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Pillar[5]arenes, a type of novel macrocycles containing di-substituted hydroquinone units linked by methylene bridges in para-positions, have attracted extensive attention in supramolecular chemistry as interesting candidates to be used in the preparation of host-guest complexes. Functionalization by means of rim substitution and sustaining an ordered substituent arrangement on both sides of the rim is important for the development of new pillararene-based materials. In order to achieve this, the rim inversion process of rotating the hydroquinone units through the pillar[5]arenes has to be controlled. In this context we have studied the effect of different types of hydroquinone substituents on the rotational energy profile using density functional theory combined with the hybrid M06-2X functional. The influence of polar ([sbnd]CH2F, [sbnd]CH2Cl, [sbnd]CH2OH, [sbnd]CH2SH, [sbnd]CH2NH2) and nonpolar alkyl ([sbnd]CH3, [sbnd]CH2CH3, [sbnd]CH2CH2CH3, [sbnd]CH(CH3)2 and [sbnd]CH2CH2CH2CH3) substituents on the on the energy barriers of the rotation mechanism, and different local minima was investigated. The stabilization of the intermediate structures by non-covalent van der Waals and interactions and also by hydrogen bonds constitute a major factor affecting barrier heights. In case of polar substituents, the largest barriers were found for [sbnd]CH2OH and [sbnd]CH3 substitutions and the lowest ones for [sbnd]CH2SH and [sbnd]CH2NH2. For the alkyl series, the barrier decreased significantly up to propyl due to increasing stabilizing dispersion interactions while it increased again for n-butyl since the chain did not fit in well the cavity to rotate through.

This study has been performed to understand the effect of donor strength on photovoltaic performance of Dye-sensitized Solar Cells (DSSCs). For this purpose, Density Functional Theory (DFT) and time domain DFT calculations were carried out. The results reveal that triphenylamine based Dye 2 and carbazole based Dye 4 with di-substituted donor moieties showed red shifted absorption wavelengths, higher oscillator strength and improved electron injection leading to the larger short-circuit photocurrent density (JSC). It is expected that these dyes might show larger open-circuit photovoltage (VOC) as well. These results disclose that di-substitution of the donor moiety would be an efficient strategy to enhance JSC and VOC for better light to power conversion efficiency in DSSCs.

Ab initio calculations based on density functional theory have been employed to study electronic and optical properties of lithium ferrite spinel (LiFe5O8, LFO) based on density functional theory. The calculated of structural properties are in a good agreement with previously reported experimental results. The calculated band gap is indirect with a value of 2.3 eV, which overestimated the experimental value of 1.9 eV. The top of the valence band and the bottom of the conduction band of the LFO are dominated by the 3d states of Fe3+(1) (8c site) and Fe3+(2) (12d site). The magnetic moment calculated for the ion of Fe3+ 12d site was 3.90 μβ and 3.1 μβ for the 8c site. The electron transitions that generate the absorption edge of the compound are characterized by d-d transitions of Fe3+(1,2) at 12d and 8c sites, which agree with the experimental. The calculated value of the static dielectric constant (ω → 0), obtained from calculation of refractive index, is 1.66.

The mechanism of silver(I)-mediated trifluoromethylation of aryldiazonium salts has been studied comprehensively with density functional theory (DFT). Three stages constitute the trifluoromethylation pathway, namely (i) dissociation of the aryldiazonium salt, (ii) formation of the key disilver(I) intermediate and (iii) disilver(I)-mediated oxidative addition/reductive elimination (OA/RE) reaction. Thereinto, oxidative addition is the rate-determining step in the whole reaction. A radical pathway can be ruled out according to the present calculations. Moreover, the counterion in aryldiazonium salt has great influences on the trifluoromethylation as follows: (i) affecting the dissociation of aryldiazonium salt; (ii) participating in the formation of disilver(I) intermediates.

In the current work, we employ pristine antimonene nanosheet (SbNS), Sn and Te substituted SbNS as a base substrate for the adsorption of diethanolamine (DEA) and quaternium-15 (Q15) based on density functional theory (DFT) analysis. We used SbNS as a base material for adsorption of the toxic vapors DEA and Q15. We initially assured the stable SbNS structure using formation energy. Moreover, the other important attributes for the adsorption studies such as band structure, energy of adsorption, Bader charge transfer, density of states variability along with electron density variation have been scrutinized upon adsorption of DEA and Q15 molecules on SbNS. The outcome of this research provides evidence for the possible detection of DEA and Q15, which is a major constituent of soaps, detergents, and lubricants. The results of this report suggest that antimonene nanosheet can be used to detect the presence of DEA and Q15 molecules.

The removal of trace benzene from vinyl acetate with zeolitic imidazolate frameworks (ZIFs), a kind of metal-organic frameworks (MOFs) with formula unit M(IM)2 is studied. ZIF-2, ZIF-3, ZIF-6, ZIF-8, ZIF-10, and ZIF-68 are selected to study the adsorption of benzene and vinyl acetate. Density functional theory (DFT) method is used to study the interaction of the adsorbed molecules with the metal and organic linkers of ZIFs. Various adsorption positions are examined and the preferred configurations are obtained. The adsorption isotherms of benzene and vinyl acetate in pure components and benzene/vinyl acetate mixtures (0.01%/99.99%) in ZIFs at 373 K are obtained by molecular simulation. The calculation results showed that ZIF-68 has the highest selectivity for benzene.

We report molecules with a planar tetracoordinate carbon (ptC) or silicon (ptSi) atom(s) for the first time within Si3C2H2 elemental composition using density functional theory and coupled-cluster (CC) quantum chemical calculations. In total, nine isomers of Si3C2H2 (1-9) have been theoretically investigated. These include the lowest-energy trigonal bipyramidal geometry (1) and the other eight isomers (2-9) with either a ptC or ptSi atom(s). Among the latter, four isomers are identified to be local minima (2, 5, 6, and 9), three are found to be transition states (3, 4, and 8), and one geometry is found to be a second-order saddle-point (7) on the singlet ground electronic state of Si3C2H2 potential energy surface at various levels of theory employed here. While the isomer with a ptC atom show aromatic characteristics (5), the isomers with ptSi atom(s) show either aromatic (2) or anti-aromatic characteristics (6 and 9). Apart from 1, the kinetic stabilities of the latter four isomers also remain as an open-ended question at the moment. However, unlike 1, the latter four isomers are associated with a non-zero dipole moment ( μ ≠ 0 ). Therefore, energetic, aromatic, and spectroscopic parameters have been documented here, which may trigger the laboratory search for these elusive molecules in the future.

