Guided by the self-assembled process
and mechanism, the strategy
of in situ Schiff base reaction would be capable of bringing a feasible
method to construct and synthesize lanthanide compounds with distinct
structures and magnetic properties. A mononuclear Dy(III) compound
was synthesized through a multidentate Schiff base ligand and a chelating
β-diketonate ligand, which was named as [Dy(L)(bppd)]·CH3OH [1; H2L = N,N′-bis(2-hydroxy-5-methyl-3-formylbenzyl)-N,N′-bis(pyridin-2-ylmethyl)ethylenediamine
and bppd = 3-bis(pyridin-2-yl)propane-1,3-dione]. Furthermore, a new
binuclear Dy(III) compound, [Dy2(H2Lox)(bppd)3]·8CH3OH [2; H4Lox
= N,N′-bis[2-hydroxy-5-methyl-3-(hydroxyiminomethyl)benzyl]-N,N′-bis(pyridin-2-ylmethyl)ethylenediamine],
was obtained via an in situ synthetic process. Under similar synthetic
conditions, [Dy(L)(ctbd)] [3; ctbd = 1-(4-chlorophenyl)-4,4,4-trifluoro-1,3-butanedione]
and [Dy2(H2Lox)(ctbd)3]·CH3OH·C4H10O (4) were
synthesized by modifying the β-diketonate ligand and in situ
Schiff base reaction. Compound 3 is a mononuclear configuration,
while compound 4 exhibits a binuclear Dy(III) unit. Therein,
formylbenzyl groups of H2L in 1 and 3 were changed to (hydroxyiminomethyl)benzyl groups in 2 and 4, respectively. In isomorphous 2 and 4, two Dy(III) centers are connected through two
phenol O– atoms of the H2Lox2– ligand to form a binuclear structure. Eight-coordinated Dy(III)
ions with different distortions can be observed in 1–4. The crystals of 1 and 3 suffered
dissolution/precipitation to obtain 2 and 4, respectively. The relationship between the structure and magnetism
in compounds 1–4 was discussed through
the combination of structural, experimental, and theoretical investigations.
Especially, the rates of quantum tunneling of magnetization of 1–4 were theoretically predicted and are
consistent with the experimental results. For 2 and 4, the theoretically calculated dipolar parameters J
dip are consistent with the experimental observation
of weak ferromagnetic coupling.
Solvent responsive magnets compose a class of molecule-based materials where latticed solvents driven structural transformation leads to the switching of magnetic properties. Herein, we present a special type of magnet...
Smart wet-spun fibers for highly programmable release of therapeutic drug have been rarely reported. Herein, thermalresponsive composite fibers were successfully prepared by core-sheath wet-spinning technology in present study. They consisted of a model drug of natural antibacterial
berberine chloride hydrate (BCH) and a drug carrier of temperature responsive shape memory polyurethane (SMPU). The obtained composite fibers featured with well-controlled microscopic morphologies, exhibiting significantly enhanced thermal stability and superb mechanical properties. In
vitro drug release test and corresponding release kinetics study were performed for investigation of BCH's release behavior. Results demonstrated that the release behaviors of BCH from the core-sheath fibers were pH-dependent, influenced by both diffusion from pore channels and the solubility
of BCH in the release mediums, and BCH imbedded only in core part showed a longer release period compared with that in both core and sheath parts of the composite fibers. More importantly, the release rate of BCH can be simply controlled by changing the initial shapes of fibers through stretching
and fixation of the stretched deformations. Furthermore, the antibacterial durability of the smart composites fibers was demonstrated and tracked according to the growth inhibition against both negative E. coli and positive S. aureus bacteria strains. All these results suggest
that the developed composite fibers can be promising candidates as smart drug delivery vehicles for highly adjustable doses of target drugs towards practical applications.
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