B3LYP-D3 Methods Research Articles

Design of novel molecular switches using the C20 & C40 nanobud

A molecular switch is a molecule that can reversibly switch between two or more stable states under the influence of environmental factors such as electric current or field, presence of other ions, ligands, pH change, light, etc. Using density functional theory calculations at B3LYP, M06-2X, WB97XD and B3LYP-D3 computational level, we investigate the possibility of using C20 & C40 nanobud as a molecular switch. For this purpose, the effect of different electric fields (0, 0.002, 0025, 0.003, 0.004 and 0.006 a.u.) on structural, electrical and nonlinear optical properties was investigated. It was shown that with the increase of the electric field, the dihedral angle and the bond length of the molecule changes greatly, and a sudden change in the dihedral angle can indicate the switch become ON. Also, with the increase of the electric field, the distance between the HOMO and LUMO orbitals decreases, and this changes increased greatly in a certain range of the electric field, which indicates the change of the state of the molecular switch to ON. The effect of the field on the optical properties of the switch also showed that with the increase in the intensity of the field, the values of α, β and μ increased, and this change was in a specific range of a very strong electric field, which corresponds exactly to the change of the dihedral angle and the behavior of HLG. The M06-2X, WB97XD and B3LYP-D3 methods were used to check the accuracy of the data, and it was shown that the results of these two methods are approximately the same as the results of the calculations related to the B3LYP method.

Comparison between PBE-D3, B3LYP, B3LYP-D3 and MP2 Methods for quantum mechanical calculations of polarizability and IR-NMR spectra in C24 isomers, including a novel isomer with D2d symmetry

In this study, we have performed a comprehensive theoretical analysis of C24 isomers in the gaseous phase using the PBE-D3/cc-pVTZ, B3LYP/cc-pVTZ, B3LYP-D3/cc-pVTZ and MP2/6-31G methods. We have also considered the basis set cc-pVTZ for the MP2 method, and carried out optimized (single point) calculations in three isomers (in the remaining two isomers where the convergence was too time consuming) in order to reveal the potentiality of the method. Our investigation covered a wide range of properties, including geometry optimizations, chemical stability, polarizabilities, nuclear screening constants, Fermi (FE), gap (GE) and atomization energies (AE), thermodynamic analysis, reactivity index, as well as IR and NMR spectra. These calculations were performed for the ring (D12h), sheet (D6h) and two cage (D6d and Oh) configurations. Interestingly, we also proposed a new structure, the bracelet (D2d) arrangement, which appeared to be stable according to the PBE, B3LYP and B3LYP-D3 methods, but was classified as a transition state by the MP2 method. The results consistently indicated that the D6h isomer is the most stable one among the C24 isomers studied, while the D2d isomer was found to be the least stable. Regarding the gap energy (GE), the B3LYP and B3LYP-D3 methods consistently yielded higher values compared to the PBE’s, with an average DFT (PBE and B3LYP) GE of 1.89 eV, whereas the MP2 method showed a substantially higher GE value of 7.6 eV, representing an increase of approximately 75%. Additionally, the polarizabilities of the C24 isomers were found to be overestimated by the PBE, B3LYP and B3LYP-D3 methods when compared to the corresponding MP2 values. The PBE-D3 method consistently produced higher polarizabilities for the C24 isomers in comparison to the B3LYP, B3LYP-D3 and MP2 methods. The investigation confirms that the Oh (D12h) isomer has the smallest (largest) polarizability, as agreed upon by all methods. Moreover, the polarizability of D12h is notably affected by the selected DFT method, while that of Oh displays lower sensitivity but shares similarities with D6d. However, for the newly proposed D2d isomer, the polarizability is ranked third (fourth) in ascending order with the PBE-D3 (B3LYP-D3) method. This highlights the importance of considering the electronic correlation and dispersion effects in accurately predicting polarizabilities. The results obtained from the different methods shed light on the impact of the methodology choice on the predicted properties, emphasizing the need for careful consideration when analyzing and interpreting theoretical results for such various geometries.