Genetic algorithm combined with density functional theory has been used to study (CuF)n (n = 1–12) clusters. The clusters are optimized by TPSSh/Lanl2dz (Cu)/6-31G(d) (F) method. Benchmark calculations have been carried out to find out suitable method and basis sets to calculate energies. The refined energies of the isomers have been computed using B3LYP/Lanl2tz (Cu)/6-311G(d) (F) method based on benchmark calculations. When n = 1–6, the clusters keep single cyclic conformations with Dnh symmetries; when n = 6–12, the clusters are three-dimensional structures. For (CuF)12 cluster, two new low-lying isomers have been discovered, which are catenane and ring-at-ring structures, respectively. According to the vertical and adiabatic ionization energies of the clusters, (CuF)4, (CuF)8 and (CuF)12 are relatively more stable than their neighbors. The noncovalent interactions (NCI) index has been introduced to study the intramolecular interactions of (CuF)4, (CuF)8 and (CuF)12 clusters. The results reveal that the clusters are magic sizes at n = 4, 8, 12. Our calculations can give a clear picture of the size evolution for (CuF)n (n = 1–12) clusters.

Recently, the bulk-heterojunction (BHJ) organic photovoltaic cells (OPVs) have attracted more attention owing to their potentials in low-weight, cost-effective, semi-transparent, colorful, and flexible. As one of the most promising candidates non-fullerene small molecule acceptors (SMA) in BHJ OPVs, fluoranthene-fused imide (FFI) derivatives can effectively regulate energy level and absorption by functional modification of active sites on its backbone. Nevertheless, it is still a challenge to design molecules based on FFI materials to achieve significant improvements in optoelectronic performance. Therefore, the key to this work is to explore the influence of introducing functional substituents at different active sites of FFIs on the photoelectric properties. By introducing different number of substituent groups with different electron-withdrawing and electron-donating capacities at FFI backbones active sites, could lead to construct “D-A-D” structures. By density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations, we demonstrated that constructing “D-A-D” structure in FFI derivatives wouldn’t impact apparently on charge transfer process, because the nearly vertical dihedral angles exhibit in these geometrical configurations between between “D units” and “A units”. This has become a main factor limiting the performance improvement of FFI-based SMAs with “D-A-D” structures. On the contrary, it would be an effective approach to control the number of electron-withdrawing groups reasonably at FFI backbone in order to design more excellent performance for FFIs.

Density functional theory (DFT) and time-dependent DFT calculations using the CAM-B3LYP functional were performed to investigate the electronic and optical properties of 2,7-Ph2-naphtho[1,2-d:5,6-d′]bis-(oxaphosphole) (Ph2-NBOP). Furthermore, we examined the effect of several structural modifications of Ph2-NBOP on the energy gap between the highest occupied and lowest unoccupied molecular orbital (HOMO and LUMO, respectively). The HOMO-LUMO gap (ΔEH-L) can be tuned by controlling the π-orbital overlap. Substituting As for P hinders the effective π-orbital overlap due to the inherently different size of pz orbitals perpendicular to the molecular plane, and results in a decrease of ΔEH-L (5.58 eV) than that (5.79 eV) of Ph2-NBOP. Moreover, asymmetric addition of substituents to the terminal phenyl ring increases the polarization of P or As, leading to a decrease in ΔEH-L due to the more ionic character of the corresponding bonds. Based on these results, we designed a minimal ΔEH-L model (CN1(NH2)1-NBOAs), P atoms of Ph2-NBOP are replaced to As and both CN and NH2 are attached to the terminal points of the phenyl rings of Ph2-NBOP, whose ΔEH-L (4.88 eV) is almost 1 eV smaller than that (5.79 eV) of Ph2-NBOP.

In this study, the nondissociative CO adsorption on the bimetallic clusters of Ni4M (M = Mo, Sc, Y) have been investigated using density functional theory. Different adsorption mode are considered and 9 stable Ni4M-CO complex are resulted for each Ni4M nanoclusters. We found that CO adsorption is thermodynamically favorable on the clusters and the average adsorption energies of optimized geometries are −42, −35 and −33 kcal/mol for Ni4Mo, Ni4Sc and Ni4Y clusters, respectively. Also, the maximum adsorption energies are found to be −67, −53 and −47 kcal/mol for Ni4Mo, Ni4Sc and Ni4Y, respectively. The most stable complexes obtained upon interaction of CO with Ni4M mainly arise from C…Ni4M interaction in preference over a O…Ni4M connection. A thorough analysis led to the conclusion that the Ni4Mo has the maximum average value HOMO-LUMO gap HLG and Ni4Y has minimum HLG.

We present a study on the adsorption process of p-group atoms on the α-Al2O3 corundum phase (0 0 0 1) surface by the density functional theory. The band gap is tuneable from an insulator to wide bandgap semiconducting nature by adsorption of p-group atoms (B, C, N, O, F) owing physisorption and chemisorption process on the alumina (0 0 0 1) surface. Adsorption energies are also calculated for all complex systems for centre top, Al-top and O-top sites. The hybridization of adsorbed p-group atoms, tune the electronic properties along to the n-type and p-type nature, which light up the new way to develop possible nanodevice. We also carried out electronic band structure, projected density of state (PDOS), electron localised function (ELF) and optical properties to understand the behaviour of adsorbed adatoms on the substrate. The result concludes that extra adatoms with α-Al2O3 shows the excellent adsorption in an ultraviolet region and work as UV mirrors.

The structures of CunNi55−n (n = 0–55) nanoparticles are generated by artificial bee colony algorithm, and the structural, magnetic and electronic properties of the CunNi55−n nanoparticles are performed by the density functional theory calculation. The calculation results show that the core-shell structure Cu42Ni13 is the most stable structure of all CunNi55−n NPs, besides, the Cu atoms prefer to appear on the surface and the Ni atoms prefer to occupy the interior place. As for magnetism, the total magnetic moment decreases with the increase of Cu atom. The results are shown that the average Bader charge of Ni atom and the d-band center of Ni atom have a positive correlation with the excess energy. On the contrary, the d-band center of Cu atom has a negative correlation with the excess energy.

