Chiral Zn3Ln3 Hexanuclear Clusters of an Achiral Flexible Ligand.

Multifunctional single-molecule magnets (SMMs) have sparked great interest, but chiral SMMs obtained via spontaneous resolution are rarely reported. We synthesized a series of chiral trinuclear hepta-coordinate lanthanide complexes [ZnII3LnIII3] (1 for Dy, 2 for Tb, 3 for Gd, and 4 for Dy0.07Y0.93) using the achiral flexible ligand H2L (2,2'-[1,2-ethanediylbis[(ethylimino)methylene]]bis[3,5-dimethylphenol]). The complexes crystallize in the chiral P63 group space, and two enantiomers of different chirality are spontaneously resolved. Three [Zn(L)Cl]- anions utilize the two phenoxy oxygen atoms of each L2- to coordinate with three lanthanide ions, respectively, and the three hepta-coordinate D5h lanthanide ions are arranged in a triangle. The chirality comes from the propeller arrangement of the peripheral three bidentate chelate L2- ligands like octahedral [M(AA)3]n+/- (M = transition metal ions; AA = bidentate chelate ligands, e.g., 2,2'-bipyridine, 1,10-phenathroline, ethylenediamine, acac- or oxalate). Complex 1 exhibits an AC susceptibility signal and is frequency-dependent, which is typical of SMMs. Complex 4, doped with a large amount of diamagnetic Y(III) in Dy(III), exhibits Ueff = 48.3 K and τ0 = 4.4 × 10-8 s in experiments. Complex 2 shows circularly polarized luminescence and apparent photoluminescence, typical of the f-f transitions of Tb(III).

Structural Modulation of Fluorescent Rhodamine-Based Dysprosium(III) Single-Molecule Magnets.

Two rhodamine 6G-based mononuclear dysprosium complexes, [Dy(LR)(LA)2](ClO4)3·Et2O·1.5MeOH·0.5H2O (1) and [Dy(LR)(H2O)4(MeCN)](ClO4)3·2H2O·MeCN (2) (LR = salicylaldehyde rhodamine 6G hydrazone, LA = 2-pyridylcarboxaldehyde benzoyl hydrazone), are synthesized, aiming at improving the magnetic behavior by modulating their coordination environment. Both complexes own one exclusive short Dy-Ophenoxy coordination bond as the predominant bond and exhibit single-molecule magnet behavior under zero dc field with the energy barrier (Ueff/kB) of 90 K (1) and 320 K (2) and apparent hysteresis at 1.9 K. The ab initio calculations indicate that the short Dy-Ophenoxy bond determines the direction of magnetic anisotropic axis for 1 and 2. The quantum tunneling of magnetization (QTM) between the ground Kramers doublets (KDs) in 1 cannot be neglected, leading to an experimental Ueff/kB much lower than the calculated energy of the first excited state (318.2 K). For 2, the stronger magnetic anisotropy and negligible QTM between the ground KDs guarantees that the energy barrier is close to the calculated energy of first KDs (320.8 K). On the other hand, the presence of ring-opened xanthene moiety makes complexes 1 and 2 in the solid state emit red light with emission bands of 645 and 658 nm, respectively.

MicroRNA-141-3p inhibits retinal neovascularization and retinal ganglion cell apoptosis in glaucoma mice through the inactivation of Docking protein 5-dependent mitogen-activated protein kinase signaling pathway.

