Effect of N-phenyl substituent on thermal, optical, electrochemical and luminescence properties of 3-aminophthalimide derivatives.

The seven N-phthalimide derivatives substituted with the amine group at the 3-C position in the phenylene ring were synthesized. The effect of N-substituent chemical structure was investigated. The thermal, electrochemical and optical studies were performed and supported by the density functional theory calculations (DFT). The electrochemical investigations of the synthesized low-molecular phthalimides revealed the one oxidation and reduction process with the HOMO energy level under - 5.81 eV and energy-band gap below 3 eV. The N-phthalimide derivatives were emitted light in a blue spectral region in solutions (in polar and non-polar) with the quantum yield between 2 and 68%, dependent on the substituent at the nitrogen atom, solvent and concentration. The N-phthalimide derivatives were emissive also in a solid state as a thin film and powder. They were tested as a component of the active layer with PVK:PBD matrix and as an independent active layer in the organic light-emitting diodes. The registered electroluminescence spectra exhibited the maximum emission band in the 469-505 nm range, confirming the possibility of using N-phthalimides with PVK:PBD matrix as the blue emitters.

Novel Azocoumarin Derivatives-Synthesis and Characterization.

The paper presents synthesis and characterization of nine new thiazolyl-(phenyldiazenyl)-2H-chromen-2-one dyes. The impact of substituent structure in thiazole ring in the synthesized azocoumarin derivatives on electrochemical properties, photoisomerization process and photovoltaic response was examined. The dyes were electrochemically active and undergo reduction and oxidation processes. They showed low electrochemically estimated energy band gap in the range of 1.71-2.13 eV. Photoisomerization process of the synthesized molecules was studied in various solvents such as ethanol, chloroform and N,N-dimethylformamide (DMF) upon the UV illumination. It was found that novel azodyes showed reversible trans-cis-trans isomerization and exhibited long thermal back to the trans form, that was even 7 days in DMF. Selected azocoumarin were molecularly dispersed in polystyrene for preparation of guest-host azopolymer systems to study the cis-trans thermal isomerization of obtained dyes in solid state. The photovoltaic activity of the azochromophores was tested in bulk-heterojunction solar cells. They acting as weak donors in device with structure ITO/PEDOT:PSS/dye:PC70BM/Al. No photovoltaic response of cells with azocoumarin derivatives bearing 4-fluorobenzene, 3,4-dichlorobenzene, or 4-(1-adamantyl) unit was found. Additionally, dye which showed the best activity was examined in three-component solar cells ITO/PEDOT:PSS/PTB7:PC70BM:dye/PFN/Al.

Synthesis and Physicochemical Characterization of Novel Dicyclopropyl-Thiazole Compounds as Nontoxic and Promising Antifungals.

There is a need to search for new antifungals, especially for the treatment of the invasive Candida infections, caused mainly by C. albicans. These infections are steadily increasing at an alarming rate, mostly among immunocompromised patients. The newly synthesized compounds (3a-3k) were characterized by physicochemical parameters and investigated for antimicrobial activity using the microdilution broth method to estimate minimal inhibitory concentration (MIC). Additionally, their antibiofilm activity and mode of action together with the effect on the membrane permeability in C. albicans were investigated. Biofilm biomass and its metabolic activity were quantitatively measured using crystal violet (CV) staining and tetrazolium salt (XTT) reduction assay. The cytotoxic effect on normal human lung fibroblasts and haemolytic effect were also evaluated. The results showed differential activity of the compounds against yeasts (MIC = 0.24-500 µg/mL) and bacteria (MIC = 125-1000 µg/mL). Most compounds possessed strong antifungal activity (MIC = 0.24-7.81 µg/mL). The compounds 3b, 3c and 3e, showed no inhibitory (at 1/2 × MIC) and eradication (at 8 × MIC) effect on C. albicans biofilm. Only slight decrease in the biofilm metabolic activity was observed for compound 3b. Moreover, the studied compounds increased the permeability of the membrane/cell wall of C. albicans and their mode of action may be related to action within the fungal cell wall structure and/or within the cell membrane. It is worth noting that the compounds had no cytotoxicity effect on pulmonary fibroblasts and erythrocytes at concentrations showing anticandidal activity. The present studies in vitro confirm that these derivatives appear to be a very promising group of antifungals for further preclinical studies.

