Carbon-13 NMR Chemical Shifts Research Articles

Synthesis, molecular structure, spectral characterization, and biological activities of ethyl 2-(4-(4-chlorobenzyl)-3-methyl-6-oxopyridazin-1(6H)-yl)acetate

The structure of the ethyl 2-(4-(4-chlorobenzyl)-3-methyl-6-oxopyridazin-1(6H)-yl)acetate (COAP) was revealed using single crystal X-ray diffraction method, was solved and refined using the Bruker SHELXTL Software Package, using the space group P 1 21/n 1, with Z = 4 for the formula unit, C16H17ClN2O3. Its spectroscopic and electronic properties were investigated by spectroscopic methods such as 1H and 13C NMR, FT-IR and UV–vis. The electronic structure properties of the compound were investigated with quantum mechanical calculations. It was observed that crystal packaging is provided by CH…O type hydrogen bonds. Also, spectroscopic properties such as FT-IR vibrational wave numbers, proton and carbon NMR chemical shifts and UV–vis. absorption parameters were calculated. In addition, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) analyses and Molecular Electrostatic Potential (MEP) surface, NBO analysis were computed to understand the reactive regions of the title compound. All computations were performed by using DFT/B3LYP quantum chemical method with 6–311++G(d,p) basis set to compare with the experimental results. The calculations showed that HOMO orbitals localized on π and n orbitals of pyridazine while LUMO orbitals localized on π* orbitals of pyridazine. The major contribution to electronic transitions originated from HOMO LUMO transition calculated at 292.16 nm. Hirshfeld surface analysis was investigated to visualization van der Waals distances, and the space occupied by molecules and to determine the contact regions. The computed geometry parameters and vibrational wavenumbers were in good agreement with the experimental results. Moreover, the potential inhibitory activities of the compound were evaluated on enzymes α-glucosidase. Besides, the compound was tested for it potential in vitro anti-inflammatory activities by Heat induced hemolysis. The results showed that the product had a good percentage of heat induced Hemolysis inhibition.

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.

Conformational stability, quantum computational, spectroscopic, molecular docking and molecular dynamic simulation study of 2-hydroxy-1-naphthaldehyde

Experimental FTIR, NMR and UV-visible spectrum analyses were used to describe the title compound 2-Hydroxy-1-Naphthaldehyde. The optimized molecular geometry and vibrational wave numbers were determined by using the DFT approach and B3LYP/6-311++G(d, p) basis set. VEDA was used to determine the vibrational assignments. The GIAO technique was used to compute carbon and proton NMR chemical shifts in CDCl3. The most reactive location of the 2H1NA molecule, according to MEP map analysis, is the site containing the oxygen atom. TD-DFT approach was used to produce the theoretical UV-visible spectrum in MeOH and gas phase. HOMO-LUMO and Donor-Acceptor (NBO) interactions were investigated for the title compound. In addition, nonlinear optical characteristics, ELF and Fukui activity were investigated. Temperature-dependent thermodynamic characteristics were also computed. The 3D intermolecular interactions of the crystal surface were characterised using Hirshfeld surface analysis, whereas the 2D interactions were explained using fingerprint plots. 2H1NA was stabilized by the development of H—H/H—C/H—O contacts. The bioactive probability of the title molecule was theoretically demonstrated by computing the electrophilicity index. In a biological study six different receptors, molecular docking was performed to evaluate the best ligand-protein interactions and likeness to the active substance. Biomolecular stability was investigated using a molecular dynamics simulation.

Spectroscopic characterization of 4,5-diphenyl-2-(2,4,5-trimethoxyphenyl)-1H-imidazole obtained from the condensation of benzyl. Experimental and DFT approach

