A microporous metal–organic framework (MOF) Eu3(MFDA)4(NO3)(DMF)3 (1, H2MFDA = 9,9-dimethylfluorene-2,7-dicarboxylic acid) has been solvothermally synthesized and structurally characterized by single-crystal X-ray diffraction. 1 is a three-dimensional coordination polymer with pcu type rod-packing structure, through which 1D rhombic channels penetrate. The solvent-free form 1a could be obtained by direct heating of 1. Both 1 and 1a exhibit high intensity red light emissions with high quantum yields and long luminescence lifetimes when excited at 336 nm at ambient temperature. The potential of 1a for nitro explosive sensing is studied through luminescence quenching experiments, which show that 1a is a potential luminescent sensory material for nitro explosives.
A series of dicyanomethylene-1,4-dihydropyridine (DCMP) derivatives with aggregation-induced emission (AIE) were designed and synthesized. These target compounds emit low fluorescence in THF solutions because of the free rotation of the phenyl and dihydropyridine rings about the axes of the olefinic double bonds and the resultant nonradiative decay process, but they exhibit strong fluorescence in the aggregate state because of the restriction of intramolecular rotation (RIR), as confirmed by solution thickening and cooling experiments. Compared with the almost-planar dicyanomethylene-4H-pyran (DCM) derivative DCM-1 with aggregation-caused quenching (ACQ), DCMP-5 with AIE takes a highly twisted conformation by replacing the oxygen atom of the DCM skeleton with an N-ethyl group, as revealed by crystallographic data and theoretical calculations. Depending on the different electron-donating substituents, the solids of these compounds emit yellow or orange fluorescence. Moreover, the cyano group endows DCMP-5 with a strong self-assembly ability under proper conditions, and the obtained regular microparticles emit bright orange fluorescence. These materials will broaden the new family of AIE-exhibiting fluorophores.
Residual dipolar coupling (RDC) is a powerful structural parameter for the determination of the constitution, conformation, and configuration of organic molecules. Herein, we report the first liquid crystal-based orienting medium that is compatible with MeOH, thus enabling RDC acquisitions of a wide range of intermediate to polar organic molecules. The liquid crystals were produced from self-assembled oligopeptide nanotubes (AAKLVFF), which are stable at very low concentrations. The presented alignment medium is highly homogeneous, and the size of RDCs can be scaled with the concentration of the peptide. To assess the accuracy of the RDC measurement by employing this new medium, seven bioactive natural products from different classes were chosen and analyzed. The straightforward preparation of the anisotropic alignment sample will offer a versatile and robust protocol for the routine RDC measurement of natural products.
Using
Dy(dbm)3(H2O) and Dy(btfa)3(H2O)2 to react with enantiopure N-donors, (−)/(+)-4,5-pinenepyridyl-2-pyrazine (L
R
/L
S
), respectively, two
pairs of chiral DyIII enantiomers, Dy(dbm)3L
R
/Dy(dbm)3L
S
(
R-1-Dy/
S-1-Dy) and Dy(btfa)3L
R
/Dy(btfa)3L
S
(
R-2-Dy/
S-2-Dy) were
obtained, wherein one of the benzene rings of dbm– (dibenzoylmethanate) in
R-1-Dy/
S-1-Dy is displaced by the −CF3 group of btfa– (4,4,4-trifluoro-1-phenyl-1,3-butanedionate)
in
R-2-Dy/
S-2-Dy. Interestingly, this substitution results not only in giant differences
in their single-ion magnetic (SIM) performances but also in their
completely different nonlinear optical (NLO) responses.
R-1-Dy presents a large effective energy barrier
(U
eff = 265.47 K) under zero applied field,
being more than 4 ×
R-2-Dy (61.40
K). The discrepancy on their magnetic performances has been further
elucidated by ab initio calculations. Meanwhile,
R-1-Dy/S-1-Dy display the
strongest third-harmonic generation responses (35/33 × α-SiO2) among the known lanthanide NLO-active coordination compounds
(CCs). On the contrary,
R-2-Dy/S-2-Dy exhibit moderate second-harmonic generation responses
(0.65/0.70 × KDP). These results not only give the first example
of the CCs with both SMM/SIM behavior and a THG response but also
provide an efficient strategy for achieving the function regulation
and switch in multifunctional CCs.
