B3PW91 Functionals Research Articles

Enhancing the performance of pyridyl carboxamide-N,N-dimethyl amino chalcone (PCC) as a dye sensitizer for dye-sensitized solar cells (DSSCs) through the incorporation of electron donor moieties

This study has focused on enhancing the performance of pyridyl carboxamide-N,N-dimethyl amino chalcone (PCC) as a sensitizer for dye-sensitized solar cells (DSSCs) by strategically incorporating electron donor moieties identified in a literature review. Our reviewing the previous reports highlights the pivotal role of electron donors in optimizing light harvesting, electron injection, and overall power conversion efficiency in organic dye sensitizers, particularly those following a donor-bridge-acceptor (D-π-A) architecture. The selected donor moieties, including dithieno[3,2-b:2′,3′-d]thiophene (DTT), benzodithiophene (BDT), triphenylamine (TPA), carbazole (CBZ), and triazatruxene (TAZ), are systematically introduced into the molecular structure of PCC (abbreviated as PCC-DTT, PCC-BDT, PCC-TPA, PCC-CBZ, and PCC-TAZ, respectively). The performance of these modified compounds is rigorously evaluated using density functional theory (DFT) methods. Validation results revealed that the most reliable method for PCC derivative characterization involved the combination of the functional B3PW91 with a 6-31G(d) basis set. The results indicate that the incorporation of certain donor moieties, particularly BDT, significantly enhances the electronic and optical properties of PCC, including lower HOMO energy levels, a narrow energy gap (Egap), enhanced absorption intensity, and a redshift in absorption peaks. Evaluation of photovoltaic properties including electron injection (ΔGinj), and open circuit voltage (Voc), indicated facilitating spontaneous electron injection from the dyes to the TiO2 conduction band. Notably, PCC-TAZ demonstrated the lowest electron regeneration (ΔGreg), suggesting a notable potential for efficient electron regeneration.

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

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

DFT study of the intrinsic electronic, optical, NBO, transport, and thermodynamic properties of 12,12-dimethyl-7-phenyl-7,12-dihydrobenzo[a]acridine-3-carbonitrile (BACN)

In this study, we investigate the structural, vibrational, electronic, optical, transport, and thermodynamic properties of pure BACN using density functional theory (DFT). The B3LYP, B3PW91, CAM-B3LYP and ωB97XD functionals associated with the basis sets 6-31G(d,p) and 6-311G(d,p) were used. With regard to the electronic and transport properties, analysis of the HOMO and LUMO frontier orbitals, the gap values obtained and the reorganisation energies show that BACN is a good donor-acceptor semiconductor and has a good hole transport capacity. The study of non-linear optical properties shows that BACN is a good candidate for applications in nonlinear optics (NLO) because of its first-order hyperpolarisability, which is higher than that of urea. The time density functional theory (TD-DFT) approach was used for the photophysical analysis of BACN. It was found that BACN exhibits a maximum absorption in the near-UV range, peaking at 222.42 nm, and strong emission in the near-UV range with a maximum wavelength value of 229.75 nm through TD-CAM-B3LYP/6-311G(d,p). The Stokes shift values obtained indicate that the molecule is chemically stable. The full width at half-maximum (FWHM) and radiative lifetime values for this molecule are 19.924 nm and 16.071 ns, respectively. These results show that BACN is a fluorescent material that can be used as an emitter material for designing and improving the colour purity of organic light-emitting diodes (OLEDs).

Phenomenological description of the acidity of the citric acid and its deprotonated species: informational-theoretical study.

