Xiaocun Lu

Stoichiometric Self-Assembly of Shape-Persistent 2D Complexes: A Facile Route to a Symmetric Supramacromolecular Spoked Wheel

An approach to multicomponent coordination-driven self-assembly of the first terpyridine-based, shape-persistent, giant two-dimensional D(6h) supramacromolecular spoked wheel is reported. Mixing core T6, rim T3, and Zn(II) or Cd(II) ions in a stoichiometric ratio (1:6:12) permitted the selective generation of a highly symmetric spoked wheel in 94% isolated yield via geometric and thermodynamic control. The products were characterized by a combination of traveling-wave ion mobility mass spectrometry and NMR techniques together with TEM imaging, which agreed with computational simulations.

Self-Assembly of a Supramolecular, Three-Dimensional, Spoked, Bicycle-like Wheel†

Where theres a wheel, theres a way: The terpyridine-based title system has been synthesized through a facile self-assembly process. Two tris(terpyridine) ligands possessing angles of either 120° or 60° between adjacent tpy units were mixed with a stoichiometric amount of Zn(2+) (2:6:12) to generate the desired coordination-driven bicycle-like wheel (90 % yield).

Probing a hidden world of molecular self-assembly: concentration-dependent, three-dimensional supramolecular interconversions.

A terpyridine-based, concentration-dependent, facile self-assembly process is reported, resulting in two three-dimensional metallosupramolecular architectures, a bis-rhombus and a tetrahedron, which are formed using a two-dimensional, planar, tris-terpyridine ligand. The interconversion between these two structures is concentration-dependent: at a concentration higher than 12 mg mL(-1), only a bis-rhombus, composed of eight ligands and 12 Cd(2+) ions, is formed; whereas a self-assembled tetrahedron, composed of four ligands and six Cd(2+) ions, appears upon sufficient dilution of the tris-terpyridine-metal solution. At concentrations less than 0.5 mg mL(-1), only the tetrahedron possessing an S4 symmetry axis is detected; upon attempted isolation, it quantitatively reverts to the bis-rhombus. This observation opens an unexpected door to unusual chemical pathways under high dilution conditions.

Construction of a highly symmetric nanosphere via a one-pot reaction of a tristerpyridine ligand with Ru(II).

A three-dimensional, highly symmetric, terpyridine-based, spherical complex was synthesized via the coordination of four novel, trisdentate ligands and six Ru(2+) ions, and it exhibits excellent stability over a wide range of pH values (1-14). Structural confirmation was obtained by NMR and ESI-TWIM-MS.

Dendron-Functionalized Bis(terpyridine)–Iron(II) or –Cadmium(II) Metallomacrocycles: Synthesis, Traveling-Wave Ion-Mobility Mass Spectrometry, and Photophysical Properties

The synthesis, purification, structural analysis, and photophysical properties of a series of five-, six-, and seven-sided Fe(II) macrocycles and the corresponding hexameric Cd(II) macrocycle, all prepared by self-assembly of a 120° bis(terpyridine) ligand modified with first- and second-generation 1→3 C-branched dendrons, are reported. All metallomacrocycles were fully characterized by (1)H and (13)C NMR spectroscopy, traveling-wave ion-mobility mass spectrometry (TWIM MS), molecular modeling, UV/Vis absorption spectroscopy, photoluminescence, and cyclic voltammetry. A gradual increase of the collision cross sections of the Fe(II) metallomacrocycles was observed with a successive increase of the number and molecular size of the ligands. The combination of ion-mobility mass spectrometry and NMR techniques unveils structural features that agree well with calculations. Extinction coefficients and emission are significantly modulated by increasing the ring size and changing the metal ion center from Fe(II) to Cd(II) .