Fifteen new lignans, gymnothelignans A−O (1−15), bearing tetrahydrofuran with variable conformations belonging to three potentially related skeletons were isolated from Gymnotheca chinensis Decne. The structures were elucidated by means of detailed spectroscopic analysis. Absolute configurations were assigned using X-ray singlecrystal diffraction and chemical transformations. Moreover, by the homology, compounds 1−11 and eupomatilones were confirmed to have uniform R-configuration at C-5. However, a synthesized congener has long been mistaken as 5-epimer of eupomatilone-6. This work provides guidance for the absolute configuration establishment of the subeupomatilone family with trans-H-4−H-5 configuration.
Reaction of the chiral ligand (-)-4,5-pinenepyridyl-2-pyrazine (L) with Ln(hfac)3·2H2O precursors [hfac(-) = 1,1,1,5,5,5-hexafluoroacetylacetonate, Ln = Sm(3+) (1), Eu(3+) (2), Tb(3+) (3) and Dy(3+) (4)] in methanol solution led to the formation of four noncentrosymmetric lanthanide complexes with the general formula [Ln(hfac)3L]n·H2O. The single-crystal X-ray diffraction analyses revealed that they are isostructural and take a one-dimensional (1D) chain structure based on the Ln(hfac)3L repeating units, in which the nine-coordinate Ln(3+) ions reside in a tricapped trigonal prism (TTP) environment never reported in previous 1D chain lanthanide complexes. The investigations of their photophysical properties showed that complexes 1, and 3 exhibit characteristic emissions of Sm(3+), Eu(3+) and Tb(3+) ions with respective luminescent lifetime values of 0.065, 1.066 and 0.129 ms, while complex 4 does not display any emission. The different luminescent intensities and lifetimes among them were further discussed in detail. Moreover, the magnetic properties of complexes 1-4 were assessed with a special emphasis on the Dy(3+) complex 4. Alternating-current (ac) magnetic susceptibility measurements indicated that field-induced two-step slow magnetic relaxation processes were observed in 4, indicating the single-molecule magnet (SMM) behavior of 4. In addition, the noncentrosymmetric complexes 1-4 crystallizing in the same polar point group (Cs) exhibit both ferroelectric and nonlinear optical properties at room temperature. All these features make them multifunctional crystalline molecule materials.
Six d10 metal metal-organic coordination polymers, {[Zn2(Htpim)2(tp)2]·2H2O}
n
(1), {[Cd3(H0.5tpim)4(pa)2(H2O)2]·5H2O}
n
(2), [Zn(Htpim)2(Htma)]
n
(3), {[Zn4(Htpim)4(ip)4]·2H2O}
n
(4), [Cd(Htpim)(ca)]
n
(5), and {[Cd4(Htpim)2(d-ca)4(H2O)2]·5H2O}
n
(6) (Htpim = 2,4,5-tri(4-pyridyl)-imidazole, H2tp = terephthalic acid, H2pa = phthalic acid, H3tma = trimesic acid, H2ip = isophthalic acid, H2ca = racemic camphor acid, d-H2ca = d-camphor acid), have been prepared and structurally characterized. In all complexes, the rigid ligand Htpim exhibits different coordination modes and leads to the formation of various architectures. Complex 1 shows a two-dimensional (2D) network with (6,3) topology, where hydrogen-bonding interactions further link these sheets to a three-dimensional (3D) supramolecular structure. Complex 2 exhibits a 2D layer with (53)(54) network topology. Complex 3 is a corrugated 2D layer with (4,4) topology, and the separated layers are connected through weak π−π stacking interactions to generate a 3D supramolecular architecture. Complex 4 is a rhombic 2D layer with (4,4) topology, and the 3D overlapped array is formed by hydrogen-bonding and π−π stacking interactions. A 3D diamondoid framework with 4-fold interpenetration is found in 5. Complex 6 contains a complicated 3D framework, and the vacancy is occupied by the guest water molecules. Their luminescent properties have been investigated in the solid state.
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