Vertical Potentials Research Articles

Non-linear optical properties of hybrid materials of (OLi3) superalkali doped perylene diimide (PDI) derivative: comprehensively study via silico-technique

PDI-Imidazole and PDI-Imidazole combined with OLi3 (OLi3@PDI-Imidazole) were the two types of materials that we examined in this study to see how light behaved in each of the complex. To explore this, we employed the three different method such as rB3LYP/6–31G(d, p) DFT, CAM-B3LYP and WB97XD. The impact of PDI-Imidazole and OLi3@PDI-Imidazole geometries, maximum absorption ( λmax ), FMO, vertical ionization energies ( EVI ), Binding Energies ( Eb ), Hyperpolarizabilities, DOS, Dipole Moments (μ), ESP, EDDM, and Global Reactivity parameters have been examined. The type of contacts as well as the vibrational frequencies of PDI-Imidazole and OLi3@PDI-Imidazole were investigated using NCl, iso-surface, Raman spectroscopy, and IR research. The electron transport characteristics of the OLi3@PDI-Imidazole surface was significantly enhanced in comparison to the PDI-Imidazole surface by lowering the bandgap energies from 1.27 eV to 1.03 eV. In contrast to the pure PDI-Imidazole surface, which had lower values for linear polarizability ( α0 ) (547.08 au) and first hyperpolarizability ( β0 )(201.133au), OLi3@PDI-Imidazole surface displayed significant enhancements in linear polarizability ( α0 = 706.472 au) and first hyperpolarizability ( β0 = 21314.360 au). It was observed by TD-DFT calculations that all the compounds had appreciable improvements in their interaction energies, HOMO–LUMO and UV–vis absorption and vertical ionization potential. Future development of nonlinear optical (NLO) devices has been discovered to benefit from the addition of OLi3 to the PDI-Imidazole surface.

Effect of Oriented External Electric Fields on the Electronic Properties of Linear Acenes: A Thermally Assisted Occupation DFT Study.

Recently, oriented external electric fields (OEEFs) have earned much attention due to the possibility of tuning the properties of electronic systems. From a theoretical perspective, one can resort to electronic structure calculations to understand how the direction and strength of OEEFs affect the properties of electronic systems. However, for multi-reference (MR) systems, calculations employing the popular Kohn-Sham density functional theory with the traditional semilocal and hybrid exchange-correlation energy functionals can yield erroneous results. Owing to its decent compromise between accuracy and efficiency for MR systems at the nanoscale (i.e., MR nanosystems), in this study, thermally assisted occupation density functional theory (TAO-DFT) is adopted to explore the electronic properties of n-acenes (n = 2-10), containing n linearly fused benzene rings, in OEEFs, where the OEEFs of various electric field strengths are applied along the long axes of n-acenes. According to our TAO-DFT calculations, the ground states of n-acenes in OEEFs are singlets for all the cases examined. The effect of OEEFs is shown to be significant on the vertical ionization potentials and vertical electron affinities of ground-state n-acenes with odd-number fused benzene rings. Moreover, the MR character of ground-state n-acenes in OEEFs increases with the increase in the acene length and/or the electric field strength.

Unveiling the effects of thallium and bismuth p-n doping on germanium-based clusters (n5 to n12) for applications in semiconductor materials

We report a computational investigation utilizing density functional theory (DFT) concerning the pure Gen, as well as their doped analogues (BiGen-1, TlGen-1) and p-n doped BiTlGen-2 clusters with n ranging from 5 to 12. To get a deeper insight in their properties, we focus on the size dependency of these Gen, BiGen-1, TlGen-1, and BiTlGen-2 clusters as well as their shape, relative stabilities, and thermochemical characteristics including binding energy, fragmentation energy, second-order energy difference, and HOMO-LUMO energy gaps. The systematic observations from the data of binding energies indicate that BiGen-1, TlGen-1 and BiTlGen-2 cluster have more structural and thermodynamic stability when compared with the pure Gen clusters. To validate the electronic characteristics of these clusters, additional energy gap-related parameters such as chemical hardness, vertical ionization potentials (VIP), and vertical electron affinities (VEA) are also computed. The doping seems to stabilize the Gen clusters and the highest stability has been achieved for BiGe7, TlGe9, and BiTlGe7 clusters as suggested by the combined effect of all these parameters.

