Zhi-o Gu

A green strategy for lithium isotopes separation by using mesoporous silica materials doped with ionic liquids and benzo-15-crown-5

Three new mesoporous silica materials IL15SGs (HF15SG, TF15SG and DF15SG) doped with benzo-15-crown-5 and imidazolium based ionic liquids (C8mim+PF6−, C8mim+BF4− or C8mim+NTf2−) have been prepared by a simple approach to separating lithium isotopes. The formed mesoporous structures of silica gels have been confirmed by transmission electron microscopy image and N2 gas adsorption–desorption isotherm. Imidazolium ionic liquids acted as templates to prepare mesoporous materials, additives to stabilize extractant within silica gel, and synergetic agents to separate the lithium isotopes. Factors such as lithium salt concentration, initial pH, counter anion of lithium salt, extraction time, and temperature on the lithium isotopes separation were examined. Under optimized conditions, the extraction efficiency of HF15SG, TF15SG and DF15SG were found to be 11.43, 10.59 and 13.07xa0%, respectively. The heavier isotope 7Li was concentrated in the solution phase while the lighter isotope 6Li was enriched in the gel phase. The solid–liquid extraction maximum single-stage isotopes separation factor of 6Li–7Li in the solid–liquid extraction was up to 1.046xa0±xa00.002. X-ray crystal structure analysis indicated that the lithium salt was extracted into the solid phase with crown ether forming [(Li0.5)2(B15)2(H2O)]+ complexes. IL15SGs were also easily regenerated by stripping with 20xa0mmolxa0L−1 HCl and reused in the consecutive removal of lithium ion in five cycles.

Spin crossover-graphene nanocomposites: facile syntheses, characterization, and magnetic properties

A facile way to fabricate spin crossover-graphene nanocomposites has been developed, and [Fe(Htrz)2(trz)](BF4)–graphene (SCO-G) nanocomposites have been successfully synthesized and characterized. SEM and TEM demonstrated that [Fe(Htrz)2(trz)](BF4) nanoparticles (ca. 50 nm) were distributed uniformly onto the surface of the graphene. Interestingly, graphene as a substrate produced an effect on the spin crossover properties of [Fe(Htrz)2(trz)](BF4) nanoparticles.

SCO@SiO2@Au core–shell nanomaterials: enhanced photo-thermal plasmonic effect and spin-crossover properties

We report here an effective synthetic route to gold coated spin-crossover core–shell nanocomposites (SCO@SiO2@Au) in which [Fe(Htrz)2(trz)](BF4)@SiO2 (SCO@SiO2) served as a support to the Au nanoparticles. The obtained core–shell nanocomposites were studied using numerous characterization techniques to define the structure, morphology, composition and especially the spin-crossover properties. The transmission electron micrographs illustrated that Au nanoparticles with an average diameter around 2.5 nm were decorated uniformly on the surface of SCO@SiO2. X-ray photoelectron spectroscopy measurements further confirmed the successful incorporation of gold nanoparticles on spin-crossover core. The Raman spectrum indicated that the plasmonic Au nanoparticles caused an efficient photo-thermal heating in the SCO@SiO2@Au nanocomposites, leading to a ∼100 times reduction of laser energy needed for spin state switching compared with SCO@SiO2. The magnetic study demonstrated that the embedded Au nanoparticles not only influenced the spin transition temperatures but also changed the widths of hysteresis loops. SCO@SiO2@Au nanocomposites may be applied to various areas where the fascinating spin-crossover core and the functional gold shell can be beneficial.

The solid–liquid extraction separation of lithium isotopes by porous composite materials doped with ionic liquids and 2,2′-binaphthyldiyl-17-crown-5

A green and efficient solid–liquid extraction method of lithium isotopes separation by porous composite materials doped with imidazolium ionic liquids and 2,2′-binaphthyldiyl-17-crown-5 has been reported in this paper. The composite materials of mesoporous silica and impregnated resin were synthesized by sol–gel and direct impregnation process, respectively. Various extraction parameters such as the concentration of lithium salt, anion of lithium salt, initial pH, time and temperature were investigated. Under optimized conditions, the maximum single-stage separation factor of 6Li/7Li was 1.048xa0±xa00.002, the maximum extraction efficiency was 15.86xa0%. The sorbents can be regenerated easily with HCl solution and reused repeatedly.

Enantioselective DNA condensation induced by heptameric lanthanum helical supramolecular enantiomers.

DNA condensation induced by a pair of heptameric La(III) helical enantiomers M-[La7(S-L)6(CO3)(NO3)6(OCH3)(CH3OH)7]·2CH3OH·5H2O and P-[La7(R-L)6(CO3)(NO3)6(OCH3)(CH3OH)5(H2O)2]·2CH3OH·4H2O (M-La and P-La, L=2-(2-hydroxybenzylamino)-3-carbamoylpropanoic acid) has been investigated by UV/vis spectroscopy, fluorescence spectroscopy, CD spectroscopy, EMSA, RALS, DLS, and SEM. The enantiomers M-La and P-La could induce CT-DNA condensation at a low concentration as observed in UV/vis spectroscopy. DNA condensates possessed globular nanoparticles with nearly homogeneous sizes in solid state determined by SEM (ca. 250 nm for M-La and ca. 200 nm for P-La). The enantiomers bound to DNA through electrostatic attraction and hydrogen bond interactions in a major groove, and rapidly condensed free DNA into its compact state. DNA decompaction has been acquired by using EDTA as disassembly agent, and analyzed by UV/vis spectroscopy, CD spectroscopy and EMSA. Moreover, the enantiomers M-La and P-La displayed discernible discrimination in DNA interaction and DNA condensation, as well as DNA decondensation. Our study suggested that lanthanum(III) enantiomers M-La and P-La were efficient DNA packaging agents with potential applications in gene delivery.

