The bigger, the better: In the last decade, the development of organic electronics, and particularly of organic field‐effect transistors, carbon nanotubes, and graphene, has spurred efforts to ...prepare larger acenes. Stable, large acenes have been obtained and fully characterized. Developments in the synthesis of heptacenes, as well as the very recent synthesis of octacene and nonacenes, are highlighted.
An extensive study of the redox properties of metal nitride endohedral fullerenes (MNEFs) based on DFT computational calculations has been performed. The electronic structure of the singly oxidized ...and reduced MNEFs has been thoroughly analyzed and the first anodic and cathodic potentials, as well as the electrochemical gaps, have been predicted for a large number of M3N@C2n systems (M=Sc, Y, La, and Gd; 2n=80, 84, 88, 92, and 96). In particular, calculations that include thermal and entropic effects correctly predict the different anodic behavior of the two isomers (Ih and D5h) of Sc3N@C80, which is the basis for their electrochemical separation. Important differences were found in the electronic structure of reduced M3N@C80 when M=Sc or when M is a more electropositive metal, such as Y or Gd. Moreover, the changes in the electrochemical gaps within the Gd3N@C2n series (2n=80, 84, and 88) have been rationalized and the use of Y‐based computational models to study the Gd‐based systems has been justified. The redox properties of the largest MNEFs characterized so far, La3N@C2n (2n=92 and 96), were also correctly predicted. Finally, the quality of these predictions and their usefulness in distinguishing the carbon cages for MNEFs with unknown structures is discussed.
Redox properties in M3N§C2n: Redox properties as first anodic and cathodic peaks in voltammograms, as well as the localization of the spin density, have been analyzed for a large series of metal nitride endohedral fullerenes (see figure) by means of DFT computational calculations. Good correlations between the predicted values and the experimental results were found.
Display omitted
•Brønsted-Lewis acidic ionic liquids were designed by quantum chemical calculation.•Calculating the HOMO-LUMO gap of catalytic system, the catalytic activities were predicted.•The ...catalysts for the preparation of 5-HMF from cellulose were optimized, all while reducing the cost of the catalyst.•The method provides the basic outline of molecular design for Brønsted-Lewis acidic ionic liquids.•The method has significance for directional design of synergistic catalysts in tandem reactions.
As a key renewable chemical for plastics and fine chemicals, the preparation of 5-hydroxymethylfurfural (5-HMF) from cellulose is an important research topic. The conversion of cellulose to 5-HMF in high yields is difficult owing to the recalcitrant and heterogeneous nature of cellulose. In this work, six types of Brønsted–Lewis acidic ionic liquids (ILs) were designed, which can catalyse the conversion of cellulose to 5-HMF in different tandem reaction steps. Cellulose disaccharide is used as a model compound to calculate the structure and frontier orbital energy of the catalytic system by density functional theory, and thus predict catalytic activity. Based on the HOMO-LUMO orbital energy, the order of catalytic activity of Brønsted–Lewis acidic ILs is as follows: HnmpZn2Cl5 > HnmpZnCl3 > HSO3-(CH2)3-MIMZn2Cl5 > HSO3(CH2)3-MIMZn2Cl5 > HSO3-(CH2)3-NEt3Zn2Cl5 > HSO3-(CH2)3-NEt3ZnCl3. Subsequently, six types of ILs were synthesised and used to catalyse cellulose conversion into 5-HMF. It was found that HnmpZn2Cl5 exhibited the highest efficiency with a 5-HMF yield of 39.29%, as predicted. The accuracy of the theoretical calculation was verified. This research has the potential to reduce the cost of catalysts by providing an important theoretical and practical screening method for the directed design of synergistic catalysts in tandem reactions.
