White Phosphorus Is Air-Stable Within a Self-Assembled Tetrahedral Capsule

Mal, Prasenjit; Breiner, Boris; Rissanen, Kari; Nitschke, Jonathan R.

doi:10.1126/science.1175313

Cited by 1,062 publications

(640 citation statements)

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“…There have been previous examples of stimuli-responsive molecular cages (41,61) and baskets (45)(46)(47)(48)(49)(50)(51)(52)62) for targeted delivery; however, most of the systems lack the spontaneous spectral or other kinds of responses to facilitate instant signal detection. In contrast, the guest release and capture processes of the current molecular rectangles are capable of being probed by UV-vis absorption and emission titration studies.…”

Section: Resultsmentioning

confidence: 99%

Multiaddressable molecular rectangles with reversible host–guest interactions: Modulation of pH-controlled guest release and capture

Chan

Lam

Tanaka

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

122

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A series of multiaddressable platinum(II) molecular rectangles with different rigidities and cavity sizes has been synthesized by endcapping the U-shaped diplatinum(II) terpyridine moiety with various bisalkynyl ligands. The studies of the host-guest association with various square planar platinum(II), palladium(II), and gold(III) complexes and the related low-dimensional gold(I) complexes, most of which are potential anticancer therapeutics, have been performed. Excellent guest confinement and selectivity of the rectangular architecture have been shown. Introduction of pH-responsive functionalities to the ligand backbone generates multifunctional molecular rectangles that exhibit reversible guest release and capture on the addition of acids and bases, indicating their potential in controlled therapeutics delivery on pH modulation. The reversible host-guest interactions are found to be strongly perturbed by metal-metal and π-π interactions and to a certain extent, electrostatic interactions, giving rise to various spectroscopic changes depending on the nature of the guest molecules. Their binding mode and thermodynamic parameters have been determined by 2D NMR and van't Hoff analysis and supported by computational study. noncovalent interactions | platinum complex | luminescence T he study of metal-metal interactions has drawn enormous attention since the past two decades because of the intriguing spectroscopic and photophysical properties arising from the close proximity of the metal centers (1, 2). Square planar d 8 platinum(II) complexes with coordination unsaturation are one of the important classes of metal complexes that have been extensively explored because of their capability to exhibit metalmetal interactions and display rich photophysical properties (3-26). Platinum(II) terpyridine complexes have been found to exhibit rich polymorphism in the solid state (16)(17)(18)(19)(20) owing to their square planar coordination geometry, which permits facile access to Pt(II)···Pt(II) interactions as well as π-π interactions between the chromophores. It was not until 2001 that the first successful synthesis of platinum(II) terpyridine alkynyl complexes, which possess enhanced solubility and luminescence compared with the chloro counterpart, was reported (16). Additional efforts have been devoted to the use of the system to respond to external stimuli, such as variation in solvent composition (17, 18), pH (19, 20), temperature (21, 22), addition of ionic (24-26), and polymeric species (27,28), in which spectral changes induced by strong Pt(II)···Pt(II) and π−π interactions have been displayed.In the past few decades, enormous efforts have been devoted to the construction of molecular architectures by fusing the organic framework to the transition metal centers through selfassembly processes (29-57). There has been continuous interest in the construction of stimuli-responsive metallosupramolecular architectures with diverse sizes, shapes, and symmetries to rationalize the criteria for molecular recognition and impa...

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Section: Resultsmentioning

confidence: 99%

Multiaddressable molecular rectangles with reversible host–guest interactions: Modulation of pH-controlled guest release and capture

Chan

Lam

Tanaka

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

122

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“…[1] These may have hollow interiors where additional guest molecules or ions may be bound, and their ability to act as host assemblies means that a number of metallo-cage systems are being developed as nano-scale hosts and reaction vessels, with applications including the trapping of reactive species, [2] enabling unusual reactivities and catalysis [3] and templating nanoparticle formation. [4] Metallo-cages, also known as coordination cages, are examples of host assemblies where the individual molecular or ionic components do not necessarily have host-function themselves, which is a distinction from molecular hosts, which are individual molecules capable of binding guests.…”

Section: Introductionmentioning

confidence: 99%

Solvent‐Dependent Self‐Assembly Behaviour and Speciation Control of Pd₆L₈ Metallo‐supramolecular Cages