Structures, vibrational spectra and microbiological activity of 5-methylbenzotriazole tautomers stabilized by N-H···N intermolecular hydrogen bonds

Three tautomeric forms (1H-, 2H-, 3H-) of 5-methylbenzotriazole (5MeBTA) and the tetramer, which includes the 1H-5MeBTA and 3H-5MeBTA tautomers connected by N3−H⋅⋅⋅N3 and N1−H⋅⋅⋅N2 intermolecular hydrogen bonds, have been studied by density functional theory (DFT) using B3LYP, B3LYP-D3 and ωB97XD methods combined with the 6–31++G(d,p) basis set. Calculations for the tetramer have revealed that intermolecular N3⋅⋅⋅N3 distances range from 2.881 to 2.851 Å, while the N1⋅⋅⋅N2 distances vary between 2.965 and 2.915 Å. These distances are very similar to those reported for the crystal of 5MeBTA (R. K. Belter, F. R. Fronczek, CCDC 1971683, 2019). The theoretical Raman and infrared spectra of the tetramer are in a very good agreement with the FT-Raman and FT-IR spectra of 5MeBTA in the solid state, measured in this work. A detailed interpretation of the experimental vibrational spectra has been made on the basis of the calculated potential energy distribution (PED). Microbiological studies in vitro were conducted for 5MeBTA and benzotriazole (BTA) against six bacterial strains (E. coli, K. pneumoniae, P. aeruginosa, B. subtilis, L. monocytogenes and S. aureus) and two fungal strains (A. niger and C. albicans). The results have shown that the substitution by the methyl group at the C-5 atom of BTA leads to an increase in activity against tested strains, in comparison to BTA. For 5MeBTA, the inhibition zones for bacteria and fungi range from 12 mm to 20 mm, and from 13 mm to 24 mm, respectively. The title compound has revealed particularly strong activity against A. niger, C. albicans and L. monocytogenes (with inhibition zones ≥ 20 mm).

Mechanistic Analysis of Alkyne Haloboration: A DFT, MP2, and DLPNO-CCSD(T) Study.

Stereocontrol of the alkyne haloboration reaction has received attention in many experimental but few theoretical studies. Here we present a detailed quantum-chemical study of mechanisms leading to Z versus E isomers of haloboration products, considering acetylene and propyne combined with BCl3, BBr3, and BI3. Calculations using B3LYP-D3, MP2, and DLPNO-CCSD(T) methods are used to study polar reactions between the alkyne and BX3 in the absence and presence of an additional halide anion whose content in the reaction mixture can be controlled experimentally. The formation of anti-haloboration products via radical mechanisms is also explored, namely, by adding BX3 to (Z)-halovinyl radical. For the anti-haloboration of propyne, the radical route is prohibited by the regiochemistry of the initiating halopropenyl radical, while the polar route is unlikely due to a competitive allene generation. In contrast, energetically accessible routes exist for both syn- and anti-bromoboration of acetylene; hence, careful control of reaction conditions is necessary to steer the stereochemical outcome. Methodologically, MP2 results correspond better to the DLPNO-CCSD(T) energies than the B3LYP-D3 results in terms of both reaction barrier heights and relative ordering of energetically close stationary points.

Structural and FTIR spectroscopic studies of matrix-isolated 3-thio-1,2,4-triazole complexes with dinitrogen. First experimental evidence for the UV-induced formation of thiol⋯N2 complexes

Complexes of 3-thio-1,2,4-triazole (ST) with N2 were studied theoretically by the B3LYP-D3 method and experimentally by FTIR spectroscopy combined with the matrix isolation technique and UV laser irradiation. The computational results show that ST interacts specifically with dinitrogen in several different ways. For the 1:1 complexes of the most abundant ST thione tautomer, three stable minima have been located on the potential energy surface. The two most stable structures, containing both the N-H⋯N hydrogen bond and the S⋯N van der Waals contact, were detected experimentally in the argon matrix after deposition. Interestingly, it was found that laser irradiation at λ = 270 nm, apart from generating the thiol tautomer of ST, also leads to the formation of its corresponding complexes, characterized by N-H⋯N hydrogen bonds. What is more, it appeared that the efficiency of hydrogen atom transfer in ST complexed with N2 is lower than in the monomeric form.

