Degree Of Delocalization Research Articles

Does the Traditional Band Picture Correctly Describe the Electronic Structure of n-Doped Conjugated Polymers? A TD-DFT and Natural Transition Orbital Study.

Doped conjugated polymers have a variety of potential applications in thermoelectric and other electronic devices, but the nature of their electronic structure is still not well understood. In this work, we use time-dependent density functional theory (TD-DFT) calculations along with natural transition orbital (NTO) analysis to understand electronic structures of both p-type (e.g., poly(3-hexylthiophene-2,5-diyl), P3HT) and n-type (e.g., poly{[N,N'-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)}, N2200) conjugated polymers that are both p-doped and n-doped. Of course, the electronic transitions of doped conjugated polymers are multiconfigurational in nature, but it is still useful to have a one-electron energy level diagram with which to interpret their spectroscopy and other electronic behaviors. Based on the NTOs associated with the TD-DFT transitions, we find that the "best" one-electron orbital-based energy level diagram for doped conjugated polymers such as P3HT is the so-called traditional band picture. We also find that the situation is more complicated for donor-acceptor-type polymers like N2200, where the use of different exchange-correlation functionals leads to different predicted optical transitions that have significantly less one-electron character. For some functionals, we still find that the "best" one-electron energy level diagram agrees with the traditional picture, but for others, there is no obvious route to reducing the multiconfigurational transitions to a one-electron energy level diagram. We also see that the presence of both electron-rich and electron-poor subunits on N2200 breaks the symmetry between n- and p-doping, because different types of polarons reside on different subunits leading to different degrees of charge delocalization. This effect is exaggerated by the presence of dopant counterions, which interact differently with n- and p-polarons. Despite these complications, we argue that the traditional band picture suffices if one wishes to employ a simple one-electron picture to explain the spectroscopy of n- and p-doped conjugated polymers.

Spin-Dependent Regulation of The Electronic and Magnetic Properties of Poly(3-Alkylthiophene) Oligomers and Their Composites with Aromatic Nanoadditives

The energy and spin parameters of poly(3-alkylthiophene) oligomers and their composites with aromatic hydrocarbons are calculated. The coexistence of polarons with different degrees of delocalization in the studied compounds has been identified. Periodic changes in the electronic and spin properties of composites were detected, initiated by the interaction of oligomers with aromatic nanoadditives. The anisotropic parameters of the spin Hamiltonians of the studied systems are obtained and their high-resolution EPR spectra are calculated.

Elevating Nonlinear Optical Response Through D-Electron Modulation in Metal-Organic Frameworks.

Electronic structure and excited state behavior is of pronounced influence on regulation of nonlinear optical (NLO) response. Herein, a serials of transition metal ions bearing different d-electron numbers were in situ coordinated within porphyrinic metal-organic frameworks (MOFs), creating NLO-responsive M-metal (metal=Fe, Co, Ni, Cu, and Zn) frameworks. It demonstrated that the NLO properties can be optimized with the increased occupancy of the d-shell, which enhances the degree of delocalization. Specifically, the full-filled (d10) electron configuration of Zn2+ stabilizes the electronic structure, combination with π-π* local excitation character of M-Zn, promoting charge transfer process and resulting in outstanding NLO properties. Moreover, parameters related to the nonlinear process (β, n2, Imχ(3), Reχ(3) and χ(3)) of M-Zn are calculated to be higher than those of other materials, consistent with theoretical calculations. This work paves the way for NLO modulation based on electronic analysis and provides a promising approach for constructing high-performance NLO materials.

Pulsed Laser Ablation of Oxygen deficiency Enriched Superlattice Vanadium Pentoxide (V2O5) Ultrathin Nextrode aiming for Flexible Binder-less Tandem Energy Harvesting Devices.

