Polymorph transformation in a mixed-stacking nickel-dithiolene complex with the derivative of 4,4'-bipyridinium.

In this study, two polymorphs of the [1,1'-dibutyl-4,4'-bipyridinium][Ni(mnt)2] salt (1) were synthesized. The dark-green polymorph (designated as 1-g) was prepared under ambient conditions by the rapid precipitation method in aqueous solutions. Subsequently, the red polymorph (labeled as 1-r) was obtained by subjecting 1-g to ultrasonication in MeOH at room temperature. Microanalysis, infrared spectroscopy, thermogravimetry (TG), differential scanning calorimetry (DSC), and powder X-ray diffraction (PXRD) techniques were used to characterize the two polymorphs. Both 1-g and 1-r exhibit structural phase transitions: a reversible phase transition at ∼403 K (∼268 K) upon heating and 384 K (∼252 K) upon cooling for 1-g (1-r) within the temperature range below 473 K. Interestingly, on heating 1-r to 523 K, an irreversible phase transition occurred at about 494 K, resulting in the conversion of 1-r into 1-g. Relative to 1-r, 1-g represents a thermodynamically metastable phase wherein numerous high-energy conformations in butyl chains of cations are confined within the lattice owing to quick precipitation or rapid annealing from higher temperatures. Through variable-temperature single crystal and powder X-ray diffractions, UV-visible spectroscopy, dielectric spectroscopy, and DSC analyses, this study delves into the mechanism underlying phase transitions for each polymorph and the manual transformation between 1-g and 1-r as well.

Two-step thermotropic phase transition and dielectric relaxation in 1D supramolecular lead iodide perovskite [NH4@18-crown ether]PbI3.

The supramolecular lead iodide perovskite crystals, {[NH4(18-crown-6)]PbI3}∞ (1), (18-crown-6 = 1,4,7,10,13,16-hexaoxacyclooctadecane), was successfully achieved by a facile solvent evaporation strategy using a DMF solution containing equal molar quantities of PbI2, NH4I and 18-crown-6. The supramolecular perovskite was characterized by microanalysis for C, H and N elements, thermogravimetric (TG) analysis, differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD) and single crystal X-ray diffraction techniques. DSC measurements demonstrated that 1 experiences a two-step thermotropic phase transition around 333 K and 383 K, respectively. The phase transition is relevant to the disorder-order transformation of the 18-crown-6 molecule at ∼333 K, while both breaking-symmetry and ordered-disordered transformation of the 18-crown-6 molecule occurred at ∼383 K. In addition, the sharp change of the PbI6 coordination octahedron distortion degree plays a synergistic role in the two-step phase transition. The dielectric relaxation occurs above 243 K in 1 and is mainly attributed to the displacement of the NH4+ ions relative to the ring of the 18-crown-6 molecule and {PbI3}∞ chain induced by an AC electrical field.

Encapsulation of cuprous/cobalt sites in metal organic framework for enhanced C2H4/C2H6 separation.

Adsorbents based on CuI for π-complexative separation of C2H4/C2H6 have attracted widespread interests. However, they are still confronting some challenges, for example, (i) a low separation efficiency, resulted from the ineffective reduction of CuII to CuI along with aggregation, and (ii) poor stability due to the oxidation of CuI to inactive CuII. In this study, active Cu and auxiliary Co species are simultaneously encapsulated within the nanopores of MIL-101 using a double-solvent (DS) method to obtain CuCoM-DS. The Cu species at the interior of MIL-101 are homogeneously dispersed and can be completely reduced to CuI without any structural damage to MIL-101. The resulting CuCoM-DS exhibits a superior performance in C2H4/C2H6 separation not only to the pristine MIL-101, but to the counterpart samples of single Cu and/or Cu/Co at the exterior of MIL-101. The best sample of 1.5CuCoM-DS adsorbent is capable to adsorb 50.5 mL·g-1 of C2H4, and the C2H4/C2H6 selectivity is 2.6 at 100 kPa. Both C2H4 uptake and C2H4/C2H6 selectivity are higher than those reference samples. Moreover, 1.5CuCoM-DS preserves over 90% of fresh C2H4 uptake after the exposure to atmospheric air for 12 days. This study provides new design ideas for confining bimetallic sites in MOFs for broad applications.

