Feng-Rong Dai

Synthetic supercontainers exhibit distinct solution versus solid state guest-binding behavior.

The phase-dependent host-guest binding behavior of a new family of synthetic supercontainers has been probed in homogeneous solution and at liquid-liquid, solid-liquid, and solid-gas interfaces. The synthetic hosts, namely, type II metal-organic supercontainers (MOSCs), are constructed from the assembly of divalent metal ions, 1,4-benzenedicarboxylate (BDC) linker, and sulfonylcalix[4]arene-based container precursors. One member of the MOSCs, MOSC-II-tBu-Ni, which is derived from Ni(II), BDC, and p-tert-butylsulfonylcalix[4]arene (TBSC), crystallizes in the space group R3 and adopts pseudo face-centered cubic (fcc) packing, whereas other MOSCs, including TBSC analogue MOSC-II-tBu-Co, p-tert-pentylsulfonylcalix[4]arene (TPSC) analogues MOSC-II-tPen-Ni/Co, and p-tert-octylsulfonylcalix[4]arene (TOSC) analogues MOSC-II-tOc-Ni/Mg/Co, all crystallize in the space group I4/m and assume a pseudo body-centered cubic (bcc) packing mode. This solid-state structural diversity is nevertheless not reflected in their solution host-guest chemistry, as evidenced by the similar binding properties of MOSC-II-tBu-Ni and MOSC-II-tBu-Co in solution. Both MOSCs show comparable binding constants and adsorb ca. 7 equiv of methylene blue (MB) and ca. 30 equiv of aspirin in chloroform. In contrast, the guest-binding behavior of the MOSCs in solid state reveals much more variations. At the solid-liquid interface, MOSC-II-tBu-Co adsorb ca. 5 equiv of MB from an aqueous solution at a substantially faster rate than MOSC-II-tBu-Ni does. However, at the solid-gas interface, MOSC-II-tBu-Ni has higher gas uptake than MOSC-II-tBu-Co, contradicting their overall porosity inferred from the crystal structures. This discrepancy is attributed to the partial collapse of the solid-state packing of the MOSCs upon solvent evacuation. It is postulated that the degree of porosity collapse correlates with the molecular size of the MOSCs, i.e., the larger the MOSCs, the more severe they suffer from the loss of porosity. The same principle can rationalize the negligible N2 and O2 adsorption seen in the larger MOSC-II-tPen-Co and MOSC-II-tOC-Ni/Mg/Co molecules. MOSC-II-tPen-Ni features an intermediate molecular size and endures a partial structural collapse in such a way that the resulting pore dimension permits the inclusion of kinetically smaller O2 (3.46 Å) but excludes larger N2 (3.64 Å), explaining the observed remarkable O2/N2 adsorption selectivity.

Preparation, characterization, and photophysical properties of Pt-M (M = Ru, Re) heteronuclear complexes with 1,10-phenanthrolineethynyl ligands

When 3-ethynyl-1,10-phenanthroline (HCCphen) or 3,8-diethynyl-1,10-phenanthroline (HCCphenCCH) is utilized as a bifunctional bridging ligand via stepwise molecular fabrication, a series of Pt-Ru and Pt-Re heteronuclear complexes composed of both platinum(II) terpyridyl acetylide chromophores and a Ru(phen)(bpy)2/Re(phen)(CO)3Cl subunit were prepared by complexation of one or two Pt((t)Bu3tpy)(2+) units to the mononuclear Ru(II) or Re(I) precursor through platinum acetylide sigma coordination. These Pt-Ru and Pt-Re complexes exhibit intense low-energy absorptions originating from both Pt- and Ru (Re)-based metal-to-ligand charge-transfer (MLCT) states in the near-visible region. They are strongly luminescent in both solid states and fluid solutions with a submicrosecond range of lifetimes and 0.27-6.58% of quantum yields in degassed acetonitrile. For the Pt-Ru heteronuclear complexes, effective intercomponent Pt --> Ru energy transfer takes place from the platinum(II) terpyridyl acetylide chromophores to the ruthenium(II) tris(diimine)-based emitters. In contrast, dual emission from both Pt- and Re-based (3)MLCT excited states occurs because of less efficient intercomponent Pt --> Re energy transfer in the Pt-Re heteronuclear complexes.

pH‐Modulated Molecular Assemblies and Surface Properties of Metal–Organic Supercontainers at the Air–Water Interface

The orientation of metal-organic supercontainer (MOSC) molecules in Langmuir films was systematically studied at the air-water interface. The acidity of the aqueous subphases plays a significant role in tuning the orientation of MOSC molecules in the Langmuir films. Furthermore, Langmuir-Blodgett films of MOSCs were prepared and the uniform multilayer structures demonstrated various surface properties, depending on their conditions of fabrication. Our use of Langmuir films provides a novel approach to access tunable assemblies of MOSC molecules in two-dimensional thin films.