Henkelis

Fisher

Warriner

et al. 2014

Chemistry A European J

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“…To keep the two objects nearly concentric against the gravitational force, R has to be smaller than ≈ 1µm for the typical metal or liquid densities considered here. A variety of applications may benefit from our analysis; in cancer therapy new treatments utilize nanocarriers that trap drug particles inside R ≈ .1µm polymer or lipid membrane shells [8] and molecular cages are proposed as containers for the storage of explosive chemicals [9]. Our results may guide the search for better materials and sizes of the enclosing cell.…”

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confidence: 99%

Stable Levitation and Alignment of Compact Objects by Casimir Spring Forces

Rahi

Zaheer

2010

Phys. Rev. Lett.

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We investigate a stable Casimir force configuration consisting of an object contained inside a spherical or spheroidal cavity filled with a dielectric medium. The spring constant for displacements from the center of the cavity and the dependence of the energy on the relative orientations of the inner object and the cavity walls are computed. We find that the stability of the force equilibrium can be predicted based on the sign of the force, but the torque cannot be.The Casimir force between atoms or macroscopic objects arises from quantum fluctuations of the electrodynamic field [1,2]. In all known examples it is found that the force is attractive, as long as the space between the objects is empty, and the magnetic susceptibility of the objects is negligible compared to their electric susceptibilities. But when space is filled with a medium with electric permittivity M intermediate between that of two objects, 1 < M < 2 , the force between the two becomes repulsive [3]. This effect has recently been verified experimentally [4]. But while repulsive forces are nothing new, they become interesting for applications when they produce stable equilibria, which, for example, the Coulomb force cannot.For an infinite cylinder enclosed in another, the Casimir force has recently been shown to have a stable equilibrium in the two directions perpendicular to the cylinder axes, when the material properties are chosen so that the force between two slabs of the same materials would be repulsive [5]. If the inner and outer cylinders have square cross sections, the direction of the torque exerted by one cylinder on the other is found to agree qualitatively with the predictions of the pairwise summation or proximity force approximations (PSA or PFA). Orientation dependence of the Casimir energy has also been studied recently for a small spheroid facing another spheroid or an infinite plate [6], or for a small spheroid located inside a spherical metal cavity [7]. (The smallness of the spheroid refers to keeping only the first term in the series expansion of the Casimir energy in the largest length scale of the spheroid.) The preferred orientation of the small spheroid flips when it is moved between the inside and the outside of the spherical shell; there is no torque if the spheroid faces an infinite metal plate, which is the limit of an infinitely large shell.In this paper we investigate the first configuration, depicted in Fig. 1, in which a compact object levitates stably due to the Casimir force alone. We characterize the Casimir energyby the spring constant k and the coefficients k n in a series expansion in a/R, where a is the magnitude of the displacement from the center of the cavity and R the radius of the (undeformed) spherical cavity. (k has units of energy here.) Unlike the case of infinite cylinders, where one object can be displaced along the cylinder axes without changing the energy, our case exhibits, for appropriately chosen materials, true stability in all directions and applies to realistic situations. For example...

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White Phosphorus Is Air-Stable Within a Self-Assembled Tetrahedral Capsule

Cited by 1,062 publications

References 28 publications

Multiaddressable molecular rectangles with reversible host–guest interactions: Modulation of pH-controlled guest release and capture

Multiaddressable molecular rectangles with reversible host–guest interactions: Modulation of pH-controlled guest release and capture

Solvent‐Dependent Self‐Assembly Behaviour and Speciation Control of Pd₆L₈ Metallo‐supramolecular Cages

Stable Levitation and Alignment of Compact Objects by Casimir Spring Forces

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White Phosphorus Is Air-Stable Within a Self-Assembled Tetrahedral Capsule

Cited by 1,062 publications

References 28 publications

Multiaddressable molecular rectangles with reversible host–guest interactions: Modulation of pH-controlled guest release and capture

Multiaddressable molecular rectangles with reversible host–guest interactions: Modulation of pH-controlled guest release and capture

Solvent‐Dependent Self‐Assembly Behaviour and Speciation Control of Pd6L8 Metallo‐supramolecular Cages

Stable Levitation and Alignment of Compact Objects by Casimir Spring Forces

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Solvent‐Dependent Self‐Assembly Behaviour and Speciation Control of Pd₆L₈ Metallo‐supramolecular Cages