Tuning Bro̷nsted Acidity by up to 12 p Units in a Redox-Active Nanopore Lined with Multifunctional Metal Sites.

Electrostatic interactions, hydrogen bonding, and solvation effects can alter the free energies of ionizable functional groups in proteins and other nanoporous architectures, allowing such structures to tune acid-base chemistry to support specific functions. Herein, we expand on this theme to examine how metal sites ( = H, Zn, Co, Co) affect the p of benzoic acid guests bound in discrete porphyrin nanoprisms () in CDCN. These host-guest systems were chosen to model how porous metalloporphyrin electrocatalysts might influence H transfer processes that are needed to support important electrochemical reactions (e.

Cage Match: Comparing the Anion Binding Ability of Isostructural Versus Isofunctional Pairs of Metal-Organic Nanocages.

Affinities of six anions (mesylate, acetate, trifluoroacetate, p-toluenecarboxylate, p-toluenesulfonate, and perfluorooctanoate) for three related Pt -linked porphyrin nanocages were measured to probe the influence of different noncovalent recognition motifs (e. g., hydrogen bonding, electrostatics, π bonding) on anion binding.

Controlling Intramolecular and Intermolecular Electronic Coupling of Radical Ligands in a Series of Cobaltoviologen Complexes.

Controlling electronic coupling between multiple redox sites is of interest for tuning the electronic properties of molecules and materials. While classic mixed-valence (MV) systems are highly tunable, e.g.

Gram-scale synthesis of a covalent nanocage that preserves the redox properties of encapsulated fullerenes.

Discrete nanocages provide a way to solubilize, separate, and tune the properties of fullerenes, but these 3D receptors cannot usually be synthesized easily from inexpensive starting materials, limiting their utility. Herein, we describe the first fullerene-binding nanocage (Cage) that can be made efficiently on a gram scale. Cage was prepared in up to 57% yield by the formation of pyridinium linkages between complemantary porphyrin components that are themselves readily accessible.

Accessing three oxidation states of cobalt in ML nanoprisms with cobalt-porphyrin walls.

Nanocages with porphyrin walls are common, but studies of such structures hosting redox-active metals are rare. Pt-linked ML nanoprisms with cobalt-porphyrin walls were prepared and their redox properties were evaluated electrochemically and chemically, leading to the first time that cobalt-porphyrin nanocages have been characterized in Co, Co, and Co states.

Uptake, Trapping, and Release of Organometallic Cations by Redox-Active Cationic Hosts.

The host-guest chemistry of metal-organic nanocages is typically driven by thermodynamically favorable interactions with their guests such that uptake and release of guests can be controlled by switching this affinity on or off. Herein, we achieve this effect by reducing porphyrin-walled cationic nanoprisms and to zwitterionic states that rapidly uptake organometallic cations Cp*Co and CpCo, respectively. Cp*Co binds strongly ( = 1.

Unexpected Formation of Metallofulleroids from Multicomponent Reactions, with Crystallographic and Computational Studies of the Cluster Motion.

New multicomponent reactions involving an isocyanide, terminal or internal alkynes, and endohedral metallofullerene (EMF) Lu N@C yield metallofulleroids which are characterized by mass-spectrometry, HPLC, and multiple 1D and 2D NMR techniques. Single crystal studies revealed one ketenimine metallofulleroid has ordered Lu N cluster which is unusual for EMF monoadducts. Computational analysis, based on crystallographic data, confirm that the endohedral cluster motion is controlled by the position of the exohedral organic appendants.

A delocalized cobaltoviologen with seven reversibly accessible redox states and highly tunable electrochromic behaviour.

Co mediates electronic coupling between two N-Me-pyridinium-terpyridine ligands that are related to redox-active N,N-dialkyl-4,4'-bipyridinium dications (viologens). Borderline Class II/III electronic delocalization imparts the cobaltoviologen complex with distinct electronic properties (e.g.

The Influence of Redox-Active Linkers on the Stability and Physical Properties of a Highly Electroactive Porphyrin Nanoprism.

