Filling the Missing Links of M_3<i>n</i> Prototype 3d-4f and 4f Cyclic Coordination Cages: Syntheses, Structures, and Magnetic Properties of the Ni₁₀Ln₅ and the Er_3<i>n</i> Wheels

In this paper, we proposed a number rule for 3d-4f and 4f cyclic coordination cages (CCCs); that is, CCCs consisting of vertex-sharing M₄(μ₃-OH)₄ (M = 3d transition metal or 4f lanthanide ions) units should have 3 × <i>n</i> metal centers (abbreviated M_3<i>n</i>), where <i>n</i> represents the number of the M₄(μ₃-OH)₄ subunits. Under this number rule we reasoned that some species of CCCs, for example, the pentadecanuclear 3d-4f wheel and the pure 4f wheels with 9 or 18 centers, should practically have existed. However, there are no such complexes reported in the literature. To realize such CCCs we employed a mixed-ligand approach, that is, to simultaneously use the primary and the ancillary ligands for syntheses. This approach successfully leads to the isolation of two families of CCCs, namely, the Ni₁₀Ln₅ (Ln = Gd and Y) mixed-metal wheels and the Er_3<i>n</i> (<i>n</i> = 4, 5, and 6) pure 4f metal wheels. These two families of CCCs unambiguously fill the missing links of the M_3<i>n</i> prototype CCCs. Moreover, dominated ferromagnetic interaction indicates high ground-spin state for the Gd₅Ni₁₀ wheel. The ferromagnetic interactions between the nickel centers are verified using the diamagnetic Y­(III) analogue, which reveals an averaged coupling constant (<i>J</i> = 2.7 cm^–1), while accompanied by a large negative zero-field splitting parameter (<i>D</i> = −6.1 cm^–1) for single Ni­(II) ions. Interestingly, the Y­(III)-diluted Er₁₂ wheel shows slow magnetic relaxation behavior, presumably indicating the magnetically anisotropic nature of the erbium­(III) ions

Topological Self-Assembly of Highly Symmetric Lanthanide Clusters: A Magnetic Study of Exchange-Coupling “Fingerprints” in Giant Gadolinium(III) Cages

The creation of a perfect hollow nanoscopic sphere of metal centers is clearly an unrealizable synthetic challenge. It is, however, an inspirational challenge from the viewpoint of chemical architecture and also as finite molecular species may provide unique microscopic insight into the origin and onset of phenomena such as topological spin-frustration effects found in infinite 2D and 3D systems. Herein, we report a series of high-symmetry gadolinium­(III) (<i>S</i> = 7/2) polyhedra, <b>Gd₂₀</b>, <b>Gd₃₂</b>, <b>Gd₅₀</b>, and <b>Gd₆₀</b>, to test an approach based on assembling polymetallic fragments that contain different polygons. Structural analysis reveals that the <b>Gd₂₀</b> cage resembles a dodecahedron; the vertices of the <b>Gd₃₂</b> polyhedron exactly reveal symmetry <i>O</i>_<i>h</i>; <b>Gd₅₀</b> displays an unprecedented polyhedron in which an icosidodecahedron <b>Gd₃₀</b> core is encapsulated by an outer <b>Gd₂₀</b> dodecahedral shell with approximate <i>I</i>_<i>h</i> symmetry; and the <b>Gd₆₀</b> shows a truncated octahedron geometry. Experimental and theoretical magnetic studies show that this series produces the expected antiferromagnetic interaction that can be modeled based on classical spins at the Gd sites. From the magnetization analyses, we can roughly correlate the derivative bands to the Gd–O–Gd angles. Such a magneto-structural correlation may be used as “fingerprints” to identify these cages

Core–Shell Ag@SiO₂ Nanoparticles Concentrated on a Micro/Nanofluidic Device for Surface Plasmon Resonance-Enhanced Fluorescent Detection of Highly Reactive Oxygen Species

A micro/nanofluidic device integrating a nanochannel in a microfluidic chip was developed for sensitive fluorescent determination of highly reactive oxygen species (hROS) enhanced by surface plasmon resonance-enhanced fluorescence (SPREF). The nanochannel was simply fabricated by polyaniline nanostructures modified on a glass slide. Core–shell Ag@SiO₂ nanoparticles were concentrated in front of the nanochannel for fluorescence enhancement based on the SPREF effect. As a demonstration, hROS in the mainstream of cigarette smoke (CS) were detected by the present micro/nanofluidic device. The fluorescent probe for trapping hROS in puffs of CS employed a microcolumn that was loaded with a composite of DNA (conjugated fluorophores, FAM) and Au membrane (coated on cellulose acetate). With a laser-induced fluorescence detection device, hROS was determined on the basis of the amount of FAM groups generated by DNA cleavage. With the optimization of the trapping efficiency, we detected about 4.91 pmol of hROS/puff in the mainstream CS. This micro/nanofluidic-SPREF system promises a simple, rapid, and highly sensitive approach for determination of hROS in CS and other practical systems