Theoretical study on the interaction between cis-2 bis(benzofuro)[60]fullerene derivative and NO dominated double gas molecule

The interaction between cis-2 bis(benzofuro)[60]fullerene derivative and NO dominated double gas molecule was studied at the 6–311G(d,p) basis set level by density functional theory B3LYP-D3 method. The geometric structures of six interaction systems were optimized, and the optimized configurations were analyzed by electronic properties, infrared chromatography and independent gradient model to reveal the essence of intermolecular interaction. The results shows that NONO2, NON2, NOCO, NOCO2 and NOHCN are co-adsorbed on the surface of the compound in physical form, and the binding energies are −77.62 kJ/mol, −24.24 kJ/mol, −27.43 kJ/mol, −39.28 kJ/mol and −36.29 kJ/mol, respectively. The van der Waals interaction between gas molecules makes the three molecular interaction system have synergistic adsorption or competitive adsorption effect. Among them, the synergistic effect of NONO2 co-adsorption system is the biggest, and there is a strong attraction between NO and NO2 molecules. Compared with the interaction system of single gas molecule with cis-2 bis(benzofuro) [60]fullerene derivative, the interaction intensity of double gas molecule with the derivative is significantly improved.

Benchmarking computational chemistry approaches on iminodiacetic acid

In the present study, theoretical harmonic vibrational frequencies (IR and Raman), carbon and proton NMR chemical shifts, geometric parameters, atomic charges (only for heteroatoms), reactivity indices (eLUMO, eHOMO, electronegativity, and hardness), and thermodynamical data (inner energy, enthalpy, Gibbs free energy, and entropy) of iminodiacetic acid (IDA) molecule have been investigated. We utilized ORCA software for B3LYP and HF (combined with Pople and Karlsruhe basis sets) calculations and MOPAC2016 software for semi-empirical calculations (AM1, PM3, and PM6). Theoretical vibrational frequencies and carbon and proton NMR chemical shifts have been compared with the corresponding experimental data. Although there was a strong correlation between the experimental and computational vibrational frequencies at low frequencies (<2200 cm−1), the computational predictions of vibrational frequencies were unsuccessful at high frequencies (>2200 cm−1). Distinctly, the studied computational approaches appeared to perform better in the prediction of carbon and proton NMR chemical shifts. Theoretical vibrational frequencies were also compared to each other to understand the impact of method choice (HF vs B3LYP D3 vs semi-empirical methods), dispersion correction (B3LYP D3 vs B3LYP), water solvation (SMD supplemented vs non-supplemented calculations), the family of basis set (Pople vs Karlsruhe basis sets), numbers of zeta (double vs triple zeta), polarization function (polarized vs nonpolarized basis sets), and diffusion function (diffusion supplemented vs non-supplemented basis sets). Moreover, geometric parameters, heteroatom charges, reactivity indices, and thermodynamical data produced by distinct computational approaches, as well, were compared to each other. Based on these comparisons, we detected critical factors (such as water solvation) acting on the computation of geometries, energies, and charges.

Structure and IR spectroscopic properties of complexes of 1,2,4-triazole and 3-amino-1,2,4-triazole with dinitrogen isolated in solid argon

Complexes of 1,2,4-triazole (TR) and 3-amino-1,2,4-triazole (AT) with N2 were studied computationally employing MP2 and B3LYPD3 methods and experimentally by FTIR matrix isolation technique. The results show that both triazoles interact specifically with dinitrogen in several different ways. For the 1:1 complexes of 1,2,4-triazole five stable minima were located on the potential energy surface. The most stable of them comprises a weak hydrogen bond formed between the NH group of the ring and the lone pair of the nitrogen molecule. The second most stable structure is bound by the N⋯π bond formed between one of the N atoms of the N2 molecule and the triazole ring. Three other complexes are stabilized by the C-H⋯N and N⋯N van der Waals interactions. In the case of 3-amino-1,2,4-triazole, the two most stable dinitrogen complexes are analogous to those found for the 1,2,4-triazole and involve N-H⋯N and N⋯π bonds. In other structures amino or CH groups act as proton donors to the N2 molecule. The N⋯N van der Waals interactions are also present. The analysis of the infrared spectra of low temperature matrices containing TR or AT and dinitrogen indicates that in both systems mostly 1:1 hydrogen-bonded complexes with the NH group interacting with N2 are present in solid argon.