PI3K/Akt signaling pathway is involved in the neurotrophic effect of senegenin.

Neurodegenerative diseases are frequently associated with the loss of synapses and neurons. Senegenin, extracted from the Chinese herb Polygala tenuifolia Willd, was previously found to promote neurite outgrowth and neuronal survival in primary cultured rat cortical neurons. The aim of the present study was to investigate the underlying mechanisms of senegenin-induced neurotrophic effects on rat cortical neurons. Primary cortical rat neurons were treated with various pharmacological antagonists and with or without senegenin, and subjected to MTT and western blot analysis to explore the effects of senegenin on cell survival as well as the activation of signaling pathways. Neurite outgrowth and neuronal survival induced by senegenin were significantly inhibited by A2A receptor antagonist ZM241385 and specific phosphoinositide-3 kinase (PI3K) inhibitor LY294002, but not by tropomyosin receptor kinase A receptor inhibitor K252a, mitogen-activated protein kinase kinase inhibitor PD98059 or protein kinase C inhibitor GÖ6976. Furthermore, senegenin enhanced the phosphorylation of Akt, which was blocked by LY294002. The present study revealed that the PI3K/Akt signaling pathway may be involved in the neurotrophic effects of senegenin.

[Identification of nuclear localization signals of pseudorabies virus gene UL49].

Tegument protein VP22 is encoded by Pseudorabies Virus (PRV) UL49. To identify the nuclear localization signals of UL49, it is necessary to determine the transport mechanism and biological functions of the VP22 protein. In this study, we identified two nuclear localization signals from UL49, NLS1 (5RKTRVA ADETASGARRR21) and NLS2 (241PGRKGKV247). The functional nuclear localization signal (NLS) of UL49 was identified by constructing truncated or site-specific UL49 mutants. The deletion of both NLS1 and NLS2 abrogated UL49 nuclear accumulation, whereas the deletion of NLS1 or NLS2 did not. Therefore, both NLS1 and NLS2 are critical for the nuclear localization of UL49. And our resuts showed that NLS2 is more important in this regard.

Observation of hysteretic magnetic phase transitions coupled with orientation motion of ions and dielectric relaxation in a one-dimensional nickel-bis-dithiolene molecule solid.

The second polymorph, the ß-crystal, of the nickel-bis-dithiolene compound [4'-CF3bzPy][Ni(mnt)2], where 4'-CF3bzPy = 1-(4'-trifluoromethylbenzyl)pyridinium and mnt(2-) = maleonitriledithiolate, was obtained. The variable-temperature single crystal structures, magnetic behavior in 1.8-300 K and dielectric nature in 123-373 K have been investigated for the ß-crystal. This polymorph experiences two hysteretic magnetic phase transitions in a narrow temperature region (190-217 K) with the thermal hysteresis loops ca. 6 K and ca. 11 K. The two hysteretic magnetic phase transitions are coupled with two isostructural phase transitions (IPTs), respectively, which are driven by the novel step-wise dynamic orientation motion of the anion and cation in the ß-crystal. There is an absence of a dielectric anomaly in the structural transformation temperature interval. However, a dielectric relaxation, related to the dipole motion of polar CF3 groups in the cations under an ac electrical field, emerges in the high-temperature phase.

Intercalated supramolecular compounds of kaolinite with ethanolamine and ethylene glycol: structures and dielectric properties.

Kaolinite (K), a polar and layered aluminosilicate mineral, was used as the host; ethanolamine (EOA) and ethylene glycol (EG) were inserted into the kaolinite interlayer to give the intercalated supramolecular compounds kaolinite-ethanolamine (K-EOA) and kaolinite-ethylene glycol (K-EG), respectively. The intercalation of EOA and EG resulted in an increase in the d(001)-value by 3.4 and 3.68 Å, which corresponds to expansion of the interlayer space by 156.7 Å(3) in K-EOA and 169.6 Å(3) in K-EG, respectively. The characteristic infrared-active ν(O-H) modes ν1, ν2 and ν3 besides ν5, which were quite sensitive to the host-guest interaction, were not significantly affected by intercalation in K-EOA and K-EG, and two intercalated compounds showed lower deintercalation temperature (115 and 109 °C for K-EOA and K-EG, respectively). These are due to weakly intermolecular interactions between the intercalant molecules and the kaolinite framework, which is in agreement with the theoretical analysis of crystal structures of the intercalated compounds. K-EOA and K-EG showed novel dielectric relaxation behavior, which originates from the dynamic orientation motion of intercalant molecules.