For the initial instance, oxygen deficiency-enriched vanadium pentoxide (O─V2O5@500) thin film electrodes are tuned by the Pulsed Laser Ablation technique. The O─V2O5@500 thin film electrode shows remarkable electrochemical performances confirming the greater potential window of -0.4 to 0.9V versus Hg/HgO in an alkaline electrolyte; also, the O─V2O5@ 500 thin film electrode exhibits a noteworthy volumetric capacity of 167.7 mAh cm-3 (areal capacity of 73.3 µAh cm-2). Additionally, Density Functional Theory (DFT) theory calculations are carried out for oxygen-deficient V2O5. From the partial density of states (pDOS) and partial charge density analysis, it is clear that oxygen vacancy improves the electrical conductivity due to the higher degree of electron delocalization of V─O─V near the vacancy and enhances the redox properties due to the formation of in-gap states. Further, it is reported that a O─V2O5@ 500 ||PVA-KOH|| Bi2O3 A-650 thin film supercapbattery (TFSCB) device attains an exceptional discharge volumetric capacitance of 182.85 F cm-3 (equal volumetric capacity of 124.5 mAh cm-3). Furthermore, the TFSCB device exhibits an extraordinary maximum volumetric energy (power) density of 14.28 mWh cm-3 (1.66W cm-3); TFSCB succeeds in supreme capacity retention of 86% with outstanding coulombic efficiency of 94.4% after 21 000 cycles.

3d-metal macrocyclic complexes containing porphyrazine/ perfluoroporphyrazine and fluoro ligands: Structural and thermodynamic parameters according to the various DFT model chemistries

By using three independent of density functional theory (DFT) model chemistries with functionals B3PW91, M06 and OPBE, and the TZVP basis set, combining the D3 version of Grimme’s dispersion with the original D3 damping function, the molecular structures of three types of 3[Formula: see text] element (M) macrocyclic coordination compounds — homoligand with porphyrazine (H2L1), heteroligand with porphyrazine and two axially oriented fluoro ligands and heteroligand with perfluoroporphyrazine (H2L2) and two axially oriented fluoro ligands having [ML1], [ML1(F)2] and [ML2(F)2] compositions, respectively, were calculated. The values of the most important bond lengths, bond and non-bond angles in the resulting metal complexes, and NBO analysis data are presented. It was noted that almost each of these complexes contains a coplanar MN4 chelate unit and a group of N4 atoms, as well as coplanar 5- and 6-membered rings; moreover, both of them are pairwise identical to each other in terms of the sums of bond angles (540[Formula: see text] and 720[Formula: see text], respectively) and their assortments. Bond angles formed by M atoms and two fluorine atoms are 180[Formula: see text]; bond angles formed by fluorine, M and nitrogen atoms are 90[Formula: see text]. NBO analysis of all the above 3[Formula: see text]-metal chelates was carried out, and based on the data, a high degree of delocalization of the electron density in these coordination compounds was stated. The values of the standard enthalpy [Formula: see text], entropy [Formula: see text] and Gibbs energy [Formula: see text] of formation of these compounds were also calculated. Particular attention was paid to the fact that according to these data, for the ([ML1]) and ([ML1(F)2]) complexes the values of [Formula: see text] and [Formula: see text] are positive, whereas for ([ML2(F)2]) complexes they are negative, and in the series [ML1] – [ML1(F)2] – [ML2(F)2] there is an increase in the thermodynamic stability of the complexes, which is undoubtedly due to the presence of peripheral fluorine substituents in the [ML2(F)2] structure. There was also good agreement between similar parameters calculated by different DFT methods, both qualitatively and quantitatively.

Enhanced Electron Delocalization Induced by Ferromagnetic Sulfur doped C3N4 Triggers Selective H2O2 Production.