Mechanistic investigation and machine learning exploration of structure-activity relationship of NHC-Mn catalyzed ester hydrosilylation reaction

This study aims to deeply investigate the mechanism of NHC-Mn catalyzed ester hydrosilylation reaction and the impact of different ligands on reaction activity through the comprehensive application of DFT calculations and machine learning technologies. We initially proposed four possible reaction mechanisms including two radical mechanisms and two 2e mechanisms. Then calculate the potential energy surfaces of them. It was demonstrated through calculations that the radical mechanisms were implausible, while the 2e outer-sphere mechanism was proven to be reasonable. A detailed analysis of the Si–H bond activation step in different reaction mechanisms highlighted the crucial role of steric effects in the process. Furthermore, the rate-determining step in the 2e mechanism (outer-sphere), the hydride transfer process, was also thoroughly studied. Eventually, a predictive model was successfully constructed using machine learning methods, which is a model based on the Ridge algorithm with 17 features that accurately predict the impact of different types of ligands on the reaction barrier. Analysis of the model revealed important factors affecting reaction activity, such as the vertical ionization potential of the metal hydride intermediate, the charge on the metal hydride, and the bond order of the Mn–H bond.

Exploring the nonlinear optical characteristics of supersalt-decorated graphyne via DFT analysis: unveiling quantum insights into light-matter interaction

In this comprehensive study, we explore into the nonlinear optical (NLO) properties of graphyne (GRY) and its compounds decorated with a super salt (OLi3BeF3), namely GRY@SS1, and GRY@SS2) using the rB3LYP/6−31G(d,p) DFT method. Our findings reveal a substantial enhancement in the electron transfer properties of decorated compounds compared to the pristine GRY surface. This enhancement is evidence by the reduction in the bandgap energies (Eg) from 3.52 eV to 1.68 eV and remarkable boost in maximum absorption ( λmax) from 372.66 to 807.73 nm. Noteably, GRY@SS2 exhibits a significant increase in linear polarizability ( α0 ) (538.18 au), first hyperpolarizability ( β0 ) (3872.76 au), and second hyperpolarizability ( γ0 ) (1.00 × 106) due to reduced excitations energies compared to the GRY ( α0 = 448.61, β0 = 0.14 and γ0 = 5.97 × 105 au). NBO charges show that electrons are transferring from the dopant (supersalt) to the GRY sheet. Furthermore, Non-covalent interactions (NCl), iso-surface, infrared (IR), 1H NMR, and 13C NMR studies have been conducted to provide insights into the nature of interactions, vibrational frequencies, and structural-functional aspects of GRY and GRY@SS1, and GRY@SS2. According to TD-DFT calculations, all compounds demonstrate superior vertical ionization potential, UV–vis absorbance, HOMO–LUMO characteristics, as well as interaction energies. Our results underscore the potential of these compounds as valuable NLO materials, particularly highlighting the promising prospects of GRY@SS2.

Hydrogen storage on MgO supported TiMgn (n = 2–6) clusters: A first principle investigation

The current study explores the potential of MgO-supported finite-sized TiMgn (n = 2–6) nanoclusters as hydrogen storage materials, employing density functional theory with a spin-polarized generalized gradient approximation (GGA). These systems' structural stability and electronic characteristics reveal that supported clusters offer superior hydrogen storage capabilities compared to their unassisted counterparts. Various parameters, including cluster-adsorption energy (Eads), hydrogen-adsorption energy in supported clusters (Eads-H), HOMO-LUMO gap, vertical ionization potential (VIP), vertical electron affinity (VEA), chemical potential (μ), and chemical hardness (ɳ) are computed. Substrate support notably enhances the thermodynamic stability and chemical reactivity of the TiMg5 cluster when contrasted with the bare TiMg5 cluster. Furthermore, a remarkable increase in the gravimetric hydrogen storage density, from 1.63 wt% for bare Mg5 clusters to 3.45 wt% for bare TiMg5 clusters, reaching 5.62 wt% in the supported TiMg5 cluster system is observed. These findings indicate the substrate-supported TiMg5 cluster as a promising candidate for hydrogen storage applications.

