Split-valence 6-31G Research Articles

Chemical modification and doping of poly(p-phenylenes): A theoretical study.

Conjugated polymers (CPs) have been recognized as promising materials for the manufacture of electronic devices. However, further studies are still needed to enhance the electrical conductivity of these type of organic materials. The two main strategies for achieving this improvement are the doping process and chemical modification of the polymer chain. Therefore, in this article, we conduct a theoretical investigation, employing DFT calculations to evaluate the structural, energetic, and electronic properties of pristine and push-pull-derived poly(p-phenylene) oligomers (PPPs), as well as the analysis at the molecular level of the polymer doping process. As a primary conclusion, we determined that the PPP oligomer substituted with the push-pull group 4-EtN/CNPhNO2 exhibited the smallest HOMO-LUMO gap (Eg) among the studied oligomers. Moreover, we observed that the doping process, whether through electron removal or the introduction of the dopant anion ClO4-, led to a substantial reduction in the Eg of the PPP, indicating an enhancement in the polymer's electrical conductivity. DFT calculations were conducted using the PBE0 functional along with the Pople's split valence 6-31G(d,p) basis set, which includes polarization functions on all atoms (B97D/6-31G(d,p)).

Levobunolol-imprinted polymer: a theoretical study.

Levobunolol is a β-blocker drug prescribed for the control and prevention of cardiovascular events, such as individuals with cardiac arrhythmia or a history of myocardial infarction. Creating a levobunolol-specific molecularly imprinted polymer (MIP) allows for enhanced selectivity, efficient sample preparation, controlled drug delivery, and improved sensing and detection capabilities. In this sense, the aim of this study was to obtain through DFT calculations the synthesis protocol of a MIP for levobunolol testing different functional monomers (FMs), solvents, and cross-linker agents (CLAs). The analysis of structural and energetic data led to the identification of the optimal MIP synthesis parameters, which involves the use of (trifluoromethyl)-arylic acid (TFMAA) as the functional monomer, toluene and chloroform as the solvents, and pentaerythritol triacrylate (PETRA) as the cross-linking agent. This rational design offers valuable insights for experimentalists seeking to efficiently synthesize a MIP for this important β-blocker drug. DFT calculations were conducted using the B97D functional along with the Pople's split valence 6-31G(d,p) basis set, which includes polarization functions on all atoms (B97D/6-31G(d,p)).

Introducing a novel C50N10 azafullerene with chained nitrogen atoms on a buckyball pole: structure, stability, vibration, and electronic properties.

Fullerenes are of high significance due to their unique chemical properties and various applications in technology, particularly materials science, drug delivery, electronics, and nanoelectronics. In the recent years, many attempts have been focused to introduce new heteroatom-doped fullerenes having advanced chemical properties and tunable electronic traits, which make them a potential candidate for application in many branches of sciences. In this study, a novel C50N10 azafullerene with a fascinating structure of chained nitrogen atoms on a buckyball pole, with different electronic and optical properties compared to its other analogs, is introduced and trace of N-N substructures on the surface of C60 fullerene cage is investigated. For this molecule, four structural isomers including 3 structures with chain N atoms on a fullerene buckyball pole (NP isomers) and one isomer with separated N atoms (SN isomer) have been studied. All isomers have been studied with and without symmetry constraints, and the symmetry influence on the structure and stability of each isomer has been investigated. Although the studied NP structures have lower stability than the SN isomer, some reasons (such as their more all-carbon hexagonal rings, breaking some of their N-N bonds for partial opening of the cage and creating bigger rings in order to get rid of the unfavorable strain, as well as decreasing the N-N lone pair repulsions) lead to the acceptable stability of these structures with the bonded N atoms. The results of atomization energy and vibrational frequency calculations indicate that isomers with the bonded N atoms have acceptable stabilities and do not decompose into their constituent components. Investigation on the structural parameters demonstrates important roles of the number of all-carbon hexagonal rings, the number of N-N junction, and the molecule symmetry in the stability of the structures with the bonded N atoms. Study on the electronic and optical properties indicates that the target structures exhibit high electronic polarizability, relatively small HOMO/LUMO gap, high first- and second-order hyperpolarizability, and also large third-order nonlinear optical properties. All calculations have been performed using Gaussian G09 software using density functional theory (DFT) approach. Three-parameter Beck hybrid exchange functional (B3) hybridized with nonlocal correlation functional of Lee, Yang, and Parr (LYP) has been employed as the level of DFT calculations. All optimizations have been performed at double-zeta polarized (DZP) split valence 6-31G(d,p) and also at split valence TZP 6-311G(d,p) basis sets. The global minimum structures have been confirmed by frequency calculations at the same level of optimizations. The natural bond orbital (NBO) analyses, frontier orbital surfaces imaging, atomic charges, and charge transfer analyses have been achieved by GenNBO program package.

