Self-assembly of dendritic tris(crown ether) hexagons and their complexation with dibenzylammonium cations.

The construction of a new series of dendritic tris(crown ether) hexagons via coordination-driven self-assembly is described. Combining 120° crown ether-containing diplatinum(II) acceptors with 120° dendritic dipyridyl donors in a 1:1 ratio allows for the formation of a new family of dendritic triple crown ether derivatives with a hexagonal cavity in quantitative yields. The number and the position of these pendant groups can be precisely controlled on the hexagonal metallacycle. The structures of all dendritic multiple crown ether hexgaons are confirmed by multinuclear NMR ((1)H and (31)P), ESI-MS and ESI-TOF-MS, and elemental analysis. The complexation of these dendritic trivalent receptors with dibenzylammonium cations was investigated by (1)H NMR titration experiments. The thermodynamic binding constants between the receptors and guests were established by using the nonlinear least-squares fit method based on (1)H NMR titration experiments. It was found that the association constants of each assembly decrease correspondingly upon the increase of the generation of the dendrons from [G0] to [G3], which might be caused by the steric effect of the dendrons on host-guest complexation.

Construction of coordination-driven self-assembled [5 + 5] pentagons using metal-carbonyl dipyridine ligands.

The coordination-driven self-assembly of two metal-carbonyl-cluster-coordinated dipyridyl donors, (4-C(5)H(4)N)(2)C[triple bond]CCo(2)(CO)(6) (1) and (4-C(5)H(4)N)(2)C[triple bond]CMo(2)Cp(2)(CO)(4) (2), with a linear diplatinum(II) acceptor ligand was investigated. The structures of the resulting self-assembled polygons were found to be controlled by the steric bulk of the metal-carbonyl cluster adduct. The use of a sterically less imposing ligand 1 resulted in a pentagon-hexagon mixture, which was characterized by electrospray ionization time-of-flight mass spectroscopy. The exclusive formation of a [5 + 5] pentagon was achieved by the self-assembly of the bulkier molybdenum donor ligand 2 with a linear organoplatinum(II) acceptor ligand. Molecular force field modeling was used to study the structural details of the pentagonal and hexagonal architectures. The first Fe(3)-Co(6)-Pt(6) trimetal [3 + 3] hexagon was also synthesized via the combination of 1 with a 120 degrees ferrocenyldiplatinum(II) acceptor.

Synthesis of six-component metallodendrimers via [3 + 3] coordination-driven self-assembly.

A new class of 120 degrees dendritic di-Pt(II) acceptor subunits has been designed and synthesized, from which six-component hexagonal metallodendrimers were easily formed with 120 degrees dendritic dipyridine donors via [3 + 3] coordination-driven self-assembly. The structures of all metallodendrimers are confirmed by multinuclear NMR, ESI-TOF-MS/ESI-FTMS, and elemental analysis. MMFF force-field simulations indicates that all metallodendrimers have a hexagonal ring with an internal radius of approximately 1.4 nm.

Mass measurement accuracy comparisons between a double-focusing magnetic sector and a time-of-flight mass analyzer.

We report a direct comparison of the mass measurement accuracies (MMAs) obtained on different mass spectrometry instrument types; a magnetic sector as the 'gold standard' and an electrospray ionization time-of-flight (ESI-TOF) instrument. Sixty samples, obtained from the Department of Chemistry at North Carolina State University, were analyzed on each instrument. Data are presented and compared between the different instruments. The average absolute MMAs achieved for the magnetic sector and Agilent ESI-TOF mass spectrometers were 3.0 and 1.1 ppm, respectively.

Coordination-driven self-assembly of cavity-cored multiple crown ether derivatives and poly[2]pseudorotaxanes.

The synthesis of a new 120 degree diplatinum(II) acceptor unit and the self-assembly of a series of two-dimensional metallacyclic polypseudorotaxanes that utilize both metal-ligand and crown ether-dialkylammonium noncovalent interactions are described. Judiciously combining complementary diplatinum(II) acceptors with bispyridyl donor building blocks, with an acceptor and/or donor possessing a pendant dibenzo[24]crown-8 (DB24C8) moiety, allows for the formation of three new rhomboidal bis-DB24C8, one new hexagonal tris-DB24C8, and four new hexakis-DB24C8 metallacyclic polygons in quantitative yields. The size and shape of each assembly, as well as the location and stoichiometry of the DB24C8 macrocycle, can be precisely controlled. Each polygon is able to complex two, three, or six dibenzylammonium ions without disrupting the underlying metallacyclic polygons, thus producing eight different poly[2]pseudorotaxanes and demonstrating the utility and scope of this orthogonal self-assembly technique. The assemblies are characterized with one-dimensional multinuclear ((1)H and (31)P) and two-dimensional ((1)H-(1)H COSY and NOESY) NMR spectroscopy as well as mass spectrometry (ESI-MS). Further analysis of the size and shape of each assembly is obtained through molecular force-field simulations. (1)H NMR titration experiments are used to establish thermodynamic binding constants and poly[2]pseudorotaxane/dibenzylammonium stoichiometries. Factors influencing the efficiency of poly[2]pseudorotaxane formation are discussed.

A new family of multiferrocene complexes with enhanced control of structure and stoichiometry via coordination-driven self-assembly and their electrochemistry.

The design and synthesis of a new family of multiferrocene complexes with enhanced control of structure and stoichimetry via coordination-driven self-assembly is described. Insight into the structure and electronic properties of all supramolecules was obtained by electrochemical studies. The collective results provide an enhanced understanding of the influence of structural factors on the electrochemistry of multifunctional electroactive supramolecular architectures.