In spite of the fact that molecular acidity is a fundamental physicochemical property of molecular systems, the vast majority of theoretical studies have focused attention on monoprotic acids and on the prediction of pKa's. Polyprotic acids, represent a challenge for electronic structure calculations since the multiple acidic sites result in a vast group of species with different conformations and reactivities. In this work, Information-theoretic (IT) concepts of localizability, order and uniformity are applied to the Citric Acid and its deprotonated species through the one-electron density functionals: Shannon entropy (S), Fisher information (I) and Disequilibrium (D), respectively. We pursue the goal of characterizing the acidity of the aforementioned species with the aim to associate the IT concepts to chemical features such as the polarizability of the protonated/deprotonated species, the liability of the acidic sites, atomic electrostatic potentials, covalent bonding. IT analyses looks very promising for future studies on the acidity of specific deprotonation-sites of polyprotic acids. Density functional theory (DFT) calculations were performed with Gaussian 09 program. A sensitivity analysis of the IT-measures was performed for the citric acid and the citrate using B3LYP, B3PW91, BPW91, M05-2X, M06-2X and PBEPBE functionals with the 6-311++g(3df,2p), 6-311++g(d,p), 6.311+g(d,p) and aug-cc-pVDZ basis sets. The rest of the analysis was performed with the M05-2X/6-311+G(d,p) level of theory. Additionally, aqueous media was considered by use of the SMD solvent model. The IT-measures were calculated using a suite of programs developed in our laboratory jointly with the DGRID software package.

Optical spectra of EGFR inhibitor AG-1478 for benchmarking DFT functionals

Optical spectroscopy (UV–vis and fluorescence spectroscopy) is sensitive to the chemical environment and conformation of fluorophores and therefore, serves as an ideal probe for the conformation and solvent responses. Tyrosine kinase inhibitors (TKI) such as AG-1478 of epidermal growth factor receptor when containing a quinazolinamine scaffold are fluorophores. It is, however, very important to benchmark density functional theory (DFT) method against optical spectral measurements, when time-dependent DFT is applied. In this study, the performance of up to 22 DFT functionals is benchmarked with respect to the measured optical spectra of AG-1478 in dimethyl sulfoxide (DMSO) solvent. It is discovered when combined with the 6–311++G(d, p) basis set, there are top seven functionals; B3PW91, B3LYP, B3P86, PBE1PBE, APFD, HSEH1PBE, and N12SX DFT-VXC functionals are identified as the top performers. Becke’s three-parameter exchange functional (B3) tends to generate accurate optical spectra to form the best three functionals, B3LYP, B3PW91 and B3P86. Specifically, B3PW91 was recommended for studying the optical properties of 4-quinazolinamine TKIs, B3LYP was found to be excellent for absorption spectrum, while B3P86 was identified as the best for emission spectrum. Any further corrections to B3LYP, such as CAM-B3LYP, LC-B3LYP, and B3LYP-D3 result in larger errors in the optical spectra of AG-1478 in DMSO solvent. These best three (B3Vc) functionals are reliable tools for optical properties of the TKIs and therefore the design of new agents with larger Stokes shift for medical image applications. To obtain reliable optical spectra for this class of 4-quinazolinamine based TKIs, it is important to include the electron correlation energy.

Properties of 3-fluoroprop-2-enoic acids, chemical shifts and indirect spin-spin coupling constants: A DFT study

Nuclear magnetic resonance (NMR) parameters, shielding constants, and indirect spin-spin coupling constants (SSCC) in a large set of model compounds were calculated using the combination of the B3PW91, B3LYP, and BHandH functionals with the 6-311+(d,p), 6-311++G(d,p), 6-311++G(2d,p), and 6-311++G(3df, 3pd) basis sets, in order to verify the most appropriate methods for calculating these parameters. Selected methods were applied to calculate the NMR parameters in (2E)- and (2Z)-3-fluoroprop-2-enoic acids. Optimization of structures revealed four stable rotamers of each isomer, E and Z, of 3-fluoroprop-2-enoic acid. The internal molecular energy of s-cis and s-trans syn rotamers indicated that they are favorable in solution. All rotamers of 3-fluoroprop-2-enoic acid are coplanar except E s-trans anti, which has a "twisted" structure due to repulsion between hydrogen atoms CFH and HO. Topological analysis of the electronic structure of molecules including properties of critical points revealed noncovalent F...OH and F...HO bonds in Z s-trans syn and anti rotamers, respectively. The molecules of acid tend to form dimers and trimers in solution via hydrogen bonds O...H, CH...O, and CH...F, with binding energies ranging from a few to over a dozen kcal per mol. Theoretical chemical shifts and SSCCs were analyzed in detail to find a dependence on the geometry of individual rotameters. Calculations revealed a 5J(F,H) of -31 Hz in Z s-trans-anti rotamer containing the F...HO hydrogen bond, while this SSCC ranges from -1.9 to 1.4 Hz in the remaining rotamers. Intermolecular SSCCs across hydrogen bonds range from -3 to 7 Hz in dimers and trimers. Theoretical NMR parameters were compared with available experimental data.