Role of radical quenching activity of dihydrocanaric acid in the treatment of cancer-experimental and theoretical.

In the present study, we have experimentally and theoretically studied the free-radical quenching property of dihydrocanaric acid (DCA) isolated from seedpods of Holarrhena antidysenterica. A modified method was used to estimate the nitric oxide scavenging effect of the DCA (significant activity of 75.22%) along with methanolic extract of seed pods of Holarrhena antidysenterica (72.80%) compared to the ascorbic acid as standard (40.60%). Studies have also been conducted for superoxide scavenging activity of the DCA (78.82%) and methanolic extract of seed pods (84.28%) compared to quercetin as standard (82.08%). Theoretically, it has been determined by density-functional theory(DFT) calculations using M06-2X hybrid functional and the double-ζ- split-valence 6-31G (d, p) basis set that the nitric oxide scavenging activity of the compound is by the addition of NO radical at double bond position. Predicted biological activity profile of DCA suggests that it has less activity probability (Pa) for toxicity (Pa = 0.730), cytotoxicity (Pa = 0.208), compared to those chemical entities that are already known as anticancer agents indicating that DCA is less toxic and more tolerable for normal cells. Furthermore, molecular docking studies of the DCA with different studied cancer-related receptors [Estrogen receptor (-60.12kcal/mol), epidermal growth factor receptor (EGFR) (-30.33kcal/mol), estrogen receptor alpha (-4.82kcal/mol), uPAR (-32.55kcal/mol) and an enzyme having lipid kinase activity phosphoinositide 3-kinase (-55.94kcal/mol)] were found to have better binding affinities compared to betulinic acid and doxorubicin. Thus, our findings suggest that the DCA could be a safer and effective alternative in fighting cancer with minimal side effects.

Synthesis, electronic structure and spectral fluorescent properties of vinylogous merocyanines derived from 1,3-dialkyl-benzimidazole and malononitrile

A vinylogous series of merocyanines were synthesized with 1,3-dibutyl-benzimidazole and malononitrile residues as the donor and acceptor terminal groups. These dyes do not comprise carbonyl groups, which are prone to the strong specific solvation by polar solvents up to hydrogen bond formation, and nevertheless they possess distinct reversed solvatochromism, i.e. their molecules have very high dipolarity. At that, they are soluble in a wide range of solvents from n-hexane to ethanol and do not aggregate readily. They were studied thoroughly by UV/Vis, fluorescence, IR, and NMR spectroscopy methods. Their structure and spectral properties in the ground and excited fluorescent states were modelled at the DFT level both in vacuum and in solvents of various polarities by using the PCM solvent field simulation. The calculations were performed using several hybrid functionals (B3LYP, CAM-B3LYP, and wB97XD) and the split-valence 6-31G (d,p) basis set.

Scaled Quantum Mechanical scale factors for vibrational calculations using alternate polarized and augmented basis sets with the B3LYP density functional calculation model

The Scaled Quantum Mechanical (SQM) method of scaling calculated force constants to predict theoretically calculated vibrational frequencies is expanded to include a broad array of polarized and augmented basis sets based on the split valence 6-31G and 6-311G basis sets with the B3LYP density functional. Pulay’s original choice of a single polarized 6-31G(d) basis coupled with a B3LYP functional remains the most computationally economical choice for scaled frequency calculations. But it can be improved upon with additional polarization functions and added diffuse functions for complex molecular systems. The new scale factors for the B3LYP density functional and the 6-31G, 6-31G(d), 6-31G(d,p), 6-31G+(d,p), 6-31G++(d,p), 6-311G, 6-311G(d), 6-311G(d,p), 6-311G+(d,p), 6-311G++(d,p), 6-311G(2d,p), 6-311G++(2d,p), 6-311G++(df,p) basis sets are shown. The double d polarized models did not perform as well and the source of the decreased accuracy was investigated. An alternate system of generating internal coordinates that uses the out-of plane wagging coordinate whenever it is possible; makes vibrational assignments via potential energy distributions more meaningful. Automated software to produce SQM scaled vibrational calculations from different molecular orbital packages is presented.