We use density functional theory (DFT) to report the interaction of silicon nanoparticle and crystalline silica with the nucleobases of DNA/RNA-adenine (A), guanine (G), cytosine (C), thymine (T) and uracil (U). We obtain and analyse the binding energies, structural parameters and charge transfer to determine the strength between silicon cluster/quartz and nucleobases. The results show that the strength of the silicon cluster interaction with the nucleobases molecules follows the order G > C > U > A > T and the quartz-nucleobases interaction follows the order G > U > T > C > A. The amount of charge transferred from nucleobases to silicon cluster and quartz, is the highest in case of silicon-guanine and quartz-guanine complex and is the lowest in case of the silicon-thymine and quartz-thymine complex. Charge transfer trend is reversed in case of silicon-uracil and quartz-uracil complex. The computed results show that the silicon cluster made maximum damage to guanine molecule while its interaction with the uracil is the lowest.

Electron transport through benzene-based molecule is the fundamental issue of the electrical properties of graphene and other conjugated π-systems. To improve the device performance of conjugated π-systems, we designed a series of benzene models and analyzed the effect of bonding environments on the molecular conductance of benzene. By combing density functional theory and the non-equilibrium Green’s function method, it is found that the conductance of isolated benzene in a saturated sp3 carbon chain is a little higher than that in a conjugated sp2 oligophenyl chain, due to its lower attenuation with increasing unit number. The intermolecular d-p-π coupling acts as an important positive factor favoring to improve the conductance, whereas the d-p-σ decoupling is a negative factor to reduce the conductance. In conjugated π-systems, the intramolecular π-π conjugation has enhanced by the increasing unit number, which is another positive factor contributing to the high conductivity with long molecular length. These analyses not only help to enrich our knowledge about electron transport through conjugated π-systems, but also guide the design of graphene-based electronic devices.

In this work, the electronic structure and optical properties of two-layered hydrogenated GaN were investigated. The results were obtained via first principle calculations based on density functional theory (DFT) using GW approximation and two particle Bethe–Salpeter equation along with electron-hole effect. The results show that direct band gap of the sample change from 1.67 eV to, 4.1 eV considering electron-electron effects. Based on our findings, the first peak obtained from the imaginary part of the dielectric function for the direction parallel to the nanosheet plane observed in 3 eV, the energy corresponding to the first bound exciton state was obtained as 1.1 eV. The first absorption peak was observed in two parallel and perpendicular directions to the plane being invisible region.

The structures, metallophilic interactions and electronic excitation energy of linear metal chain complexes PdmPtn[PH2(CH2PH)m+n-2CH2PH2]3 (m + n = 2–5) (1–18) have been investigated by using MP2 and density functional theory (DFT) methods. Calculated results indicated that geometries of PdmPtn(PH2CH2PH2)3 (m + n = 2) (1–3) optimized by SVWN5 method are well consistent with those by MP2 method and experiment. Then, SVWN5 functional was used to the investigation of the large system of PdmPtn[PH2(CH2PH)m+n-2CH2PH2]3 complexes. The lowest energy structures of complexes 1–18 optimized by SVWN5 method are singlet. The lengths of Pd∙∙∙Pd and Pt∙∙∙Pt of Pdm[PH2(CH2PH)m-2CH2PH2]3 (m > 2) and Ptn[PH2(CH2PH)n-2CH2PH2]3 (n > 2) complexes at SVWN5 level are shorter than those of Pd2(PH2CH2PH2)3 and Pt2(PH2CH2PH2)3, indicating the interactions of Pd∙∙∙Pd and Pt∙∙∙Pt increase with the increase of the size of Pdm[PH2(CH2PH)m-2CH2PH2]3 and Ptn[PH2(CH2PH)n-2CH2PH2]3 complexes. Pd atoms in the mixed PdmPtn[PH2(CH2PH)m+n-2CH2PH2]3 complexes are favorable to locate at the ends of the metal chain. The lengths of Pd∙∙∙Pd and Pt∙∙∙Pt bonds in the mixed metal chain of PdmPtn[PH2(CH2PH)m+n-2CH2PH2]3 complexes have no significantly variation compared with those of the Pdm+n[PH2(CH2PH)m+n-2CH2PH2]3 and Ptm+n[PH2(CH2PH)m+n-2CH2PH2]3. But, the distances of Pd∙∙∙Pt of the mixed metal chain of PdmPtn[PH2(CH2PH)m+n-2CH2PH2]3 (m + n > 2) complexes are shorter than those of PdPt(PH2CH2PH2)3, showing the interaction between Pd and Pt increases as the increase of m + n. The WBIs of Pd∙∙∙Pd, Pd∙∙∙Pt and Pt∙∙∙Pt of complexes 1–18 are in the range of 0.22–0.25, 0.27–0.29 and 0.31–0.35, respectively, thus, there are weak interactions between adjacent transition metals in complexes 1–18. QTAIM analysis indicates that the interactions of Pd∙∙∙Pd, Pd∙∙∙Pt and Pt∙∙∙Pt of complexes 1–18 are not covalent, ionic or charge-shift bond. The gradient isosurfaces of complexes 1–18 show that the interaction between the adjacent transition metals is metallophilic interactions. The first electronic excitation energy of complexes 1–18 associated with HOMO → LUMO transition nonlinearly increases with m+n. In addition, the first electronic excitation energies of PdmPtn[PH2(CH2PH)m+n-2CH2PH2]3 complexes follow the order of Pdm+n[PH2(CH2PH)m+n-2CH2PH2]3

The application and versatility of photolabile protecting groups (PPGs) have continued to expand since their inception almost 50 years ago. In the present work we employ density functional theory (DFT) to characterize ground and excited state properties of several compounds with PPGs and to explore possible, controllable photodissociation reactions that remove these PPGs. The reaction mechanism is examined by analyzing the DFT results as well as dynamical simulations of nonadiabatic electron transfer reactions using multilayer multiconfiguration time-dependent Hartree theory. The photoexcited compounds appear to undergo ultrafast back electron transfer to the ground electronic state via internal conversion. For some compounds, the electronic-nuclear couplings facilitate sufficient photo energy transfer to the nuclear degrees of freedom that dominate the reaction coordinate, leading to the dissociation reaction that removes the PPGs.