Quantum Chemical Investigations on the Hydrogen-Bonded Interactions of Bioactive Molecule N2-(4-Methoxysalicylidene) Arginine Hemihydrate

The geometry optimization, natural bond orbital analysis, and vibrational analysis of a Schiff base compound N2-(4-Methoxysalicylidene) Arginine Hemihydrate (4MSAH) were carried out using the density functional B3PW91 method with the 6–31 G (d,p) basis set. Natural Bond Orbital (NBO) analysis is carried out to examine the various intra and inter molecular interactions of molecular system. Normal coordinate analysis was carried out to elucidate the vibrational modes and the assignments were made on the potential energy distribution. From the vibrational analysis, it is endorsed that the stretching wave number of hydrogen bond donor COO- and hydrogen bond acceptor NH2 + is shifted due to the interaction. MO (Molecular Orbital) analysis was accomplished to propose the biological activity of the molecule and the impact of the transition of electrons from n→π* was studied using the UV transmittance spectrum. The molecular orbital contributions are studied by using DOS spectral analysis. Topological studies of 4MSAH were conducted utilizing the Electron Localization Function (ELF) and the Local orbital locator (LOL). Hirshfeld surface analysis and reduced density gradient analysis were conducted to investigate distinct covalent and non-covalent interactions. Molecular docking was employed on antifungal proteins to explore protein-ligand interactions and verify the compound’s bioactivity.

Structural and theoretical study based on DFT calculations of 3-Methyl-4-[3-ethoxy-(2-p-metilbenzenesulfonyloxy)-benzylidenamino]-4,5-dihydro-1H-1,2,4-triazol-5-one

The moleculer geometric optimization of 3-Methyl-4-[3-ethoxy-(2-p-metilbenzenesulfonyloxy)-benzylidenamino]-4,5-dihydro-1H-1,2,4-triazol-5-one compound was obtained using HF method and B3LYP, B3PW91 functionals in DFT method at the 6-31G(d,p) basis sets. The experimental spectral investigations of molecule performed using FT-IR values and 1H/13C-NMR chemical shifts. Computational IR data was determined at the Veda4f program. Thereotical 1H- and 13C-NMR(DMSO) isotropic shift values were calculated according to GIAO method. The experimental spectral values were compared with computed data. Experimental data obtained from the literature. Also, the theoretical results obtained with different methods and functionals were compared with each other. Furthermore, chemical hardness (η), electronegativity (χ), ionization potential (I), chemical softness (σ), electron affinity (A) parameters were determined with HOMO-LUMO energies calculations. Thermodynamics properties, mulliken atomic charges, geometric properties, dipole moments, total energy were calculated and the molecular surfaces such as the electron spin potantial (ESP), molecular electrostatic potential (MEP), the total density, the electron density, the electrostatic potential of the molecule were designated. Additionaly, the non linear optical (NLO) properties of the molecule were investigated

Computational Insights on the Potential of Some NSAIDs for Treating COVID-19: Priority Set and Lead Optimization.

The discovery of drugs capable of inhibiting SARS-CoV-2 is a priority for human beings due to the severity of the global health pandemic caused by COVID-19. To this end, repurposing of FDA-approved drugs such as NSAIDs against COVID-19 can provide therapeutic alternatives that could be utilized as an effective safe treatment for COVID-19. The anti-inflammatory activity of NSAIDs is also advantageous in the treatment of COVID-19, as it was found that SARS-CoV-2 is responsible for provoking inflammatory cytokine storms resulting in lung damage. In this study, 40 FDA-approved NSAIDs were evaluated through molecular docking against the main protease of SARS-CoV-2. Among the tested compounds, sulfinpyrazone 2, indomethacin 3, and auranofin 4 were proposed as potential antagonists of COVID-19 main protease. Molecular dynamics simulations were also carried out for the most promising members of the screened NSAID candidates (2, 3, and 4) to unravel the dynamic properties of NSAIDs at the target receptor. The conducted quantum mechanical study revealed that the hybrid functional B3PW91 provides a good description of the spatial parameters of auranofin 4. Interestingly, a promising structure–activity relationship (SAR) was concluded from our study that could help in the future design of potential SARS-CoV-2 main protease inhibitors with expected anti-inflammatory effects as well. NSAIDs may be used by medicinal chemists as lead compounds for the development of potent SARS-CoV-2 (Mpro) inhibitors. In addition, some NSAIDs can be selectively designated for treatment of inflammation resulting from COVID-19.