Theoretical investigation of new thiazolothiazole-based D-π-A organic dyes for efficient dye-sensitized solar cell

Novel ten organic donor-π-acceptor dyes (D-π-A), used for dye-sensitized solar cells (DSSCs), based on thiazolothiazole were studied by density functional theory (DFT) and time dependant DFT (TDDFT) approaches to shed light on how the π-conjugation order influence the performance of the dyes. The electron acceptor (anchoring) group was 2-cyanoacrylic for all dyes whereas the electron-donor unit varied and the influence was investigated. The theoretical results have shown that TDDFT calculations using the Coulomb attenuating method CAM-B3LYP with the polarized split-valence 6-31G (d,p) basis sets and the polarizable continuum model (PCM) were reasonably capable of predicting the excitation energies, the absorption and the emission spectra of the molecules. The LUMO and HOMO energy levels of these dyes can ensure a positive effect on the process of electron injection and dye regeneration. The trend of the calculated HOMO–LUMO gaps nicely compares with the spectral data. Key parameters in close connection with the short-circuit current density (Jsc), including light-harvesting efficiency (LHE), injection driving force (ΔGinject) and total reorganization energy (λtotal), were discussed. In addition, the estimated values of open-circuit photovoltage (Voc) for these dyes were presented. The calculated results of these dyes reveal that the D6 dye can be used as a potential sensitizer for TiO2 nanocrystalline solar cells due to its best electronic and optical properties and good photovoltaic parameters.

Density functional theory studies of new bipolar carbazole–benzothiazole: Electronic and vibrational properties

An intramolecular donor–acceptor compound containing carbazole as a donor group and two benzothiazole rings as electron acceptors, has been theoretically studied using the density functional theory (DFT) with the hybrid B3LYP exchange correlation function and the split valence 6-31G* basis set. The ground-state geometries’ optimization was carried out, showing a reduction in the band gap when going from the bicarbazole ((Cz)2) to the carbazole attached to benzothiazole rings in both sides (Cz–(Bzt)2). Structural parameters, electronic and vibrational properties have been analyzed and discussed in terms of conjugative pathway between the electron-donating and electron-accepting moieties. It is predicted that benzothiazole systems exhibit large optical responses based on intramolecular charge transfer (CT) process. Optical properties may be altered by changing the compound’s molecular structure by a series of π-bridges, such as ethylene (eth) and phenylene-vinylene (PV) units. These modifications lead to obtain a resulting compound having better optoelectronic properties, through the redistribution of its HOMO and LUMO energy levels. On the other hand and in order to check the real properties of the resulting compound, calculations have also been performed for all compounds in solvated media (chloroform). The obtained results reveal a significant influence of solvation on optical properties, due to the change of the spectral response caused by the increase of ground state CT process.

Micro-solvation of the Zn2+ ion—a case study

The structures and thermodynamic parameters of hydrated zinc ion clusters incorporating a single zinc ion and up to eighteen water molecules have been determined with a quantum mechanical hybrid density functional, namely B3LYP using cc-PVDZ basis functions for H and O and a split valence 6-31G (d, p) basis function for Zn. The geometries for all the zinc ion water clusters are optimized with several initial guess structures and without imposing any initial symmetry restriction. Zinc metal ion is found to be preferably four coordinated for smaller sizes of hydrated cluster but attains an octahedral coordination for larger sizes (n >or= 11) of hydrated cluster. Structures with seven or more than seven water molecules attached directly to the central zinc ion are not found. The calculated gas phase coordination number in the first solvation sphere of a large hydrated zinc metal ion is found to be six and the same is also confirmed in the force field based classical molecular dynamics simulation study for an aqueous zinc ion and thus confirms the experimental findings. The equilibrium zinc-oxygen distance of 2.09328 A at the present B3LYP level of study is in excellent agreement with the X-ray diffraction result of 2.093 +/- 0.002 A for a hexahydrated zinc cluster.