For the 2D metal-free carbon catalysts, the atomic coplanar architecture enables a large number of pz orbitals to overlap laterally, thus forming π-electron delocalization, and the delocalization degree of the central atom dominates the catalytic activity. Herein, designing sulfur-doped defect-rich graphitic carbon nitride (S-Nv-C3N4) materials as a model, we propose a strategy to promote localized electron polarization by enhancing the ferromagnetism of ultra-thin 2D carbon nitride nanosheets. The introduction of sulfur (S) further promotes localized ferromagnetic coupling, thereby inducing long-range ferromagnetic ordering and accelerating the electron interface transport. Meanwhile, the hybridization of sulfur atoms breaks the symmetry and integrity of the unit structure, promotes electron enrichment and stimulating electron delocalization at the active site. This optimization enhances the *OOH desorption, providing a favorable kinetic pathway for the production of hydrogen peroxide (H2O2). Consequently, S-Nv-C3N4 exhibits high selectivity (>95 %) and achieves a superb H2O2 production rate, approaching 4374.8 ppm during continuous electrolysis over 300 hour. According to theoretical calculation and in situ spectroscopy, the ortho-S configuration can provide ferromagnetic perturbation in carbon active centers, leading to the electron delocalization, which optimizes the OOH* adsorption during the catalytic process.

Unveiling the Multifaceted Nature of 4‐(4‐Methylphenyl Thio)benzophenone: Electronic Structure and Excited States in Gas Phase and Solvents

AbstractBenzophenone and its derivatives are widely used as UV filters and UV‐ink photoinitiators. The photoinitiating properties of benzophenones depend on their degree of conjugation and delocalization within the molecule. By understanding how conjugation, delocalization, and different substituents affect these properties, benzophenone derivatives can be customized for specific applications. Using quantum mechanical calculations based on B3LYP/6‐311++G(d, p) density functional theory (DFT), chemical reactivity, stability, and photoinitiating capabilities of 4‐(4‐methylphenylthio)benzophenone are analyzed. This includes studying its physical and chemical properties in the gas phase, as well as its excited state electronic transitions, vibrational characteristics, and spectroscopic properties both in gas phase and in various solvents. The DFT‐computed infrared spectra match experimental results. The UV/Visible spectra shows absorption towards longer wavelengths due to extended delocalization of π‐electrons. In different solvents with varying polarity, the absorption spectra exhibit high‐intensity peaks, shift in excitation energy and wavelengths based on the polarity of the solvent. This knowledge allows for the development of novel initiators with customized light absorption, excited state lifetimes, and reaction selectivities, which can enhance processes like UV‐curing, photopolymerization, and other light‐driven reactions.

Thiocarbonyl-Bridged N-Heterotriangulenes for Energy Efficient Triplet Photosensitization: A Theoretical Perspective.

Structurally-rigid metal-free organic molecules are of high demand for various triplet harvesting applications. However, inefficient intersystem crossing (ISC) due to large singlet-triplet gap ( ) and small spin-orbit coupling (SOC) between lowest excited singlet and triplet often limits their efficiency. Excited electronic states, fluorescence and ISC rates in several thiocarbonyl-bridged N-heterotriangulene ( S-HTG) with systematically increased thione content ( 0-3) are investigated implementing polarization consistent time-dependent optimally-tuned range-separated hybrid. All S-HTGs are dynamically stable and also thermodynamically feasible to synthesize. Relative energies of several low-lying singlets ( ) and triplets ( ), and their excitation nature (i. e., or ) and SOC are determined for these S-HTGs in dichloromethane. Low-energy optical peak displays gradual red-shift with increasing thione content due to relatively smaller electronic gap resulted from greater degree of orbital delocalization. Significantly large SOC due to different orbital-symmetry and heavy-atom effect produces remarkably high ISC rates ( ~1012 s-1) for enthalpically favoured ( ) channel in these S-HTGs, which outcompete radiative fluorescence rates (~108 s-1) even directly from higher lying optically bright singlets. Importantly, high energy triplet excitons of ~1.7 eV resulting from such significantly large ISC rates from non-fluorescent make these thiocarbonylated HTGs ideal candidates for energy efficient triplet harvest including triplet-photosensitization.

