Quantitative Understanding of Guest Binding Enables the Design of Complex Host–Guest Behavior

We report a detailed binding study addressing both the thermodynamics and kinetics of binding of a large set of guest molecules with widely varying properties to a water-soluble M₄L₆ metal–organic host. The effects of different guest properties upon the binding strength and kinetics were elucidated by a systematic analysis of the binding data through principal component analysis, thus allowing structure–property relationships to be determined. These insights enabled us to design more complex encapsulation sequences in which multiple guests that were added simultaneously were bound and released by the host in a time-dependent manner, thus allowing multiple states of the system to be accessed sequentially. Moreover, by inclusion of the pH-sensitive guest pyridine, we were able to further extend our control over the binding by creating a reversible pH-controlled three-guest sequential binding cycle

Icosahedral Pt-Centered Pt₁₃ and Pt₁₉ Carbonyl Clusters Decorated by [Cd₅(μ-Br)₅Br_5−<i>x</i>(solvent)_<i>x</i>]^<i>x</i>+ Rings Reminiscent of the Decoration of Au−Fe−CO and Au-Thiolate Nanoclusters: A Unifying Approach to Their Electron Counts

The new [Pt13(CO)12{Cd5(μ-Br)5Br2(dmf)3}2]2− and [Pt19(CO)17{Cd5(μ-Br)5Br3(Me2CO)2}{Cd5(μ-Br)5Br(Me2CO)4}]2− clusters have been obtained in good yields by reaction of [Pt12(CO)24]2− with CdBr2·H2O in dmf at 90 °C and structurally characterized by X-ray diffraction. Their structures consist of a Pt-centered Pt13(CO)12 icosahedron and a Pt19(CO)17 interpenetrated double icosahedron, respectively, decorated by two Cd5(μ-Br)5Br5−x(solvent)x rings. Their surface decoration may be related to that of Au−Fe−CO clusters as well as to the staple motifs stabilizing gold−thiolates nanoclusters. An oversimplified and unifying approach to interpret their electron count is suggested

Icosahedral Pt-Centered Pt₁₃ and Pt₁₉ Carbonyl Clusters Decorated by [Cd₅(μ-Br)₅Br_5−<i>x</i>(solvent)_<i>x</i>]^<i>x</i>+ Rings Reminiscent of the Decoration of Au−Fe−CO and Au-Thiolate Nanoclusters: A Unifying Approach to Their Electron Counts

The new [Pt13(CO)12{Cd5(μ-Br)5Br2(dmf)3}2]2− and [Pt19(CO)17{Cd5(μ-Br)5Br3(Me2CO)2}{Cd5(μ-Br)5Br(Me2CO)4}]2− clusters have been obtained in good yields by reaction of [Pt12(CO)24]2− with CdBr2·H2O in dmf at 90 °C and structurally characterized by X-ray diffraction. Their structures consist of a Pt-centered Pt13(CO)12 icosahedron and a Pt19(CO)17 interpenetrated double icosahedron, respectively, decorated by two Cd5(μ-Br)5Br5−x(solvent)x rings. Their surface decoration may be related to that of Au−Fe−CO clusters as well as to the staple motifs stabilizing gold−thiolates nanoclusters. An oversimplified and unifying approach to interpret their electron count is suggested

Icosahedral Pt-Centered Pt₁₃ and Pt₁₉ Carbonyl Clusters Decorated by [Cd₅(μ-Br)₅Br_5−<i>x</i>(solvent)_<i>x</i>]^<i>x</i>+ Rings Reminiscent of the Decoration of Au−Fe−CO and Au-Thiolate Nanoclusters: A Unifying Approach to Their Electron Counts

The new [Pt13(CO)12{Cd5(μ-Br)5Br2(dmf)3}2]2− and [Pt19(CO)17{Cd5(μ-Br)5Br3(Me2CO)2}{Cd5(μ-Br)5Br(Me2CO)4}]2− clusters have been obtained in good yields by reaction of [Pt12(CO)24]2− with CdBr2·H2O in dmf at 90 °C and structurally characterized by X-ray diffraction. Their structures consist of a Pt-centered Pt13(CO)12 icosahedron and a Pt19(CO)17 interpenetrated double icosahedron, respectively, decorated by two Cd5(μ-Br)5Br5−x(solvent)x rings. Their surface decoration may be related to that of Au−Fe−CO clusters as well as to the staple motifs stabilizing gold−thiolates nanoclusters. An oversimplified and unifying approach to interpret their electron count is suggested

New Findings in the Chemistry of Iron Carbonyls: The Previously Unreported [H_4−<i>n</i>Fe₄(CO)₁₂]^<i>n</i>− (<i>n</i> = 1, 2) Series of Clusters, Which Fills the Gap with Ruthenium and Osmium

