A theoretical study of the electron paramagnetic resonance spectra and local environment in copper(II) complexes with different imidazole and chlorido ligands.

Copper(II) chloride anionic coordination complexes with different imidazole-derived ligands due to the potential cytotoxic activity play the important role in protein. By investigating the experimental electron paramagnetic resonance (EPR) and ultraviolet-visible (UV-vis) spectra of [CuCl(C6H10N2)4]Cl, [CuCl(C6H10N2)4]Cl, [CuCl2(C4H6N2)4], and [Cu2Cl2(C5H8N2)6]Cl2·2H2O, the local structure of the corresponding Cu2+ centers and the role of different ligands are obtained. Based on the well-agreed EPR parameters and the d-d transitions (10Dq), the four Cu2+ centers show tetragonal and orthorhombic distortion, corresponding to the different anisotropies of EPR signals. In addition, the general rules of governing the impact of methanol in imidazolylalkyl derivatives are also discussed, especially the influence on the local environment (symmetry, distortion, covalency, and crystal field) of above four copper(II) chloride anionic coordination complexes. Therefore, the obtained results in this study will be beneficial to provide a theoretical basis for the experimental design of desired copper-containing imidazolyl alkyl derivatives.

An investigation of the role of transition metal ions impurities in CdO: Local structure and electronic properties.

According to the high-order perturbation formulae of 3d5 (Mn2+ ) and 3d9 (Cu2+ ) ions in octahedron, the local structures and electron paramagnetic resonance (EPR) parameters (g factors and hyperfine structure constants A) for Cu2+ and Mn2+ in CdO are theoretically studied in a consistent way. Due to the Jahn-Teller effect, both the substituted sites of Cu2+ and Mn2+ show the tetragonally elongated distortion with different elongation τ. Meanwhile, the crystal field and covalency around doped Cu2+ and Mn2+ are obtained, which can account for the electronic properties in doped CdO. In order to make further investigation of the potential optical and electrical properties, the band structure and density of states (DOS) of pure and transition metal ions (TMs) doped CdO are comparably calculated through density functional theory (DFT). The results show that the band gap of Mn2+ - and Cu2+ -doped CdO can be effectively reduced, due to the improved covalency between the central ions and ligand ions.

Investigations of the temperature-dependent electron paramagnetic resonance spectra and local structures for a cobalt(II) porphyrin complex within a metal-organic framework.

The interaction between an adsorbed CO molecule and the unsaturated coordinated Co2+ center in the metal-organic framework (MOF) PCN-224 is investigated by analyzing the electron paramagnetic resonance (EPR) parameters (g factors and hyperfine structure constants) and the adsorption energies at various temperatures. Six- and five-coordinated octahedral models (four planar N with two and one axial CO molecules, respectively) are constructed to simulate the local structures of the Co2+ centers at different temperatures. Because of the Jahn-Teller effect of the Co2+ centers, the C2-Co-N4 and C-Co-N4 combinations undergo different tetragonal elongation distortions along the C4 axis, characterized by the relative elongation ΔZ and displacement ΔZ' of Co2+ at different temperatures. Given the agreement between the calculated and experimental EPR parameters, as well as the adsorption properties, the six- and five-coordinated models are regarded as suitable for low- and high-temperature systems, respectively. These studies may be helpful to understand the properties of similar MOFs with adsorbed molecules under the effect of ambient temperature.

Studies on the local structures for the trigonal Ni3+ centers in cathode materials LiAly Co1-y O2 (y = 0, 0.1, 0.5, and 0.8).

The local angular distortions Δθ are theoretically studied for the various Ni3+ centers in LiAly Co1-y O2 at different Al concentrations (y = 0, 0.1, 0.5, and 0.8) based on the perturbation calculations of electron paramagnetic resonance g factors for a trigonally distorted octahedral 3d7 cluster with low spin (S = 1/2). Due to the Jahn-Teller effect, the [NiO6 ]9- clusters are found to experience the local angular distortions (Δθ ≈ 5°-9°) along the C3 axis. The variation trend of Δθ with y is in accordance with that of anisotropy (Δg = g||  - g⊥ ). As the substitutions can weaken bond strengths between transition metal and oxygen and the structural stability plays an important role in cathode performances, detailed investigations on the structural properties of the cathode materials LiAly Co1-y O2 can be practically helpful to understand the performances of these materials. The oxy-redox properties of LiAly Co1-y O2 systems are comprehensible in the framework of Ni3+ /Ni4+ couples, and the trigonally compressed octahedral [NiO6 ]9- clusters are applicable to the clarification of the electrochemical properties of lithium nickel oxide batteries. It appears that LiAl0.8 Co0.2 O2 with the largest Al concentration may correspond to the smallest distortion among the mixing systems.

Sesquiterpene amino ether and cytotoxic phenols from Dendrobium wardianum Warner.

A new bibenzyl derivative, dendrocandin V (1) and a new sesquiterpene amino ether, wardianumine A (2), together with eleven known compounds, including phenanthrenes (denbinobin (3), 9,10-dihydro-denbinobin (4), mostatin (5), loddigesiinols A (6)), bibenzyls (moscatilin (7), 5-hydroxy-3,4'-dimethoxybibenzyl (8), 3,4-dihydroxy-5,4'-dimethoxy bibenzyl (9), dendrocandin A (10), gigantol (11), dendrocandin U (12)) and an alkaloids (dihydroshihunine, 13) were isolated from the EtOH extraction of stems of Dendrobium wardianum Warner. Isolation of the new compound 2 indicated that N,N-dimethylethanolamine as the key adduction in the synthesis of dendroxine and its analogs in Dendrobium species. The hypothetical biosynthetic pathway of 2 was then postulated. Inspired by literature and traditional usage of the herbal medicine, some compounds were sent for cytotoxic activity and the results indicated that compounds 1, 3, 4, 5 showed cytotoxic activities against five human cancer cell lines (HL-60, A-549, SMMC-7721, MCF-7, and SW-480) with IC50 from 2.33-38.48µM. Among those compounds, 3 and 4 showed cell line selectivity with strong activity comparable to DDP.

[Rapid identification of Dendrobium plants based on near infrared diffuse reflection spectroscopy].

Near infrared diffuse reflection spectra of 15 species' 171 samples of Dendrobium combined with chemometrics statistical analysis were used to build prediction model, in order to discriminate different species of Dendrobium quickly and nondestructively. Hotelling T2 was applied to stability analysis of spectrum of 5 random drawing samples, and the results showed that the samples spectrum possessed good stability. Orthogonal test L24 (2 x 4 x 3 x 8) was designed to optimize optical path type, spectral band, derivative and smooth. The result of orthogonal test was analyzed by principal component analysis, which revealed that when 6500-4000 cm(-1) spectral band was applied, and with multiplicative scatter correction, second derivative, Norris smooth, and the number of principal components 7, the spectrum distinguishing accuracy was 100%. With the optimized condition of orthogonal test as the input value of partial least squares discriminant analysis and random drawing 123 samples as calibration set to establish the prediction model, and the rest 48 samples as prediction set were use to assess the property of the prediction model, the results indicated that the accumulating contribution rate of the first 3 principal components of the model was 99.36%, the identification of the standard deviation was +/- 0.1, and the correct recognition rate of the model was 97.92%. The results were satisfied. The method provided a new way for the rapid identification of different species of Dendrobium, and also supplied a reference for the authentication of medicinal plants.