An experimental and theoretical study of the 4,5-diphenyl-2-(2,4,5-trimethoxyphenyl)-1H-imidazole [DiPhTMImz] spectroscopic properties were carried out. The molecular structure of compound DiPhTMImz was determined by SCXRD; the compound crystallized in the orthorhombic system and Pna21 space group with Z = 4. Fourier transform infrared (FT-IR) spectroscopy, proton, carbon NMR chemical shift, and absorption wavelength analysis have been performed using the DFT/B3LYP method with a 6–311+G(d,p) basis set. The assignments of main vibrational modes were computed with the scaled quantum mechanism (SQM) method. At the same time, the 13C and 1H isotropic chemical shifts were calculated using the gage-invariant atomic orbital (GIAO) method. Besides, the ultraviolet-visible spectrum was predicted by the time-depend DFT approach. On the other hand, mapped molecular electrostatic potential surfaces (MEPS) were performed to estimate the nucleophilic and electrophilic sites in the molecules. The non-covalent intermolecular interactions energies of several molecular pairs were quantified using the PIXEL method and Hirshfeld surface analysis to evaluate the relative contributions of different interactions, such as the N‒H···N or N‒H···O hydrogen bonds in the crystal structure. The stability of the molecule from hyper-conjugative interactions and charge delocalization has been analyzed using natural bond (NBO) analyses.

Synthesis, structural, spectral, antioxidant, bioactivity and molecular docking investigations of a novel triazole derivative

The structural, spectroscopic and electronic properties of 4-(4-nitrophenyl)-5-(pyridin-3-yl)-2,4-dihydro-3H-1,2,4-triazole-3-thione have been analyzed by using single crystal X-ray diffraction (SCXRD), 1H and 13C NMR chemical shifts and FT-IR spectroscopic methods both theoretically and experimentally. The tautomeric (thiol and thione) energetic analysis results, structural optimization parameters (bond lengths and angles), vibrational wavenumbers, proton and carbon NMR chemical shifts, UV-Vis. parameters, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) analyses and Molecular Electrostatic Potential (MEP) surface have been calculated by using DFT/B3LYP quantum chemical method with 6-311++G(2d,2p) basis set to compare with the experimental results. The computed geometry parameters, vibrational wavenumbers, and NMR chemical shifts have been in good agreement with the experimental results. It should be noted that the radical scavenging activities of the title compound have been evaluated by using different test methods i.e. 2,2-Diphenyl-1-picrylhydrazyl (DPPH), N,N-dimethyl-p-phenylenediamine (DMPD) and 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS). According to obtained results, the title compound displayed DPPH (SC50 19.42 ± 0.11 μg/mL), DMPD (SC50 21.13 ± 0.08 μg/mL) and ABTS (SC50 38.17 ± 0.25 μg/mL) scavenging activities. Also, these results have been compared with Butylated hydroxyanisole (BHA), Rutin (RUT) and Trolox (TRO) used as standard compounds. The physicochemical, pharmacokinetic, and toxicity features of the compound have been determined by using drug-likeness and in silico ADMET investigations. The interaction results with SARS-CoV-2 main protease (Mpro) of the title ligand compound have been analyzed via the help of molecular docking study. Communicated by Ramaswamy H. Sarma

Structural, Spectroscopic (FT-IR, Raman, NMR and UV-Vis.) and Theoretical Investigations of Cyclopentolate

In this study, the structural and spectroscopic characterizations (FT-IR, Laser-Raman, 1H and 13C NMR and UV-vis spectra) of cyclopentolate were performed using experimental and theoretical methods. Four conformational structures and optimized molecular geometries of the molecule were examined. The vibrational wavenumbers, proton and carbon-13 NMR chemical shifts, UV-Vis. parameters were theoretically obtained for the most stable form of the molecule and the HOMO-LUMO analyses were performed with DFT/B3LYP method at aug-cc-pVDZ basis set. The weak intra-molecular hydrogen bond interaction in O45-H46…N23 group was determined. The 1H and 13C NMR chemical shifts were experimentally and theoretically investigated. The assignments of theoretical vibrational modes were obtained using VEDA 4 software in terms of potential energy distribution (PED). The theoretically and experimentally obtained data were found to be consistent with each other.