Microhydration of Cs+ ion: A density functional theory study on Cs+–(H2O)n clusters (n=1–10)

Structure, energy enthalpy, and IR frequency of hydrated cesium ion clusters, Cs+-(H2O)n (n=1-10), are reported based on all electron calculations. Calculations have been carried out with a hybrid density functional, namely, Becke's three-parameter nonlocal hybrid exchange-correlation functional B3LYP applying cc-PVDZ correlated basis function for H and O atoms and a split valence 3-21G basis function for Cs atom. Geometry optimizations for all the cesium ion-water clusters have been carried out with several possible initial guess structures following Newton-Raphson procedure leading to many conformers close in energy. The calculated values of binding enthalpy obtained from present density functional based all electron calculations are in good agreement with the available measured data. Binding enthalpy profile of the hydrated clusters shows a saturation behavior indicating geometrical shell closing in hydrated structure. Significant shifts of O-H stretching bands with respect to free water molecule in IR spectra of hydrated clusters are observed in all the hydrated clusters.

Polymeric light emitting properties and structural relationships of fluorene-based conjugated copolymers containing various hole transporting derivatives

A series of new fluorene-based alternating polymers (PF-CZ50, PF-DPA50, PF-PXZ50, PF-PZB50) composed of comonomers containing well-known hole-transporting moieties, namely carbazole, diphenylamine, phenoxazine, and phenothiazine, respectively, were synthesized via Suzuki coupling reactions. The molecular structures of the polymers were characterized with 1H NMR spectroscopy and elemental analysis, and their photophysical, electrochemical, and electroluminescence properties were investigated. The absorption and photoluminescence (PL) emission maxima of the copolymers in the solid state varied depending on which hole-transporting unit was present. Although the polymers’ LUMO levels are similar, the differences between their HOMO levels mean they have different hole-transportation properties. Light-emitting devices using the polymers as emitting layers were fabricated with ITO/PEDOT:PSS/polymer/Ca/Al configurations. The emitted light of these polymers ranged from yellowish green to red for the sequence PF-CZ50, PF-DPA50, PF-PXZ50, and PF-PZB50. Especially, PF-PXZ50 and PF-PZB50 emitted almost pure red with good brightness. The planarity of the hole-transporting moieties in the polymers is the main factor affecting the efficiency of these electroluminescence (EL) devices. The planarity of each hole-transporting moiety was calculated by computational analysis using the ab initio Hartree–Fock (HF) with the split-valence 6-31G∗ basis set. As the magnitude of the non-planarity of the hole-transporting moieties increased, it was found that the EL quantum efficiency of the polymers was enhanced. Compared to PF-CZ50 containing planar carbazole moieties, PF-DPA50 containing a non-planar diphenylamine moiety showed better EL performances without a significant change of the emitting color. In the case of PF-PXZ50 and PF-PZB50, their emission color was red-shifted, and the EL quantum efficiency of their LED devices was enhanced, with respect to the result for PF-CZ50, because of their extra heteroatoms (oxygen and sulfur respectively), which bend the molecules and strengthen their activities as electron donors.

Geometrical and electronic properties of neutral and charged cesium clusters Csn(n=2–10): A theoretical study

We have investigated the structure and electronic properties of cesium clusters following all electron ab initio theoretical methods based on configuration interaction, second-order Moller-Plesset (MP2) perturbation theory, and density-functional theory. Becke's three-parameter nonlocal hybrid exchange-correlation functional (B3LYP) is found to perform best on the present systems with a split valence 3-21G basis function. We have calculated the optimized geometries of neutral and singly charged cesium clusters having up to ten atoms, their binding energy per atom, ionization potentials (IPs), and adiabatic electron affinity (EA). Geometry optimizations for all the clusters are carried out without imposing any symmetry restriction. The neutral clusters having up to six atoms prefer planar structure and three-dimensional structure is preferred only when the number of atoms in a cluster is more than six. There is a good agreement between the present theoretical and reported experimental IP values for the neutral clusters with cluster size n<or=10. Calculated EA is also in good agreement with the available experimental data for the small Cs clusters. Similar calculations have also been carried out for small Rb clusters and the performance of B3LYP is equally good. Thermodynamic properties such as enthalpy and entropy for small Cs and Rb clusters have also been calculated and are well compared with the experimental data.

Reactivity of C10H7+ and C10D7+ with H2 AND D2.

