Zaijun Li

Novel copper-azido magnetic molecular tapes: syntheses, structures, and magnetic properties

The reactions of copper(II) ions with azido ligands in the presence of different chelating amine ligands gave three one dimensional copper-azido molecular tapes, [Cu2(N-Pren)(N3)4]n (1), [Cu2(N-Buen)(N3)4]n (2) and [Cu3(tren)(N3)6]n (3) [N-Pren = N-propylethylenediamine; N-Buen = N-butylethylenediamine; tren = tris(2-aminoethyl)amine]. Complexes 1 and 2 are composed of 1D coordination chains based on the step-like tetranuclear copper(II) clusters which feature three types of azido bridging modes (μ-1,1, μ-1,3 and μ-1,1,1). Complex 3 is a novel 1D molecular tape featuring zigzag hexanuclear copper-azido subunits with only end-on azido bridges. Magnetic studies show ferromagnetic coupling in 1 and 2, and antiferromagnetic coupling in 3. The magnetic data for 1 and 2 were fitted with a tetranuclear copper theoretical model.

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.

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.

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