A reaction force approach of amide bond formation between ammonia and formic acid is demonstrated along with each atom’s contribution to structural changes and electronic reordering of the chemical reaction. The B3LYP/6-31G(d,p) level of density functional theory based calculations were carried out to explore transition states (TSs) of stepwise and concerted amide bond formation reaction pathways. Various stages that characterize structural and electronic properties in the progress of reaction are identified from reaction force calculations on energetics of geometries obtained from intrinsic reaction coordinate (IRC) pathways. The reaction works in preparative region of the pathway are less than that in relaxation stage, reflecting favorable formation of product geometries (Formamide and water). More than 80% of the activation energy comes from structural changes in preparative region. A comparison of reaction force profiles and reaction works in preparative region of TS1 and TS2 of stepwise path and TS3 of concerted path discloses that both the stepwise and concerted mechanisms are equally competent in terms of kinetic feasibility. The atomic resolution of pathways unveils that, hydrogen and oxygen forming the water molecule contribute significantly to the negative reaction energy of product geometries. The preferential contribution of the atoms comes from enhanced negative charge of the oxygen and positive charge on hydrogen in the progress of reaction.

The structural and electronic properties of different transition-metal atoms (TM = Cr, Mn, Fe, Co, Cu, Zn, Pd, Ag, Pt, Au) doped into Nin neutral and ionic clusters (n = 13, 19, 55) were investigated using density functional theory calculations with the PBE exchange-correlation energy functional. The properties of the Nin−1TM clusters differed substantially from those of Nin, implying that the substitution of a transition-metal atom (TMA) strongly affected the stability and electronic properties of the resultant clusters. The cluster size effect and element type influence are discussed. The stability and the total magnetic moments of Nin−1TM neutral and ionic clusters were found to increase as a function of cluster size. The size of the clusters had little effect on the amount of charge transferred. The AIP decreased with increasing cluster size, while the AEA is exhibited the opposite trend. All of the aforementioned electronic properties exhibited different degrees of variation due to doping of different TMAs.

The aim of this study is to explore the mechanisms of CO oxidation to CO2 over some C59X heterofullerenes (X = B, P, Si and S) through systematic dispersion-corrected density functional theory calculations. The adsorption energy of O2 over these fullerenes becomes more negative in the order of C59S

Quasi-fullerenes ( C n - q , where q stands for quasi) are novel molecules that exhibit geometries such as carbon cages with interesting electronic structure properties due to the diversity on the shape of the rings in their structure. In this work, we studied the structural stability and electronic structure properties of possible endohedral metallo quasi-fullerenes M@ C n - q (M = Sc, Ti, V, Cr; n = 42, 48 and 60). These systems have been systematically investigated using density functional theory calculations. We calculated binding energies with the zero-point energy correction to determine the stability of these new endohedral compounds. We found that the bond between Sc with the carbon cages is mostly covalent. Moreover, all metals transferred charge to the cage. The stability and reactivity were also evaluated with the following criteria: hardness ( η ), chemical potential ( μ ) and HOMO–LUMO gaps ( Δ E HOMO - LUMO ). The charge distributions were studied with NBO population analysis, molecular electrostatic potential isosurfaces and electron localization functions. The cage aromaticity was evaluated in accordance to nuclear independent chemical shift methodology, and it was disclosed that the insertion of these metals increased aromaticity, showing that this property may play a crucial role in the stabilization of the endohedral species. We also studied thermal stability for the Sc@ C n - q series with Lagrangian molecular dynamics using Atom Center Density Matrix Propagation method. This work may aid to understand the possibility to determine the formation of new carbon cages with the ability to trap metal atoms.

In this paper, the adsorption characteristics of dimetridazole on anatase TiO2(1 0 1) and (0 0 1) crystal surfaces has been studied by using density functional theory. Adsorption structures of dimetridazole on anatase TiO2(1 0 1) and (0 0 1) crystal surfaces have been optimized under vacuum, water, acidic and alkaline conditions, respectively. The optimum adsorption site, adsorption energy and the electronic structure of the stable adsorption model were calculated. By analyzing the optimal adsorption site, we found that the possibility of degradation of dimetridazole on the surface of TiO2 and reaction site of degradation were the opening ring of C N bond on the imidazole ring. By comparing the adsorption characteristics of dimetridazole on two different crystal planes of TiO2 under acidic and alkaline conditions, we found that the adsorption wavelengths of electron transition between conduction bands and valence bands of dimetridazole on anatase TiO2(1 0 1) crystal plane are within the range of visible wavelength. The results show that TiO2(1 0 1) can effectively utilize visible light and catalyze the adsorption and degradation reaction of dimetridazole on TiO2(1 0 1) surface. Our results show that TiO2(1 0 1) crystal surface can effectively use visible light under acidic and alkaline conditions. Our conclusion can explain the experimental result that the use of visible light on TiO2(0 0 1) face is greatly affected by the environment.

Understanding energies and structures related to boron adsorption by d -glucamine group has an essential role in the improvement of boron removal from wastewater. In this study, we carried out a molecular scale analysis of boron adsorption by density functional theory (DFT) computations. All 30 species of boron-bonding d -glucamine were considered in an adsorption site model. Moreover, a total of 24 bis- d -glucamine adsorption sites, including five-membered and six-membered chelate rings were calculated. The values of ΔH and ΔG in the boron adsorption reaction were obtained by the PW6B95-D3ATM/ma-def2-TZVP//PBE0/6-31 + G(d,p) level of theory with the SMD solvation energy. Moreover, the 11B NMR chemical shift was also computed to compare the experimental results. Our computational results concluded that the adsorption of boron was achieved through two d -glucamine groups. The boron-adsorbed species has five-membered and/or six-membered chelate rings. The predicted 11B NMR chemical shift of the species matched with the experimental value. We conclude that the adsorption of boron by the bis- d -glucamine site is an endothermic reaction despite adsorption, which means the driving force of the reaction is entropy. These results suggested that there is a possibility for improvement in boron adsorption from the design of the adsorption functional group.