We have investigated, both theoretically and experimentally, the reactions of naphthylium C10H7+ and d-naphthylium C10D7+ ions with H2 and D2. Cross sections as functions of the collision energy have been measured for a variety of reaction channels. Theoretical calculations have been carried out at the density functional theory level which utilizes the hybrid functional B3LYP and the split-valence 6-31G* basis set. The key features of the potential energy surfaces and the relevant thermochemical parameters have been calculated and they provide insights on the reaction mechanisms. The bimolecular reactivity of C10H7+ with H2 is dominated by the production of naphthalene cation C10H8+. The reaction is not a direct atom-abstraction process, but instead it proceeds via the formation of a stable intermediate complex C10H9+ of sigma type geometry, with a significant mobility of hydrogen along the ring. This mobility allows the scrambling of the hydrogen atoms and causes the successive statistical fragmentation of the complex into a variety of product channels. Elimination of one H(D) atom appears to be favored over elimination of one H2 or HD molecule. Alternatively, the intermediate complex can be stabilized either by collision with a third body or by emission of a photon.

Reactions of N+ ions with benzene: a theoretical study on the C6NH6+ potential energy surface

The nitrenium ions of formula C6NH6+ arising from the reaction between benzene molecules and atomic nitrogen ions, N+(3P), are investigated by means of theoretical methods so that their structures and relative stabilities are calculated. Our study is carried out by utilizing the DFT hybrid functional B3LYP in conjunction with the split valence 6-31G* basis set. Both the triplet and the singlet state C6NH6+ cations are considered. The electron deficient N+ ions attack the π electron density of benzene and yield the cation labelled T1 in which the nitrogen interacts with the edge of benzene. This addition is exothermic by 7.69 eV and barrierless. From T1, the insertion of N+ into the benzene CC bond gives the triplet azepine nitrenium cation, T5, whilst its insertion into the CH bond yields the triplet phenylnitrenium cation, T6, via the intermediate T3. However, further C6NH6+ structures and isomerization pathways are investigated in order to obtain a comprehensive analysis of the potential energy surface under study.

Reactions of N+ ions with benzene: a theoretical study on the C6NH6+ potential energy surface

The nitrenium ions of formula C6NH6+ arising from the reaction between benzene molecules and atomic nitrogen ions, N+(3P), are investigated by means of theoretical methods so that their structures and relative stabilities are calculated. Our study is carried out by utilizing the DFT hybrid functional B3LYP in conjunction with the split valence 6-31G* basis set. Both the triplet and the singlet state C6NH6+ cations are considered. The electron deficient N+ ions attack the π electron density of benzene and yield the cation labelled T1 in which the nitrogen interacts with the edge of benzene. This addition is exothermic by 7.69 eV and barrierless. From T1, the insertion of N+ into the benzene CC bond gives the triplet azepine nitrenium cation, T5, whilst its insertion into the CH bond yields the triplet phenylnitrenium cation, T6, via the intermediate T3. However, further C6NH6+ structures and isomerization pathways are investigated in order to obtain a comprehensive analysis of the potential energy surface under study.

Substituent effects on benzdiyne: a density functional theory study.

Density functional theory (DFT) studies were performed to investigate the effect of substituents on the properties of benzdiyne derivatives. Twelve substituted benzdiynes-C(6)X(2), where X = F, Cl, Br, Me, CF(3), CN, OH, NO(2), NH(2), OMe, NMe(2), and Ph-were considered along with the unsubstituted 1,4-benzdiyne. The structures, vibrational frequencies, and IR intensities of these benzdiynes were studied with a popular three-parameter hybrid density functional (B3LYP) combined with the split-valence 6-31G(d) basis set and Dunning's correlation-consistent polarized triple-zeta (cc-pVTZ) basis set. The relative stabilities of the substituted benzdiynes were studied with the help of reaction energies of isodesmic reactions, which showed that the electron-withdrawing groups destabilized the benzdiynes more than they did the corresponding benzenes, whereas the electron-donating groups stabilized the benzdiynes more than they did their benzene counterparts. Correlation analyses revealed that field/inductive effects played a more important role than did resonance effects. The changes in atomic charges and spin populations due to the substituents were also studied. The asymmetric nu(Ctbd1;C) stretching modes obtained were close to the 1500-cm(-)(1) mark. Reinvestigation of the experimental results supported these results; a weak IR band at 1486 cm(-)(1) was assigned to this asymmetric stretching mode in C(6)(CF(3))(2) F. Some other benzdiynes also had large IR intensity values for their asymmetric nu(Ctbd1;C) vibrational modes due to the coupling with other vibrational modes. Heats of formation for the substituted benzdiynes were obtained from the reaction energies calculated at the B3LYP/cc-pVTZ level of theory.