Spectral, DFT and molecular docking investigations on Etodolac

The title compound (RS) -2- (1, 8-Diethyl- 4, 9-dihydro-3H- pyrano [3, 4-b] indol-1-yl) acetic acid (Etodolac) was characterized by experimental FTIR, FT-Raman, NMR and UV-Visible spectral analysis. The optimized molecular geometry and vibrational wave numbers were calculated by employing the method of DFT and B3LYP/6-311++G(d, p) basis set. The vibrational assignments were calculated using VEDA program. Carbon and Proton NMR chemical shifts were calculated in different solvents by GIAO method. Theoretical UV-Visible spectrum was obtained in DMSO and in gas phase using TD-DFT method. For the title compound, HOMO-LUMO and Donor- Acceptor (NBO) interactions were studied. In addition, MEP map was traced to find the reactive sites of Etodolac. Further, NLO properties such as dipole moment, linear and first order hyperpolarizabilities have been studied to reveal NLO nature of the title compound. Also the thermodynamic properties with respect to temperature were calculated. All the theoretical predictions were carried out by using DFT-B3LYP method at the level of 6–311++G(d, p). Finally to find its biological importance, the molecular docking interaction was studied to reveal that Etodolac is a selective inhibitor of COX (cyclooxygenase) enzyme.

Structural, Spectroscopic (FT-IR, Raman, NMR and UV-Vis.) and Computational Studies on Nphenylpropanamide

Structural, vibrational, magnetic and electronic properties of N-phenylpropanamide were analyzed experimentally and theoretically. The molecular geometry optimization parameters, vibrational wavenumbers, proton and carbon NMR chemical shifts, frontier molecular orbitals and UV-Vis. wavelengths were computed with DFT/B3LYP method at the 6-311+G(d,p) basis set to compare the experimental data obtained from the literature. Calculated harmonic vibrational wavenumber assignments were obtained from the potential energy distribution (PED) analysis. Considering that the N-H…O intermolecular hydrogen bond interaction in crystal packing of N-phenylpropanamide may exist, molecular structure parameters and vibration frequencies of these groups in this interaction were investigated. UV-Vis. electronic absorption parameters, HOMO-LUMO analyses and molecular electrostatic potential (MEP) surface of N-phenylpropanamide were studied to explicate electronic transitions, intramolecular charge transfer and interaction sites in the molecule.

Crystal structure, spectroscopic and electronic features of 6-(Chloromethyl)uracil

The structural, spectroscopic and electronic features of the 6-(Chloromethyl)uracil (6CMU) have been characterized by using single crystal X-ray diffraction (XRD), 1H and 13C NMR, UV–Vis. and vibrational (FT-IR and Raman) spectroscopies. The classical geometry analyses of intermolecular interactions, which were performed on the basis of experimental crystal structure, have been supported by Hirshfeld surface analysis. Theoretical molecular geometry optimization parameters (bond lengths and angles), vibrational wavenumbers, proton and carbon NMR chemical shifts, UV–Vis. parameters (wavelengths, excitation energies, oscillator strength) and the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energies have been calculated using density functional theory (DFT/B3LYP) quantum chemical method with 6–311++G (d,p) basis set to compare with the experimental results. Assignments of the vibrational wavenumbers have been carried out by Potential Energy Distribution (PED) analyses by using VEDA 4 software. UV–Vis. electronic absorption parameters, HOMO-LUMO analyses, Natural Bond Orbital (NBO) results and Molecular Electrostatic Potential (MEP) surface of 6CMU have been studied to explicate electronic transitions, intramolecular charge transfer and interaction sites in the molecule. The computed vibrational wavenumbers, NMR chemical shifts and UV–Vis. parameters have been in good agreement with the corresponding experimental data and literature.

Experimental (FT-IR, Raman and NMR) and Theoretical (B3LYP, B3PW91, M06-2X and CAM-B3LYP) Analyses of PTert-Butylphenyl Salicylate

The spectroscopic investigations of p-tert-butylphenyl salicylate (C17H18O3) molecule were performed using 13C and 1H NMR chemical shifts, FT-IR and Raman spectroscopies. Molecular geometric optimizations, vibrational frequencies, Carbon-13 and Proton NMR chemical shifts (in vacuum and chloroform), HOMO-LUMO properties, natural bond orbital (NBO) analysis, nonlinear optical properties and thermodynamic parameters of p-tert-butylphenyl salicylate molecule was studied using B3LYP, B3PW91, M06-2X and CAM-B3LYP functionals in DFT method at the 6-311++G(d,p) basis set. NBO analysis was carried out to investigate the intramolecular hyrogen bonding (O-H...O) in the title molecule. Some of the molecular properties such as ionization potential (I), electron affinity (A), chemical hardness (h), chemical softness (z), electronegativity (χ), chemical potential (μ) and electrophilicity index (w) parameters were determined via HOMO and LUMO energies of the title molecule. Also, quantum chemical computations were performed to determine the dipole moment (µtotal), mean polarizability (α), anisotropy of the polarizability (∆α) and first hyperpolarizability (β0) values. Thermochemical properties of the title molecule were investigated with the aforementioned calculation levels. The recorded experimental spectroscopic results were found to be in good agreement with the computed data.