A series of organoplatinum (II) complexes with different electron-donating substituents are designed and investigated using density functional theory (DFT) and time-dependent DFT approaches. By analyzing the ground and excited structures, absorption spectra, charge transport, and phosphorescence properties of five Pt(II) complexes, it is possible to forecast that [Pt(trpy)(C CAr′)]PF6 (Ar′ = 2,6-Me2C6H3) (complex 2c·PF6) could be an efficient phosphorescent material due to its better balanced electron/hole-transport performance. The emission transition of terpyridyl arylacetylide Pt(II) complexes is associated with 3MLCT/3LLCT transitions, while the emission transition of phenyl-bipyridine arylisocyanide Pt(II) complexes has 3MLCT/3LLCT/3IL character. To understand the structure-property relationships of the dimeric structures of Pt(II) complexes, we examined the regions and distribution of the different intermolecular non-covalent weak interactions by studying the dimers of pincer-type Pt(II) complexes. RDG analysis visualizes the regions of intermolecular Pt⋯Pt and π-π interactions in dimers. This work offers rich insight into the essential characteristics of Pt(II) aggregations and provides helpful information for designing the new and improved luminescent materials.

To get a better understanding of the catalyst chemistry of iron clusters, four representative Fen (n = 1–4) clusters were chosen to systematically investigate the carbonization processes through subsequently adding carbon atoms by using density functional theory calculations. With respect to the quantum results, the analysis of structures, stabilities, and magnetic moments were conducted. It is found that there are three typical peaks of the chemisorption energies for all the clusters studied during the carbonization processes. The third type of peaks is the adsorption energies of critical structures that indicate the formations of the typical long carbon chains. These structures contain 10, 13, 14, and 17 carbon atoms corresponding to Fe1, Fe2, Fe3, and Fe4 pure clusters, respectively, which generate different numbers of carbon chains with the varying lengths. Furthermore, the total magnetic moments of four pure iron clusters would be reduced by the formations of Fe C bonds, and their values would change with the adding carbon atoms.

The molecular structure, vibrational frequencies, and enthalpy of formation of SF5OOO radical have been examined using several functionals such as pure GGA, hybrid GGA, meta-GGA, and “double hybrid” from density functional theory (DFT). The results show the existence of three conformations with symmetries Cs′, Cs and C1 for the SF5OOO radical, each differing in the spatial distribution and interactions of the oxygen atoms. All the functionals used in this study were capable of predicting the experimental vibrational frequencies, albeit with small differences in some of the vibrational bands. The thermochemistry studies were carried out with high-level Gn theories (G3MP2B3, G3B3, G4MP2 and G4), which provided reliable enthalpies of formation of −218.3 ± 1.3, −217.2 ± 1.6, and −218.0 ± 1.5 kcal mol−1 for SF5OOO (Cs), SF5OOO (Cs′) and SF5OOO (C1) at 298 K. The relative stability of the three conformations was found to be almost identical with interconversion barriers at 0 K less than lower 1 kcal mol−1. Finally, application of bond additivity corrections (BAC) to the G3MP2B3 and G3B3 methods made the enthalpy of formation converge to the values obtained with the G4MP2 and G4 methods.

Aniline aminolysis reaction of pyromellitic (PMDA) and 1,4,5,8-naphthalenetetracarboxylic (NTDA) dianhydrides is investigated by means of density functional theory (BP86-D3(BJ)/def2-TZVP). The concerted mechanism is shown to be more favorable for both substrates, in comparison to the stepwise one, with the aminolysis of PMDA presenting lower activation energy than the reaction of NTDA. This result is shown to be related to the lower ring tension in NTDA. Solvation also shows significant influence on the kinetics and thermodynamics of these reactions, as determined by two different methods, implicit with the universal solvation model SMD, and explicit with alchemical FEP molecular dynamics simulations. The comparison between SMD and FEP enables us to explore possible inaccuracies on the SMD model, and examine the suitability of the FEP approach as a physics-based method for the calculation of the solvent contribution in different reactions.

Many experimental detections and theoretical calculations have shown that the small molecules CO2, N2, CO, H2O and NH3 can be adsorbed on the graphene-family nanomaterials. The molecule CO2 can form tetrel bonds with N2, CO, H2O and NH3, respectively. Hence, it is significant to study the adsorption behavior of the tetrel bonding on graphene. In this work, the van der Waals-corrected density functional theory calculations have been carried out to study the adsorption behavior of the tetrel-bonded complexes CO2∙∙∙N2, CO2∙∙∙CO, CO2∙∙∙H2O and CO2∙∙∙NH3 on graphene. The results clearly show that, from a free state to the state on graphene, the length of the tetrel bond becomes longer and the strength of the tetrel bond becomes weaker, although the changes are not very large for both quantities. The energy decomposition analysis reveals that the effects of graphene on the tetrel bonds are largely dependent on both electrostatic and dispersion type interactions.

The structure and stability of the high energy water molecules inside the CB7 cavity was studied using the dispersion corrected density functional theory (DFT) and molecular dynamics (MD). The intermolecular distance between the O and H in the water molecule was found to decrease upon the encapsulation of water molecules inside the cavity, indicating the increase in the stability of water clusters. The computed binding energies were found to be sensitive to the choice of functional. Energy decomposition analysis (EDA) shows that the repulsive Pauli interaction decides the stability of the water complex. In all the encapsulated systems, except the eight water clusters, the electrostatic interactions have supremacy over the dispersive term, due to the large polarization induced by the water clusters. Molecular electrostatic potentials of entrapped systems show the charge distribution between CB7 and water clusters. QTAIM analysis indicates the existence of noncovalent intramolecular interactions between CB7 and water clusters and ellipticity values to be least for 8H2O@CB7. The topological of ρ(r) fields at the urido nitrogen plane in CB7, proves the stronger bonding with water molecules. Thus, entrapped water molecules are not electronically innocent inside the cage and have noncovalent interaction with hydrophobic part of CB7 molecule. Atom centered Density Matrix Propagation (ADMP) molecular dynamic studies shows that the water clusters are stable with respect to their isolated cluster geometry, inside the cucurbituril and the change in potential energy surface is due to the distortion in the geometry of the CB7 unit.