Investigations of adsorption behavior and anti-cancer activity of curcumin on pure and platinum-functionalized B12N12 nanocages

Recently boron nitride (BN) nanoparticles have been considered as good carrier candidates in drug delivery systems. Herein, the loading of curcumin (CUR) in different possible states onto a platinum functionalized B12N12 nanocage was studied to improve their solubility and stability using density functional theory (DFT) and time-dependent density functional theory (TDDFT) models by B3LYP and B3PW91 functionals. It was found that the Pt atom in complex I can be strongly bound to B12N12 surface through the B---Pt---N coordination bond or B-Pt-N covalent bond compared to complexes II and III. We investigate the adsorption of CUR onto Pt-B12N12 in gas and solvent (water) phases. IR spectra and UV absorption were computed and investigated in order to identify the most significant alteration that take place as a consequence of interactions between the CUR and Pt-B12N12 nanocage. The decorated Pt on the B12N12 nanocage improves the adsorption of CUR with larger binding energy for both functionals. The strong binding of CUR with Pt-B12N12 can happen by larger charge transfer from the CUR to the cage, which leads to a substantial increase in dipole moment and energy gap change. The study of molecular docking indicates that CUR through its β-diketo group adsorbed on Pt and B atoms of the Pt-B12N12 nanocage and showed the best binding affinity and inhibition potential of tyrosine regulated kinase 2 (DYRK2) and human epidermal growth factor receptor 2 (HER2) as compared with the pure B12N12 nanocage. The results of molecular docking and in silico analysis of absorption, distribution, metabolism, excretion, and toxicity revealed that the chosen complexes agree with the Lipinski Rule and have appropriate pharmacokinetic features which could be used as templates for the development of novel anti-inflammatory agents with substantial anticancer activity.

Synthesis, Characterization, Crystal Structure and Quantum Chemical Calculations of 2-oxo-2H-chromen-3-yl Acetate

This paper is focused on a combined experimental and theoretical study of 3-substituted coumarin derivative, the 2-oxo-2H-chromen-3-yl acetate (I). The compound was synthesized by reacting chroman-2,3-dione and acetic anhydride in dried diethyl ether in the presence of dried pyridine and crystallized in the orthorhombic crystal system with Pbca space group. The lattice parameters of the structure are a=14.6770 (1), b=7.1079 (1), c=17.6767 (2) Å, α=β=γ=90° with 8 molecules per unit cell (Z=8). The compound has been characterized structurally by Spectroscopy utilizing ¹H NMR, ¹³C NMR and IR techniques and by crystallography using the X-Ray diffraction (XRD) analysis. In the crystallographic study, the positions of the atoms were determined by direct methods and refined to a final R value of 0.038 for 1768 independent reflections. The stabilization of the structure is provided by intermolecular C-H•••O hydrogen bonds extending along [010] direction. Likewise, the presence and nature of intermolecular contacts are determined by the 3-D molecular Hirshfeld surface and 2-D fingerprint plot analysis which indicate the main contributions to the Hirshfeld surface, 38.7% for O ••• H and 28.7% for H •• H. Moreover, the molecular geometry of (I) was as well minimized utilizing density functional theory (DFT/RB3LYP), the frequency calculations with RB3LYP method, the basic <i>ab initio</i> model i.e the restricted Hartree-Fock (RHF) and the exchange component of Perdew and Wang’s 1991 functional B3PW91 methods with the 6-311⁺⁺G(d, p) basis set in ground state. The derived structural parameters highlight very good correlation with the crystallographic results. Frontier molecular orbitals (HOMO-LUMO), their energy gap, the non-linear optical effects (NLO) and related reactive parameters were also computed to better apprehend the properties of the molecule.