DFT investigates the mechanisms of cross-dehydrogenative coupling between heterocycles and acetonitrile

The mechanisms between CH3CN and 1,3-dimethyl-1H-indole, initiated by DCP (dicumyl peroxide), have been studied with the B3LYP-D3 method with def2TZVP basis set for all atoms, and the SMD model was applied to simulate the solvent of acetonitrile. The computational results show that the homolytic process of DCP, catalysed by CuCl or CuI, can decrease the energy barrier, and the recycle procedure of Cu catalyst has been described. Then the Csp3-H activation of CH3CN has been investigated. The introduction of the cyano group is an anti-Markovnikov reaction and region-selectivity would be fulfilled. Localised orbital bonding analysis, localised orbital locator (LOL) isosurfaces, and electron spin density isosurface graphs could be used to interpret the phenomena. The results could provide valuable insights into these types of interactions and related ones. Highlights The homolytic mechanisms of DCP catalyzed by CuCl or CuI are proposed. The anti-Markovnikov's reaction between 1,3-dimethyl-1H-indole and free radical is investigated. Localized orbital bonding analysis, localized orbital locator (LOL) isosurfaces and electron spin density isosurface graphs have been used to interpret the phenomena.

Matrix Isolation FTIR and Theoretical Study of Weakly Bound Complexes of Isocyanic Acid with Nitrogen.

Weak complexes of isocyanic acid (HNCO) with nitrogen were studied computationally employing MP2, B2PLYPD3 and B3LYPD3 methods and experimentally by FTIR matrix isolation technique. The results show that HNCO interacts specifically with N2. For the 1:1 stoichiometry, three stable minima were located on the potential energy surface. The most stable of them involves a weak, almost linear hydrogen bond from the NH group of the acid molecule to nitrogen molecule lone pair. Two other structures are bound by van der Waals interactions of N⋯N and C⋯N types. The 1:2 and 2:1 HNCO complexes with nitrogen were computationally tracked as well. Similar types of interactions as in the 1:1 complexes were found in the case of the higher stoichiometry complexes. Analysis of the HNCO/N2/Ar spectra after deposition indicates that the 1:1 hydrogen-bonded complex is prevalent in argon matrices with a small amount of the van der Waals structures also present. Upon annealing, complexes of the 1:2 and 2:1 stoichiometry were detected as well.

Adsorption of the guanine molecule over the pristine, Nb-, and Au-doped boron nitride nanosheets: a DFT study

A theoretical study has been conducted onto the pristine, Nb-, and Au-doped boron nitride (BN) nanosheets using DFT calculations with the B3LYP-D3 method in order to evaluate their stabilities and electronic properties. The interaction of the guanine molecule with these clusters was also examined in order to determine their adsorption properties. The calculations show that the HOMO-LUMO energy gap (Eg) of the BN nanosheet was strongly decreased upon its doping with Nb and Au atoms, implying a strong enhancement in its surface reactivity. The interaction of the guanine with the BN nanosheet was found to be weak, which leads a slight variation in its energy gap; therefore, a low sensitivity of this nanosheet toward the guanine molecule was observed. The guanine adsorption over the NbBN cluster is very strong, and the calculated adsorptions energies are in the range of −36.7 to −60.2 kcal mol−1, suggesting a great chemical adsorption. For the AuBN cluster, the guanine molecule has been chemisorbed onto its surface with adsorption energies which vary from −24.2 to −38.4 kcal mol−1, which are lower than those obtained for the NbBN cluster. Upon adsorption process, the energy gap of the NbBN cluster was greatly increased, which leads to a decrease in its electrical conductivity; thereby, it cannot be a suitable sensor for the detection of the guanine molecule. On the contrary, the energy gap of the AuBN cluster was reduced by the effect of the guanine adsorption on its surface, indicating an increase in its electrical conductivity; thus, the AuBN cluster possesses a great electronic sensitivity to the guanine molecule. Based on the transition state theory, the recovery time of the guanine desorption from the AuBN cluster was estimated of 27.6 s, reflecting that the Au-doped BN nanosheet could be employed as an appropriate nanosensor for the guanine molecule detection with a short recovery time.