Structures and stabilities of naturally occurring cyclodextrins: a theoretical study of symmetrical conformers.

A molecular modeling study of symmetrical conformers ofα-,β-, and γ-cyclodextrins in the gas and aqueous phases was carried out using the M06-2X density functional method, with SMD employed as an implicit solvation model. Eight symmetrical conformers were found for each cyclodextrin. Values of geometrical parameters obtained from the modeling study were found to agree well with those obtained from X-ray diffraction structures. A vibrational analysis using harmonic frequencies was performed to determine thermodynamic quantities. The GIAO method was applied to determine proton and carbon-13 NMR chemical shifts, which were then compared with corresponding chemical shifts reported in the literature. Hydrogen-bonding patterns were analyzed using geometrical descriptors, and quantum chemical topology was explored by QTAIM analysis. The results of this study indicated that four of the eight conformers studied for each cyclodextrin are the most populated in aqueous solution. These results provide the foundations for future studies of host-guest complexes involving these cyclodextrins. Graphical abstract δΔGsolvation: variation of free Gibss energy of solvation.

Spectroscopic and chemical reactivity analysis of D-Myo-Inositol using quantum chemical approach and its experimental verification

This paper describes the spectroscopic ( $$^1\hbox {H}$$ and $$^{13}\hbox {C}$$ NMR, FT-IR and UV–Visible), chemical, nonlinear optical and thermodynamic properties of D-Myo-Inositol using quantum chemical technique and its experimental verification. The structural parameters of the compound are determined from the optimized geometry by B3LYP method with $$6\text {-}311{+}{+}\hbox {G}$$ (d,p) basis set. It was found that the optimized parameters thus obtained are almost in agreement with the experimental ones. A detailed interpretation of the infrared spectra of D-Myo-Inositol is also reported in the present work. After optimization, the proton and carbon NMR chemical shifts of the studied compound are calculated using GIAO and $$6\text {-}311{+}{+}\hbox {G}$$ (d,p) basis set. The search of organic materials with improved charge transfer properties requires precise quantum chemical calculations of space-charge density distribution, state and transition dipole moments and HOMO–LUMO states. The nature of the transitions in the observed UV–Visible spectrum of the compound has been studied by the time-dependent density functional theory (TD-DFT). The global reactivity descriptors like chemical potential, electronegativity, hardness, softness and electrophilicity index, have been calculated using DFT. The thermodynamic calculation related to the title compound was also performed at B3LYP $$/$$ $$6\text {-}311{+}{+}\hbox {G}$$ (d,p) level of theory. The standard statistical thermodynamic functions like heat capacity at constant pressure, entropy and enthalpy change were obtained from the theoretical harmonic frequencies of the optimized molecule. It is observed that the values of heat capacity, entropy and enthalpy increase with increase in temperature from 100 to 1000 K, which is attributed to the enhancement of molecular vibration with the increase in temperature.

Structural, spectroscopic, electronic, nonlinear optical and thermodynamic properties of a synthesized Schiff base compound: A combined experimental and theoretical approach