Boron nitride nanostructures as effective adsorbents for melphalan anti-ovarian cancer drug. Preliminary MTT assay and in vitro cellular toxicity

Boron nitride (BN) is an interesting material and has attracted the attention of many scholars in the last decade due to its surprising properties. Herein, a simple and inexpensive method is disclosed for the preparation of hexagonal boron nitride and the synthesized nanosheets are characterized by means of FT-IR, SEM, TEM, XRD, TGA and XPS. Then, the fabricated nanostructure is subjected to the delivery of melphalan anti-cancer drug to attain ~42% loading. After that, density functional theory (DFT) calculations are performed to study the adsorption and detection of melphalan anti-cancer drug on the surface of pure and Mg, C, Al, Si, Ge, and Ga doped boron nitride nanostructures by using B3LYP and B3PW91 functionals. The doped XB11N12 nanostructures facilitate adsorption of melphalan compared to the pristine B12N12 by increasing the electrophilicity and chemical hardness of the doped nanoparticles. However, the B3PW91 functional gives rise to both higher adsorption energy and energy gap difference compared to B3LYP functional. In addition, the PCM and SMD calculations show that the selected adsorption complexes are stable in the water phase, as a preferred medium for the in vivo conditions. Furthermore, the computations show greater sensitivity of GeB12N12 to the presence of melphalan, therefore, this nanostructure can be regarded as a suitable sensor for detection of melphalan anti-cancer drug in biological systems. Finally, the in vitro cellular toxicity and viability of GeB12N12 nanoparticles was examined on OVCAR-3 cancer cells. The inhibitory dose ID50 of GeB12N12 nanoparticles confirmed that this material can be achieved as an acceptable vehicle for delivery of melphalan. Moreover, the effect of GeB12N12 nanoparticles (15 μg/mL) on the average growth curves of OVCAR-3 cancer cells showed a decrease of the MTT signal compared to the untreated cells and GeB12N12 can reduce the metabolic activity of the performed cancer cells.

Strategy for the vibrational circular dichroism study of a glycosylflavonoid evaluated as its peracetate. The case of bioactive 7-O-β-D-glucopyranosylchrysin

As it is difficult to study polyhydroxylated natural products by vibrational circular dichroism (VCD) due to their very limited solubility in infrared transparent solvents, 7-O-β-D-glucopyranosylchrysin (1), isolated from Mimosa rosei, was acetylated to provide 7-O-(2ʹʹ,3ʹʹ,4ʹʹ,6ʹʹ-tetraacetyl-β-D-glucopyranosyl)-5-acetylchrysin (2). Density functional theory (DFT) VCD spectra of 2 were calculated using the B3LYP, B3PW91, and PBEPBE functionals and the DGDZVP basis set to ascertain a good level of theory for calculating this kind of compounds. Statistical comparison of the experimental and calculated VCD spectra revealed that the frequently employed B3LYP and B3PW91 functionals provided good confidence levels with similar statistical results, allowing band assignments for the pyranoside portion of 2. This is the first report on a satisfactory statistical validation of a VCD measurement for such a glycopyranoside. In addition, in vitro cytotoxicity studies of 1 and 2 against the human colon cell line HT-29 and the human melanoma cell line UACC-62 by the MTT method were assayed. Moreover, the immunomodulatory response of 1 and 2 was evaluated by measuring TNF-α, IL-1β, and IL-10 levels by the ELISA technique. The results revealed low cytotoxicity of both compounds against cancer cells. However, flavonoid 1 upregulated the IL-1β production in lipopolysaccharide (LPS)-induced THP-1 macrophage, thus suggesting the potential of this molecule as an immunostimulant for cancer treatment.