Systematic Analysis of the Role of Substituents in Oxiranes, Oxetanes, and Oxathietanes Chemical Shifts.

The important role substituents play on proton chemical shifts in heterocyclic compounds was investigated in detail. For this purpose, a considerable number of model oxiranes, oxetanes, and oxathietanes with different substituents were studied in a systematic way. In addition, the oxygen and sulfur heteroatom influence on the chemical shift values was analyzed. The density functional theory (DFT) approximation was employed together with the M06 and the B3LYP functionals and the aug-pcS-1 and the 6-311++G** basis sets. We carried out a careful analysis of the shift values and the changes in the corresponding molecular electrostatic potential surfaces due to substitution. We observed that chemical shift values for the protons closest to the substituents are larger for the chloro and fluoro derivatives than those for the cyano and ethynyl ones. The presence of oxygen as well as sulfur in the ring causes an increase of the chemical shift values, most pronounced for the atom closest to the substituent. A large decrease of the proton shifts was observed when going from methylenecyclopropane to methyleneoxirane that can be attributed to π-electron resonance. Protons diagonal to the substituents behaved in a different way depending on their cis or trans disposition with respect to them. The conclusions of the present study will be useful in theoretical and experimental work on NMR spectra of heterocyclic compounds.

Tropinone-Derived Alkaloids as Potent Anticancer Agents: Synthesis, Tyrosinase Inhibition, Mechanism of Action, DFT Calculation, and Molecular Docking Studies.

A new series of hybrid compounds with tropinone and thiazole rings in the structure was designed and synthesized as potential anticancer agents. They were tested against human multiple myeloma (RPMI 8226), lung carcinoma (A549), breast adenocarcinoma (MDA-MB-231), and mouse skin melanoma (B16-F10) cell lines. Toxicity was tested on human normal skin fibroblasts (HSF) and normal colon fibroblasts (CCD-18Co). The growth inhibition mechanism of the most active derivative was analyzed through investigation of its effect on the distribution of cell cycle phases and ability to induce apoptosis and necrosis in RPMI 8226 and A549 cancer cells. The tyrosinase inhibitory potential was assessed, followed by molecular docking studies. Compounds 3a-3h show high anticancer activity against MDA-MB-231 and B16-F10 cell lines with IC50 values of 1.51-3.03 µM. Moreover, the cytotoxic activity of the investigated compounds against HSF and CCD-18Co cells was 8-70 times lower than against the cancer cells or no toxicity was shown in our tests, with derivative 3a being particularly successful. The mechanism of action of compound 3a in RPMI 8226 cell was shown to be through induction of cell death through apoptosis. The derivatives show ability to inhibit the tyrosinase activity with a mixed mechanism of inhibition. The final molecular docking results showed for IC50 distinct correlation with experiment.

Towards understanding the interaction of (S)-thalidomide with nucleobases.

Interaction of (S)-thalidomide molecule with four nucleobases: adenine, guanine, cytosine and thymine, is investigated in details employing density functional theory methods. Different mutual positions of the molecules are considered, with the starting geometries enabling hydrogen bond interactions between the monomers. Optimization of geometrical parameters is carried out within the B3LYP/6-311G** approximation and followed by evaluation of vibrational frequencies. Binding and interaction energies are calculated employing exchange-correlation functionals including long-range corrections and properly diffuse basis sets. The strongest interaction exists within the (S)-thalidomide-guanine complex. Interestingly, in one of the investigated (S)-thalidomide-guanine complexes two bifurcated hydrogen bonds are observed. The two hydrogens involved in one of them are bonded to a carbon atom in the α position relative to carbonyl group. The present study can be useful in the design of new anticancer and antiviral drugs interacting selectively with DNA or RNA.