Retinal neovascularization occurs in various ocular disorders including proliferative diabetic retinopathy and secondary neovascular glaucoma, resulting in blindness. This paper aims to investigate the effect of microRNA-141-3p (miR-141-3p) on retinal neovascularization and retinal ganglion cells (RGCs) in glaucoma mice through the Docking protein 5 (DOK5)-mediated mitogen-activated protein kinase (MAPK) signaling pathway. Chip retrieval and difference analysis were used for the potential mechanism of miR-141-3p on glaucoma. All modeled mice were transfected with different expression of mimic or inhibitor. The expressions of miR-141-3p, DOK5, and related genes and proteins of the MAPK signaling pathway were detected by Reverse transcription quantitative polymerase chain reaction and western blot analysis. Cell proliferation, lumen formation, and apoptosis in the retinal vascular epithelial cells and RGCs were detected using Matrigel angiogenesis and terminal deoxynucleotidyl transferase mediated dUTP nick-end labeling assays. Moreover, a total of 63 and 294 differentially expressed genes were obtained in GSE2378 and GSE9944 chips, and 4 genes were within the intersection of the chips. In addition, the results showed that miR-141-3p was found to inhibit the DOK5 gene and activate the MAPK pathway. The number of RGCs, the expression of p38, extracellular-signal-regulated kinases (ERK), Jun N-terminal kinase (JNK), IGF-1, VEGF, HIF1-α, Bax, caspase-3, and the extent of p38, ERK, and JNK phosphorylated were decreased with miR-141-3p upregulation. Lastly, the results obtained showed that miR-141-3p inhibited the proliferation of retinal vascular epithelial cells and inhibited angiogenesis, as well as promoted apoptosis of RGCs. The study suggests that miR-141-3p inhibits retinal neovascularization in glaucoma mice by impeding the activation of the DOK5-mediated MAPK signaling pathway.

Two new cobalt(II) rhodamine 6G hydrazone complexes: structure, fluorescence and magnetism.

Two new CoII complexes, namely bis{N-[(6-bromopyridin-2-yl)methylidene]-2-[6-ethylamino-3-(ethyliminiumyl)-2,7-dimethyl-3H-xanthen-9-yl]benzene-1-carbohydrazonate}cobalt(II) bis(perchlorate)-dichloromethane-methanol (1/1/2), [Co(C32H30BrN5O2)2](ClO4)2·CH2Cl2·2CH3OH or [CoII(L)2](ClO4)2·CH2Cl2·2CH3OH, (1), and the bis(tetrafluoridoborate) salt, [Co(C32H30BrN5O2)2](BF4)2·CH2Cl2·2CH3OH or [CoII(L)2](BF4)2·CH2Cl2·2CH3OH, (2) (L is commonly 6-bromopyridine-2-carbaldehyde rhodamine 6G hydrazone), have been successfully constructed and characterized. The crystal structure analysis revealed that complexes (1) and (2) are mononuclear and have a CoIIN4O2 distorted octahedral structure. The large π-conjugated xanthene moiety of the L ligand causes strong intermolecular π-π stacking interactions, yielding a supramolecular one-dimensional chain. Complexes (1) and (2) display an obvious fluorescence emission near 560 nm in the solid state. Magnetic investigations show that both (1) and (2) are paramagnetic, dominated by the structural distortion and spin-orbit coupling of CoII.

Rhodamine 6G-Labeled Pyridyl Aroylhydrazone Fe(II) Complex Exhibiting Synergetic Spin Crossover and Fluorescence.

Here, we use a pyridinecarbaldehyde rhodamine 6G hydrazone ligand (L) to synthesize an Fe(II) complex 1 for the search of new fluorescent-spin crossover (SCO) materials. Single-crystal structural determinations suggest that the Fe(II) ion is chelated by two ring-opened ligands (L-o) to form a FeN4O2 coordination environment, and intermolecular π---π contacts of the xanthene groups connect the adjacent molecules to form a supramolecular one-dimensional chain. Magnetic susceptibility measurements on complex 1 show that three-step SCO takes place in the temperature range of 120-350 K, and its desolvated form 1-d exhibits SCO around room temperature ( Tc↑ = 343 K and Tc↓ = 303 K) with a wide hysteresis loop of 40 K. Moreover, complex 1-d displays light-induced excited spin-state trapping phenomenon. Intriguingly, the fluorescence intensity of the maximum emission at 560 nm for complex 1-d displays discontinuous variation in the range of 250-400 K, indicative of the occurrence of synergetic fluorescence and SCO.

Rhodamine Salicylaldehyde Hydrazone Dy(III) Complexes: Fluorescence and Magnetism.