Adsorption of NO3−, PO43− and ClO4− ions on graphene and doped graphene (B, Al, N, P, Si, BN and 3BN) has been studied using density functional theory considering coronene as graphene model system. The considered oxoanions adsorb preferably on doped coronene, validating the key role of nature of dopant on stability of the complexes. Adsorption of the oxoanions is fairly strong in gas phase and presence of solvent phase decreases the stability of the complexes depending on solvent dielectrics. Results confirm the physisorption (anion⋯π interaction) of oxoanions on un-doped/BN/3BN-doped coronene while chemisorptions of the same on B/Al/P/Si doped coronene. The complexation is exothermic and spontaneous in most cases. Moreover, spectral analysis showed significant variation in electronic properties of un-doped/doped coronene upon complexation.

The low cost, highly stable and earth abundant furan-based small molecules have been recognized to be prospective and innovative organic semiconductor materials (OSMs) for optoelectronic applications. In this article, we explore various optoelectronic properties of conjugated isomers containing bifuran (TFFT) and bithiophene (FTTF) by employing the density functional theory (DFT) based ultrasoft pseudopotential approach. Our investigations specify the TFFT as a wide and direct bandgap semiconductor with bandgap value of 2.00 eV. Whereas, the bandgap of FTTF is found to be reduced by 0.239 eV in comparison with TFFT owing towards the effect from p-orbitals of carbon and sulfur atoms present at the center of molecular crystal structure. The reduction in the energy and the density of states (DOS) for the compounds in current study endorsed that bandgap could be tuned to any desired value for optoelectronic applications through derivatives designing. Moreover, the achieved outcomes for optoelectronic parameters like dielectric function, conductivity, refractive index, reflectivity, extinction coefficient and energy loss function validates their suitability to use them in electro-optical devices.

Based on the density functional theory (DFT) level, the thermal reaction of PtOH+ with methane has been investigated theoretically using the empirically parametrized hybrid functional B3LYP. The favorable path for the reaction of PtOH+ + CH4 is the channel of the elimination of H2O. The overall reaction is exothermic by 16.5 kcal/mol. The NBO analysis demonstrated that the ligand effect resulting in the electronic occupies in the quasi-restricted orbitals and also shows a proton-coupled electron transfer component in 3TS2-H2O. By comparing among the reactions of Pt+, [Pt(H)(OH)]+ and PtOH+ with CH4, PtOH+ is more reactive to methane than Pt+ and [Pt(H)(OH)]+ thermodynamically. These results can not only deepen the understanding of the mechanism, but also guide the reasonable design of catalysts.

Trifluoromethyl-substituted cyclometalated platinum(II) (TSCP) is a useful material for oxygen molecule detection and determination. Through quantum chemical computation, we propose a quenching mechanism to explain the nature of oxygen sensing. The luminescence mechanism of TSCP involves phosphorescent emission and the TSCP-O2 complex internal conversion. By applying the density functional theory (DFT) method, we computed the frontier molecular orbitals and electron configurations of TSCP and the TSCP-O2 complex. In addition, using the time-dependent density functional theory (TDDFT) method, we computed the excited energies and geometric optimization of the excited state of TSCP and the TSCP-O2 complex. According to the computation results, the luminescence of TSCP is due to localized excitation, while that of the TSCP-O2 complex is due to delocalized excitation. We computed the radiative and non-radiative rate constants of TSCP and the TSCP-O2 complex and elucidated their photophysical processes. For TSCP, after excitation, first the electron jumped from the S1 to T1 state by intersystem crossing, and eventually back to the S0 state by phosphorescence emission. Instead, for the TSCP-O2 complex without spin flip, the electron jumped directly from the T1 to T0 state by internal conversion.

The electronic and structural properties of the four copolymers, PBDPQU, PBDPBT, PBDPDPP, and PBDPTP, are investigated by density functional theory and time-dependent density functional theory. The research purpose is to rationalize the relationship between observed experimental performances and structural properties. The properties that can affect open-circuit voltage (VOC) and short-circuit current (JSC) are comprehensively investigated, which refer to absorption spectra, frontier molecular orbital, charge transport properties, and exciton dissociation abilities at the copolymer/PCBM interface. The results indicate that the favourable photovoltaic performances of PBDPBT are due to large VOC, lower the highest occupied molecular orbital (HOMO), and small effective mass (m*). Furthermore, the unfavourable performance of PBDPTP mainly originates from the higher HOMO level and weak ability of exciton dissociation at interface, while the intermediate properties aforementioned for PBDPQU and PBDPDPP determine their intermediate photovoltaic performances. In conclusion, the theoretical results agree well with the experimental ones.

The real-time time-dependent density functional theory (RT-TDDFT) is rapidly gaining prominence as an alternative approach to capture optical properties of molecular systems, which warrants the necessity to benchmark the traditional linear response (LR) method and the RT approach. We calculate the absorption spectra of noble metal nanoparticles with a variety of sizes and shapes to demonstrate the consistency of the two methods over a broad range of energy. The RT spectrum obtained using a grid-based basis set with pseudopotentials achieves results in good agreement with the LR spectrum obtained with large QZ4P atom-centered basis sets. Factors that lead to convergence of the spectra are considered. In addition, the real-time variation of the electron density is visualized to show the collective oscillation of electron density for the plasmon modes of noble metal nanoparticles. The RT approach is most useful when calculating wide absorption spectra of larger gold or silver nanoparticles.

Density functional theory (DFT) computations were carried out to investigate structural, energetic, and electronic properties of CO2 adsorbed on neutral sodium iodide clusters ((NaI)n, n = 1–10). For this purpose, the geometry of each cluster was optimized based on electrostatic guidelines to generate initial structures that interact with CO2 molecules. In this line, various structures of CO2-cluster complexes were investigated. Interaction energies, equilibrium distances, and charge transfer parameters of the complexes were evaluated. The quantum theory of atoms in molecules and natural bond orbitals method were applied to better understand the nature of interaction between CO2 molecule and these clusters. The results indicated that CO2 molecules have weak interactions with these clusters.