Asymmetric Spirocyclization Enabled by Iridium and Brønsted Acid-Catalyzed Formal Reductive Cycloaddition

A catalytic, enantioselective spirocyclization of formanilides or formylindolines and enamides has been developed herein. The reaction proceeds through a sequential iridium-catalyzed hydrosilylatio...

Benchmarking DFT-D Dispersion Corrections for Anharmonic Vibrational Frequencies and Harmonic Scaling Factors.

Improvements in the form of the DFT-D empirical dispersion corrections to hybrid density functional theory are shown to have made corrections sufficiently accurate to improve the calculation of both anharmonic frequencies and scaled harmonic vibrational frequencies across a wide range of commonly tested molecules. The Becke-Johnson damping function is noted as being particularly versatile across the molecules tested, and the B3LYP-D3M(BJ) and B3LYP-D3(CSO) methods are found to be the most widely applicable. Dispersion corrections are shown to be important for accurately describing carbon-hydrogen bond stretching vibrations, and standard triple-dipole based three-body terms are found to cause large errors in these anharmonic frequencies. Preliminary results also indicate that there is a cancellation of error at this level of theory when using smaller finite difference step sizes to calculate anharmonic derivatives of the nuclear potential energy surface.

Experimental and Multireference ab Initio Investigations of Hydrogen-Atom-Transfer Reactivity of a Mononuclear MnIV-oxo Complex.

A combined experimental-computational study of hydrocarbon oxidation by the MnIV-oxo complex of the neutral, pentadentate N4py ligand [N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine] offers support for a complex reaction coordinate involving multiple electronic states. Variable-temperature kinetic investigations of ethylbenzene oxidation by [MnIV(O)(N4py)]2+ yield experimental activation parameters that were used to evaluate computationally predicted energy barriers. Both density functional theory (DFT) and multireference complete-active-space self-consistent-field (CASSCF) computations with n-electron valence state perturbation theory (NEVPT2) corrections were employed to investigate the hydrogen-atom-transfer reaction barriers for the 4B1 and 4E states. The 4B1 state is the ground state in the absence of substrate, and the 4E state is related to the ground state by a one-electron MnIV e(dxz,3dyz) to MnIV b1(dx2-y2) excitation. A comparison of the DFT, CASSCF/NEVPT2, and experimental results shows that the B3LYP-D3 method underestimates the activation barriers of both electronic states by ca. 10 kcal mol-1. In contrast, the enthalpic barrier predicted for the 4E state by the CASSCF/NEVPT2 method is within 2 kcal mol-1 of the experimental value. The 4E state is early, with dominant structural distortions in the Mn-Nequatorial distances and perturbations to Mn═O bonding that lead to strong electronic stabilization of interactions between the MnIV-oxo unit and substrate C-H bond. While previous DFT studies were qualitatively correct in their ordering of the 4B1 and 4E transition states, this combined use of experimental and CASSCF/NEVPT2 methods provides an ideal means of assessing the two-state reactivity model of MnIV-oxo complexes.