Conformational Stability and Vibrational Relaxation as a Function of Halogen Substitution in Benzene sulfonamides: A Theoretical Study

AbstractStudying the vibrational energy flow within molecules can help us better understand their reactivity and facilitate the design of novel functional groups for potential drug candidates. This study examined the conformation of benzene sulfonamide in solvents and vacuum. Potential energy surfaces were computed for the two possible conformations, showing that the conformers’ stability varied with the medium. Additionally, the vibrational energy redistribution of halogen‐substituted benzene sulfonamide conformers was studied in solvents and vacuums. The lifetimes of the halogen stretching mode C−X (where X=F, Cl, or Br) in the substituted benzene sulfonamides were calculated and compared. The solvent and vacuum media lifetimes followed the order: C−Cl>C−Br>C−F. However, the degree of delocalization of vibrational energy was found to vary between them.

Enhanced Electron Delocalization Induced by Ferromagnetic Sulfur doped C 3 N 4 Triggers Selective H 2 O 2 Production

For the 2D metal‐free carbon catalysts, the atomic coplanar architecture enables a large number of pz orbitals to overlap laterally, thus forming π‐electron delocalization, and the delocalization degree of the central atom dominates the catalytic activity. Herein, designing sulfur‐doped defect‐rich graphitic carbon nitride (S‐Nv‐C3N4) materials as a model, we propose a strategy to promote localized electron polarization by enhancing the ferromagnetism of ultra‐thin 2D carbon nitride nanosheets. The introduction of sulfur (S) further promotes localized ferromagnetic coupling, thereby inducing long‐range ferromagnetic ordering and accelerating the electron interface transport. Meanwhile, the hybridization of sulfur atoms breaks the symmetry and integrity of the unit structure, promotes electron enrichment and stimulating electron delocalization at the active site. This optimization enhances the *OOH desorption, providing a favorable kinetic pathway for the production of hydrogen peroxide (H2O2). Consequently, S‐Nv‐C3N4 exhibits high selectivity (>95%) and achieves a superb H2O2 production rate, approaching 4374.8 ppm during continuous electrolysis over 300‐hour. According to theoretical calculation and in‐situ spectroscopy, the ortho‐S configuration can provide ferromagnetic perturbation in carbon active centers, leading to the electron delocalization, which optimizes the OOH* adsorption during the catalytic process.

Density functional theory study on interatomic forces and electronic properties of ConMoP(n = 1 ~ 5) cluster

AbstractTo delve into the microscopic property variations of the ConMoP(n = 1 ~ 5) cluster, this study employs density functional theory at the B3LYP/def2‐TZVP quantum chemistry level. The paper conducts a comprehensive theoretical analysis of the clusters, examining parameters such as bond lengths, bond angles, electronic localization function (ELF), interaction region indicator function (IRI), independent gradient model based on the Hirshfeld partition, deformation density, electronic space range, chemical hardness and softness, polarizability, and dipole moment. The optimization process reveals 16 stable configurations for the ConMoP(n = 1 ~ 5) cluster, predominantly taking on a steric form. As the cluster size increases, the electronic delocalization of Co atoms intensifies, while the electronic properties of Mo atoms remain relatively stable. Notably, P atoms maintain a high degree of electronic delocalization. The interatomic forces within the clusters predominantly exhibit covalent bonding, with no evident repulsive effects observed between atoms. The bonding between metal atoms in the clusters leans toward a preference for covalent interaction. The degree of dispersion in the clusters increases with their growth, particularly evident in configuration 5‐a, which displays a broader spatial distribution. Configuration 3‐a demonstrates the most favorable activity, showcasing a relatively stable structure. Overall, configuration 3‐a emerges as a focal point for catalytic reactions. This article provides a more comprehensive analysis of the ConMoP(n = 1 ~ 5) cluster, yielding diverse results and enhancing the theoretical understanding of this cluster.

