Study of stacking interactions between two neutral tetrathiafulvalene molecules in Cambridge Structural Database crystal structures and by quantum chemical calculations

Tetrathiafulvalene (TTF) and its derivatives are very well known as electron donors with widespread use in the field of organic conductors and superconductors. Stacking interactions between two neutral TTF fragments were studied by analysing data from Cambridge Structural Database crystal structures and by quantum chemical calculations. Analysis of the contacts found in crystal structures shows high occurrence of parallel displaced orientations of TTF molecules. In the majority of the contacts, two TTF molecules are displaced along their longer C 2 axis. The most frequent geometry has the strongest TTF–TTF stacking interaction, with CCSD(T)/CBS energy of −9.96 kcal mol−1. All the other frequent geometries in crystal structures are similar to geometries of the minima on the calculated potential energy surface.

Chloro- and Dichloro-methylsulfonyl Nitrenes: Spectroscopic Characterization, Photoisomerization, and Thermal Decomposition

Chloro- and dichloro-methylsulfonyl nitrenes, CH2ClS(O)2N and CHCl2S(O)2N, have been generated from UV laser photolysis (193 and 266 nm) of the corresponding sulfonyl azides CH2ClS(O)2N3 and CHCl2S(O)2N3, respectively. Both nitrenes have been characterized with matrix-isolation IR and EPR spectroscopy in solid N2 (10 K) and glassy toluene (5 K) matrices. Triplet ground-state multiplicity of CH2ClS(O)2N (|D/hc| = 1.57 cm−1 and |E/hc| = 0.0026 cm−1) and CHCl2S(O)2N (|D/hc| = 1.56 cm−1 and |E/hc| = 0.0042 cm−1) has been confirmed. In addition, dichloromethylnitrene CHCl2N (|D/hc| = 1.57 cm−1 and |E/hc| = 0 cm−1), formed from SO2-elimination in CHCl2S(O)2N, has also been identified for the first time. Upon UV light irradiation (365 nm), the two sulfonyl nitrenes R–S(O)2N (R = CH2Cl and CHCl2) undergo concomitant 1,2-R shift to N-sulfonlyamines R–NSO2 and 1,2-oxygen shift to S-nitroso compounds R–S(O)NO, respectively. The identification of these new species with IR spectroscopy is supported by 15N labeling experiments and quantum chemical calculations at the B3LYP/6-311++G(3df,3pd) level. In contrast, the thermally-generated sulfonyl nitrenes CH2ClS(O)2N (600 K) and CHCl2S(O)2N (700 K) dissociate completely in the gas phase, and in both cases, HCN, SO2, HCl, HNSO, and CO form. Additionally, ClCN, OCCl2, HNSO2, •NSO2, and the atmospherically relevant radical •CHCl2 are also identified among the fragmentation products of CHCl2S(O)2N. The underlying mechanisms for the rearrangement and decomposition of CH2ClS(O)2N and CHCl2S(O)2N are discussed based on the experimentally-observed products and the calculated potential energy profile.

Preformation probability of two-proton emitters

Within the cluster-core model picture using the preformed cluster model, proton rich, 2-proton emitting nuclei are studied. The experimentally established [Formula: see text]Fe, [Formula: see text]Ni, [Formula: see text]Zn and [Formula: see text]Kr are investigated in terms of simple potential energy surfaces for all possible cluster plus core configurations of the 2-proton emitting nuclei. The calculated potential energy surfaces reveal a strong minimum for 2-proton-cluster plus core configuration. In addition, the calculations are carried out for the theoretically studied 2-proton emitters such as [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text], which also reveal 2-proton cluster plus core configuration as the favorable one possessing strong minimum in the potential energy surface. Furthermore, the calculated potential energies are used to calculate the preformation probability by solving the stationary Schrödinger equation of motion in mass asymmetry coordinate. The formation yield also clearly reveals a larger formation probability for the 2-proton cluster plus core configuration for all the nuclei studied. The Q-value systematic of 1-proton, 2-proton, 4-proton and 4He is also analyzed.

Drug Design Outlook by Calculation of Second Virial Coefficient as a Nano Study

Intermolecular potential energy surface for an interaction of drug with Na has been examined using HF level of theory with 6-31G* basis set. The name of drug is meso-tetrakis (p-sulphonatophenyl) porphyrin (here after abbreviated to TSPP) . The numbers of Na⁺ have a significant effect on the calculated potential energy curve (including position, depth, and width of the potential well). Counterpoise (CP) correction has been used to show the extent of the basis set superposition error (BSSE) on the potential energy curves obtained for TSPPNa. The second virial coefficients are calculated by these data.