Three new dysprosium(III) complexes [Dy2(HL1-o)2(L1)(NO3)3][Dy(NO3)5]·1.5ACE·0.5Et2O (1), [Dy(L1)3]·2.5MeOH·MeCN (2), and [Dy(L2)3]·MeOH·MeCN (3) (HL1 = rhodamine B salicylaldehyde hydrazine, HL2 = rhodamine B 3-methylsalicylaldehyde hydrazine) were synthesized and characterized. Purple complex 1 contains two ring-open ligands HL1-o and shows fluorescence of the rhodamine amide moiety, whereas yellow complexes 2 and 3 are comprised of ring-close ligands (L1/2)- and display fluorescence of the salicylaldehyde Schiff base part. For 2 and 3, Dy(III) ions are nine coordinated by the six oxygen and three nitrogen atoms of three chelate (L1/2)- ligands, but the arrangements of the three ligands are different owing to the methyl substituent on HL2. There are three short predominant Dy-Ophenoxy bonds in 2 and 3. The largest Ophenoxy-Dy-Ophenoxy angle is 148.64(17)° for 2 and 89.63(13)° for 3. Magnetic studies reveal that complex 2 is a field-induced single-molecule magnet ( Ueff = 104.2 K under a dc magnetic field of 2000 Oe), and 3 exhibits only a magnetic relaxation behavior owing to the quantum tunneling of magnetization (QTM). Furthermore, ab initio calculations illustrate that the disposition of predominant Dy-Ophenoxy bonds affects the magnetic anisotropy of the Dy(III) ions and relaxation processes of complexes 2 and 3.

Iron(iii) complexes of 2-methyl-6-(pyrimidin-2-yl-hydrazonomethyl)-phenol as spin-crossover molecular materials.

Four new mononuclear Fe(iii) complexes 1-4 of 2-methyl-6-(pyrimidin-2-yl-hydrazonomethyl)-phenol (H2L) have been synthesized and characterized by magnetic susceptibility measurements and single-crystal X-ray diffraction analysis. Complexes 1-3 are ionic compounds with the formula [Fe(HL)2]X·nsolvent (X = ClO4- (1), BF4- (2) and Cl- (3)), while complex 4 ([Fe(HL)(L)]) is neutral. The central Fe(iii) ion in complexes 1-4 is coordinated by four nitrogen and two oxygen atoms of two Schiff base ligands HL- or L2-, and the coordination geometries of FeIII are all distorted octahedral. Magnetic measurements indicate that complex 1 shows an abrupt spin transition with a thermal hysteresis of 32 K (T1/2↓ = 158 K and T1/2↑ = 190 K), and complex 4 exhibits a gradual incomplete spin transition. Complexes 2 and 3 are high spin with a room-temperature χmT value of 4.32 cm3 K mol-1 and 4.39 cm3 K mol-1, respectively.

Chiral six-coordinate Dy(iii) and Tb(iii) complexes of an achiral ligand: structure, fluorescence, and magnetism.

Two new chiral six-coordinate lanthanide complexes (1 for Dy and 2 for Tb) have been synthesized using the achiral flexible ligand H2L (2,2'-[1,2-ethanediylbis[(methylimino)methylene]]bis[4,5-dimethylphenol]). Both complexes crystallize in the chiral P1 group space, and the enantiomers [Zn(L)Cl]3Dy·MeOH·0.5H2O (Λ-1), [Zn(L)Cl]3Dy·1.5H2O (Δ-1), [Zn(L)Cl]3Tb·1.5H2O (Λ-2) and [Zn(L)Cl]3Tb·H2O (Δ-2) are isolated in the reaction. Three [Zn(L)Cl]- anions coordinate to the central lanthanide ion using two phenoxo oxygen atoms of L2-, and the lanthanide ion has the coordination geometry of D3. Complex 1 exhibits a field-induced slow magnetization relaxation, which is typical of a single-ion magnet (SIM). Ab initio calculations on complex 1 and studies on magneto-structural correlationship of six-coordinate Dy(iii) SIMs indicate that the small energy barrier of complex 1 might be related to the absence of a unique anisotropic axis for the regular octahedral coordination configuration of Dy(iii) and the high quantum tunneling gap between the ground states (mJ = ±15/2). Complex 2 displays green photofluorescence and triboluminescence.