The adsorption of bromomethane (CH3Br) onto the outer surface of the pristine armchair (5,5) single-walled aluminum nitride nanotube (AlNNT), boron nitride nanotube (BNNT), carbon nanotube (CNT), and silicon carbide nanotube (SiCNT) were investigated using density functional theory (DFT). The geometry optimization was performed by using the PBEPBE/6-31G(d) level of theory through 1D periodic boundary conditions (in which, each unit cell containing 40 atoms). Moreover, NBO and QTAIM analyses were also performed by using the same level of theory but using the complete nanotubes (each nanotube consists of 200 atoms). For further investigation, single point energy calculations were applied to each system using the CAM-B3LYP/DEF2-TZVP level of theory. The obtained adsorption energies indicate that among all of the aforementioned nanotubes, AlNNT exhibits the strongest affinity for the adsorption of the CH3Br molecule with the most negative adsorption energy. Based on the NBO and QTAIM results, it can be inferred that CH3Br tends to be chemisorbed onto the AlN and SiC nanotubes, whereas, in the case of CNT and BNNT, the adsorption is through weak van der Waals interactions and a physisorption process. Therefore, the results of this work may be useful in designing new types of nanosensor devices.

In this research, the origins of regioselective behavior of ruthenium catalyzed azide-alkyne cycloaddition reaction were assessed via the quantum chemistry approaches. In this respect, density functional theory calculations were performed to investigate the structural and energetic properties of regioisomeric triazole products and their corresponded transition states in the presence of ruthenium as the catalyst. Moreover, the solvation effects were examined via polarized continuum model computing in the presence of 1,2-dichloro ethane (1,2-DCE) and dimethyl formamide (DMF) to interpret the regioselectivity. In the next step, in order to present a more concise rationalization for the mechanistic role of ruthenium catalyst in regioselective synthesis of 1,5-disubstituted 1,2,3-triazoles, we assessed the topological properties of electron density in isomeric products and their corresponded transition states by employing the quantum theory of atoms in molecules. In this route, we concentrated on calculation of electron density, its laplacian and other electronic energy density indicators in some key bond critical points (BCPs) which have a significant role in regioselective production of 1,5-disubstituted 1,2,3-triazoles.

This work presents an implementation of the original orbital-free Hohenberg-Kohn density functional theory in a form that is able to predict chemical bonding in molecules. The method is completely parameter-free and does not require analytical functional approximations. Instead, the proposed method is based on the idea that atoms are meaningful pieces of a molecule and thus, a promolecule, build from frozen spherical atomic entities, serves as a suitable model for the latter. This idea is imposed on the physical equations, originating from density functional theory converted into a bifunctional formalism. The viewpoint proposed in this study offers a new strategic way of subsequent approximation levels in orbital-free density functional theory. In this work the zeroth order approximation is shown to predict chemical bonding in molecules, providing a concept of the chemical bond without involving orbitals.

This work investigated computationally with density functional theory calculations at the M06/6-311G∗ level, the ring opening reaction of various methyl-, phenyl- and carbonyl- substituted aziridines to obtain azomethine ylides and the subsequent 1,3-dipolar cycloaddition reaction with acetaldehyde leading to 3-methyl and 4-methyl regioisomers and endo- and exo- stereoisomers. The activation barrier for the electrocyclic ring opening of the parent aziridine is very high (51.3 kcal/mol) but is lowered by at least 15.5 kcal/mol upon methyl and ester group substitutions. In the reaction of 1,3-diphenyl-2,2-methoxycarbonylaziridine A2 with acetaldehyde, the ring opening step is rate-determining with an activation barrier of 28.9 kcal/mol. The activation barrier for the formation of the 4-methyl isomer from this reaction is at least 7.4 kcal/mol lower than that for the formation of the 3-methyl isomer, which is in accord with the experimentally-observed regioselectivity. Also, the formation of the exo isomer is more favoured than the endo isomer as the barrier of the former is 2.7 kcal/mol compared to 6.1 kcal/mol for the latter. There is an inverse correlation between the activation barriers for the electrocyclic cleavage of the aziridines and the electrophilicities of the resulting azomethine ylides. The results are rationalized in terms of perturbation molecular orbital theory.

The mechanism of the iron-catalyzed olefin synthesis reaction was investigated using the density functional theory (DFT) calculations. The catalytic performances of the FeCl3 and FeCl2 in different spin states for the olefin synthesis reaction were studied in detail. Both of the two reactions are found to proceed predominantly on high spin state potential energy surfaces, sextet and quintet respectively. The whole catalytic cycle can be divided into three stages: the dehydration step, the electrophilic addition step, and the deprotonation step. The electrophilic addition transition state has the highest energy in the whole catalytic cycle, which is consistent with the experimental prediction. According to the results, (E)-alkene is the main product in both the FeCl3 and the FeCl2 catalyzed olefin synthesis reaction. The geometry, mechanism, and the overall reaction barriers of the olefin synthesis reaction are very similar when FeCl2 and FeCl3 are used as catalysts. The reaction barrier of FeCl2 catalyst is lower than that of FeCl3, showing that FeCl2 may be more effective in this kind of olefin synthesis reaction.

In this study, the fragmentation mechanism of deprotonated asparagine (Asn) was investigated in detail using density functional theory at the BHandHLYP/6-311++G(2df,2pd) level of theory. The H2O-, NH3- and CO2-loss fragmentation reaction profiles constructed by the relative Gibbs free energies of the located stationary points were used to analyze the preferred dissociation pathways and the structures of the resulting molecular ion products. Furthermore, we also examined the temperature dependence of the thermodynamics and kinetics of key dissociation reactions, which provided further insight into the dominant fragmentation channel and the corresponding product distribution under different experimental dissociation energies. This study offered a computational support for building the fragmentation model of deprotonated amino acids.

Carbon suboxide (C3O2) has a sizable fraction in the atmosphere. The environmental fate of C3O2 was studied by density functional theory. Methanol (MeOH), dimethylamine (DMA), and methane sulfonic acid (MSA) are typical atmospheric nucleation precursors. This study investigated how the acidic, neutral and basic precursors impact atmospheric new particle formation. The formation of 1:1 and 1:2 complexes were studied. The binding energies and geometric parameters clearly show that MSA is the strongest hydrogen bond donor than MeOH and DMA. This is consistent with the comparable red shifts and QTAIM analysis of the MSA-containing complexes. The neutral precursor (MeOH) and the basic one (DMA) were found to weakly interact with C3O2. Thus, the acidic species would promote the nucleation with the neutral C3O2.