Conformational dimorphism ino-nitrobenzoic acid: alternative ways to avoid the O...O clash

Polymorphism is a challenging phenomenon and the competitive packing alternatives which are characteristic for polymorphs may be encountered for essentially rigid molecules. A second crystal form of the well known compoundo-nitrobenzoic acid, C7H5NO4, an important intermediate in the production of dyes, pharmaceuticals and agrochemicals, is described. Although obtained serendipitously, its intra- and intermolecular features match expectations from database searches and theoretical calculations. O—H...O hydrogen-bonded carboxylic acid dimers represent the building blocks in both polymorphs. For steric reasons and in agreement with a calculated potential energy surface, the carboxylic acid and nitro groups cannot simultaneously be coplanar with the benzene ring but have to tilt. In the well established crystal form, this out-of-plane torsion is more pronounced for the nitro substituent. In contrast, the new polymorph is characterized by a major tilt of the carboxylic acid group. The molecules in both alternative crystal forms achieve a similar compromise with respect to acceptable intramolecular O...O contacts.

The spectroscopic NMR analysis of 2-dicyanovinyl-5-phenylthiophene by the density functional method

Quantum chemistry calculations have been performed by using the Gaussian03 program to compute the optimized geometry and harmonic vibrational frequency of 2-dicyanovinyl-5-phenylthiophene (C14H8N2S) in the ground state. Atomic charges at B3LYP/6-311++G(d,p) level are also calculated. Potential energy distributions (PEDs) using MOLVIB program are also used to interpret the theoretical vibrational spectra of the title compound. A detailed interpretation of the infrared spectra of the title compound is reported. The theoretical spectrograms for the IR spectra of the title compound have been constructed. The crystal structure obtained by molecular mechanics belongs to the P21 space group, with lattice parameters Z = 2, a = 6.6745 Å, b = 14.7672 Å, c = 11.0986 Å, ρ = 0.921 g cm–3. In addition, the 13C and 1H NMR are further investigated by the B3LYP/6-311++G(d,p) and B3LYP/6-311++G(2d,2p) methods.

THEORETICAL INVESTIGATION ON THE INSERTION REACTIONS OF THE GERMYLENOIDH2GeLiFWITHRH(R=Cl,SH,PH2)

The insertion reactions of the germylenoid H2GeLiF with RH (R = Cl, SH , PH2) were studied for the first time by using the DFT B3LYP and QCISD methods. The geometries of the stationary points on the potential energy surfaces of the reactions were optimized at the B3LYP/6-311+G (d,p) level of theory. The calculated results indicated that the mechanisms of the insertion reactions of H2GeLiF with HCl , H2S , and PH3are identical to each other. The QCISD/6-311++G(d,p)//B3LYP/6-311+G(d,p) calculated potential energy barriers of the three reactions are 81.80, 123.39 and 205.56 kJ/mol, and the reaction energies for the three reactions are -58.74, -33.51 and -13.35 kJ/mol, respectively. Under the same situation, the insertion reactions should occur easily in the following order H–Cl > H–SH > H–PH2. The insertion reaction in THF solution is easier than in gas phase.

Calculated Vibrational Properties of Ubisemiquinones

Density functional theory has been used to calculate harmonic normal mode vibrational frequencies for unlabeled and isotope-labeled ubisemiquinones in both the gas phase and in several solvents. It is shown that four methoxy group conformations are likely to be present in solution at room temperature. Boltzmann weighted infrared and Raman spectra for the four conformers were calculated, and composite spectra that are the sum of the Boltzmann weighted spectra were produced. These composite spectra were compared to experimental FTIR and resonance Raman spectra, and it is shown that the calculated band frequencies, relative band intensities, and C13 and O18 isotope-induced band shifts are in excellent agreement with experiment. The calculations show that the C=O and C=C modes of ubisemiquinone strongly mix with methoxy methyl CH bending vibrations, and that the degree of mixing is altered upon isotope labeling, resulting in complicated changes in mode frequencies, intensities, and composition upon isotope labeling. Upon consideration of the calculated potential energy distributions of the normal modes of ubisemiquinone, and how they change upon isotope labeling, an explanation of some puzzling features in previously published Raman spectra is provided.

Possible schemes of photoassociation processes in the KLi molecule with newly calculated potential energy curves

We present four promising schemes for photoassociative formation of KLi molecule in its ground electronic state. Analysis is based on newly calculated adiabatic potentials supported by transition dipole moments and Franck-Condon factors.