A Schiff base compound, 2-[(1H-benzimidazol-2-ylimino)methyl]-4-bromophenol (BISB), was synthesized and its spectroscopic characterization was performed using experimental methods such as FT-IR, Raman, proton and carbon-13 NMR chemical shifts and UV–Vis. spectroscopies. Density functional theory (DFT/B3LYP/6-311G(d,p)) computations were used to investigate the optimized molecular geometry, conformational forms, harmonic vibrational wavenumbers, NMR chemical shifts, UV–Vis. spectroscopic parameters, natural bond orbital (NBO) analysis, HOMO-LUMO energies, nonlinear optical (NLO) properties, molecular electrostatic potential (MEP) map, atomic charges and thermodynamic properties of the BISB molecule. The assignments of vibrational modes were performed by means of potential energy distribution (PED) using VEDA4 program. The NBO analysis was used to investigate intramolecular hyrogen bonding (OH⋯N), bond species, hyperconjugation interactions and intramolecular charge transfers (ICTs). Considering the computed HOMO and LUMO energies, the quantum molecular descriptors such as ionization potential (I), electron affinity (A), chemical hardness (η), chemical softness (ζ), electronegativity (χ), chemical potential (μ) and electrophilicity index (ω) parameters were investigated for the BISB molecule. DFT computations were also performed to determine the dipole moment (μ), the mean polarizability (α), the anisotropy of the polarizability (Δα) and the first hyperpolarizability (β0) values. The recorded experimental spectroscopic results are in a good harmony with the computed data.

Theoretical and spectroscopic (FT-IR, NMR and UV–Vis.) characterizations of 3-p-chlorobenzyl-4-(4-carboxybenzylidenamino)-4,5-dihydro-1H-1,2,4-triazol-5-one molecule

Fourier transform infrared (FT-IR) spectroscopy in the region 400–4000 cm−1, proton and carbon-13 NMR chemical shifts and UV–Vis. absorption wavelengths of 3-p-chlorobenzyl-4-(4-carboxybenzylidenamino)-4,5-dihydro-1H-1,2,4-triazol-5-one molecule have been experimentally investigated. For monomeric and dimeric forms of the title molecule, the optimized molecular structure analyses, vibrational wavenumbers, 13C and 1H NMR chemical shifts and electronic absorption wavelengths of the title molecule have been performed at DFT/B3LYP method with 6-311G(d,p) basis set. The HOMO and LUMO analyses have been theoretically done by using the mentioned calculation level. The obtained experimental values have been compared with calculated data. The computed vibrational frequencies, NMR chemical shifts and UV–Vis. wavelengths have been found to be in a good agreement with experimental values and spectral results of similar structures in the literature.

Thiol–thione tautomeric analysis, spectroscopic (FT-IR, Laser-Raman, NMR and UV–vis) properties and DFT computations of 5-(3-pyridyl)-4H-1,2,4-triazole-3-thiol molecule

In this study, the 5-(3-pyridyl)-4H-1,2,4-triazole-3-thiol molecule (C7H6N4S) molecule has been characterized by using FT-IR, Laser-Raman, NMR and UV–vis spectroscopies. Quantum chemical calculations have been performed to investigate the molecular structure (thione–thiol tautomerism), vibrational wavenumbers, electronic transition absorption wavelengths in DMSO solvent and vacuum, proton and carbon-13 NMR chemical shifts and HOMOs-LUMOs energies at DFT/B3LYP/6-311++G(d,p) level for all five tautomers of the title molecule. The obtained results show that the calculated vibrational wavenumbers, NMR chemical shifts and UV–vis wavelengths are in a good agreement with experimental data.

Rapid chemical characterisation of stilbenes in the root bark of Norway spruce by off-line HPLC/DAD-NMR.

Stilbenes are plant secondary metabolites that have shown promising and varied biological activities. Stilbenes are presently actively studied for the exploitation of this primary raw material resource, involving the concept of biorefining. Methods for the rapid discovery of new and known stilbene structures from various plant sources are thus keenly sought. To establish a simple and rapid technique of off-line HPLC with a diode-array detector (DAD) and NMR for the unambiguous structural elucidation of stilbene structures in the root bark of Norway spruce [Picea abies (L.) Karst.]. The stilbene containing fraction was extracted from the plant bark with an ethanol:water mixture (95:5, v/v) preceded by defatting of hydrophobic compounds with n-hexane using the accelerated solvent extraction technique. A portion of the ethanol-water soluble extract was hydrolysed with β-glucosidase to prepare stilbene aglycones. The extracts were further purified and enriched using a polymeric adsorbent. Stilbene-enriched extracts were directly characterised by off-line HPLC/DAD-NMR in conjunction with HPLC/DAD and HPLC/DAD with electrospray ionisation MS(n). Trans-isorhapontin and trans-astringin were identified as the major, and trans-piceid as a minor, stilbene glucosides of the bark of roots of Picea abies. Not only stilbene glucosides but also the corresponding stilbene aglycones, such as trans-resveratrol, trans-piceatannol and trans-isorhapontigenin, were rapidly identified from the hydrolysed extract. The acquired heteronuclear single-quantum coherence and heteronuclear multiple bond correlation spectra were used to assign the complete carbon NMR chemical shifts of trans-isorhapontin and trans-astringin without the need of acquiring a (13)C-NMR spectrum. The off-line HPLC/DAD-NMR method is expedient for the unambiguous identication of structurally similar stilbenes in plant extracts.