Hirshfeld surface and theoretical studies of 2,2,2-trichloro-N,N-bis(2-(2,2,2-trichloroacetamido)phenyl)acetamide compound

The vibrational frequencies, atomic charges and the related properties of the 2,2,2-trichloro-N,N-bis(2-(2,2,2-trichloroacetamido)phenyl)acetamide (H2LNNN) were investi-gated by Ab-initio Hartree-Fock (HF) and Density Functional Theory (DFT) methods such as BLYP, B3LYP, B3PW91 and mPW1PW91 functionals with 6-31G(d,p) and 6-311G(d,p) basis sets. The experimentally determined parameters were compared with those calculated theoretically and they were found to complement each other with a very good correlation. The theoretical vibrational spectrum of H2LNNN molecule was interpreted by means of potential energy distributions using the SQM 2.0 program. The Hirshfeld surface analysis was carried out to discuss the role of the hydrogen bonds and other intermolecular contacts in crystal lattice. Hirshfeld surface analysis revealed the occurrence of Cl⋯H, Cl⋯Cl, Cl⋯C, H···H, O⋯H, C···H and Cl···π interactions that display an important role on the crystal packing stabilization of the compound.

Hypervalent halogen hydrides HalHn (Hal = Cl, Br, I; n = 3, 5, 7): DFT and ab initio stability prediction

Stability—both kinetic and thermodynamic—and structure of hypervalent halogen hydrides and respective ionic species were investigated using B3LYP, B3PW91 and MPW1PW91 DFT functionals and second-order Moller-Plesset perturbation theory (MP2) with Def2-TZVPPD basis set (for I atoms) and aug-cc-pVTZ basis set (for Br, Cl and H atoms). Various dissociation pathways were considered: respective reaction enthalpies and H2 elimination activation enthalpies were calculated. At these levels of theory, all of the HalHn species (Hal = Cl, Br, I; n = 3, 5, 7) have covalently bound local minima (except for ClH7) and have a relatively significant kinetic stability with respect to H2 elimination, which indicates the possibility of them being, at the very least, spectroscopically observable, if not isolable. The first candidates for isolation/observation appear to be IH3 and IH5. To aid future identification of hypervalent halogen hydrides, harmonic frequencies for these compounds were calculated. Also, NBO analyses were performed and natural electron configurations, Wiberg bond indices and HOMO–LUMO gaps for these species were determined.

Spectral and structural properties of carotenoids - DFT and thermochemical calculations

The published data on Raman νC=C values of carotenoids and some polyenes with the number of conjugated C=C bonds (NC=C) up to 19 were tabulated. The experimental data were compared with the DFT calculated ones. It is shown that the dependences of νC=C on 1/NC=C for β-carotene homologues and linear carotenoids lie on two different straight lines, which tend to intersect with increasing NC=C. The DFT calculations with PBE, BPBE, BLYP and BPW91 functionals lead to the frequencies that are smaller than the experimental ones. However, with B3LYP one gets highly overestimated values. For PBE functional the difference between experimental and calculated values increases linearly with NC=C. One may believe that this is due to the increase of vibrations anharmonicity.The C=C bond strengths (DC=C) of 7 polyenes from butadiene to decapentaene were estimated and a linear dependence of DC=C on DFT calculated rC=C values was obtained. Using the dependence, the DC=C values for different С = С bonds of carotenoids were estimated and tabulated.The effective numbers of conjugated C=C bonds (NC=Ceff) of β-carotene homologues were estimated using the published spectral data by comparing the E0-0 values dependences on 1/NC=C for β-carotene homologues and linear carotenoids. It was shown that NC=Ceff increases linearly with NC=C, and for the longest β-carotene homologue – dodecapreno-β-carotene – NC=Ceff is nearly equal to NC=C. It follows from the result, that the longer is the conjugated chain of β-carotene homologue, the greater is the influence of its linear trans-part on the spectral properties of the compound.

The nature of the T=T double bond (T\u2009=\u2009B, Al, Ga, In) in dialumene and its derivatives: topological study of the electron localization function (ELF)

The local electronic structure of the Al=Al bond was studied in dialumene and derivatives of dialumene in which the Al atoms were substituted by B, Ga, or In atoms. DFT calculations were performed using the B3LYP, B3PW91, PBE0, M06-L, and M06-2X functionals. Topological analysis of the electron localization function described the covalent bonds mentioned above using the disynaptic basins Vi=1,2(B,B), Vi=1,2(Al,Al), V(Ga,Ga), and Vi=1,2(In,In). The basin populations were smaller than 4 e, as expected for a double bond: B=B 2.97 e, Al=Al 3.44–3.5 e, Ga=Ga 3.58 e, and In=In 3.86 e. The Al=Al, Ga=Ga, and In=In bonds were found to be intermediate in character between single and double bonds. Topological analysis of the ρ(r) field for dialumene showed a non-nuclear attractor along the Al=Al bond, with a pseudoatom basin population of 0.937 e. NBO analysis suggested that a double bond occurred only in the molecules containing Al, Ga, or In atoms. The character of the Ga=Ga bond was observed to be strongly dependent on the effective core potential used in the calculations.