Disorder-order transformation and significant dislocation motion cooperating with a surprisingly large hysteretic magnetic transition in a nickel-bisdithiolene spin system.

The compound [4'-CF3bzPy][Ni(mnt)2] (1) (where 4'-CF3bzPy = 1-(4'-(trifluoromethyl)benzyl)pyridinium and mnt(2-) = maleonitriledithiolate) was synthesized and displays a magnetic bistability with a surprisingly large thermal hysteresis loop (~49 K). X-ray crystallographic studies reveal that in the high-temperature (HT) phase the anions and cations form mixed stacks, with alternating anion dimers (AA) and cation dimers (CC) in an ...AACCAACC... fashion along the crystallographic a + b direction, and disordered CF3 groups in the cations are aligned into a molecular layer parallel to the crystallographic (001) plane. However, in the low-temperature (LT) phase, the c-axis length of the unit cell is roughly doubled, and the asymmetric unit switches from one [4'-CF3bzPy][Ni(mnt)2] pair in the HT phase to two [4'-CF3bzPy][Ni(mnt)2] pairs. Most interestingly, the CF3 group in the cations becomes ordered, and the conformation of one of two crystallographically different cations changes significantly. A dislocation motion between the neighboring molecular layers emerges as well. The analyses of the magnetic susceptibilities and the density functional theory calculations suggest that the antiferromagnetic exchange interaction within one of two types of [Ni(mnt)2]2(2-) dimers in the LT phase is much stronger than that within the [Ni(mnt)2]2(2-) dimer in the HT phase. The lattice reorganization during this phase transition is proposed to be responsible for the wide thermal hysteresis loop.

Influence of isotope substitution on lattice and spin-Peierls-type transition features in one-dimensional nickel bis-dithiolene spin systems.

Four new 1D spin-Peierls-type compounds, [D(5)]1-(4'-R-benzyl)pyridinium bis(maleonitriledithiolato)nickelate ([D(5)]R-Py; R=F, I, CH(3), and NO(2)), were synthesized and characterized structurally and magnetically. These 1D compounds are isostructural with the corresponding non-deuterated compounds, 1-(4'-R-benzyl)pyridinium bis(maleonitriledithiolato)nickelate (R-Py; R=F, I, CH(3), and NO(2)). Compounds [D(5)]R-Py and R-Py (R=F, I, CH(3), and NO(2)) crystallize in the monoclinic space group P2(1)/c with uniform stacks of anions and cations in the high-temperature phase and triclinic space group P1 with dimerized stacks of anions and cations in the low-temperature phase. Similar to the non-deuterated R-Py compounds, a spin-Peierls-type transition occurs at a critical temperature for each [D(5)]R-Py compound; the magnetic character of the 1D S=1/2 ferromagnetic chain for [D(5)]F-Py and the 1D S=1/2 Heisenberg antiferromagnetic chain for others appear above the transition temperature. Spin-gap magnetic behavior was observed for all of these compounds below the transition temperature. In comparison to the corresponding R-Py compound, the cell volume is almost unchanged for [D(5)]F-Py and shows slight expansion for [D(5)]R-Py (R=I, CH(3), and NO(2)) as well as an increase in the spin-Peierls-type transition temperature for all of these 1D compounds in the order of F>I≈CH(3)≈NO(2). The large isotopic effect of nonmagnetic countercations on the spin-Peierls-type transition critical temperature, T(C), can be attributed to the change in ω(0) with isotope substitution.

Observation of intramolecular vibrations cooperating with the magnetic phase transition in a nickel-bis-dithiolene compound.

