Composition-defined nanosized assemblies that contain heterometallic early 4d/5d-transition-metals

The controlled assembly of early transition metals remains a challenging research target, especially with respect to the generation of heterometallic molecules and nanomaterials. In this study, metal chlorides of the early 4d/5d-transition-metals, i.e., ZrCl₄, NbCl₅, MoCl₅, HfCl₄, TaCl₅, and WCl₆, were stoichiometrically introduced into a tetraphenylmethane-core dendritic-phenylazomethine generation 4 dendrimer in the presence of an optimal amount of organic ligands such as pyridine and 3-chloropyridine. The coordinative interactions between the metal chlorides and the imines in the dendrimers indicated a positive correlation for the Lewis acidity of the metals. Moreover, it was clearly demonstrated for the first time that heterometallic assemblies of defined composition contain four kinds of early 4d/5d-transition-metals, such as Ta^V, Nb^V, Mo^V, and Zr^IV, which was confirmed by UV-vis titration, XPS, and HAADF-STEM/EDS measurements. The results of this study should provide access to new routes to produce nanomaterials composed of heterometallic early 4d/5d-transition metals.

Cd2+ coordination: an efficient structuring switch for polypeptide polymers

Stimuli-responsive polypeptides have practical applications in devices and therapeutic delivery. Here we report that coordination to Cd²⁺ metal species can be used as a robust stimulus to control both, α-helix and β-sheet secondary structuring of polypeptide polymers.

Smart metallopoly(l-glutamic acid) polymers: reversible helix-to-coil transition at neutral pH

Coordination to Zn species can be reversibly used to control the helix-to-coil transition of synthetic poly(l-glutamic acid) polymers at a neutral pH of 7.

Synthesis of triple-bond-containing 1-hydroxy-1,1-bisphosphonic acid derivatives to be used as precursors in "click" chemistry: two examples

The synthesis of novel (ω-alkynyl-1-hydroxy-1,1-diyl)bisphosphonic acid tetramethyl esters (1a-c), their P,P'-dimethyl esters (2a-c), and two trimethyl ester derivatives (3a and 3b) is reported. The prepared compounds can be attached to many kinds of molecules containing azide (-N3) functionalities using a "click" chemistry approach. As an example, bisphosphonate trimethyl ester 3a and P,P'-dimethyl ester 2b were attached to triethylene glycol to form triethylene glycol-bisphosphonate conjugates 4 and 5 as model compounds for further studies in, for example, nanoparticle targeting.