DFT calculations of metal-organic I-III-VI semiconductor clusters: Benchmark of exchange-correlation functionals and localized basis sets

The primary objective of this work was to find the numerical methods suitable for DFT calculations of ternary I-III-VI semiconductor quantum dots emerging as new functional materials which demonstrate an increasing need to comprehend their complex physicochemical properties. The benchmarking analysis of 8 exchange-correlation functionals and 11 basis sets including all-electron and effective core potential ones was performed. Four metal-organic molecules, widely used as a single-precursor in the synthesis of A-In-X2 semiconductor quantum dots (A = Cu, Ag; X = S, Se) were considered as simple representatives of ternary semiconductor quantum dots. The geometrical parameters of the optimized structures were compared to the X-ray diffraction data. The hybrid PBE0 and B3PW91 functionals were found to be the best performing methods especially when connected with cc-PVDZ or Def2-SVP basis sets. The methods widely used in the previous calculations of II-VI semiconductor quantum dots, namely B3LYP functional and LANL2DZ or SBKJC basis sets, in this case resulted in lower agreement with the experimental data.

DFT/TD-DFT calculation, photophysical properties, DNA/protein binding and catecholase activity of chelating ligand based trigonal bipyramidal copper(II) complexes

Cu(II) complexes [Cu(L)(bipy)]ClO4 (1) and [Cu(L)(phen)]ClO4 (2) (where HL = 2-[(3-Methylamino-propylimino)-methyl]-phenol, bipy = 2,2′-bipyridine and phen = 1,10-phenanthroline) have been synthesized and characterized by single crystal X-ray diffraction studies, FT-IR spectra, ESI-MS, electronic absorption, and emission spectroscopy. Both the Cu(II) complexes are mononuclear with five coordinated distorted trigonal bipyramidal geometries and the π-conjugated bipy and phen favor the formation of 2D supramolecular structures with CH … π and π … π interactions. DFT/TD-DFT calculations were performed using B3LYP, B3PW91 and MPW1PW91 functionals to explain the experimentally observed molecular structure and electronic absorption spectral properties. Complexes are active for catalytic oxidation of 3,5-di-tert-butylcatechol (3,5-DTBC) to 3,5-di-tert-butylquinone (3,5-DTBQ) in presence of molecular oxygen. Interactions of complexes with bovine serum albumins (BSA) and human serum albumins (HSA) have been studied by electronic absorption and emission spectroscopy and the calculated values of binding constants are 6.91 × 105 L mol−1 (1-BSA), 6.16 × 105 L mol−1 (1-HSA), 6.57 × 105 L mol−1 (2-BSA) and 3.80 × 105 L mol−1 (2-HSA). Electronic absorption and fluorescence spectroscopic studies reveal that interactions of complexes with CT-DNA occur through intercalative binding mode.

Theoretical design of new small molecules with a low band-gap for organic solar cell applications: DFT and TD-DFT study

In search of novel high-performance materials for use in organic solar cells, we used density-functional theory and time-dependent density functional theory to design a series of organic small molecules derived from the recently synthesized BT(-2T-DCV-Hex)2 donor molecule. In this work, we replaced the BT unit by different acceptors in order to improve their electronic properties, optical absorption and performance in organic solar cell applications. We found that the hybrid functional B3PW91 with the 6-31G(d) basis set gave highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of the BT(-2T-DCV-Hex)2 in better agreement with the experimental oxidation and reduction potentials. However, the range-separated hybrid functional WB97XD was the most appropriate functional for describing the maximum absorption wavelength. Our calculation indicate that the designed small molecules donor proposed here are expected to offer better performances compared to the BT(-2T-DCV-Hex)2, such as a lower HOMO energy, a narrower HOMO-LUMO energy gap, a larger absorption range and may lead to power conversion efficiencies reaching the (7–9)% range.