Microscopic solvent-solute interactions, reactivity studies, structure properties and anti cancer activity of 1-(1-benzofuran-5-yl)-N-methylbutan-2-amine

Cancer continues to be a major threat to mankind, as seen by the 19.3 million people who received treatment for the disease in 2020. The study employed quantum mechanical calculations utilising (DFT) B3LYP, using a 6–311++ G(d,p) basis set, to analyse structural characteristics and intramolecular interactions and pharmaceutical aspect of anti-cancer. The study utilised various spectroscopy techniques, including FT-IR, FT-Raman and UV–Vis to examine the molecular arrangements of 1-(1-benzofuran-5-yl)-N-methylbutan-2-amine (1BF5MB).Significant interactions were seen because of the electron-density shift of nitrogen atom's lone pair (LP (O1)) to its antibonding orbital (σ ∗ ) (C13-H30), with an E(2) of 8.51 Kcal/mol. This indicates a substantial degree of electron delocalization. TDM analysis displays graphs that illustrate the capacity to transmit charges. ALIE analysis utilises the colour blue to represent the stable sigma bonds, namely those associated with hydrogen atoms that produce protons. Evaluating the drug-likeness and ADMET assessment enabled the biological features of (1BF5MB). This compound may be deemed a strong anti-tubercular treatment agent due to its relatively low binding affinities for the specific receptors.These results indicate that the drugs block these receptors.

The Physical Mechanism of Linear and Nonlinear Optical Properties of Nanographene-Induced Chiral Inversion.

Based on density functional theory (DFT) and wave function analysis, the ultraviolet and visible spectrophotometry (UV-Vis) spectra and Raman spectra of 1-meso and 1-rac obtained by the chiral separation of chiral nanographenes are theoretically investigated. The electron excitation properties of 1-meso and 1-rac are studied by means of transition density matrix (TDM) and charge density difference (CDD) diagrams. The intermolecular interaction is discussed based on an independent gradient model based on Hirshfeld partition (IGMH). The interaction of 1-meso and 1-rac with the external environment is studied using the electrostatic potential (ESP), and the electron delocalization degree of 1-meso and 1-rac is studied based on the magnetically induced current under the external magnetic field. Through the chiral separation of 1-rac, two enantiomers, 1-(P, P) and 1-(M, M), were obtained. The electrical-magnetic interaction of the molecule is revealed by analyzing the electron circular dichroism (ECD) spectra of 1-meso, 1-(P, P) and 1-(M, M), the transition electric dipole moment (TEDM) and the transition magnetic dipole moment (TMDM). It is found that 1-(P, P) and 1-(M, M) have opposite chiral properties due to the inversion of the structure.

Aryne‐Based Synthesis of Cyclobutadiene‐Containing Oligoacenes and Related Extended Biphenylene Derivatives

AbstractA previously undescribed aryne derived from a π‐extended biphenylene, 2,3‐didehydrobenzo[b]biphenylene, has been developed. The participation of this new aryne building block in [4+2] and palladium‐catalyzed [2+2+2] cycloaddition reactions has been applied to the synthesis of a variety of polycyclic conjugated hydrocarbons (PCHs) with appealing structures which combine (aromatic) benzene and (antiaromatic) cyclobutadiene (CBD) rings. Among them, a family of unsubstituted (or barely substituted) CBD‐oligoacenes has been accessed by iterative Diels‐Alder reactions of the new aryne with furans and/or isobenzofurans, followed by deoxygenative aromatization of the resulting epoxy‐derivatives. The experimental and computational studies of the newly synthesized PCHs suggest an important degree of electron delocalization along the polycyclic skeleton, more pronounced in the linearly fused derivatives. The computed ACID plots reveal clockwise current density vectors at the peripheral bonds, originating from the σ contributions of the antiaromatic cyclobutadiene rings.

Thermodynamic model for voltammetric responses in conducting redox polymers.