Corrosion inhibition efficiency of some phosphoramide derivatives: DFT computations and MD simulations

The structural and electronic characteristics of some phosphoramide derivatives with the general formula 4-X-C6H4-C(O)-NH-P(O)(OCH3)2 where X = H, F, Cl, Br, CH3, CF3, CCl3 and CBr3 as well as their H-bonded structures with HCl were investigated for application as corrosion inhibitors using density functional theory (DFT) computations accomplished at both B3LYP-D3 and B3PW91-D3 levels of theory using 6-31+G(d,p) basis set in water. A comparison of the ΔEbinding values using the two B3LYP-D3 and B3PW91-D3 methods established that the B3LYP-D3 provided more negative binding energies. The H…N bond distances in the H-bonded structures 9–16 were varied in the range of 2.179–2.272 Å and 2.109–2.255 Å using the B3LYP-D3 and B3PW91-D3 methods, respectively, indicating the phosphoramides 1–8 formed strong hydrogen bonds with the HCl molecule which was favorable for the inhibition of the corrosion using these compounds. The compounds 8 and 16 (both containing CBr3 substituent) illustrated the lowest band gap and hardness whereas the greatest electrophilicity index among structures 1–8 and 9–16, respectively, approving they had the most reactivity to attach the metal surface and afford the most efficient corrosion inhibition. Consequently, compounds 8 and 16 were proposed as the most appropriate corrosion inhibitors. The molecular dynamics (MD) simulations were performed on PA-Fe and PA-Fe-W systems (where PA = compound 16, Fe = iron and W=H2O) at four temperatures (298.15, 308.15, 318.15 and 328.15 K) and it was found that the strongest PA-Fe interactions were occurred at the lowest temperature confirming the most effective anticorrosion capacity was happened at 298.15 K. For an efficient anticorrosion application, the 3PA-Fe-W was selected as the most suitable anticorrosion system because it exhibited desirable strong interactions between the Fe atoms and PA species as well as moderate diffusion rate of the PA molecules and good anticorrosion loading.

Impact of neutral and acidic species on cycloalkenes nucleation

Non-covalent hydrogen bond interactions between the π cloud of cycloalkenes and three atmospheric common nucleation precursors (H2S, H2O, and MeOH) have been investigated using DFT and CCSD(T). The structures and the energies of the 1:1 and 1:2 adducts were computed with the B3LYP-D3 method. The analysis of the investigated electronic properties and geometric parameters shows that cyclohexene is a stronger hydrogen bond acceptor than cyclopentene, then followed by 1,4-cyclohexadiene and 1,3-cyclohexadiene. Comparable red shifts of the OH-/SH-stretching vibrational frequencies were noticed for the studied clusters. Increasing the ring size enhances the hydrogen bond interaction, and increasing the π delocalization decreases the hydrogen bond interactions. This is further confirmed by Bader’s quantum theory of atoms in molecules. The nonadditivity effects were observed in the trimolecular complexes. All the complexes were analyzed by energy decomposition analysis to divide the interaction energy into individual components. Furthermore, the dipole moments and atmospheric implications were also investigated.

Protonation and Reduction of the FeMo Cluster in Nitrogenase Studied by Quantum Mechanics/Molecular Mechanics (QM/MM) Calculations.

We have performed a systematic computational study of the relative energies of possible protonation states of the FeMo cluster in nitrogenase in the E0-E4 states, i.e., the resting state and states with 1-4 electrons and protons added but before N2 binds. We use the combined quantum mechanics and molecular mechanics (QM/MM) approach, including the complete solvated heterotetrameric enzyme in the calculations. The QM system consisted of 112 atoms, i.e., the full FeMo cluster, as well all groups forming hydrogen bonds to it within 3.5 Å. It was treated with either the TPSS-D3 or B3LYP-D3 methods with the def2-SV(P) or def2-TZVPD basis sets. For each redox state, we calculated relative energies of at least 50 different possible positions for the proton, added to the most stable protonation state of the level with one electron less. We show quite conclusively that the resting E0 state is not protonated using quantum refinement and by comparing geometries to the crystal structure. The E1 state is protonated on S2B, in agreement with most previous computational studies. However, for the E2-E4 states, the two QM methods give diverging results, with relative energies that differ by over 300 kJ/mol for the most stable E4 states. TPSS favors hydride ions binding to the Fe ions. The first bridges Fe2 and Fe6, whereas the next two bind terminally to either Fe4, Fe5, or Fe6 with nearly equal energies. On the other hand, B3LYP disfavors hydride ions and instead suggests that 1-3 protons bind to the central carbide ion.