Soot particles from flames were found to have quantum confinement behavior in recent UV–visible absorption measurements. However, the impact of surface functionalization was not considered in the ...previous interpretation. In this work, polycyclic aromatic hydrocarbon (PAH) clusters was selected as a model system of soot to explore the impact of surface functionalization on the optical properties. The HOMO–LUMO gap of PAH clusters with formyl group (–CHO) substitutions was computed using the B3LYP method with the 6-31G(d) basis set. The results showed that the HOMO–LUMO gaps of PAH clusters strongly depend on the surface coverage of –CHO groups on particle, and a higher coverage always yield a reduced gap value. Combining the observation from X-ray photoelectron spectroscopy measurements, the impact of functional groups was computed as 0.27–0.71 eV. Detailed analysis on the electronic structures of HOMO and LUMO reveals that the –CHO groups lower the LUMO energy to a great extent, while they have limited impact on the HOMO energy. Furthermore, we use the LUMO composition as a key descriptor to evaluate the impact of functionalization on LUMO energy, and a theoretical limit of gap reduction was calculated as 1.1 eV for both pyrene and coronene clusters.
Display omitted
•Theoretical and phytochemical study of 8-hydroxyisodiospyrin.•Spectroscopic and electronic structure simulations.•Non-covalent interaction of gases with HDO.•Inter-molecular study ...via DFT calculations.
Comprehensive theoretical and experimental studies of a natural product, 8-hydroxyisodiospyrin (HDO) have been carried out. Based on the correlation of experimental and theoretical data, an appropriate computational model was developed for obtaining the electronic, spectroscopic, and thermodynamic parameters of HDO. First of all, the exact structure of HDO is confirmed from the nice correlation of theory and experiment, prior to determination of its electroactive nature. Hybrid density functional theory (DFT) is employed for all theoretical simulations. The experimental and predicted IR and UV–vis spectra B3LYP/6-31+G(d,p) level of theory have excellent correlation. Inter-molecular non-covalent interaction of HDO with different gases such as NH3, CO2, CO, H2O is investigated through geometrical counterpoise (gCP) i.e., B3LYP-gCP-D3/6-31G∗ method. Furthermore, the inter-molecular interaction is also supported by geometrical parameters, electronic properties, thermodynamic parameters and charge analysis. All these characterizations have corroborated each other and confirmed the electroactive nature (non-covalent interaction ability) of HDO for the studied gases. Electronic properties such as Ionization Potential (IP), Electron Affinities (EA), electrostatic potential (ESP), density of states (DOS), HOMO, LUMO, and band gap of HDO have been estimated for the first time theoretically.
The structure and growth of a series of Lu-doped germanium clusters, LuGe
n
q
(n = 2-14, q = 0, −1) have been investigated by previous photoelectron spectroscopy (PES) and density functional theory ...(DFT) calculations. The ground states of the anionic LuGe
n
-
clusters obtained from DFT calculations are verified by comparing simulated PES with experimental results. The simulated PES for smaller clusters LuGe
n
-
(n ≤ 6) display relatively simple spectral patterns, suggesting high symmetry structures. It is observed that the pentagonal bipyramid shape is the basic framework for the nascent growth process of LuGe
n
-
(n = 2-8). The structures of LuGe
n
-
(n = 2-13) clusters are all exohedral structures with the Lu atom adsorbed at the surface of the bare Ge
n
-
clusters, while LuGe
14
-
is the smallest endohedral Lu-doped germanium cluster with the Lu atom completely fallen into the germanium frame. It is found that the LuGe
n
-
clusters with even n are more stable than those with odd n and in the LuGe
n
clusters there is an opposite trend. Especially, the LuGe
n
q
(n = 9, 12, q = 0, −1) clusters are extremely stable compared to other size clusters. HOMO-LUMO gap shows that the chemical stability of bare Ge
n
-
(n = 2-14) clusters are stronger than that of LuGe
n
q
(n = 2-14, q = 0, −1) clusters owing to the doping of a Lu atom.
A red star is born A new route for the preparation of large and insoluble molecular starphenes by decarbonylation of soluble precursors in the solid state is described in the Research Article on page ...7752 by Andrej Jancarik, Andre Gourdon, and co‐workers. Scanning tunneling microscopy/spectroscopy in ultrahigh vacuum and absorption spectroscopy in frozen matrices, with both experiments run at liquid helium temperature, show that the electronic delocalization among the three pentacene branches is rather limited.
Water nano-rings in electric fields Rai, Smita; Rai, Dhurba; Gobre, Vivekanand V.