Critical roles of soil composition and pollutant properties on the degradation of PPCPs during ferrous/persulfate processes

Pharmaceuticals and personal care products (PPCPs) are widely used worldwide and cause potential soil pollution. Fe2+-activated persulfate (PS) processes (Fe-PAPs) are promising techniques for soil remediation. However, a knowledge gap exists in the mechanistic insights into the dominant factors affecting the degradation of different PPCPs in varied soil types. This study systematically investigated the roles of soil components and pollutant properties in the degradation of three PPCPs (triclosan (TCS), triclocarban (TCC), and naproxen (NPS)) in the nine soils in the Fe2+/PS system. The degradation efficiencies of TCS and NPS ranged from 10.92 % to 91.62 % and 46.59 % to 99.81 %, respectively, whereas nearly no degradation was observed for TCC. PPCPs with high water solubility, high energies of the highest occupied molecular orbital (EHOMO), low pKa values, low energy gap (ΔE), or low vertical ionization potential (VIP) were more favorable for degradation. XPS analysis suggested that aliphatic carbon (Ali–C–C(H)), ether or alcohol carbon (C–O), and aldehyde or ketonic carbon (CO) on SOM significantly inhibited TCS degradation. The results of ROS quenching experiments showed that SO4•− and 1O2 played major roles in TCS and NPS degradation in the six soils, with the relative contributions ranged from 24.82 % to 99.14 % and 0.15 % to 73.40 %, respectively. The interaction between soil components, active species, and pollutants resulted in the distinct intermediates of TCS and NPS in different soils. Our findings provide in-depth insights into the role of soil composition and pollutant properties on the remediation of PPCP-contaminated soils in Fe-PAPs.

Newly Designed Quasi-intrinsic Photosensitizers for Fluorescence Image-Guided Two-Photon Photodynamic Therapy with Type I/II Photoreactions.

In this work, a set of quasi-intrinsic photosensitizers are theoretically proposed based on the 2-amino-8-(1'-β-d-2'-deoxyribofuranosyl)-imidazo[1,2-α]-1,3,5-triazin-4(8H)-one (P), which could pair with the 6-amino-5-nitro-3-(1'-β-d-2'-deoxyribofuranosyl)-2(1H)-pyridone (Z) and keep the essential structural characters of nucleic acid. It is revealed that the ring expansion and electron-donating/electron-withdrawing substitution bring enhanced two-photon absorption and bright photoluminescence of these monomers, thereby facilitating the selective excitation and tumor localization through fluorescence imaging. However, instead of undergoing radiative transition (S1 → S0), the base pairing induced fluorescence quenching and rapid intersystem crossing (S1 → Tn) are observed and characterized by the reduced singlet-triplet energy gaps and large spin-orbit coupling values. To ensure the phototherapeutic properties of the considered base pairs in long-lived T1 state, we examined the vertical electron affinity as well as vertical ionization potential for production of superoxide anions via Type I photoreaction, and their required T1 energy (0.98 eV) to generate singlet oxygen 1O2 via Type II mechanism.

The Influence of Oxidized Imino-Allantoin in the Presence of OXOG on Double Helix Charge Transfer: A Theoretical Approach.

