Dendrimer-Based Multinuclear Gold(I) Complexes

Magnetically controllable dual-mode nanoprobes for cell imaging with an onion-liked structure

A magnetically controllable dual-mode optical probe is demonstrated for cellular imaging with an onion-liked structure, which can exhibit both surface enhanced Raman scattering (SERS) and fluorescence signals. For obtaining such a nanoprobe, Fe3O4 nanoparticles were first encapsulated into an inner layer of silica, which were then coated with a second layer of gold nanoshell (designated as Fe3O4@SiO2@Au). By adjusting the thickness of the gold shell, the surface plasmon resonance (SPR) of Fe3O4@SiO2@Au nanoparticles can be easily tuned from visible to near-infrared (NIR) region. Afterwards, the prepared Fe3O4@SiO2@Au nanoparticles were tagged with a third layer of Raman reporters to exhibit SERS signals and further coated with an outmost layer of dye-doped silica to generate fluorescence. When being excited at different wavelengths as 515nm and 633nm, the distinct fluorescence and SERS signals can be separately observed. More interestingly, an enhanced cellular uptake of the presented nanoprobes was observed in the presence of a magnetic field, which was proved by both fluorescence and SERS images. This onion-liked multi-modal nanoplatform has great potential in bio-imaging, targeted delivery applications and biological separations.

Metal‐Containing Polymers

The focus of this article is on the synthesis, properties, and applications of metal‐containing polymers. These polymers may be classified based on the types of metal–ligand bonding, and whether the metal is an integral part of the polymer backbone or pendent to the polymer backbone. The first class of polymers discussed are those with metals σ‐bonded to organic spacers in their backbones. Examples of metal–metal single and multiple bonds are also described. Metallocenes and coordination polymers are two classes of polymers where the metal is π‐coordinated to the organic ligands. The coordination of metals to porphyrins, phthalocyanines, Schiff base ligands, as well as to many other types of ligands are described. Another major class of polymers are those where the metal is pendent to the polymer backbone. These polymers include materials with metallic moieties π‐coordinated to unsaturated ligands in their backbones. Polymers with metallic moieties in their side chains are also described. A brief overview of star polymers and dendrimers is also included.

Synthesis, electrochemistry, and interactions with beta-cyclodextrin of dendrimers containing a single ferrocene subunit located "off-center"

Two series of dendrimers containing a single ferrocene unit located in the focal point of these macromolecules have been synthesized and characterized. The first series of dendrimers has considerable lipophilic character, with tert-butyl ester groups located in their peripheral regions. In contrast, the second series of dendrimers was obtained by the hydrolysis of these peripheral ester groups, yielding water-soluble dendrimers with carboxylic acid groups in their surfaces. The electrochemical properties of these macromolecules were strongly affected by the dendritic groups attached to the ferrocene subunits. Host-guest interactions between the water-soluble dendrimers and the well-known receptor beta-cyclodextrin were also investigated. The dendritic groups were found to hamper markedly the formation of inclusion complexes between the cyclodextrin receptor and the dendrimer's ferrocene unit.

Dithiocarbamate-Functionalized Dendrimers as Ligands for Metal Complexes

Zeroth- and first-generation poly(amido)amine dendrimers have been functionalized with dithiocarbamate end groups and reacted with ruthenium complexes, to form metallodendrimers. Monomeric ruthenium dithiocarbamate complexes were also prepared as model compounds and their spectroscopic data compared with those of the metallodendrimers. The novel compounds were characterized using NMR spectroscopy ((1)H and (13)C) and mass spectrometry. The compound [Ru(S(2)CNMe(2))(PPh(3))(eta(5)-C(5)H(5))] has also been characterized crystallographically.