Electroactive polymer materials are known to play important roles in a vast spectrum of modern applications such as in supercapacitors, fuel cells, batteries, medicine, and smart materials, etc. They are usually divided into two main groups: first, conducting π-conjugated organic polymers, which conduct electricity by cation-radicals delocalized over a polymer chain; second, redox polymers, which conduct electricity via an electron-hopping mechanism. Polymer materials belonging to these two main groups have been thoroughly studied and their thermodynamic and kinetic models have been built. However, in recent decades a lot of mixed-type materials have been discovered and investigated. To the best of our knowledge, a thermodynamic-based description of conducting redox polymers (CRPs) has not been provided yet. In this work, we present a thermodynamic model for voltammetric responses of conducting redox polymers. The derived model allows one to extract thermodynamic parameters of a CRP including the polaron delocalization degree and redox active groups interaction constant. The model was verified with voltammetric experiments on three recently synthesized CRPs and showed a satisfactory predictive ability. The simulated data are in good agreement with the experiment. We believe that developing theoretical descriptions for CRPs and other types of electroactive materials with the ability to simulate their electrochemical responses may help in future realization of new systems with superior characteristics for electrochemical energy storage, chemical sensors, pharmacological applications, etc.

Ultrafast excited-state dynamics of Luteins in the major light-harvesting complex LHCII

Carotenoid pigments are known to present a functional versatility when bound to light-harvesting complexes. This versatility originates from a strong correlation between a complex electronic structure and a flexible geometry that is easily tunable by the surrounding protein environment. Here, we investigated how the different L1 and L2 sites of the major trimeric light-harvesting complex (LHCII) of green plants tune the electronic structure of the two embedded luteins, and how this reflects on their ultrafast dynamics upon excitation. By combining molecular dynamics and quantum mechanics/molecular mechanics calculations, we found that the two luteins feature a different conformation around the second dihedral angle in the lumenal side. The s-cis preference of the lutein in site L2 allows for a more planar geometry of the π\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\pi$$\\end{document}-conjugated backbone, which results in an increased degree of delocalization and a reduced excitation energy, explaining the experimentally observed red shift. Despite these remarkable differences, according to surface hopping simulations the two luteins present analogous ultrafast dynamics upon excitation: the bright S2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$S_2$$\\end{document} state quickly decays (in ∼\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sim$$\\end{document} 50 fs) to the dark intermediate Sx\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$S_x$$\\end{document}, eventually ending up in the S1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$S_1$$\\end{document} state. Furthermore, by employing two different theoretical approaches (i.e., Förster theory and an excitonic version of surface hopping), we investigated the experimentally debated energy transfer between the two luteins. With both approaches, no evident energy transfer was observed in the ultrafast timescale.Graphical abstract

Theoretical study of the effect of D-A type polymer donors on the performance of Y6-based organic solar cells

Non-fullerene organic solar cells (OSCs) based on Y6 molecule have developed rapidly in recent years, and the power conversion efficiency (PCE) varies greatly when the OSC device constructed by Y6 and donor molecules with small structural difference. In this work, the influence of six donor-acceptor (D-A) polymer donors on Y6-based OSCs were focused. The ground-state properties (planarity, frontier molecular orbital energy levels, driving force), excited-state properties of donors (primary indicators, Coulomb attraction) and donor/acceptor interfaces (Frenkel excitation (FE) and charge transfer (CT) states, electron coupling and charge separation rates) were discussed. The results show that symmetrical alkyl chains in the acceptor unit is favorable for maintaining planarity of molecule, while fluorination induces twisting in the thiophene bridge and acceptor unit. And the investigated high-performance molecules have desirable driving force, smaller Coulomb attraction and significant degree of holes and electrons delocalization. Also, the highest-performance system has multiple charge transfer pathways, which can improve charge separation efficiency. At the same time, high-performance systems often have better planarity and more favorable substituent positions. The high-performance donor/Y6 systems have more advantage in charge separation than the low-performance systems. This work provides a fundamental understanding of the impact of D-A type donor materials on the cell performance and theoretical guidance for further optimization of polymer donor materials in Y6-based OSCs.