Ab-Initio molecular geometry and normal coordinate analysis of pyrrolidine molecule

The molecular geometry of pyrrolidine was quantum mechanically calculated using the split valence 6-31G** basis set. Electron correlation energy has been computed employing MP2 method. The molecule showed an envelope form puckered structure with inter-plane angle of 36.4° and has a total energy of −132976.80 kcal mol −1 of which a −464.86 kcal mol −1 electron correlation energy. The twist form of the molecule showed a twist angle of 10.2° from planarity and has a total energy of −132976.05 kcal mol −1 involving −464.097 kcal mol −1 electron correlation energy. The normal coordinates of the molecule were theoretically analyzed on the basis of the Cs point symmetry of the envelope form. Using initial set of force constants obtained from the ab-initio calculations the fundamental vibrational frequencies were computed. The IR and laser Raman spectra of Pyrrolidine molecules were measured. All the observed vibrational bands including combination bands and overtones were assigned to normal modes with the aid of the potential energy distribution values obtained from normal coordinate calculations. The molecular force field was obtained by refining the initial set of force constants using the least square fit method. The molecular force field was determined by refining the initial set of force constants using the least square fit method instead of using the less accurate scaling factor methods. The determined molecular force field has produced simulated frequencies best match to the observed values. The low frequency molecular out-of-plane deformation modes were observed in both infrared and Raman spectra at 298 and 163 cm −1. The barrier of ring twisting estimated from the observed ring out-of-plane vibrational mode at 163 cm −1 was found 3.1 kcal mol −1.

Ab initio study of conformational properties of cycloocta-1,5-diyne, cyclonona-1,5-diyne and cyclodeca-1,6-diyne

The structure and relative energies for the basic conformations of cycloocta-1,5-diyne ( 1), cyclonona-1,5-diyne ( 2), and cyclodeca-1,6-diyne ( 3) have been calculated by the split-valence 6-31G ∗ basis set. The chiral puckered conformer of 1, with a “non-intersecting” twofold axis of symmetry, is calculated to be more stable than the planar, D 2 h , geometry. The plane-symmetrical envelope geometry of 2 is calculated to be a transition-state, separating the unsymmetrical envelope conformers. Ring inversion of the envelope conformation takes place via twist, C 2, transition-state. The chair and boat conformers of 3 have virtually the same energies, and their interconversion take place via the half-chair transition-state.

Theoretical Studies on the Origin of β-sheet Twisting

Right-handed twisting is a fundamental structural feature of β-pleated sheets in globular proteins which is critical for their geometry and function. The origin of this twisting is poorly understood and has represented a challenge for theoretical chemistry for almost 30 years. Density functional theory using the B3LYP exchange-correlation functional and the split-valence 6-31G** basis set has been utilized to investigate the structure and conformational transitions of single and double-stranded antiparallel β-sheet models to determine the driving force for the right-handed twisting. Right-handed twisting is found to be an intrinsic property of a peptide main chain because of the difference in rotational potentials around N(sp2)−Cα(sp3) and C(sp2)−Cα(sp3) bonds. The difference arises from a tendency of the single Cα(sp3)−C(sp2) bonds to eclipse the lone pair of atoms N(sp2), which results in decreasing absolute values of dihedral angles φ but not ψ. This tendency is suppressed by hydrogen bonding between a...

Density Functional Calculations on Disaccharide Mimics: Studies of Molecular Geometries and Trans-O-glycosidic 3JCOCH and 3JCOCC Spin-Couplings

Density functional theory (DFT) using the B3LYP functional and the split-valence 6-31G* basis set has been used to investigate the structures and conformations of four β-[1→4]-linked disaccharide mimics, 1−4. Systematic functional group substitution at sites near the glycosidic linkage was used to evaluate the effects of sterics and interresidue hydrogen bonding on the preferred glycosidic torsion angles φ and ψ. Using DFT-optimized geometries, the same hybrid functional, and a specially designed basis set, vicinal NMR scalar coupling constants involving carbon (3JCOCH, 3JCOCC) across the glycosidic linkages of 1−4 were calculated as a function of the φ and ψ torsion angles, and the resulting torsional dependencies were compared to recently reported experimental Karplus curves for these coupling pathways (Bose, B.; et al. J. Am. Chem. Soc. 1998, 120, 11158−11173). The new computational data are in excellent agreement with experimental results and confirm the general shape of the experimental curves. For 3...