Polymerization of methyl methacrylate by diphenylamido bis (methylcyclopentadienyl) ytterbium complex

Methyl methacrylate (MMA) was effectively polymerized by diphenylamido bis (methylcyclopentadienyl) ytterbium complex (MeCp)2YbNPb2(THF). The reaction can be carried out over a range of polymerization temperature from - 40℃ to 40℃ and gives the poly MMA with high molecular weights. The initiation mechanism was demonstrated by diphenylamido-terminated methyl methacrylate oligomer.     

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.     

Self-selection in the self-assembly of isomeric supramolecular squares from unsymmetrical bis(4-pyridyl)acetylene ligands

A new approach wherein steric interactions between substituents of unsymmetrical bis(4-pyridyl)acetylene ligands dictate the self-selection of single isomers of [4 + 4] self-assembled squares is presented. Each [4 + 4] self-assembly is characterized by multinuclear (31)P and (1)H NMR spectroscopies and electrospray ionization mass spectrometry. NMR spectroscopic studies are used to provide a means of evaluating the efficiency of bulky substituents at proximal or remote positions relative to the Pt-N bonding motif to direct self-selection. Molecular modeling using the MMFF force field is utilized to determine the relative energy of different isomers of each assembly, and modeling results reasonably explain the trend in self-selectivity with varying pyridyl substitution.     

Construction of functionalized metallosupramolecular tetragonal prisms via multicomponent coordination-driven self-assembly

A new approach for the construction of functionalized metallosupramolecular tetragonal prisms via multicomponent, coordination-driven, template-free self-assembly is described. The combination of tetra-(4-pyridylphenyl)ethylene, a 90° Pt(II) acceptor, and ditopic bipyridine or carboxylate ligands functionalized with hydroxyl or amine groups, hydrophobic alkyl chains, or electrochemically active ferrocene, yields a suite of seven self-assembled tetragonal prisms under mild conditions. These three-dimensional metallosupramolecules were characterized by multinuclear NMR ((31)P and (1)H) and mass spectrometry. Their shapes and sizes were established using Merck Molecular Force Field (MMFF) simulations. In addition, their approximate sizes were further supported by pulsed-field-gradient spin-echo (PGSE) NMR experiments.     

Coordination-driven self-assembly of truncated tetrahedra capable of encapsulating 1,3,5-triphenylbenzene

The design and synthesis of coordinative truncated tetrahedra is described. The coordination-driven self-assembly of a truncated tetrahedron was achieved using 90° organoplatinum acceptors and a hexapyridyl ligand with six-fold symmetry under mild conditions. This tetrahedron can act as a host toward 1,3,5-triphenylbenzene. The truncated tetrahedral structures and the host-guest complex were identified using multinuclear ((31)P and (1)H) NMR spectroscopy, electrospray ionization mass spectrometry, X-ray crystallography, and pulsed-field-gradient spin-echo NMR, along with computational simulations.     

Encapsulation of Pt(iv) prodrugs within a Pt(ii) cage for drug delivery

This report presents a novel strategy that facilitates delivery of multiple, specific payloads of Pt(iv) prodrugs using a well-defined supramolecular system. This delivery system comprises a hexanuclear Pt(ii) cage that can host four Pt(iv) prodrug guest molecules. Relying on host–guest interactions between adamantyl units tethered to the Pt(iv) molecules and the cage, four prodrugs could be encapsulated within one cage. This host–guest complex, exhibiting a diameter of about 3 nm, has been characterized by detailed NMR spectroscopic measurements. Owing to the high positive charge, this nanostructure exhibits high cellular uptake. Upon entering cells and reacting with biological reductants such as ascorbic acid, the host–guest complex releases cisplatin, which leads to cell cycle arrest and apoptosis. The fully assembled complex displays cytotoxicity comparable to that of cisplatin against a panel of human cancer cell lines, whereas the cage or the Pt(iv) guest alone exhibit lower cytotoxicity. These findings indicate the potential of utilising well-defined supramolecular constructs for the delivery of prodrug molecules.     

Self-Assembly of Coordinative Supramolecular Polygons with Open Binding Sites

The design and synthesis of coordinative supramolecular polygons with open binding sites is described. Coordination-driven self-assembly of 2,6-bis(pyridin-4-ylethynyl)pyridine with 60° and 120° organoplatinum acceptors results in quantitative formation of a supramolecular rhomboid and hexagon, respectively, both bearing open pyridyl binding sites. The structures were determined by multinuclear (³¹P and ¹H) NMR spectroscopy and electrospray ionization (ESI) mass spectrometry, along with a computational study.     

Designed post-self-assembly structural and functional modifications of a truncated tetrahedron

Post-self-assembly modifications of a discrete metal-organic supramolecular structure have been developed. Such modifications allow the properties of the self-assembled supramolecular species to be changed in a simple and efficient manner (>90% yield). Initiated by the application of chemical stimuli, the post-self-assembly modifications described herein result in three distinct changes to the supramolecular system: an individual building-block component change, an overall structural modification, and a functional evolution of a [6+4] metal-organic supramolecular structure. The three modifications have been carefully examined by a range of characterization methods, including NMR and UV-vis spectroscopy, electrospray ionization mass spectrometry, pulsed field gradient spin echo NMR measurements, electrochemical analysis, and computational simulations.     

Synthesis and Crystal Structure of Tetra（（8-quinolyl）-amido-N）ytterbium Bi（tetrahydrofuran-O）lithium

The treatment of the mixture of n-BuLi with 1 equiv.8-aminoquinoline in THF in situ,which reacted further with 1/3 equiv.of YbCl3 in THF,to give the homoleptic lanthanide amide ate complex Yb(NH-C9H6N)4Li(C4H8O)2(1).The crystal structure was determined by X-ray diffraction and the following crystallographic data were obtained:C44H44N8O2YbLi,Mr = 896.85,monoclinic,space group C2/c,a = 7.8384(16),b = 22.294(5),c = 22.668(5),β = 97.614(5)°,V = 3926.3(14)3,Z = 4,Dc = 1.517 g/cm3,F(000)= 1812,μ(MoKα)= 2.431 mm-1,R = 0.0542 and wR = 0.1523 for 3372 observed reflections with I > 2σ(I).The structure of molecule 1 consists of one ytterbium atom,one lithium atom,four 8-aminoquinoline ligands and two THF molecules.The ytterbium atom is coordinated by eight nitrogen atoms of four 8-aminoquinoline ligands,forming a distorted dodecahedral geometry.     

Post-self-assembly covalent chemistry of discrete multicomponent metallosupramolecular hexagonal prisms

The multicomponent coordination-driven self-assembly of hexakis[4-(4-pyridyl)phenyl]benzene, cis-(PEt(3))(2)Pt(II)(OTf)(2), and amine- or maleimide-functionalized isophthalate forms discrete hexagonal prisms as single reaction products. The amino or maleimide groups decorating the isophthalate pillars of the prisms provide reactive sites for post-self-asssembly modifications. In this communication, we demonstrate that the hexagonal prisms can be functionalized without disrupting the prismatic cores, enabling the incorporation of new functionalities under mild conditions.