Optical recognition of alkyl nitrile by a homochiral iron(II) spin crossover host

A homochiral complex 1·MeCN was synthesized by the multicomponent self-assembly of (R)-phenylethylamine, 1-methyl-2-imidazolecarboxaldehyde and iron(II) ions in acetonitrile solution. X-ray crystallography analysis revealed that complex 1·MeCN crystallized in the chiral space group P21. The octahedral coordination mononuclear [FeL3]2+ cations are stacked into a left-handed double helix supramolecular structure along the a axis with uncoordinated acetonitrile molecules filling the helical channel. Interestingly, when 1·MeCN redissolved in racemic lactonitrile (LN) or methylglutaronitrile (MGN), the [FeL3]2+ cations can recognize one enantiomeric alkyl nitrile by forming 1·1/3(R)-LN or 1·1/3(S)-MGN crystals. 1·1/3(R)-LN and 1·1/3(S)-MGN crystallized in the P212121 space group, and the [FeL3]2+ cations are stacked in a triple helix mode with the enantiomeric alkyl nitrile captured in the helical channel. Magnetic measurement indicated that 1·MeCN displayed spin-crossover at 355 K, while the transition temperature became 220 K after desolvation. However, 1·1/3(R)-LN and 1·1/3(S)-MGN exhibited incomplete and reversible spin-crossover behaviors at about 363 K. The results demonstrated that the mononuclear iron(II) complex could be used as a host for racemic alkyl nitrile separation, and the spin-crossover property was influenced by the process of chiral recognition.

Liquid–liquid extraction to lithium isotope separation based on room-temperature ionic liquids containing 2,2′-binaphthyldiyl-17-crown-5

A novel liquid–liquid extraction system was investigated for the selective separation of lithium isotopes using ionic liquids (ILs = C8mim+PF6−, C8mim+BF4−, and C8mim+NTf2−) as extraction solvent and 2,2′-binaphthyldiyl-17-crown-5 (BN-17-5) as extractant. The effects of the concentration of lithium salt, counter anion of lithium salt, initial pH of aqueous phase, extraction temperature, and time on the lithium isotopes separation were discussed. Under optimized conditions, the maximum single-stage separation factor α of 6Li/7Li obtained in the present study was 1.046 ± 0.002, indicating the lighter isotope 6Li was enriched in IL phase while the heavier isotope 7Li was concentrated in the solution phase. The formation of 1:1 complex Li(BN-17-5)+ in the IL phase was determined on the basis of slope analysis method. The large value of the free energy change (−ΔG° = 92.89 J mol−1) indicated the high separation capability of the Li isotopes by BN-17-5/IL system. Lithium in Li(BN-17-5)+ complex was stripped by 1 mol L−1 HCl solution. The extraction system offers high efficiency, simplicity, and green application prospect to lithium isotope separation.

Dinuclear nickel(II) triple-stranded supramolecular cylinders: Syntheses, characterization and G-quadruplexes binding properties

Three dinuclear nickel triple-stranded supramolecular cylinders [Ni2(L1)3][ClO4]4 (1), [Ni2(L2)3][ClO4]4 (2) and [Ni2(L3)3][ClO4]4 (3) with bis(pyridylimine) Schiff base containing triphenyl groups in the spacers as ligands were synthesized and characterized. The human telomeric G-quadruplexes binding properties of cylinders 1-3 were evaluated by means of UV-Vis spectroscopy, circular dichroism (CD) spectroscopy and fluorescence resonance energy transfer (FRET) melting assay. UV-Vis studies revealed that the supramolecular cylinders 1-3 could bind to G-quadruplex DNA with high binding constants (Kb values ranging from 0.11-2.2×10(6) M(-1)). FRET melting studies indicated that the cylinders 1-3 had much stronger stabilizing effect on G-quadruplex DNA (ΔTm up to 24.5°C) than the traditional cylinder Ni2L3(4+) just containing diphenylmethane spacers (ΔTm=10.6 °C). Meanwhile, cylinders 1-3 were found to have a modest degree of selectivity for the quadruplex DNA versus duplex DNA in competition FRET assays. Moreover, CD spectroscopy revealed that complex 1 could induce G-quadruplex formation in the absence of metal ions solution and convert antiparallel G-quadruplex into hybrid structure in Na(+) solution. These results provided a new insight into the development of supramolecular cylinders as potential anticancer drugs targeting G-quadruplex DNA.

CCDC 801714: Experimental Crystal Structure Determination

Related Article: Zhi-Guo Gu, Bao-Xiang Wang, Jing-Jing Na, Xin-Hui Zhou, Zaijun Li|2011|Inorg.Chem.Commun.|14|839|doi:10.1016/j.inoche.2011.03.002