Peroxymonosulfate conversion to singlet oxygen over π-electron delocalized carbon nitride for selective degradation of emerging contaminants

Graphitic carbon nitride is a promising catalyst for peroxymonosulfate (PMS) activation towards removal of emerging contaminants in water environment. However, the dependence on light and the non-selectivity of PMS activation pathway limit its practical applications. In this work, a two-step thermal treatment process was developed to modulate the π-electron delocalization degree of carbon nitride. The obtained modified carbon nitride (TCN) showed excellent capability on PMS activation without light, and simultaneously achieved high selectivity on the generation of non-radical species 1O2. Based on the results of quenching and probe experiments, isotopic solvent effect, as well as in-situ capture technique, the dominant contribution of 1O2 to the degradation of pollutants was clarified. The TCN/PMS system showed highly selective degradation of electron-donating pollutants, further demonstrating the dominant role of 1O2. Combining the control experimental results, PMS was speculated to be catalytically activated mainly through the spontaneous decomposition pathway. Further, according to the characterizations results and density functional theoretical calculations, it was the delocalized π-electrons at modified C-N heterocycles that accelerated the self-decomposition reactions of PMS. The high selectivity towards 1O2 endowed good resistance of TCN/PMS system in complex water matrices, achieving efficient removal of a number of emerging contaminants.

Hyperconjugative Aromaticity-Based Circularly Polarized Luminescence Enhancement in Polyaurated Heterocycles.

Hyperconjugative aromaticity (HA) frequently appears in metalla-aromatics, but its effect on photophysical properties remains unexplored to date. Herein, we reveal two different HA scenarios in nearly isostructural triaurated indolium and benzofuranylium compounds. The biased HAs show a discernible effect on the spatial arrangement of metal atoms and thus tailor metal parentage in frontier orbitals and the HOMO-LUMO energy gap. Theoretical calculations and structural analyses demonstrate that HA not only influences the degree of electron delocalization over the trimetalated aromatic rings but also affects π-coordination of Au(I) and intercluster aurophilic interaction. Consequently, the triaurated benzofuranylium complex shows better photoluminescence performance (quantum yield up to 49.7%) over the indolium analogue. Furthermore, four pairs of axially chiral bibenzofuran-centered trinuclear and hexanuclear gold clusters were purposefully synthesized to correlate their HA-involved structures with the chiroptical response. The triaurated benzofuranylium complexes exhibit strong circular dichroism (CD) response in solution but CPL silence even in solid film. In contrast, the hexa-aurated homologues display strong CD and intense CPL signals in both aggregated state and solid film (luminescence anisotropy factor glum up to 10-3). Their amplified chiroptical response is finally ascribed to the dominant intermolecular exciton couplings of large assemblies formed through the HA-tailored aggregation of hexanuclear compounds.

Eco-Friendly Cerium-Cobalt Counter-Doped Bi2Se3 Nanoparticulate Semiconductor: Synergistic Doping Effect for Enhanced Thermoelectric Generation.

Metal chalcogenides are primarily used for thermoelectric applications due to their enormous potential to convert waste heat into valuable energy. Several studies focused on single or dual aliovalent doping techniques to enhance thermoelectric properties in semiconductor materials; however, these dopants enhance one property while deteriorating others due to the interdependency of these properties or may render the host material toxic. Therefore, a strategic doping approach is vital to harness the full potential of doping to improve the efficiency of thermoelectric generation while restoring the base material eco-friendly. Here, we report a well-designed counter-doped eco-friendly nanomaterial system (~70 nm) using both isovalent (cerium) and aliovalent (cobalt) in a Bi2Se3 system for enhancing energy conversion efficiency. Substituting cerium for bismuth simultaneously enhances the Seebeck coefficient and electrical conductivity via ionized impurity minimization. The boost in the average electronegativity offered by the self-doped transitional metal cobalt leads to an improvement in the degree of delocalization of the valence electrons. Hence, the new energy state around the Fermi energy serving as electron feed to the conduction band coherently improves the density of the state of conducting electrons. The resulting high power factor and low thermal conductivity contributed to the remarkable improvement in the figure of merit (zT = 0.55) at 473 K for an optimized doping concentration of 0.01 at. %. sample, and a significant nanoparticle size reduction from 400 nm to ~70 nm, making the highly performing materials in this study (Bi2-xCexCo2x3Se3) an excellent thermoelectric generator. The results presented here are higher than several Bi2Se3-based materials already reported.