Triazene salts: Design, synthesis, ctDNA interaction, lipophilicity determination, DFT calculation, and antiproliferative activity against human cancer cell lines.

Synthesis, characterization and investigation of antiproliferative activity of nine triazene salts against human cancer cells lines (MV-4-11, MCF-7, JURKAT, HT-29, Hep-G2, HeLa, Du-145 and DAUDI), and normal human mammary epithelial cell line (MCF7-10A) is presented. The structures of novel compounds were determined using 1H and 13C NMR, and GC-APCI-MS analyses. Among the derivatives, compound 2c, 2d, 2e and 2f has very strong activity against biphenotypic B myelomonocytic leukemia MV4-11, with IC50 values from 5.42 to 7.69 µg/ml. The cytotoxic activity of compounds 2c-2f against normal human mammary gland epithelial cells MCF-10A is 6-11 times lower than against cancer cell lines. Our results also show that compounds 2c and 2f have very strong activity against DAUDI and HT-29 with IC50 4.91 µg/ml and 5.59 µg/ml, respectively. Their lipophilicity was determined using reversed-phase ultra-performance liquid chromatography and correlated with antiproliferative activity. Our UV-Vis spectroscopic results indicate also that triazene salts tends to interact with negatively charged DNA phosphate chain. To support the experiment, theoretical calculations of the 1H NMR shifts were carried out within the Density Functional Theory.

The Role of Substituents in Optical Rotation of Oxiranes, Oxetanes, and Oxathietanes.

Taking as examples a series of oxiranes, oxetanes, and oxathietanes with different substituents, we study in a systematic way the role that the latter play on the optical rotation of the molecules. For this, we use time-dependent density functional theory together with a hierarchy of Dunning's basis sets. The B3LYP and CAM-B3LYP exchange-correlation functionals are employed. We select results obtained with the CAM-B3LYP functional and the daug-cc-pVTZ basis set as our reference values. Additionally, specific rotation in all systems is calculated with the ORP basis set, specifically designed to carry out optical rotation calculations. The present study shows its good performance in CAM-B3LYP estimations of this property, providing results close to the reference values. The proper choice of the exchange-correlation functional proves to be much more important than that of the basis set. Considering the effect of the substituents, some of the presently investigated molecules show a behavior in line with earlier findings; however we have also found systems that do not match the conclusions previously available in the literature.

Accurate calculation of optically induced birefringences in chiral systems using efficient polarized basis sets.

Using state-of-the-art ab initio methodology, we evaluate universal molecular parameters entering the expressions for various optically induced birefringences in chiral fluids. For this, we use the single and double excitation coupled cluster (CCSD) theory together with Dunning's augmented correlation consistent polarized basis sets of increasing size. As this is the first time these parameters are evaluated for chiral molecules using the CCSD approach, we choose possibly small test systems: a model asymmetric methane molecule, and (R)-fluoro-oxirane. With this choice, the convergence of the molecular parameters with the increase of the basis set size is investigated in detail. The results are compared to those obtained with the LPol-n (n = ds, dl, fs) and the ORP basis sets, and to the corresponding Density Functional Theory (DFT) counterparts. We can conclude that the DFT medium constant values are considerably far from coupled cluster, and therefore, aware of the known excellent performance of the CCSD method in the evaluation of various dynamic responses, we do not recommend the former methodology for accurate evaluation of the present properties. Regarding basis set convergence, the performace of the LPol-ds basis set is more efficient than that of the d-aug-cc-pVDZ set, and therefore, the former basis set can be a good choice when dealing with the study of larger systems.

Thiazoles with cyclopropyl fragment as antifungal, anticonvulsant, and anti-Toxoplasma gondii agents: synthesis, toxicity evaluation, and molecular docking study.