Benchmarking Hydrogen and Carbon NMR Chemical Shifts at HF, DFT, and MP2 Levels.

An extensive study of error distributions for calculating hydrogen and carbon NMR chemical shifts at Hartree-Fock (HF), density functional theory (DFT), and Møller-Plesset second-order perturbation theory (MP2) levels is presented. Our investigation employs accurate CCSD(T)/cc-pVQZ calculations for providing reference data for 48 hydrogen and 40 carbon nuclei within an extended set of chemical compounds covering a broad range of the NMR scale with high relevance to chemical applications, especially in organic chemistry. Besides the approximations of HF, a variety of DFT functionals, and conventional MP2, we also present results with respect to a spin component-scaled MP2 (GIAO-SCS-MP2) approach. For each method, the accuracy is analyzed in detail for various basis sets, allowing identification of efficient combinations of method and basis set approximations.

Prediction of Substituent Types and Positions on Skeleton of Myrcane-type Monoterpenoids using Generalized Regression Neural Network

Aim: To explore the ability of GRNN as a tool of structural elucidation in predicting the substituent types on myrcane, one of the representative skeletons of monoterpenoids. Methodology: Generalized regression neural network (GRNN) was used in the study. Carbon-13 ( 13 C) NMR chemical shift values of skeletons of 104 myrcane monoterpenoids were used as the input data used for the network. Each substituent type on the skeleton of the different compounds were coded and used as the output data for the network. These data were used to train the network while the spread constant of the GRNN was varied. After training, the network was simulated using 15 test compounds. Results: GRNN at a spread constant of 1.0gave the best result. The network had between 80 to 90% recognition rates in 14 of the 15 test compounds. The network could

A successful DFT calculation of carbon-13 NMR chemical shifts and carbon–fluorine spin–spin coupling constants in (η6-fluoroarene)tricarbonylchromium complexes

Carbon-13 isotropic shielding constants and C–F spin–spin coupling constants for fluorobenzene, 3- and 4-dimethylaminofluorobenzene as well as for their tricarbonylchromium complexes have been calculated using DFT methods.

Solvation chemical shifts of perylenic antenna molecules from molecular dynamics simulations.

Solvation-induced shifts in molecular properties can be realistically simulated by employing a dynamic model with explicit solvent molecules. In this work, (13)C NMR chemical shifts of various candidate antenna molecules for dye-sensitised solar cells have been studied by using density-functional theory calculations both in vacuo and by employing a dynamic solvation model. The solvent effects were investigated using instantaneous molecular dynamics snapshots containing the antenna molecule and surrounding acetonitrile solvent molecules. Such calculations take into account the main mechanisms of solvation-induced chemical shifts. We have analysed the contributions to the solvent shift due to the solvent susceptibility anisotropy, changes in the density of the virtual orbital space and the accessibility of the excited states to the pronouncedly local magnetic hyperfine operator. We present Lorentzian-broadened chemical shift stick spectra in which a comparison of the in vacuo and dynamic-solvation model results is graphically illustrated. The results show that the solvent-accessible atoms at the perimeter of the solute are influenced by the virtual states of the solvent molecules, which are visible to the hyperfine operators of the perimeter nuclei. This enables efficient coupling of the ground state of the solute to the magnetically allowed excited states, resulting in a positive chemical shift contribution of the perimeter nuclei. As a result of solvation, the chemical shift signals of perimeter nuclei are found to be displaced towards larger chemical shift values, whereas the nuclei of the inner region of the solute molecules show the opposite trend. The solvent susceptibility anisotropy is found to cause a small and practically constant contribution.