Redox-active metal-organic nanocages are of interest for many applications, but the development of cages with extensive redox activity is often hindered by their limited stability and solubility across multiple charge states. This report reveals that these properties can be tuned for cages with redox-active walls by incorporating additional redox activity into the linkers. In particular, new +12 charged triangular nanoprisms , were formed from three electroactive tetrakis(3-pyridyl)porphyrin walls linked by six [(TMEDA)Pt] (for ) or [(2,2'-bipy)Pt] (for ) vertices, the latter of which are also electroactive.

A Redox-Switchable Molecular Zipper.

The design and synthesis of artificial molecular switches (AMSs) displaying architectures of increased complexity would constitute significant progress in meeting the challenging task of realizing artificial molecular machines (AMMs). Here, we report the synthesis and characterization of a molecular shuttle composed of a cyclobis(paraquat-4,4'-biphenylene) cyclophane ring and a dumbbell incorporating a cyclobis(paraquat--phenylene) cyclophane "head" and a bifurcated, tawse-like "tail" composed of two oligoether chains, each containing a 1,5-dioxynaphthalene ring. In its reduced state the ring-in-ring recognition motif, between the and bisradical dicationic cyclophanes (rings), defines the [2]rotaxane, whereas in the oxidized state, the cyclobis(paraquat-4,4'-biphenylene) cyclophane encircles the two 1,5-dioxynaphthalene rings in the bifurcated "tail".

Molecular Russian dolls.

The host-guest recognition between two macrocycles to form hierarchical non-intertwined ring-in-ring assemblies remains an interesting and challenging target in noncovalent synthesis. Herein, we report the design and characterization of a box-in-box assembly on the basis of host-guest radical-pairing interactions between two rigid diradical dicationic cyclophanes. One striking feature of the box-in-box complex is its ability to host various 1,4-disubstituted benzene derivatives inside as a third component in the cavity of the smaller of the two diradical dicationic cyclophanes to produce hierarchical Russian doll like assemblies.

Shuttling Rates, Electronic States, and Hysteresis in a Ring-in-Ring Rotaxane.

The trisradical recognition motif between a 4,4'-bipyridinium radical cation and a cyclo-bis-4,4'-bipyridinium diradical dication has been employed previously in rotaxanes to control their nanomechanical and electronic properties. Herein, we describe the synthesis and characterization of a redox-active ring-in-ring [2]rotaxane 8PF that employs a tetraradical variant of this recognition motif. A square-shaped bis-4,4'-bipyridinium cyclophane is mechanically interlocked around the dumbbell component of this rotaxane, and the dumbbell itself incorporates a smaller bis-4,4'-bipyridinium cyclophane into its covalently bonded structure.

Size-Matched Radical Multivalency.

Persistent π-radicals such as MV (MV refers to methyl viologen, i.e., N,N'-dimethyl-4,4'-bipyridinum) engage in weak radical-radical interactions.

Electrophilic Activation of Silicon-Hydrogen Bonds in Catalytic Hydrosilations.

Hydrosilation reactions represent an important class of chemical transformations and there has been considerable recent interest in expanding the scope of these reactions by developing new catalysts. A major theme to emerge from these investigations is the development of catalysts with electrophilic character that transfer electrophilicity to silicon by Si-H activation. This type of mechanism has been proposed for catalysts ranging from Group 4 transition metals to Group 15 main group species.

Significant Cooperativity Between Ruthenium and Silicon in Catalytic Transformations of an Isocyanide.

Complexes [PhBP3]RuH(η(3)-H2SiRR') (RR' = Me,Ph, 1a; RR' = Ph2, 1b; RR' = Et2, 1c) react with XylNC to form carbene complexes [PhBP3]Ru(H)═[C(H)(N(Xyl)(η(2)-H-SiRR'))] (2a-c; previously reported for 2a,b). Reactions of 1a-c with XylNC were further investigated to assess how metal complexes with multiple M-H-Si bonds can mediate transformations of unsaturated substrates. Complex 2a eliminates an N-methylsilacycloindoline product (3a) that results from hydrosilylation, hydrogenation, and benzylic C-H activation of XylNC.