Synthesis and investigation of antifungal, anticonvulsant and anti-Toxoplasma gondii activities of ten novel (2-(cyclopropylmethylidene)hydrazinyl)thiazole 3a-3j are presented. Among the derivatives, compounds 3a-3d and 3f-3j possess very high activity against Candida spp. ATCC with MIC = 0.015-7.81 µg/ml. Compounds 3a-3d and 3f-3j possess also very high activity towards most of strains of Candida spp. isolated from clinical materials with MIC = 0.015-7.81 µg/ml. The activity of these compounds is similar and even higher than the activity of nystatin used as positive control. Additionally, compounds 3c and 3e showed interesting anticonvulsant activities in the MES test, whereas compounds 3f and 3i demonstrated the anticonvulsant activity in PTZ-induced seizures. Noteworthy, none of these compounds impaired animals' motor skills in the rotarod test. Moreover, thiazoles 3a, 3h, and 3j showed significant anti-Toxoplasma gondii activity, with IC50 values 31-52 times lower than those observed for sulfadiazine. The results of the cytotoxicity evaluation, anti-Candida spp. and anti-Toxoplasma gondii activity studies showed that Candida spp. and Toxoplasma gondii growth was inhibited at non-cytotoxic concentrations for the mouse L929 fibroblast and the African green monkey kidney (VERO) cells. Molecular docking studies indicated secreted aspartic proteinase (SAP) as possible antifungal target.

Performance of Property-Optimized Basis Sets for Optical Rotation with Coupled Cluster Theory.

The effectiveness of the optical rotation prediction (ORP) basis set for computing specific rotations at the coupled cluster (CC) level has been evaluated for a test set of 14 chiral compounds. For this purpose, the ORP basis set has been developed for the second-row atoms present in the investigated systems (that is, for sulfur, phosphorus, and chlorine). The quality of the resulting set was preliminarily evaluated for seven molecules using time-dependent density-functional theory (TD-DFT). Rotations were calculated with the coupled cluster singles and doubles method (CCSD) as well as the second-order approximate coupled cluster singles and doubles method (CC2) with the correlation-consistent aug-cc-pVDZ and aug-cc-pVTZ basis sets and extrapolated to estimate the complete basis-set (CBS) limit for comparison with the ORP basis set. In the compounds examined here, the ORP calculations on molecules containing only first-row atoms compare favorably with results from the larger aug-cc-pVTZ basis set, in some cases lying closer to the estimated CBS limit, while results for molecules containing second-row atoms indicate that larger correlation-consistent basis sets are necessary to obtain reliable estimates of the CBS limit.

New Basis Set for the Evaluation of Specific Rotation in Flexible Biological Molecules in Solution.

A detailed theoretical investigation of specific rotation is carried out in solution for nine flexible molecules of biological importance. Systematic search for the main conformers is followed by time-dependent density functional theory (TD-DFT) calculations of specific rotation employing a wide range of basis sets. Due to conformational flexibility of the compounds under study, the possibility of basis set size reduction without deterioration of the results is investigated. The increasing size (d-)aug-cc-pVXZ (X = D, T, Q) bases of Dunning et al., and the ORP basis set, recently developed to efficiently provide molecular specific rotation, are used for this purpose. The polarizable continuum model is employed at all steps of the investigation. Comparison of the present results with the available data obtained in a vacuum reveals considerable differences, the values in solution being much closer to the experimental specific rotation data available. The ORP basis set proves to be competitive with the d-aug-cc-pVDZ set of Dunning in specific rotation calculations carried out in solution. While having the same number of functions, the former yields, in general, results considerably closer to the reference triple-ζ values. We can thus recommend the ORP basis set to study the optical rotation in conformationally flexible molecules in solution.

Synthesis, molecular docking, ctDNA interaction, DFT calculation and evaluation of antiproliferative and anti-Toxoplasma gondii activities of 2,4-diaminotriazine-thiazole derivatives.