Precise Molecular Fission and Fusion: Quantitative Self-Assembly and Chemistry of a Metallo-Cuboctahedron†

Inspiration for molecular design and construction can be derived from mathematically based structures. In the quest for new materials, the adaptation of new building blocks can lead to unexpected results. Towards these ends, the quantitative single-step self-assembly of a shape-persistent, Archimedean-based building block, which generates the largest molecular sphere (a cuboctahedron) that has been unequivocally characterized by synchrotron X-ray analysis, is described. The unique properties of this new construct give rise to a dilution-based transformation into two identical spheres (octahedra) each possessing one half of the molecular weight of the parent structure; concentration of this octahedron reconstitutes the original cuboctahedron. These chemical phenomena are reminiscent of biological fission and fusion processes. The large 6 nm cage structure was further analyzed by 1D and 2D NMR spectroscopy, mass spectrometry, and collision cross-section analysis. New routes to molecular encapsulation can be envisioned.

Towards Molecular Construction Platforms: Synthesis of a Metallotricyclic Spirane Based on Bis(2,2′:6′,2“-Terpyridine)RuII Connectivity

The design and construction of the first multicomponent stepwise assembly of a -based (tpy=terpyridine), three-dimensional, propeller-shaped trismacrocycle, 8, are reported. Key steps in the synthesis involve the preparation of a hexaterpyridinyl triptycene and its reaction with dimeric, 60°-directional, bisterpyridine-Ru(II) building blocks. Characterization includes ESI- and ESI-TWIM-MS and TEM, along with 1D and 2D (1) H NMR spectroscopy.

Conductive Water/Alcohol-Soluble Neutral Fullerene Derivative as an Interfacial Layer for Inverted Polymer Solar Cells with High Efficiency

Dipole induced vacuum level shift has been demonstrated to be responsible for the enhanced efficiency in polymer solar cells (PSCs).The modified energy level alignment could reduce the energy barrier and facilitate charge transport, thereby increasing the efficiency of PSCs. Herein, we report a new mechanism toward enhanced efficiency by using a nondipolar water/alcohol-soluble neutral fullerene derivative to reengineer the surface of the zinc oxide (ZnO) electron extraction layer (EEL) in inverted PSCs. Because of the neutral property (ion-free) of the fullerene derivatives, no dipole moment was introduced at the EEL/active layer interface. A negligible change in open-circuit voltage was observed from inverted PSCs with the neutral fullerene derivative layer. The neutral fullerene derivative layer greatly increased the surface electronic conductivity of the ZnO EEL, suppressed surface charge recombination, and increased the short-circuit current density and fill factor. An overall power conversion efficiency increase of more than 30% from inverted PSCs was obtained. These results demonstrate that the surface electronic conductivity of the EEL plays an important role in high performance inverted PSCs.

One ligand in dual roles: self-assembly of a bis-rhomboidal-shaped, three-dimensional molecular wheel.

A facile high yield, self-assembly process that leads to a terpyridine-based, three-dimensional, bis-rhomboidal-shaped, molecular wheel is reported. The desired coordination-driven supramolecular wheel involves eight structurally distorted tristerpyridine (tpy) ligands possessing a 60° angle between the adjacent tpy units and twelve Zn(2+) ions. The tpy ligand plays dual roles in the self-assembly process: two are staggered at 180° to create the internal hub, while six produce the external rim. The wheel can be readily generated by mixing the tpy ligand and Zn(2+) in a stoichiometric ratio of 2:3; full characterization is provided by ESI-MS, NMR spectroscopy, and TEM imaging.

Shape-persistent, ruthenium(II)- and iron(II)-bisterpyridine metallodendrimers: synthesis, traveling-wave ion-mobility mass spectrometry, and photophysical properties

A class of shape-persistent metallodendrimer has been developed through a self-assembly strategy, in which 〈tpy-RuII-tpy〉 or 〈tpy-FeII-tpy〉 connectivity is utilized, as branching moieties or nodes. These metallomacromolecules were fully characterized by 1H and 13C NMR, traveling wave ion mobility mass spectrometry (TWIM MS), single crystal X-ray, UV-vis absorption, photoluminescence, and cyclic voltammetry. Significant increase in the drift times of the same charge states was observed with increasing generation of these complexes, which is in line with the change of molecular size. Moreover, the photophysical properties (molar extinction coefficients) and electrochemical stability of the complexes were noticeably different depending on size and metal ion center.