Hypercoordinate ketone adducts of electrophilic η3-H2SiRR' ligands on ruthenium as key intermediates for efficient and robust catalytic hydrosilation.

The electrophilic η(3)-H2SiRR' σ-complexes [PhBP(Ph)3]RuH(η(3)-H2SiRR') (RR' = MePh, 1a; Ph2, 1b; [PhBP(Ph)3](-) = [PhB(CH2PPh2)3](-)) are efficient catalysts (0.01-2.5 mol % loading) for the hydrosilation of ketones with PhMeSiH2, Ph2SiH2, or EtMe2SiH.

Interconversion of η3-H2SiRR' σ-complexes and 16-electron silylene complexes via reversible H-H or C-H elimination.

Solid samples of η(3)-silane complexes [PhBP(Ph)3]RuH(η(3)-H2SiRR') (R,R' = Et2, 1a; PhMe, 1b; Ph2, 1c, MeMes, 1d) decompose when exposed to dynamic vacuum. Gas-phase H2/D2 exchange between isolated, solid samples of 1c-d3 and 1c indicate that a reversible elimination of H2 is the first step in the irreversible decomposition. An efficient solution-phase trap for hydrogen, the 16-electron ruthenium benzyl complex [PhBP(Ph)3]Ru[η(3)-CH2(3,5-Me2C6H3)] (3) reacts quantitatively with H2 in benzene via elimination of mesitylene to form the η(5)-cyclohexadienyl complex [PhBP(Ph)3]Ru(η(5)-C6H7) (4).

Silane-isocyanide coupling involving 1,1-insertion of XylNC into the Si-H bond of a σ-silane ligand.

Complexes [PhBP(Ph)3]RuH(η(3)-H2SiRR') (R,R' = Me,Ph, 1a; RR' = Ph2, 1b) react with XylNC (Xyl = 2,6-dimethylphenyl) to form Fischer carbene complexes [PhBP(Ph)3]Ru(H)═[C(H)(N(Xyl)(η(2)-H-SiRR'))] (2a,b) that feature a γ-agostic Si-H bond. The ruthenium isocyanide complexes [PhBP(Ph)3]Ru(H)(CNXyl)(η(2)-HSiHRR') (6a,b) are not intermediates as they do not convert to 2a,b. Experimental and theoretical investigations indicate that XylNC is activated by initial coordination to the silicon center in 1a,b, followed by 1,1-insertion into an Si-H bond of the coordinated silane and then rearrangement to 2a,b.

Stabilization of ArSiH4(-) and SiH6(2-) anions in diruthenium Si-H σ-complexes.

Hydridosilicate anions ([ArSiH(4)](-) and [SiH(6)](2-)) were stabilized as ligands in diruthenium Si-H σ-complexes [{(PhBP(Ph(3))Ru}(2)(μ-Cl)(μ-η(3),η(3)-H(4)SiAr)] (Ar = 2-MeOC(6)H(4), Mes, Ph) and [{(PhBP(Ph)(3))Ru}(2)(μ-η(4),η(4)-H(6)Si)] (see picture). These complexes were formed under mild conditions and characterized by single-crystal X-ray diffraction (see picture), NMR and IR spectroscopy, and computational techniques.

High electrophilicity at silicon in η3-silane σ-complexes: Lewis base adducts of a silane ligand, featuring octahedral silicon and three Ru-H-Si interactions.

New η(3)-silane σ-complexes [PhBP(Ph)(3)]RuH(η(3)-H(2)SiRR') (RR' = PhMe, Ph(2)) were synthesized. Lewis bases [THF, 4-(dimethylamino)pyridine, and PMe(3)] coordinate to the silicon centers of these complexes to form stable adducts. The base adducts, [PhBP(Ph)(3)]Ru(μ-H)(3)SiRR'(base), feature three nonclassical Ru-H-Si interactions and hexacoordinate silicon centers, as determined by multinuclear NMR spectroscopy, X-ray crystallography, and computational investigations.