Synthesis, characterization, and investigation of antiproliferative activities against human cancer cell lines (MV4-11, MCF-7, and A549) and Toxoplasma gondii parasite of twelve novel 2,4-diaminotriazine-thiazoles are presented. The toxicity of the compounds was studied at three different cell types, normal mouse fibroblast (Balb/3T3), mouse fibroblast (L929), and human VERO cells. The structures of novel compounds were determined using 1H and 13C NMR, FAB(+)-MS, and elemental analyses. Among the derivatives, 4a-k showed very high activity against MV4-11 cell line with IC50 values between 1.13 and 3.21 µg/ml. Additionally, the cytotoxic activity of compounds 4a-k against normal mouse fibroblast Balb/3T3 cells is about 20-100 times lower than against cancer cell lines. According to our results, compounds 4a, 4b, 4d, and 4i have very strong activity against human breast carcinoma MCF-7, with IC50 values from 3.18 to 4.28 µg/ml. Moreover, diaminotriazines 4a-l showed significant anti-Toxoplasma gondii activity, with IC50 values 9-68 times lower than those observed for sulfadiazine. Molecular docking studies indicated DNA-binding site of hTopoI and hTopoII as possible anticancer targets and purine nucleoside phosphorylase as possible anti-toxoplasmosis target. Our UV-Vis spectroscopic results indicate also that diaminotriazine-thiazoles tends to interact with DNA by intercalation. Additionally, the structure and the interaction and binding energies of a model complex formed by compound 4a and two thymine molecules are investigated using quantum mechanical methods.

Synthesis, antimicrobial and anticonvulsant screening of small library of tetrahydro-2H-thiopyran-4-yl based thiazoles and selenazoles.

Synthesis and investigation of antimicrobial activity of 22 novel thiazoles and selenazoles derived from dihydro-2H-thiopyran-4(3H)-one are presented. Additionally, anticonvulsant activity of six derivatives is examinated. Among the derivatives, compounds 4a-f, 4i, 4k, 4 l, 4n, 4o-s and 4v have very strong activity against Candida spp. with MIC = 1.95-15.62 µg/ml. In the case of compounds 4a-f, 4i, 4k, 4 l, 4n, 4o, 4r and 4s, the activity is very strong against some strains of Candida spp. isolated from clinical materials, with MIC = 0.98 to 15.62 µg/ml. Additionally, compounds 4n-v are found to be active against Gram-positive bacteria with MIC = 7.81-62.5 µg/ml. The results of anticonvulsant screening reveal that compounds 4a, 4b, 4m and 4n demonstrate a statistically significant anticonvulsant activity in the pentylenetetrazole model, whereas compounds 4a and 4n showed protection in 6-Hz psychomotor seizure model. Noteworthy, none of these compounds impaired animals' motor skills in the rotarod test. We also performed quantum chemical calculation of interaction and binding energies in complex of 4a with cyclodextrin.

Synthesis, Antibacterial Activity, Interaction with Nucleobase and Molecular Docking Studies of 4-Formylbenzoic Acid Based Thiazoles.

BACKGROUND: Synthesis, characterization and investigation of antibacterial activity of ten novel Schiff base derivatives of 4-formylbenzoic acid is presented. Their structures were determined using 1H and 13CNMR, EI(+)-MS and elemental analyses. Additionally, DFT calculations of interaction energies in complexes of the novel drugs and DNA bases are carried out. OBJECTIVE: Design and synthesis of thiazole derivatives with benzoic acid scaffold to obtain compounds with an improved antibacterial activity. METHOD: The examined compounds were screened in vitro for antibacterial activity using the broth microdilution method. Geometrical parameters of the investigated complexes were optimized within the Density Functional Theory (DFT) approximation using the B3LYP functional and the 6-311G** basis set. The docking simulations were performed using the FlexX docking module. RESULTS: Among the derivatives, compound 4b showed very strong bacterial activity against staphylococci, MIC 1.95-3.91 µg/ml, micrococci, MIC 0.98 µg/ml, and Bacillus spp., MIC 7.81-15.62 µg/ml. The compounds 4c, 4d, 4e and 4j also showed high bioactivity against staphylococci, MIC 3.91-31.25 µg/ml, and micrococci, MIC 0.98-15.62 µg/ml. Interaction energy values for investigated guanine complexes are about 2 kcal/mol lower than for the corresponding cytosine complexes. Molecular docking studies of all compounds on the active sites of bacterial enzymes indicated gyrase B as possible target. CONCLUSION: To conclude, an efficient and economic method for the synthesis of thiazoles containing benzoic acid moiety has been developed. The results of antibacterial screenings reveal that some obtained compounds show high to very strong antibacterial activity. The DFT calculations showed that interaction of the obtained drugs with guanine is stronger than with cytosine. Molecular docking studies of all compounds on the active sites of bacterial enzymes indicated gyrase B as possible target.