The genome is continuously exposed to a variety of harmful factors that result in a significant amount of DNA damage. This article examines the influence of a multi-damage site containing oxidized imino-allantoin (OXIa) and 7,8-dihydro-8-oxo-2'-deoxyguanosine (OXOdG) on the spatial geometry, electronic properties, and ds-DNA charge transfer. The ground stage of a d[A1OXIa2A3OXOG4A5]*d[T5C4T3C2T1] structure was obtained at the M06-2X/6-D95**//M06-2X/sto-3G level of theory in the condensed phase, with the energies obtained at the M06-2X/6-31++G** level. The non-equilibrated and equilibrated solvent-solute interactions were also considered. Theoretical studies reveal that the radical cation prefers to settle on the OXOG moiety, irrespective of the presence of OXIa in a ds-oligo. The lowest vertical and adiabatic ionization potential values were found for the OXOG:::C base pair (5.94 and 5.52 [eV], respectively). Conversely, the highest vertical and adiabatic electron affinity was assigned for OXIaC as follows: 3.15 and 3.49 [eV]. The charge transfers were analyzed according to Marcus' theory. The highest value of charge transfer rate constant for hole and excess electron migration was found for the process towards the OXOGC moiety. Surprisingly, the values obtained for the driving force and activation energy of electro-transfer towards OXIa2C4 located this process in the Marcus inverted region, which is thermodynamically unfavorable. Therefore, the presence of OXIa can slow down the recognition and removal processes of other DNA lesions. However, with regard to anticancer therapy (radio/chemo), the presence of OXIa in the structure of clustered DNA damage can result in improved cancer treatment outcomes.

Theoretical design of alkaline earthides M+(36 adz) Be− (M+ = V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) with excellent nonlinear optical response and ultraviolet transparency

A novel series of alkaline earthides containing eight complexes based upon 36adz complexant are designed by placing carefully transition metals (V–Zn) on inner side and alkaline earth metal outer side of the complexant i.e., M+(36adz) Be− (M+ = V, Cr, Mn, Fe, Co, Ni, Cu and Zn). All the designed compounds are electronically and thermodynamically stable as evaluated by their interaction energy and vertical ionization potential respectively. Moreover, the true nature of alkaline earthides is verified through NBOs and FMO study, showing negative charge and excess electrons on alkaline earth metal respectively. Furthermore, true alkaline earthides characteristics are evaluated graphically by spectra of partial density state (PDOS). The energy gap (HOMO -LUMO gap) is very small (ranging 2.95 eV–1.89 eV), when it is compared with pure cage 36adz HOMO-LUMO gap i.e., 8.50 eV. All the complexes show a very small value of transition energy ranging from 1.68eV to 0.89eV. Also, these possess higher hyper polarizability values up to 2.8 x 105au (for Co+(36adz) Be−). Furthermore, an increase in hyper polarizability was observed by applying external electric field on complexes. The remarkable increase of 100fold in hyper polarizability of Zn+(36adz) Be− complex is determined after application of external electric field i.e., from 1.7 x 104 au to 1.7 x 106 au when complex is subjected to external electric field of 0.001 au strength. So, when external electric field is applied on complexes it enhances the charge transfer, polarizability and hyper polarizability of complexes and proves to be effective for designing of true alkaline earthides with remarkable NLO response.

Computational Modeling Oriented Substructure Splicing Application in the Identification of Thiazolidine Derivatives as Potential Low Honeybee Toxic Neonicotinoids.

With the aim of identifying novel neonicotinoid insecticides with low bee toxicity, a series of compounds bearing thiazolidine moiety, which has been shown to be low bee toxic, were rationally designed through substructure splicing strategy and evaluated insecticidal activities. The optimal compounds A24 and A29 exhibited LC50 values of 30.01 and 17.08 mg/L against Aphis craccivora, respectively. Electrophysiological studies performed on Xenopus oocytes indicated that compound A29 acted on insect nAChR, with EC50 value of 50.11 μM. Docking binding mode analysis demonstrated that A29 bound to Lymnaea stagnalis acetylcholine binding protein through H-bonds with the residues of D_Arg55, D_Leu102, and D_Val114. Quantum mechanics calculation showed that A29 had a higher highest occupied molecular orbit (HOMO) energy and lower vertical ionization potential (IP) value compared to the high bee toxic imidacloprid, showing potentially low bee toxicity. Bee toxicity predictive model also indicated that A29 was nontoxic to honeybees. Our present work identified an innovative insecticidal scaffold and might facilitate the further exploration of low bee toxic neonicotinoid insecticides.

