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Three new diketopyrrolopyrrole based compounds with Acceptor-Donor-Acceptor-Donor-Acceptor (A-D-A-D-A) skeletons were designed and synthesized through varying the electron-deficient core from diphenylquinoxaline (DP-Qx), thieno[3,4-c]pyrrole-4,6-dione (DP-TPD) to 2-dodecyl-6,7-diphenyl-2H-[1,2,3]triazole[4,5-g]quinoxaline (DP-TQx). We have calculated and studied the effect of central acceptor units on electronic, optical and non-optical properties. As well as, we have predicted the charge transport properties. Results indicate that change of central acceptor unit remarkably affects the molecular electronic, optical and non-optical properties. And the molecular band gap and UV/vis adsorption spectra are significantly changed. It should be noted that Compound 3 with 2-dodecyl-6,7-diphenyl-2H-[1,2,3]triazole[4,5-g]quinoxaline as core show superior non-optical properties as compare to other compounds. Our study here indicate that inserting the strong electron-deficient moieties improves intramolecular charge transfer (ICT) and charge transport properties dramatically.

Conventional NMR is generally a technique for electronic ground state molecules. In this paper, the effect of electronic excitation on nuclear magnetic shielding is theoretically illustrated by Nuclear Spin Optical Rotation (NSOR) in liquids. The near-resonance effect on the optical chemical shift in NSOR is explored by using the dressed state theory. The results indicate that in the NSOR spectrum of a molecule with nucleus I = 1/2, such effect can induce a new optical chemical shift line with the circular frequency different from that of the ground state. From it the NMR shielding of a molecule in the electronic excited state can be got directly and used to analyze excited molecule structure in liquids. For multi-nuclei molecules, the result applies to each nucleus.

A recently proposed optical chemical shift in nuclear spin optical rotation (NSOR) is studied by theoretical comparison of NSOR magnitude between chemically non-equivalent or different element nuclei in the same molecule. Theoretical expressions of the ratio R between their NSOR magnitudes are derived by using a known semi-empirical formula of NSOR. Taking methanol, tri-ethyl-phosphite and 2-methyl-benzothiazole as examples, the ratios R are calculated and the results approximately agree with the experiments. Based on those, the important influence factors on R and chemical distinction by NSOR are discussed.

Based on the thought on the antisymmetric polarizability induced by nuclear magnetic moments and theory of the Faraday effect, an analytical theoretical expression is derived for the nuclear-spin-induced optical rotation (NSOR) of diamagnetic saturated molecules in a circular cylinder. That consists of two parts, ϕ(I) and ϕ(B), induced by the intramolecular and intermolecular hyperfine interaction, respectively. By using them and the Verdet constants, NSOR for 1H in water, hexane, cyclohexane and methyl–alcohol in liquid and H2 gas have been calculated. The calculated NSOR for water agrees with the experiment and for three hydrocarbons predicts the same order of magnitude as water. For the samples studied except H2 gas, ϕ(I) and ϕ(B) are comparable in magnitude.

The potential energy surface and various reaction channels of the MSIA + OH reaction have been investigated at the CCSD(T)/6-311 + G(2d, p)//B3LYP/6-31 + G(2d, p) level of theory. Four different hydrogen-bonded complexes were formed in the reactions. The calculations indicate that there are mainly two kinds of reaction mechanisms in the studied reactions, the direct CH 3 radical-abstraction reaction and the association–decomposition reaction. Owing to the higher barrier heights, the CH 3 -abstraction pathway is not expected to be the favorable pathway. While, the association–decomposition reaction pathway, MSIA-b + OH → M2b → TS9 → H 2 O + CH 3 SO 2 → TS4 + H 2 O → SO 2 + CH 3 + H 2 O, is the most feasible reaction pathway, and SO 2 is the dominant final sulfur-containing product.

The single-molecule conductance of a dithiolated aniline trimer has been measured under potential control and also under an inert solvent. In each experiment, two sets of currents are found, differing by a factor 4, and these are tentatively assigned to differing connections to the electrodes (e.g., on-top vs. hollow sites). The conductances peak (to 17 ± 1.6 and 5.8 ± 0.85 nS) between the first and second oxidations of the molecule and change smoothly with surface potential. There is no evidence for a coexistence of oxidized and reduced molecules. Measurements made at a fixed surface potential as a function of tip to substrate bias show a peak current at 0.1 V followed by a region of negative differential resistance. This is accounted for semi-quantitatively by modification of the local potential by the applied bias altering the oxidation state of the molecule under the probe. Measurements made in toluene are Ohmic, indicating that the tip does not alter the oxidation state of the molecule in the absence of screening ions. We discuss the role of gap geometry and bonding in these processes.