Comparison of Property-Oriented Basis Sets for the Computation of Electronic and Nuclear Relaxation Hyperpolarizabilities.

In the present work, we perform an assessment of several property-oriented atomic basis sets in computing (hyper)polarizabilities with a focus on the vibrational contributions. Our analysis encompasses the Pol and LPol-ds basis sets of Sadlej and co-workers, the def2-SVPD and def2-TZVPD basis sets of Rappoport and Furche, and the ORP basis set of Baranowska-Laczkowska and Laczkowski. Additionally, we use the d-aug-cc-pVQZ and aug-cc-pVTZ basis sets of Dunning and co-workers to determine the reference estimates of the investigated electric properties for small- and medium-sized molecules, respectively. We combine these basis sets with ab initio post-Hartree-Fock quantum-chemistry approaches (including the coupled cluster method) to calculate electronic and nuclear relaxation (hyper)polarizabilities of carbon dioxide, formaldehyde, cis-diazene, and a medium-sized Schiff base. The primary finding of our study is that, among all studied property-oriented basis sets, only the def2-TZVPD and ORP basis sets yield nuclear relaxation (hyper)polarizabilities of small molecules with average absolute errors less than 5.5%. A similar accuracy for the nuclear relaxation (hyper)polarizabilites of the studied systems can also be reached using the aug-cc-pVDZ basis set (5.3%), although for more accurate calculations of vibrational contributions, i.e., average absolute errors less than 1%, the aug-cc-pVTZ basis set is recommended. It was also demonstrated that anharmonic contributions to first and second hyperpolarizabilities of a medium-sized Schiff base are particularly difficult to accurately predict at the correlated level using property-oriented basis sets. For instance, the value of the nuclear relaxation first hyperpolarizability computed at the MP2/def2-TZVPD level of theory is roughly 3 times larger than that determined using the aug-cc-pVTZ basis set. We link the failure of the def2-TZVPD basis set with the difficulties in predicting the first-order field-induced coordinates. On the other hand, the aug-cc-pVDZ and ORP basis sets overestimate the property in question only by roughly 30%. In this study, we also propose a low-cost composite treatment of anharmonicity that relies on the combination of two basis sets, i.e., a large-sized basis set is employed to determine lowest-order derivatives with respect to the field-induced coordinates, and a medium-sized basis set is used to compute the higher-order derivatives. The results of calculations performed at the MP2 level of theory demonstrate that this approximate scheme is very successful at predicting nuclear relaxation hyperpolarizabilities.

Small and efficient basis sets for the evaluation of accurate interaction energies: aromatic molecule-argon ground-state intermolecular potentials and rovibrational states.