Isomerism of the Aniline Trimer.

Weaker intermolecular forces expand the isomerization alternatives for molecular aggregation, as observed for the prototype models of the aniline trimer (An3 ) and the monohydrated aniline dimer (An2 -W) when compared to the phenol trimer. In this experiment the aniline clusters were generated in a jet-cooled expansion and probed using broadband (chirped-pulsed) microwave spectroscopy. Three isomers of the aniline trimer and two isomers of the hydrated dimer were detected and characterized in the rotational spectrum. In the homotrimer the weak N-H⋅⋅⋅N hydrogen bonds are assisted by subtle combinations of N-H⋅⋅⋅π and C-H⋅⋅⋅π interactions, producing several competing low-lying ring species in the gas phase. One of the aniline trimers is a symmetric top, topologically equivalent to the only observed phenol trimer. Conversely, addition of a water molecule to the aniline dimer introduces a leading O-H⋅⋅⋅N interaction, making water to behave as dominant hydrogen-bond pivot between the two aniline molecules. This combination of weak intermolecular interactions critically tests the performance of dispersion-corrected or parametrized density-functional methods. Evaluation of the B3LYP-D3(BJ) and M06-2X methods revealed deficiencies of the Truhlar functional to reproduce the experimental rotational data.

Theoretical investigation into the cooperativity effect between the intermolecular π∙π and H-bonding interactions in the curcumin∙cytosine∙H2O system.

In order to reveal the mechanism of drug action and design of DNA/RNA-targeted drugs containing aromatic rings, the cooperativity effects between the intermolecular π∙∙∙π and H-bonding interactions in curcumin(drug)∙∙∙cytosine(DNA/RNA base)∙∙∙H2O were investigated by the B3LYP-D3 and MP2(full) methods with the 6-311++G(2d,p) basis set. The π∙∙∙π interaction plays an important role in stabilizing the linear ternary complexes with the cooperativity effects, and the cyclic structures suffer the anticooperativity effects. The cooperativity or anticooperativity effects are notable, which could lead to a possible significant change in drug activity. The hydration is essentially the cooperativity or anticooperativity effect. These results were confirmed by the atoms in molecules (AIM), reduced density gradient (RDG), and surface electrostatic potentials analyses. The cyclic complexes are more stable, from which it can be deduced that the drug always links with the DNA/RNA base and H2O by the π∙∙∙π or H-bonding interactions, and only in this way can the drug activity be shown. Therefore, the designed DNA/RNA-targeted drugs should possess a certain number of hydrophilic groups in contact with the DNA/RNA base and H2O to reconcile drug activity by the cooperativity effect between the π∙∙∙π and H-bonding interactions, as is in agreement with many of the drugs in use. Graphical abstract RDG isosurface of ternary complex.

Assessment of the performance of four dispersion-corrected DFT methods using optoelectronic properties and binding energies of organic monomer/fullerene pairs

With the aid of different polymer materials, their properties can be adjusted so as to enhance the efficiencies of heterogeneous organic solar cells. It is known that computational investigations involving density functional theory (DFT) can play an important role in identifying polymers with favourable properties and hence in speeding up the process of designing organic solar cells with higher efficiencies. However, what is often not known is which one of the dispersion-corrected DFT (D-DFT) methods gives the most accurate results (relative to the experimental data) for the various properties of conjugated systems such as are found in heterogeneous organic solar cells. In this study, we employ ωB97x-D, B97-D3, B3LYP-D3, and PBE1PBE-D3 and assess their accuracy by computing binding energies and electronic parameters (such as HOMO and LUMO eigenvalues) of the various (promising) molecular pairings of organic monomers and fullerenes. In addition, we employ time dependent DFT (TD-DFT) to determine optical properties of monomers such as their maximum absorption wavelengths and compare them with the experimental findings. Our results show that B97-D3 and B3LYP-D3 methods give the largest binding energies relative to the other D-DFT methods and they yield (relative to experimental values) the most accurate electronic and absorption results.