Excited-state antioxidant capacity of Flavonoids based on solvent effect: A TD-DFT study

Antioxidants have caught a widespread attention because of their applications in various fields such as biomedicine, food additives, cosmetics, and so on, but nevertheless studies on the antioxidant capacity of molecules after photoexcitation are still scarce and rare. In this work, by the application of the density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods, based on the solvent effect, the antioxidant capacity of 4′-Hydroxyflavone (4′-HF), 6-Hydroxyflavone (6-HF), and 7-Hydroxyflavone (7-HF) in the S0 and S1 states are compared. In view of the frontier molecular orbitals (FMOs), depending on the HOMO energy, not only is it analyzed that the electron-donating capacity varies with the solvent, but also that the antioxidant capacity of the mostly molecules in the S1 state is better than those in the S0 state, in particular, the 6-HF in ACN in the S1 state shows a strong antioxidant capacity and is most susceptible to attack by electrophilic radicals, which is also in accordance with the conclusions drawn from the orbital weighted (OW) Fukui functions and OW double descriptors, and global indices including vertical ionization potentials (VIPs), softness (S),and so on. Moreover, absorption spectra indicate the potential of these molecules to resist UV radiation and diminished or even quenched fluorescence intensity is caused by intramolecular charge transfer as evidenced by hole-electron analysis. On the basis of the above photophysical properties, it is shown that these three molecules are expected to be one of the ingredients of sunscreens. In a nutshell, this work not only proposed the influence of solvent effect on antioxidant capacity, but also found the advantage of antioxidant capacity in the S1 state, which provides a strong support for exploring stronger antioxidant capacity.

A DFT and TD-DFT studies of the photosensitizing capabilities of thiophene-based dyes

Dye-sensitized solar cells (DSSCs) play a significant role in the development of affordable, safe, and efficient solar energy technology. In this research, we have designed nine new dyes (J01-09) by modifying an experimentally reported thiophene-based dye (DSS) in the literature. The diethylaniline in the DSS as the electron donating group was replaced with diphenylamine to reduce planarity in the dye. The designed dyes all have donor and acceptor groups linked by a π-linker group (D-π-A). Using DFT and TD-DFT, we investigated the impact of the diphenylamine moieties on the planarity, photochemical and photophysical properties of the modeled dyes in isolation. The optimized structures, UV–Vis absorption, photochemical, and photovoltaic parameters were computed to study the photosensitizing capability of the modeled dyes. The photochemical and photovoltaic parameters of the study include; open-circuit voltage (VOC), light-harvesting efficiency (LHE), driving force of electron injection (ΔGinj), driving force of regeneration (ΔGreg), excited-state lifetime (τ), ionization potential (IP), adiabatic ionization potential (AIP), vertical ionization potential (VIP), electron affinity (EA), chemical hardness (η), electrophilicity index (ω), electron-donating power (ω-) and electron-accepting power (ω+) were calculated. Our findings indicate that only J03 and J08 absorb at longer wavelengths (719 and 753 nm respectively) indicating lower absorption energy bandgap compared to the DSS dye, attributed to the extension of conjugation between the thiophene and donor groups. Also, only J03 and J08 exhibited lower ΔGinj values (−0.985 and −0.667 eV respectively) and ΔGreg values (0.245 and 0.179 eV respectively) implying the dyes can be regenerated spontaneously compared to the DSS dye. Therefore, J03 and J08 are more promising to be developed as a superior photosensitizer in DSSCs.

Ionization Patterns and Chemical Reactivity of Cytosine-Guanine Watson-Crick Pairs.

The front cover artwork is provided by Prof. Papadantonakis' group. The image shows a Watson-Crick Guanine-Cytosine pair, and the difference between vertical and adiabatic ionization potentials. Read the full text of the Research Article at 10.1002/cphc.202300946.