The structural and vibrational analysis of sulfur mustard was performed using second order Moller-Plesset and density functional theory with harmonic and anharmonic force field calculations. The extension to anharmonic calculations provides better agreement between the theoretical vibrational wavenumbers and reported experimental results. At least two conformers co-exist in the experiment is approved by two levels of theory. Based on these possible conformations, most of the relative difference between theoretical and experiment data is less than 1%. The vibrational frequencies were assigned on the basis of potential energy distribution calculation. Furthermore, the terahertz spectrum of sulfur mustard in gas phase was simulated, as well as that of its analogue 2-chloroethylethyl sulfide for comparison.

Density functional theory (DFT) calculations have been performed to understand the role of Ethylene Glycol (EG) in a remarkable catalyst-free Strecker reaction of α-CF3 ketoimine. The fluorine hydrogen bonds involved in titled reaction have been studied. To find the suitable calculation methods for the weak C F⋯H interaction, we chose seventeen density functionals and MP2 method for calculation of the structures of three typical C F⋯H hydrogen-bonded systems. Their structures were computed and compared with the available experimental data. The results show that the M05-2X and M06-2X functionals are better than the other methods. Based on these facts, the interactions between the α-CF3 ketoimine and EG were investigated at the M06-2X/6-31G(d,p) level. And the results indicate the presence of strong C F⋯H O hydrogen bond in the complexes between α-CF3 ketoimine and solvent EG. Moreover, we also studied the reaction mechanism of the titled reaction with or without the assistance of EG at the M06-2X/6-31G(d,p) level. The results show that the two possible pathways without the aid of EG have very high free energy barriers and the reaction can't proceed, which is consistent with the experiment fact. However, with the assistance of EG, the reaction activation free energy barrier can decrease greatly. For the two-EGs model with two EG molecules, the reaction free energy barrier decreases from 47.5 kcal mol−1 to 24.7 kcal mol−1. The two EGs play an important role to stabilize the transition state and decrease the activation barrier greatly. The present theoretical calculations imply the role of solvent EG in the titled interesting catalyst-free Strecker reaction of α-CF3 ketoimine. Our theoretical calculations provide a satisfactory explanation for the experiment.

The frequent and widespread use of p-nitrophenol at commercial scale is giving rise to several health hazards among living beings and damage to the ecosystem. In this work, the adsorption of para-nitrophenol (p-NP) on pristine/vacancy-graphene and Pt4-cluster doped graphene systems are investigated using density functional theory (DFT). Two modes of adsorption have been considered: perpendicular and parallel. While adsorption of p-NP on the pristine graphene substrate is unfavorable, it is found that the adsorption capacity of graphene can be significantly increased by creating defects and by doping with Pt-clusters. Different electronic properties, like partial density of states (PDOS), reveal that on doping with a Pt-cluster, the band gap of the surface decreases and the substrates start showing magnetic character. Electron density difference plots give insights into the adsorption behavior of p-NP.

This article reports the thermodynamics and kinetics of keto-enol tautomerization in 1, 3, 5-triazin-2, 4(1H, 3H)-dione (R) and its tautomers at D ensity F unctional T heory (DFT) – B3LYP/6-311++G (d, p) level. In the chosen system, five keto-enol tautomerization reactions are possible namely R ↔ P1 (Channel 1), R ↔ P2 (Channel 2), R ↔ P3 (Channel 3), P3 ↔ P4 (Channel 4), and P1 ↔ P4 (Channel 5). The reactant has three pathways leading to three different tautomers (P1, P2, and P3). Both P1 and P3 can tautomerize to a fourth product P4 through two additional pathways. The four tautomers namely P1, P2, P3, and P4 are defined as 6-Hydroxy-1H-[1,3,5]Triazine-2-one, 4-Hydroxy-5H-[1,3,5]Triazine-2-one, 4-Hydroxy-1H-[1,3,5]Triazine-2-one, and [1,3,5]Triazine-2,4-diol, respectively. Conventional T ransition S tate T heory (TST) calculations were carried out to determine pre-exponential factor (A) and activation energy (Ea) of all the five tautomerization reactions. One of the hydrogens bonded to the 6th carbon atom (according to IUPAC nomenclature) of the tri-heterocyclic triazine system (R) was replaced by six substituents (F, Cl, OH, NH2, CH3, and C2H5) consecutively to understand their influence on the kinetics and thermodynamics of the tautomerization processes. All substituents investigated enhances the reaction rate constants of the first channel by reducing the barrier height, for example, ortho-para directing and activating substituent NH2 reduces it by 3.55 kcal mol−1. Application of Mulliken population analysis for the distribution of π electron density indicates that the electron donating OH, NH2, and C2H5 substituents increases the stability of TS’s for the third channel by enhancing the aromaticity of triazine ring which leads to increased rate constants.

Here, we have studied the structural and optoelectronic properties of three series of TPA-based dyes viz. TPA-BBTA, TPA-BTA and TPA-NBT by using density functional theory (DFT). The study is performed by introducing different electron-donating and electron-withdrawing substituents to the TPA-based dyes. Based on the optimized geometries, the relative energy alignment of the frontier molecular orbitals (MO) has been analyzed. The photoelectron spectra and photovoltaic properties have also been investigated with the TDDFT approach. Our study reveals that the dyes substituted with the N(CH3)2 and OC2H5 groups will show maximum photovoltaic efficiencies along with low Δ H - L values compared to the other substituted dyes. As a result, these dyes will act as potential candidates for fabrication of dye sensitized solar cells (DSSCs).

We used the particle swarm optimization method to search a variety of isomers of (BN)4 clusters, and then using the density functional theory of quantum chemistry calculation method to optimize the structures of the chosen isomers at B3LYP/6-31G(d) level. The results show that there are seven configurations are stable stationary points on the potential energy surface. The geometry optimization, infrared spectrum, relative Gibbs free energy, vibrational spectroscopy and topological analysis are implemented for the seven representative clusters. Our results show the diversity of (BN)4 clusters. The relationship between the structural stability and their symmetry are discussed. We have obtained the lowest energy structure R1 which is the most stable structure, consistent with the previous results. We have also obtained their energy order at different temperatures by calculating the Gibbs free energy. Topological analysis of (BN)4 cluster indicates that the dominant interaction between B and N is covalent interaction.