Photophysical and anion sensing properties of platinum(II) terpyridyl complexes with phenolic ethynyl ligands

A series of platinum(II) terpyridyl complexes with phenolic ethynyl ligands have been synthesized and characterized. Their photophysical and sensing properties towards anions such as fluoride, acetate and dihydrogenphosphate have been investigated. These complexes show a colorimetric response and fluorescence quenching in the presence of anions including fluoride, acetate and dihydrogenphosphate, and selective sensing towards fluoride in some cases. The sensing mechanism has been investigated by spectrophotometric and 1H NMR titration.

Designing structurally tunable and functionally versatile synthetic supercontainers

We describe the design of a new family of molecular containers, namely, type IV metal–organic supercontainers (MOSCs), which are constructed from the assembly of a container precursor p-tert-butylsulfonylcalix[4]arene, Co(II) or Ni(II) ion, and angular flexible dicarboxylate linkers. The combination of structural robustness and tunability of these cylinder-shaped MOSCs makes them highly attractive supramolecular hosts. The type IV MOSCs exhibit a diverse range of supramolecular functions, including their selective binding with cationic guests and their tunable activity to modulate both stoichiometric and catalytic reactions, which are not readily accessible in the molecular precursors.

Oxo-Centered Triruthenium-Acetate Cluster Complexes Derived from Axial or Bridging Ligand Substitution

The oxo-centered triruthenium-acetate cluster complexes with general formula [Ru3(μ3-O)(μ-OAc)6(L)2L′]n+ (L and L′ = axial ligand, n = 0, 1, 2) show attractive ligand substitution reactivity, multiple redox behavior and rich mixedvalence chemistry. The axial ligands L and L′ are comparatively labile and readily substitutable. Although the Ru3(μ3-O)(μ-OAc)6 cluster core possesses high stability, displacement of one of the bridging acetates has been achieved by using π-delocalized N-hetrocyclic ligands with low π∗ energy levels. Ligand substitution not only affords an excellent means of tuning the redox levels of electron transfer processes, but also provides a feasible approach to design ligand-linked triruthenium cluster oligomers with desired properties. This article reviews the recent progress in the ligand substitution chemistry of oxo-centered triruthenium–acetate complexes with parent Ru3(μ3-O)(μ-OAc)6 cores. The syntheses, redox and spectroscopic properties, and mixed valence chemistry of these oxo-centered triruthenium cluster derivatives are summarized to correlate structures with properties.

Pyridinium functionalized coordination containers as highly efficient electrocatalysts for sustainable oxygen evolution

Elaborately designed octanuclear coordination containers were synthesized through the self-assembly of M2+ (M = Co, Ni), p-tert-butylsulfonylcalix[4]arene, and pyridinium functionalized angular flexible dicarboxylate linker, H2BrL1. The pyridinium functionalized coordination containers as robust molecular electrooxidation catalysts for water oxidation have been well investigated. They exhibited efficient electrocatalytic oxygen evolution reaction (OER) activity with the lowest overpotential of 0.290 V to afford 10 mA cm−2 current density and remarkable stability over 48 h without any significant shift in the overpotential. The strategy for the functionalization of coordination containers provides a novel approach to achieve sustainable oxygen evolution with high efficiency and excellent stability, and a new opportunity for designing and realizing functional supramolecular materials for energy storage and conversion technologies.

Sensitive and Specific Guest Recognition through Pyridinium-Modification in Spindle-Like Coordination Containers

An elaborately designed pyridinium-functionalized octanuclear zinc(II) coordination container 1-Zn was prepared through the self-assembly of Zn2+ , p-tert-butylsulfonylcalix[4]arene, and pyridinium-functionalized angular flexible dicarboxylate linker (H2 BrL1). The structure was determined by a single-crystal X-ray diffractometer. 1-Zn displays highly sensitive and specific recognition to 2-picolylamine as revealed by drastic blueshifts of the absorption and emission spectra, ascribed to the decrease of intramolecular charge transfer (ICT) character of the container and the occurrence of intermolecular charge transfer between the host and guest molecules. The intramolecular charge transfer plays a key role in the modulation of the electronic properties and is tunable through endo-encapsulation of specific guest molecules.

[(1,10-Phenanthrolin-5-yl)ethynyl](triphenylposphine-κP)gold(I)

The title compound, [Au(C14H7N2)(C18H15P)], was synthesized by the reaction of [AuCl( PPh3)] and 5-ethynyl-1,10-phenanthroline. The coordination geometry of gold( I) is two-coordinate ( linear) and no intermolecular Au center dot center dot center dot Au interactions are observed.