Yanlan Wang

'Click' synthesis and redox properties of triazolyl cobalticinium dendrimers.

The derivatization of macromolecules with redox-stable groups is a challenge for molecular electronics applications. The large majority of redox-derivatized macromolecules involve ferrocenes, and there are only a few reports with cobalticinium. We report here the first click derivatization of macromolecules with the cobalticinium redox group using ethynylcobalticinium hexafluorophosphate, 1. Cu(I) catalysis was used for these selective click metallodendrimer syntheses starting from 1 and providing the tripodal dendron 3 that contains three 1,2,3-triazolylcobalticinium termini and a phenol focal point and the dendrimers of generations 0, 1, and 2 containing 9, 27, and 81 triazolylcobalticinium units for the dendrimers 4, 5, and 6, respectively. Atomic force microscopy (AFM) statistical studies provided the progression of height upon increase of dendrimer generation. Cyclic voltammetry studies in MeCN and dimethylformamide (DMF) show the solvent-dependent reversibility of the Co(III/II) wave (18e/19e) and generation dependent reversibility of the Co(II/I) (19e/20e) wave in DMF. The H2PO4(-) anion is only recognized by the largest metallodendrimer 6 by a significant cathodic shift of the Co(III/II) wave.

A Simple Synthesis of Triangular All‐Metal Aromatics Allowing Access to Isolobal All‐Metal Heteroaromatics

A simple synthetic method allows the one-pot assembly of C3 -symmetric, 44-core-valence-electron, triangular Pd or Pt clusters and their heterobimetallic mixed Pd/Pt analogues. These mixed metal complexes are the first examples of stable triangular all-metal heteroaromatics. In contrast to traditional heteroaromatic molecules formed combining main-group elements, they actually retain structural and electronic features of their homonuclear analogues.

Synthesis and Redox Activity of “Clicked” Triazolylbiferrocenyl Polymers, Network Encapsulation of Gold and Silver Nanoparticles and Anion Sensing

The design of redox-robust polymers is called for in view of interactions with nanoparticles and surfaces toward applications in nanonetwork design, sensing, and catalysis. Redox-robust triazolylbiferrocenyl (trzBiFc) polymers have been synthesized with the organometallic group in the side chain by ring-opening metathesis polymerization using Grubbs-III catalyst or radical polymerization and with the organometallic group in the main chain by Cu(I) azide alkyne cycloaddition (CuAAC) catalyzed by [Cu(I)(hexabenzyltren)]Br. Oxidation of the trzBiFc polymers with ferricenium hexafluorophosphate yields the stable 35-electron class-II mixed-valent biferrocenium polymer. Oxidation of these polymers with Au(III) or Ag(I) gives nanosnake-shaped networks (observed by transmission electron microscopy and atomic force microscopy) of this mixed-valent Fe(II)Fe(III) polymer with encapsulated metal nanoparticles (NPs) when the organoiron group is located on the side chain. The factors that are suggested to be synergistically responsible for the NP stabilization and network formation are the polymer bulk, the trz coordination, the nearby cationic charge of trzBiFc, and the inter-BiFc distance. For instance, reduction of such an oxidized trzBiFc-AuNP polymer to the neutral trzBiFc-AuNP polymer with NaBH4 destroys the network, and the product flocculates. The polymers easily provide modified electrodes that sense, via the oxidized Fe(II)Fe(III) and Fe(III)Fe(III) polymer states, respectively, ATP(2-) via the outer ferrocenyl units of the polymer and Pd(II) via the inner Fc units; this recognition works well in dichloromethane, but also to a lesser extent in water with NaCl as the electrolyte.

Visible-light generation of the naked 12-electron fragment C5H5Fe+: alkyne-to-vinylidene isomerization and synthesis of polynuclear iron vinylidene and alkynyl complexes including hexairon stars.

Visible-light photolysis of [FeCp(η(6)-C(6)H(5)CH(3))][PF(6)] using a simple 100-W bulb or a compact fluorescent light bulb in the presence of terminal alkynes and dppe yielded the vinylidene complexes [FeCp(═C═CHR)(dppe)][PF(6)] that were deprotonated by t-BuOK to yield the alkynyl complexes [FeCp(-C≡CR)(dppe)]. The reaction has been extended to the synthesis of bis-, tris, tetra-, and hexanuclear iron complexes including three alkynes of the ferrocenyl family.

Review: Mixed-valent metallodendrimers: design and functions

Various types of mixed-valent metallodendrimers and star-shaped macromolecules containing ferrocenyl, biferrocenyl, or other redox-robust iron groups with rigid or flexible tethers of short and long lengths mostly studied in the authors’ laboratory including the class type in terms of Robin-Day classification and their functions including electrode modification, sensing, and nanoparticle templates are discussed in this mini review. Graphical Abstract

Catalytic Semireduction of Internal Alkynes with All-Metal Aromatic Complexes

A simple catalytic method involving all‐metal aromatic frameworks as precatalysts ensures an efficient route to (Z)‐alkenes. Aromatic triangular palladium clusters were used to reduce internal alkynes without any trace of the formation of alkane side products. These trinuclear complexes provide a catalytic system that parallels the activity and selectivity of their best mononuclear peers, and the catalyst likely operates through complementary mechanisms.

Dentromers, a Family of Super Dendrimers with Specific Properties and Applications

Dentromers (from dentro, δεντρο: tree in Greek), and meros (μεροσ, in greek: part) are introduced as a family of dendrimers constructed according to successive divergent 1 → 3 branching. The smaller dentromers have 27 terminal branches. With alcohol termini they were originally named arborols by Newkome, who pioneered 1 → 3 constructions of dendrimers and dendrons. Giant dentromers have been constructed and decorated in particular with ferrocene and other redox active groups. The synthesis, specific properties, and applications are examined in this mini review article dedicated to Don Tomalia, with an emphasis on dense peripheral packing favoring the functions of encapsulation, redox sensing, and micellar template for catalysis in water and aqueous solvents.