By evaluating a representative set of CCSD(T) ground state interaction energies for van der Waals dimers formed by aromatic molecules and the argon atom, we test the performance of the polarized basis sets of Sadlej et al. (J. Comput. Chem. 2005, 26, 145; Collect. Czech. Chem. Commun. 1988, 53, 1995) and the augmented polarization-consistent bases of Jensen (J. Chem. Phys. 2002, 117, 9234) in providing accurate intermolecular potentials for the benzene-, naphthalene-, and anthracene-argon complexes. The basis sets are extended by addition of midbond functions. As reference we consider CCSD(T) results obtained with Dunning's bases. For the benzene complex a systematic basis set study resulted in the selection of the (Z)Pol-33211 and the aug-pc-1-33321 bases to obtain the intermolecular potential energy surface. The interaction energy values and the shape of the CCSD(T)/(Z)Pol-33211 calculated potential are very close to the best available CCSD(T)/aug-cc-pVTZ-33211 potential with the former basis set being considerably smaller. The corresponding differences for the CCSD(T)/aug-pc-1-33321 potential are larger. In the case of the naphthalene-argon complex, following a similar study, we selected the (Z)Pol-3322 and aug-pc-1-333221 bases. The potentials show four symmetric absolute minima with energies of -483.2 cm(-1) for the (Z)Pol-3322 and -486.7 cm(-1) for the aug-pc-1-333221 basis set. To further check the performance of the selected basis sets, we evaluate intermolecular bound states of the complexes. The differences between calculated vibrational levels using the CCSD(T)/(Z)Pol-33211 and CCSD(T)/aug-cc-pVTZ-33211 benzene-argon potentials are small and for the lowest energy levels do not exceed 0.70 cm(-1). Such differences are substantially larger for the CCSD(T)/aug-pc-1-33321 calculated potential. For naphthalene-argon, bound state calculations demonstrate that the (Z)Pol-3322 and aug-pc-1-333221 potentials are of similar quality. The results show that these surfaces differ substantially from the available MP2/aug-cc-pVDZ potential. For the anthracene-argon complex it proved advantageous to calculate interaction energies by using the (Z)Pol and the aug-pc-1 basis sets, and we expect it to be increasingly so for complexes containing larger aromatic molecules.

Basis sets for the evaluation of van der Waals complex interaction energies: Ne-N2 intermolecular potential and microwave spectrum.

In order to obtain efficient basis sets for the evaluation of van der Waals complex intermolecular potentials, we carry out systematic basis set studies. For this, interaction energies at representative geometries on the potential energy surfaces are evaluated using the CCSD(T) correlation method and large polarized LPol-n and augmented polarization-consistent aug-pc-2 basis sets extended with different sets of midbond functions. On the basis of the root mean square errors calculated with respect to the values for the most accurate potentials available, basis sets are selected for fitting the corresponding interaction energies and getting analytical potentials. In this work, we study the Ne-N2 van der Waals complex and after the above procedure, the aug-pc-2-3321 and the LPol-ds-33221 basis set results are fitted. The obtained potentials are characterized by T-shaped global minima at distances between the Ne atom and the N2 center of mass of 3.39 Å, with interaction energies of -49.36 cm(-1) for the aug-pc-2-3321 surface and -50.28 cm(-1) for the LPol-ds-33221 surface. Both sets of results are in excellent agreement with the reference surface. To check the potentials further microwave transition frequencies are calculated that agree well with the experimental and the aV5Z-33221 values. The success of this study suggests that it is feasible to carry out similar accurate calculations of interaction energies and ro-vibrational spectra at reduced cost for larger complexes than has been possible hitherto.

The ORP basis set designed for optical rotation calculations.

Details of generation of the optical rotation prediction (ORP) basis set developed for accurate optical rotation (OR) calculations are presented. Specific rotation calculations carried out at the density functional theory (DFT) level for model chiral methane molecule, fluorooxirane, methyloxirane, and dimethylmethylenecyclopropane reveal that the ORP set outperforms larger basis sets, among them the aug-cc-pVTZ basis set of Dunning (J. Chem. Phys. 1989, 90, 1007) and the aug-pc-2 basis set of Jensen (J. Chem. Phys. 2002, 117, 9234; J. Chem. Theory Comput. 2008, 4, 719). It is shown to be an attractive choice also in the case of larger systems, namely norbornanone, ß-pinene, trans-pinane, and nopinone. The ORP basis set is further used in OR calculations for 24 other systems, and the results are compared to the aug-cc-pVDZ values. Whenever large discrepancies of results are observed, the ORP values are in an excellent agreement with the aug-cc-pVTZ results. The ORP basis set enables accurate specific rotation calculations at a reduced cost and thus can be recommended for routine DFT OR calculations, also for large and conformationally flexible molecules.