Metallocyclic Ni4Ln2M2 single-molecule magnets.

We herein report the synthesis, crystal structure and magnetic properties of nine new heterotrimetallic complexes. [Ni(Me2valpn)] (H2Me2valpn = N,N'-bis(3-methoxysalicylidene)-2,2-dimethyl-1,3-diaminopropane) was used as the precursor to construct phenoxo-bridged [Ni2Ln]3+ (Ln3+ = Dy, Tb, Gd and Y) species that were respectively connected by two [M(CN)6]3- (M = Cr, Fe or Co) anions to form octanuclear cyclic complexes, i.e. {[Ni(Me2valpn)]2Ln(H2O)M(CN)6}2 in which Ln = Y, Gd, Tb and Dy and M = Cr, Fe or Co (1-9). Each of the complexes contains many lattice-bound molecules of solvation. The Ni(ii) ions are penta-coordinate, while the Ln(iii) ions are nine coordinated with a muffin geometry. The fitting to the χmT vs. T curves of complexes 6-9 gave the parameters of JNiCr = 11.82 cm-1, JNiGd = 0.94 cm-1 and g = 2.04 for complex 6, JNiFe = 10.58 cm-1, JNiGd = 1.24 cm-1 and g = 2.03 for complex 7, JNiCr = 9.4(1) cm-1, zJ' = -0.050(2) cm-1 and g = 2.06(1) for complex 8 and JNiFe = 4.9(7) cm-1, zJ' = -0.35(2) cm-1 and g = 2.24(1) for complex 9, respectively. The dynamic magnetic investigations demonstrate that complexes 1-5 display single-molecule magnet properties with an effective energy barrier (Ueff) of 38.9 K (1, M1 = Dy, M2 = Cr), 37.2 K (2, M1 = Dy, M2 = Cr), 24.4 K (3, M1 = Dy, M2 = Co), 21.9 K (4, M1 = Tb, M2 = Cr) and 29.6 K (5, M1 = Tb, M2 = Fe), respectively. Complex 1 shows the highest energy barrier among the octanuclear [Ni4LnM2] (Ln = Dy or Tb, M = Fe, Cr, Co or W) system. Although the [Ni4Dy2Cr2] complexes have Ueff higher than that of [Ni4Dy2Fe2], complex [Ni4TbCr2] shows lower Ueff than that of [Ni4TbFe2]. The results indicate that besides the M-C[triple bond, length as m-dash]N-Ni magnetic coupling the lanthanide ions can significantly affect the magnetic performances of heterotrimetallic SMMs as well. Moreover, the SMMs are achieved when diamagnetic Co(iii) was substituted by paramagnetic Cr(iii) or Fe(iii) in the [Ni4Tb2 M2] system, suggesting that the trimetallic strategy is effective in the construction of new 3d-4f SMMs.

A novel three-dimensional CdII metal-organic framework based on [Cd6(malonate)6] metallomacrocycles with zeolite SOD (sodalite) topology: poly[ammine-µ3-malonato-cadmium(II)].

A novel Cd(II) metal-organic framework, [Cd(C(3)H(2)O(4))(NH(3))](n), was synthesized by liquid diffusion conducted in the presence of ammonia. The Cd(II) atom has seven-coordinate O(6)N pentagonal-bipyramidal geometry. Six Cd(II) centers are joined by six malonate ligands to form an S(6)-symmetric [Cd(6)(malonate)(6)] metallomacrocycle, which is further extended through a side-on chelating malonate ligand to form a three-dimensional network. Topologically, each Cd(II) center is connected to four others to yield an infinite three-periodic four-coordinated SOD (sodalite) network with point symbol {4(2)·6(4)}. The overall network structure in the crystal is maintained and stabilized by the presence of N-H...O hydrogen bonds.