A new one-dimensional (1-D) ion-pair compound, [1,7-bis(1-methylimidazolium)heptane][Ni(mnt)(2)](2) (mnt(2-) = maleonitriledithiolate), was synthesized and characterized structurally and magnetically. This compound shows a spin-Peierls-type transition at around 235 K. Its crystal structure belongs to the monoclinic system with space group C2/c and the magnetic [Ni(mnt)(2)](-) anions form uniform stacks in the high-temperature (HT) phase. The crystal undergoes a transformation into the triclinic space group P1 accompanied by the magnetic transition and the anion stacks become dimerized in the low-temperature (LT) phase. The entropy changes (ΔS) are estimated to be 0.772 J K(-1) mol(-1) for the spin-Peierls-type transition, from DSC data, which is much less than the spin entropy change (ΔS = R ln 2 ≈ 5.76 J K(-1) mol(-1)), indicating that a substantial short-range order persists above the transition temperature. The variable temperature IR spectra showed that the peak positions and intensities for the bands near 1160 and 725 cm(-1), which correspond respectively to the ν(C-C) + ν(C-S) mode of the mnt(2-) ligands and the rocking vibration mode of the methylene group γ(r)(CH(2)) in the cation moiety, undergo an abrupt change at around 240 K, close to the transition temperature. This observation demonstrates that the intramolecular vibrations of both the anion and the counter-cation probably couple with the spins to cooperate with the spin-Peierls-type phase transition in this 1-D spin system.

[Study of sexual hormone changes in prostate cancer patients before and after androgen deprivation therapy].

OBJECTIVES: To investigate and observe serum sexual hormone (testosterone, T; free testosterone, FT; dihydrotestosterone, DHT) changes in patients with prostate cancer (PCa) before and after androgen deprivation. METHODS: Serum T, FT, DHT were measured with radioimmunoassay in 16 cases with PCa respectively one week before and the fifth day after androgen deprivation. The changes of T, FT, DHT were analyzed. RESULTS: Serum T, FT, DHT declined 92.27%, 92.26%, 58.36% respectively. They were statistically significant before and after androgen deprivation (P < 0.001). CONCLUSIONS: After androgen deprivation, most T and FT were deprived while DHT declined 58.36% only. Androgen receptor competitor shall be applied continually to prohibit the action of remnant androgen.

Structural, morphological, and magnetic study of nanocrystalline cobalt-nickel-copper particles.

Nanocrystalline Co(x)Ni(y)Cu(100-x-y) particles were synthesized by the reduction of metal acetates in a mixture of polyol and Tween 80. Inductively coupled plasma (ICP) analysis revealed that the actual wt% of Co, Ni, and Cu in these nanoparticles was nearly the same as in the starting solutions. The structures of the particles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED) spectroscopy, and vibrating sample magnetometry (VSM). The results of XRD and VSM confirmed that there was no metastable alloying in the particles. The particles were composites, consisting of nanoscale crystallites of face-centered cubic (fcc) Cu, face-centered cubic (fcc) Ni, and face-centered cubic (fcc) Co. During preparation the nucleation of Cu occurred first; then small Cu nuclei acted as cores for the precipitation of Co and Ni. The particles showed an increase in saturation magnetization (M(s)) as the concentration of Co or Ni in the particles was increased. The changes of both M(s) and coercivity of the particles with increasing annealing temperatures were studied. The coercivity of the particles was very high; it could reach as high as 489 Oe for Co34.3Ni31.2Cu34.5) .

Self-assembly of L-cysteine-copper(II)/copper(I) multilayer thin films on gold.

Self-assembled multilayer thin films have been prepared on Au substrate by alternate surface derivatization with L-cysteine hydrochloride and cupric perchlorate. The layer-by-layer structure at each step of multilayer formation was investigated by X-ray photoelectron spectroscopy. The measurements indicate that there are two structure modes in the multilayers. One is that Cu(2+) sandwiches between two amino acid groups. The other one is that Cu(+) is bonded through disulfide and thiolate. This process is also confirmed by cyclic voltammetry of Cu ion at different self-assembled multilayers. Steps further on will lead to repeated multilayer films.