The complex potential energy surface for the unimolecular isomerization and decomposition of peroxyacetyl nitrate (PAN, CH3C(O)OONO2), including 11 isomers, 45 interconversion transition states and 18 major dissociation products, is probed theoretically at the G2MP2//B3LYP/6-311G(2d,2p) level of theory. The geometries and relative energies for various stationary points are determined. Based on the calculated G2MP2 potential energy surface, the possible unimolecular decomposition mechanism of PAN is proposed. It is shown that the most feasible decomposition channels of PAN are those leading to 2CH3C(O)OO + NO2, 2CH3C(O)O + 2NO3, and 2CH3 + CO2 + 2NO3, respectively. Among them, the formations of the products of the first two channels are produced by the homolytic O–N and O–O bond ruptures of PAN with the bond dissociation energies of 32.3 and 33.9 kcal/mol, respectively, while the last one is initiated by the concerted C–C and O–O bond fissions via a barrier of 36.5 kcal/mol. Our results suggest that besides the first two decomposition pathways which have been reported by the literature, the last concerted bond fission dissociation channel via a well-defined transition state is also feasible, which has been confirmed by using CBS-Q and CBS-QB3 methods. Therefore, PAN dissociation occurs mainly via the homolytic O–N or O–O bond ruptures or via the concerted C–C and O–O bond fissions while the first channel is more favorable than the last two channels.

The ground-state geometries of monolithium porphyrin (LiP) π-radical and its three reduced/oxidized species ([LiP] − , [LiP] 2− , and [LiP] + ) have been calculated with the density functional theory. The results show that LiP, [LiP] − and [LiP] + have planar D 4h structures while the [LiP] 2− dianion has a rectangular distorted D 2h structure due to the ground-state Jahn-Teller effect. LiTPP and LiOEP radicals were also studied to assess the effect of peripheral substitutions. The ground-state LiTPP has a normal porphyrin ring (D 4h effective symmetry), while the ground-state LiOEP has a porphyrin ring with pronounced bond length alternation (C 4h effective symmetry) due to the pseudo-Jahn-Teller (pJT) distortion along an A 2g -like coordinate. The spin densities of LiP, LiTPP, and LiOEP were analyzed, showing evident effects of peripheral substitution. Electronic absorption spectrum of LiP radical was calculated with the time-dependent DFT and was compared with the experimental results of LiTPP.

The ground-state structure, electronic spectrum and conformational inversion of porphyrin diacid (H4P2+) have been studied with the density functional theory. In accord with available crystallographic data of related compounds, the most stable structure of H4P2+ molecule is the one bearing a saddle-distorted porphyrin ring (D2d symmetry), with the four pyrrole rings tilted up and down alternatively with respect to the porphyrin mean plane. Electronic absorption spectrum of H4P2+ was studied by time-dependent DFT method, and the calculations were compared with the solution experimental results. The computations correctly predict excitation energies and oscillator strengths at least for the first and second excited states. The conformational inversion between the two conjugate D2d structures was studied, and a multi-step process was proposed. The structures of transition states and intermediates as well as the inversion barriers were calculated.

Using the semiclassical perturbation theory, we study the antisymmetric polarizabilities of rotational sublevels, the M-dependent splittings and shifts of the sublevels and corresponding rotational spectral lines of a linear molecule induced by a right (+) or left (−) circularly polarized resonant optical field. The deduced theoretical formulas for these quantities indicate that for rotational sublevels M of linear molecules with a non-degenerate ground electronic state, the antisymmetric polarizabilities induced by a resonant polarized optical fields exist and are the same order of magnitude of the symmetric ones. Based on them, M-dependent (both size and sign of M) splitting and shifts of the sublevels and corresponding spectral lines can be produced and the degeneracy for +M and −M sublevels can be completely broken by the circularly polarized resonant optical field. As examples, we have calculated these quantities for H2 and CO molecules. For H2 molecule, the antisymmetric and symmetric polarizabilities of the rotational magnetic sublevels in the ground electronic state X 1 Σ g + (v=0,J=1,M) , which are induced by a optical field with frequency v0 resonant with the transition X 1 Σ + g (v=0,J=1)→ B 1 Σ u + (v ′ =0,J ′ =2) , are the same order of 10 a.u.; and laser-induced M-dependent splittings and shifts for M=1,0,−1 sublevels and the corresponding resonant Rayleigh scattering lines X 1 Σ g + (v=0,J=1,M)↔ B 1 Σ u + (v ′ =0,J ′ =2,M ′ ) can be the order of 0.1–1 GHz when the intensity of circularly polarized optical field is 100 MW cm−2. Similarly the antisymmetric polarizabilities of CO molecule in the rotational magnetic sublevels X 1 Σ + (v=0,J=1,M=1) using IR field with the frequency v0 resonant with the transition X 1 Σ + (v=0,J=1)→ X 1 Σ + (v ′ =1,J ′ =2) are the same order (10 a.u.) of the symmetric ones.