Molecular physics,
05/2024, Letnik:
122, Številka:
9
Journal Article
Recenzirano
Density functional theory (DFT)-based calculations were performed for 36, 72 and 108 water molecules forming twisted ribbon-like nano-ring structures of diameter 1.54, 3.10 and 4.56 nm, respectively. ...We explore the electric field evolution of the structure, energetics and stability of the water nano-ring structures that are essentially symmetric and non-polar, or less-symmetric and polar, hydrogen-bonded clusters. The results suggest that for fields applied perpendicular to the ring, larger rings are more susceptible to the field influence, while fields applied parallel to the ring quickly transform the ring structures into arbitrary ones, regardless of the ring size. Infrared and Raman spectral analysis of local modes demonstrate the typical vibrational response of water molecules to various H-bonding environments and applied fields, providing a spectroscopic signature that can be used to identify the manifestation of such H-bonded ring networks. Our study underscores the implications of the nano-sized ring water clusters, which have the potential to be exploited in a variety of device applications.
The rare earth element doped germanium cluster represents a fundamental nanomaterial and exhibits potential in next‐generation industrial electronic nanodevices and applied semiconductors. Herein, ...the cerium‐doped germanium anionic nanocluster CeGen− (n = 5–17) has been comprehensively investigated by the double hybrid density functional theory of mPW2PLYP associated with the unbiased global searching technique of artificial bee colony algorithm. The cluster's growth pattern undergoes three stages: n = 5–9 with the replaced structure, n = 10–15 with the linked structure, and n ≥ 16 forming a Ce‐encapsulated in Ge inner cage motif. The clusters' PES, IR, and Raman spectra were simulated, and their HOMO‐LUMO gap, magnetism, charge transfer, and relative stability were predicted. These theoretical values can serve as a reference for future experiments to some extent. Moreover, the special D2d symmetry cage geometry of CeGe16− leads to a higher stability and preferred energy gap, making it an ideal candidate for further studies on its aromaticity, UV–vis spectra, and chemical bonding characteristics. In summary, CeGe16− has excellent optical activity that can be potentially employed as a building block in the development of optoelectronic functional materials.
Nanocluster CeGen− (n = 5–17) was investigated by mPW2PLYP quantum calculation associated with the ABCluster unbiased global searching technique. The structure growth pattern and various physicochemical properties of the clusters were predicted. The result shows CeGe16− has good stability, aromaticity, and broad sunlight absorption range.
Display omitted
•Structure, stabilities of dodecahedral fullerene C19X (X=Ni, Ti) and C20 have been investigated.•Quantum chemical calculations have been performed on the basis of DFT.•The doping ...effect is discussed in terms of the change in the CC bond length.•Electronic, optical properties, band gap, vibrational frequency have been calculated.
Structures and stabilities of dodecahedral fullerene C19X (X=Ni, Ti) and C20 have been investigated by quantum chemical calculations based on density functional theory. The geometrical structures, relative stabilities, dielectric constant of the doped cages were studied systematically and compared with those of the fullerene C20 cage. A series of dodecahedral functionalized derivatives have been studied at the B3LYP/6-31G level of density functional theory (DFT). The relative and formation energies of compounds, Mulliken charges, occupancy, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), the HOMO–LUMO band gap and chemical potential (μ) were calculated. The doping effect is discussed in terms of the change in the CC bond length and total dipole moment. The obtained result indicates that the CC bond length increases as a result of doping. The NBO analysis showed that there is a hyper conjugative interaction between the hetero atoms such as titanium and nickel lone-pair electron of doped fullerene with bonding and antibonding (σ∗) orbital of carbon atom of fullerene. The stability of the molecule, arising from charge delocalization, has been analyzed using Natural Bond Orbital (NBO) analysis. The nucleus – independent that more negative NICS values in doped fullerene than those of C20. The condensed Fukui Function and the newly introduced the atomic descriptors S (fk) to determine the local reactive sites of the molecular systems during electrophilic, nucleophilic and radical attacks have been calculated for the fullerene C20 compound.
PDF