Crystal Structure, Electronic Structure, and Temperature-Dependent Raman Spectra of Tl[Ag(CN)(2)]: Evidence for Ligand-Unsupported Argentophilic Interactions

The structure of thallium dicyanoargentate(I) has been determined crystallographically. The crystal structure shows an Ag-Ag distance of 3.11 Å. This is the shortest Ag-Ag distance reported for any silver dicyanide salt whose crystal structure has been determined. Raman spectra of the compound show four nu(C)(-)(N) peaks that are well-resolved in the 10-80 K temperature range. This result agrees well with group theory analysis. Extended Hückel calculations using relativistic wave functions have been carried out for two models which describe the interactions between the Ag(CN)(2)(-) ions within the crystal structure of Tl[Ag(CN)(2)]. The results of these calculations indicate the formation of potential wells at short Ag-Ag distances. The data in this study suggest the significance of ligand-unsupported silver-silver interactions (argentophilicity) in Tl[Ag(CN)(2)]. Tl-Ag interactions are determined to be insignificant in the compound. Tl[Ag(CN)(2)] crystallizes in the monoclinic space group P2(1)/c (No. 14), with a = 7.798(1) Å, b = 14.685(3) Å, c = 8.566(2) Å, beta = 91.66(2) degrees, Z = 8, R = 0.0643, and R(w) = 0.0899.

Synthesis, Characterization, and Electrochemistry of Heterometallic Dendrimers

A method for the synthesis of new heterometallic dendritic molecules containing organoplatinum centers is reported. Reaction of Pt(2)Me(4)(&mgr;-SMe(2))(2) with bpy-Fc(2) (1) (bpy-Fc(2) = 4,4'-bis(ferrocenylvinyl)-2,2'-bipyridine) gave the platinum(II) complex PtMe(2)(bpy-Fc(2)) (2). Complex 2 undergoes oxidative addition with iodomethane to yield PtMe(3)I(bpy-Fc(2)) (3) and with bis(bromomethyl)benzenes to yield complexes of the type [PtMe(2)Br(bpy-Fc(2))CH(2)-](2)R (4, R = 1,2-C(6)H(4); 5, R = 1,3-C(6)H(4); 6, R = 1,4-C(6)H(4)). 1, 3, and 4 were characterized by X-ray structure determinations. For 1, a = 11.780(3) Å, b = 10.662(3) Å, c = 11.642(3) Å, beta = 118.61(2) degrees, and V = 1283.7(6) Å(3) while, for 2, a = 11.497(2) Å, b = 22.796(6) Å, c = 15.801(3) Å, beta = 106.08(1) degrees, and V = 3979(2) Å(3). Only poor quality crystals of 4 could be obtained resulting in a partial structure refinement with a = 14.46(1) Å, b = 15.14(1) Å, c = 21.32(2) Å, alpha = 69.45(4) degrees, beta = 71.14(5) degrees, gamma = 81.86(5) degrees and V = 4140(6) Å(3). The preferred conformation for 1 places the the bipyridine groups anti with respect to each other. However, as a consequence of the coordination to the metal centers in 3 and 4, they are located cis to each other, and the cyclopentadienyl rings attached directly to the vinyl groups lie on the same plane. In compound 4 the planes containing the platinum bipyridine units lie above and below the plane of the benzene ring, presumably to minimize steric hindrance. 2 also reacts with 1,3,5-tris(bromomethyl)mesitylene, 1,2,4,5-tetrakis(bromomethyl)benzene, and 1,2,3,4,5,6-hexakis(bromomethyl)benzene in 3:1, 4:1, and 6:1 molar ratios to yield the dendritic molecules [PtMe(2)Br(bpy-Fc(2))CH(2)-](n)()R [7, n = 3, R = 1,3,5-C(6)(CH(3))(3); 8, n = 4, R = 1,2,4,5-C(6)H(2); 9, n = 6, R = 1,2,3,4,5,6-C(6)], respectively. The largest dendrimer 9 contains six platinum and 12 ferrocene centers. Each complex undergoes a single 2n-electron electrochemical oxidation (corresponding to the ferrocenium/ferrocene couple of the bpy-Fc(2) ligands), confirming that the pendant ferrocenyl units are noninteracting. The number of ferrocene centers for each complex was determined both by exhaustive electrolysis and by a chronocoulometric/voltammetric assay.