Exploring electron donor and acceptor effects: DFT analysis of ESIPT/GSIPT in 2-(oxazolinyl)-phenols for photophysical and luminophore enhancement.

Understanding excited-state intramolecular proton transfer (ESIPT) is essential for designing organic molecules to enhance photophysical and luminophore properties in the development of optoelectronic devices. In this context, an attempt has been made to understand the impact of substituents on the ESIPT process of 2-(oxazolinyl)-phenol. Electron donating (EDG: -NH2, -OCH3, and -CH3) and electron withdrawing (EWG: -Cl, -Br, -COOH, -CF3, -CN, and -NO2) substitutions have been computationally designed and screened through density functional theory (DFT) and time-dependent density-functional theory (TDDFT) calculations. Furthermore, the ground state intramolecular proton transfer and ESIPT mechanisms of these designed luminophores are explored using the transition state theory. The results reveal that molecules with EDG show higher absorption and emission peaks than molecules with EWG and also indicate that the mobility of charge carriers in 2-(oxazolinyl)-phenol derivatives is significantly influenced by substituents. We found that the EWGs decrease the reorganization energy and increase the vertical ionization potential and electron affinity values, as well as the highest occupied molecular orbital-lowest unoccupied molecular orbital gap, compared to the EDG substituted molecules. Significantly, the excited state (S1) of the keto emission (K) form shows notably larger values for the EDG substitutions. The intersystem crossing pathway efficiency weakens with reduced spin-orbit coupling matrix element in the enol form with electron-donating substituents and vice versa in the keto form during S1-T3 transitions. Our research links intramolecular proton transfers and triplet generation, making these substituted molecules appealing for optoelectronic devices. Introducing EDGs, such as -NH2, boosts the ESIPT reaction in 2-(oxazolinyl)-phenol. This study guides designing ESIPT emitters with unique photophysical properties.

DFT studies of the structural and electronic properties of PdGe n (n = 1–11) clusters and adsorption capacity for some gas molecules

Density functional theory calculations have been employed for the theoretical studies of the geometric structures and electronic characteristics of PdGe n (n = 1−11) clusters. An analysis of the second- order energy differences indicates that PdGe7 and PdGe10 clusters possess superior thermodynamic stability. PdGe10 displays the highest chemical stability and the lowest chemical activity, due to its largest energy gap value (E g). Vertical ionization potential and vertical electron affinity exhibit the decreasing and increasing trends, respectively, with the increase of the number n of Ge atoms. PdGe10 presents the highest electronegativity among these clusters. The analysis on the adsorption properties of PdGe n (n = 7,10) clusters for gas molecules (e.g. CO, NO, NO2, NH3, SO2 and H2S) yields the adsorption structures, adsorption energies, Mulliken charge transfer and the changes in the electronic properties. All the listed gas molecules chemically adsorb onto PdGe7. PdGe10 has a better adsorption performance for NO2, while its adsorption ability for CO is poorer. The potentiality of PdGe n (n = 7, 10) clusters as gas sensors is also evaluated and reveals that NO adsorption significantly affects the electronic properties, especially conductivity, of the systems. PdGe10 has an appropriate NO adsorption capacity and significant charge transfer, with the adsorption energy of −0.278 eV and the recovery time of about 10−9s, indicating its fast response and hence good potentiality as the NO sensor. In contrast, PdGe7 has a higher adsorption capability towards NO with a lower adsorption energy of −1.16 eV, leading to the difficulty in desorption and a longer recovery time of over 12 h.

