Interconversion between a Vertically Oriented Transition Metal-Complexed Figure-of-Eight and a Horizontally Disposed One

A large ring containing two pairs of transition metal-complexing fragments with alternating bi- and tridentate chelates has been shown to behave as a bimodal figure-of-eight. When coordinated to a preferentially octahedrally coordinated Fe­(II) or Cu­(II) center, the height of the molecule along the coordinating axis of the tridentate ligands (vertical on the drawing) is only ∼11 Å, whereas the height of the molecule along the same vertical axis is several times as large for the complex of the tetrahedrally coordinated copper­(I) center. This new type of molecular machine-prototype could be used as constitutive element in muscle-like dynamic systems

Copper(I)-Assembled [3]Rotaxane Whose Two Rings Act as Flapping Wings

A new copper-complexed [3]­rotaxane consisting of two coordinating 30-membered rings threaded by a two-binding-site axis has been prepared in good yield from relatively simple organic fragments. The main specificity of the system originates from the stoppering reaction, based on “click” chemistry, and thus from the presence of two triazole groups at positions next to the bidentate chelates of the axis central part. The geometry of the coordinating atoms belonging to the axis is such that the triazole groups can either be part of the coordinating fragments when the metal center is 5-coordinate or be not at all involved in coordination to the metal when the latter is 4-coordinate. To be more specific, when the two complexed metal centers are monovalent copper­(I) centers, the triazoles are not included in the metal coordination sphere, whereas when the metal centers are Cu­(II) or Zn²⁺, the triazole groups are bound to the metals. This is easily explained by the fact that Cu­(I) is preferably 4-coordinate and Cu­(II) and Zn²⁺ are 5-coordinate. The interconversion between both situations (4- or 5-coordinate) can be quantitatively induced by metal exchange (Cu­(I)/Zn²⁺) or by a redox process (Cu­(II)/Cu­(I)). It leads to important geometrical changes and in particular to a strong modification of the angle between the two rings. As a consequence, the two threaded rings undergo a motion which is reminiscent of a wing-flapping movement similar to that of birds. This flapping motion is fast and quantitative. It should lead to new functional molecular machines in the future

Photoexpulsion of Surface-Grafted Ruthenium Complexes and Subsequent Release of Cytotoxic Cargos to Cancer Cells from Mesoporous Silica Nanoparticles

Ruthenium­(II) polypyridyl complexes have emerged both as promising probes of DNA structure and as anticancer agents because of their unique photophysical and cytotoxic properties. A key consideration in the administration of those therapeutic agents is the optimization of their chemical reactivities to allow facile attack on the target sites, yet avoid unwanted side effects. Here, we present a drug delivery platform technology, obtained by grafting the surface of mesoporous silica nanoparticles (MSNPs) with ruthenium­(II) dipyridophenazine (dppz) complexes. This hybrid nanomaterial displays enhanced luminescent properties relative to that of the ruthenium­(II) dppz complex in a homogeneous phase. Since the coordination between the ruthenium­(II) complex and a monodentate ligand linked covalently to the nanoparticles can be cleaved under irradiation with visible light, the ruthenium complex can be released from the surface of the nanoparticles by selective substitution of this ligand with a water molecule. Indeed, the modified MSNPs undergo rapid cellular uptake, and after activation with light, the release of an aqua ruthenium­(II) complex is observed. We have delivered, in combination, the ruthenium­(II) complex and paclitaxel, loaded in the mesoporous structure, to breast cancer cells. This hybrid material represents a promising candidate as one of the so-called theranostic agents that possess both diagnostic and therapeutic functions

Photoexpulsion of Surface-Grafted Ruthenium Complexes and Subsequent Release of Cytotoxic Cargos to Cancer Cells from Mesoporous Silica Nanoparticles

Ruthenium­(II) polypyridyl complexes have emerged both as promising probes of DNA structure and as anticancer agents because of their unique photophysical and cytotoxic properties. A key consideration in the administration of those therapeutic agents is the optimization of their chemical reactivities to allow facile attack on the target sites, yet avoid unwanted side effects. Here, we present a drug delivery platform technology, obtained by grafting the surface of mesoporous silica nanoparticles (MSNPs) with ruthenium­(II) dipyridophenazine (dppz) complexes. This hybrid nanomaterial displays enhanced luminescent properties relative to that of the ruthenium­(II) dppz complex in a homogeneous phase. Since the coordination between the ruthenium­(II) complex and a monodentate ligand linked covalently to the nanoparticles can be cleaved under irradiation with visible light, the ruthenium complex can be released from the surface of the nanoparticles by selective substitution of this ligand with a water molecule. Indeed, the modified MSNPs undergo rapid cellular uptake, and after activation with light, the release of an aqua ruthenium­(II) complex is observed. We have delivered, in combination, the ruthenium­(II) complex and paclitaxel, loaded in the mesoporous structure, to breast cancer cells. This hybrid material represents a promising candidate as one of the so-called theranostic agents that possess both diagnostic and therapeutic functions

Photoexpulsion of Surface-Grafted Ruthenium Complexes and Subsequent Release of Cytotoxic Cargos to Cancer Cells from Mesoporous Silica Nanoparticles

Ruthenium­(II) polypyridyl complexes have emerged both as promising probes of DNA structure and as anticancer agents because of their unique photophysical and cytotoxic properties. A key consideration in the administration of those therapeutic agents is the optimization of their chemical reactivities to allow facile attack on the target sites, yet avoid unwanted side effects. Here, we present a drug delivery platform technology, obtained by grafting the surface of mesoporous silica nanoparticles (MSNPs) with ruthenium­(II) dipyridophenazine (dppz) complexes. This hybrid nanomaterial displays enhanced luminescent properties relative to that of the ruthenium­(II) dppz complex in a homogeneous phase. Since the coordination between the ruthenium­(II) complex and a monodentate ligand linked covalently to the nanoparticles can be cleaved under irradiation with visible light, the ruthenium complex can be released from the surface of the nanoparticles by selective substitution of this ligand with a water molecule. Indeed, the modified MSNPs undergo rapid cellular uptake, and after activation with light, the release of an aqua ruthenium­(II) complex is observed. We have delivered, in combination, the ruthenium­(II) complex and paclitaxel, loaded in the mesoporous structure, to breast cancer cells. This hybrid material represents a promising candidate as one of the so-called theranostic agents that possess both diagnostic and therapeutic functions