The new [HFe4(CO)12]3− cluster anion has been obtained in high yields by reduction of [Fe4(CO)13]2− or [HFe3(CO)11]− with a 6 M methylalcoholic KOH solution under a nitrogen atmosphere and isolated with miscellaneous tetrasubstituted ammonium salts. The [NEt4]3[HFe4(CO)12] salt has been characterized by IR, 1H and 13C NMR, electrospray ionization mass spectrometry, and X-ray studies. Investigation of its protonation reaction afforded spectroscopic proof for the existence of its unstable isomeric [HFe4(CO)11(CO-H)]2− and [H2Fe4(CO)12]2− conjugated acids. The latter is probably isostructural with the [H2Ru4(CO)12]2− congener. The nature of the first protonation product as a [HFe4(CO)11(CO-H)]2− adduct, involving an oxygen-bound proton, has been corroborated by the preparation and spectroscopic characterization of the corresponding [HFe4(CO)11(CO-Me)]2− dianion. The above findings demonstrate that protonation of a CO-shielded polynuclear metal anion initially occurs on one oxygen atom and then the oxygen-bound proton migrates to the metal cage. Finally, [HFe4(CO)12]3− and its [H2Fe4(CO)12]2− conjugate acid fill the previously existing gap between the chemistry of iron carbonyls and ruthenium and osmium congeners

A Self-Organizing Chemical Assembly Line

Chemical syntheses generally involve a series of discrete transformations whereby a simple set of starting materials are progressively rendered more complex. In contrast, living systems accomplish their syntheses within complex chemical mixtures, wherein the self-organization of biomolecules allows them to form “assembly lines” that transform simple starting materials into more complex products. Here we demonstrate the functioning of an abiological chemical system whose simple parts self-organize into a complex system capable of directing the multistep transformation of the small molecules furan, dioxygen, and nitromethane into a more complex and information-rich product. The novel use of a self-assembling container molecule to catalytically transform a high-energy intermediate is central to the system’s functioning

Post-assembly Modification of Tetrazine-Edged Fe^II₄L₆ Tetrahedra

Post-assembly modification (PAM) is a powerful tool for the modular functionalization of self-assembled structures. We report a new family of tetrazine-edged Fe^II₄L₆ tetrahedral cages, prepared using different aniline subcomponents, which undergo rapid and efficient PAM by inverse electron-demand Diels–Alder (IEDDA) reactions. Remarkably, the electron-donating or -withdrawing ability of the <i>para</i>-substituent on the aniline moiety influences the IEDDA reactivity of the tetrazine ring 11 bonds away. This effect manifests as a linear free energy relationship, quantified using the Hammett equation, between σ_<i>para</i> and the rate of the IEDDA reaction. The rate of PAM can thus be adjusted by varying the aniline subcomponent

Post-assembly Modification of Tetrazine-Edged Fe^II₄L₆ Tetrahedra

Post-assembly modification (PAM) is a powerful tool for the modular functionalization of self-assembled structures. We report a new family of tetrazine-edged Fe^II₄L₆ tetrahedral cages, prepared using different aniline subcomponents, which undergo rapid and efficient PAM by inverse electron-demand Diels–Alder (IEDDA) reactions. Remarkably, the electron-donating or -withdrawing ability of the <i>para</i>-substituent on the aniline moiety influences the IEDDA reactivity of the tetrazine ring 11 bonds away. This effect manifests as a linear free energy relationship, quantified using the Hammett equation, between σ_<i>para</i> and the rate of the IEDDA reaction. The rate of PAM can thus be adjusted by varying the aniline subcomponent

Post-assembly Modification of Tetrazine-Edged Fe^II₄L₆ Tetrahedra

Post-assembly modification (PAM) is a powerful tool for the modular functionalization of self-assembled structures. We report a new family of tetrazine-edged Fe^II₄L₆ tetrahedral cages, prepared using different aniline subcomponents, which undergo rapid and efficient PAM by inverse electron-demand Diels–Alder (IEDDA) reactions. Remarkably, the electron-donating or -withdrawing ability of the <i>para</i>-substituent on the aniline moiety influences the IEDDA reactivity of the tetrazine ring 11 bonds away. This effect manifests as a linear free energy relationship, quantified using the Hammett equation, between σ_<i>para</i> and the rate of the IEDDA reaction. The rate of PAM can thus be adjusted by varying the aniline subcomponent

Electronic Stabilization of Trigonal Bipyramidal Clusters: the Role of the Sn(II) Ions in [Pt₅(CO)₅{Cl₂Sn(μ-OR)SnCl₂}₃]^3– (R = H, Me, Et, ⁱPr)

The new [Pt5(CO)5{Cl2Sn­(μ-OR)­SnCl2}3]3– (R = H, Me, Et, iPr; 1–4) clusters contain trigonal bipyramidal (TBP) Pt5(CO)5 cores, as certified by the X-ray structures of [Na­(CH3CN)5]­[NBu4]2[1]·2CH3CN and [PPh4]3[4]·3CH3COCH3. The TBP geometry, which is rare for group 10 metals, is supported by an unprecedented interpenetration with a nonbonded trigonal prism of tin atoms. By capping all the Pt3 faces, the Sn­(II) lone pairs account for both Sn–Pt and Pt–Pt bonding, as indicated by DFT and topological wave function studies. In the TBP interactions, the metals use their vacant s and p orbitals using the electrons provided by Sn atoms, hence mimicking the electronic picture of main group analogues, which obey the Wade’s rule. Other metal TBP clusters with the same total electron count (TEC) of 72 are different because the skeletal bonding is largely contributed by d–d interactions (e.g., [Os5(CO)14(PR3)­(μ-H)n]n−2, n = 0, 1, 2). In 1–4, fully occupied d shells at the Ptax atoms exert a residual nucleophilicity toward the adjacent main group Sn­(II) ions permitting their hypervalency through unsual metal donation