Density functional theory study on the beryllium clusters doped with silicon atom

An all-electron calculation on BenSi (n = 1–12) clusters has been performed by using density functional theory with the generalized gradient approximation at the PW91 level. The results reveal that the lowest energy geometries of BenSi (n = 1–12) clusters may be generated by substituting a Si atom for one Be atom of the Ben+1 clusters. In addition, Si atom tends to occupy external locations of main Ben clusters and bonds with multiple Be atoms in the BenSi (n > 2) clusters. The average binding energy of BenSi clusters is higher than that of pure Ben+1 clusters, indicating that the doped of the Si atom enhances the cluster's binding force. Compared with pure Ben+1 clusters, the HOMO-LUMO GAP of Be7Si, Be8Si, and Be10Si clusters increase while the HLG of other BenSi clusters(n = 1–3,5,9,11,12) decreas. The vertical ionization potential and vertical electron affinities curves of clusters have the same general trend. The VIP of the cluster decreases gradually while the VEA increases gradually. The doping of the Si atom greatly influences the stability of pure Ben clusters, and the analysis of energy and electronic properties of BenSi clusters reveals that the Be3Si cluster is the magic number structure in the system.

Ionization Patterns and Chemical Reactivity of Cytosine-Guanine Watson-Crick Pairs.

Gas-phase and aqueous vertical ionization potentials, vIPgas and vIPaq respectively and measurements of the molecular electrostatic and local ionization maps calculated at the DFT/B3LYP-D3/ 6-311+G** level of theory and the C-PCM reaction field model for single- and double-stranded CpG and 5MeCpG pairs show that the vIPaq for single- and double-stranded pairs of C-G and 5MeC-G are practically the same, in the range of 5.79 to 5.81 eV. The aqueous adiabatic ionization potentials for single-stranded CpG and 5MeCpG are 5.52 eV and 5.51 eV respectively and they reflect the nuclear reorganization that takes place after the abstraction of the electron. The aqueous adiabatic ionization energy values that correspond to the CpG+. radical cation and the hydrated electron, e-,, being at infinite distance, adIPaq+Vo, are 3.92 eV and 3.91 eV respectively with (Vo=-1.6 eV) Analysis of data suggest that the HOMO-LUMO energy gap in the hard/soft-acid/base (HSAB) concept cannot be used a priori to determine the effect of cytosine methylation on the guanine enhanced oxidative damage in DNA.

Benchmarking model chemistry composite calculations for vertical ionization potential of molecular systems

In chemical science, the vertical ionization potential (VIP) is a crucial metric for understanding the electronegativity, hardness and softness of chemical material systems as well as the electronic structure and stability of molecules. Ever since the last century, the model chemistry composite methods have witnessed tremendous developments in computing the thermodynamic properties as well as the barrier heights. However, their performance in realm of the vertical electron processes of molecular systems has been rarely explored. In this study, we for the first time benchmarked the model chemistry composite methods (e.g., CBS-QB3, G4 and W1BD) in comparison with the commonly used Koopmans's theorem (KT), electron propagator theory (e.g., OVGF, D2, P3 and P3+) and CCSD(T) methods in calculating the VIP for up to 613 molecular systems with available experimental measurements. The large-scale test calculations strongly showed that the CBS-QB3 model chemistry composite technique can be well recommended to calculate VIP from the perspectives of accuracy, economy and applicability. Notably, the VIP values of up to 7 molecules were identified to have the absolute errors of larger than 0.3 eV at all calculation levels, which have strong hints that their VIP experimental values should be re-investigated.

On the antibacterial photodynamic inactivation mechanism of Emodin and Dermocybin natural photosensitizers: A theoretical investigation.

A DFT and TDDFT study has been carried out on monomeric anthraquinones Emodin and Dermocybin (Em, Derm) recently proposed as natural antibacterial photosensitizers able to act also against gram-negative microbes. The computational study has been performed considering the relative amount of neutral and ionic forms of each compound in water, with the variation of pH. The occurrence of both Type I and Type II photoreactions has been explored computing the absorption properties of each species, the spin-orbit coupling constants (SOC), the vertical ionization potentials and the vertical electron affinities. The most plausible deactivation channels leading to the population of excited triplet states have been proposed. Our data indicate Emodin as more active than Dermocybin in antimicrobial photodynamic therapy throughout the Type II mechanism. Our data support a dual TypeI/II activity of the monomeric anthraquinones Emodin and Dermccybin in water, in all the considered protonation states.