerically convenient functionals. Notably, the correction terms can either increase or decrease exact-exchange admixture locally in real space (and in interelectronic-distance space), leading even to regions with negative admixture in cases of particularly strong static correlations. Efficient implementations into a fast computer code (Turbomole) using seminumerical integration techniques make such local hybrid and range-separated local hybrid functionals promising new tools for complicated composite systems in many research areas, where simultaneously small delocalization errors and static correlation errors are crucial. First real-world application examples of the new functionals are provided, including stretched bonds, symmetry-breaking and hyperfine coupling in open-shell transition-metal complexes, as well as a reduction of static correlation errors in the computation of nuclear shieldings and magnetizabilities. The newest versions of range-separated local hybrids (e.g., ωLH23tdE) retain the excellent frontier-orbital energies and correct asymptotic exchange-correlation potential of the underlying ωLH22t functional while improving substantially on strong-correlation cases. The form of these functionals can be further linked to the performance of the recent impactful deep-neural-network "black-box" functional DM21, which itself may be viewed as a range-separated local hybrid.

Characterization of Excited-State Electronic Structure in Diblock π-Conjugated Oligomers with Adjustable Linker Electronic Coupling.

Diblock conjugated oligomers are π-conjugated molecules that contain two segments having distinct frontier orbital energies and HOMO-LUMO gap offsets. These oligomers are of fundamental interest to understand how the distinct π-conjugated segments interact and modify their excited state properties. The current paper reports a study of two series of diblock oligomers that contain oligothiophene (Tn) and 4,7-bis(2-thienyl)-2,1,3-benzothiadiazole (TBT) segments that are coupled by either ethynyl (-C≡C-) or trans-(-C≡C-)2Pt(II)(PBu3)2 acetylide linkers. In these structures, the Tn segment is electron rich (donor), and the TBT is electron poor (acceptor). The diblock oligomers are characterized by steady-state and time-resolved spectroscopy, including UV-visible absorption, fluorescence, fluorescence lifetimes, and ultrafast transient absorption spectroscopy. Studies are compared in several solvents of different polarity and with different excitation wavelengths. The results reveal that the (-C≡C-) linked oligomers feature a delocalized excited state that takes on a charge transfer (CT) character in more polar media. In the (-C≡C-)2Pt(II)(PBu3)2-linked oligomers, there is weak coupling between the Tn and TBT segments. Consequently, short wavelength excitation selectively excites the Tn segment, which then undergoes ultrafast energy transfer (~1 ps) to afford a TBT-localized excited state.