Artur R. Stefankiewicz

Generation of a Dynamic System of Three-Dimensional Tetrahedral Polycatenanes

Seven of the best: A dynamic combinatorial library of polycatenated tetrahedra was prepared by complexation between a dynamic Fe4L6 tetrahedral cage, constructed from ligands containing an electron‐deficient naphthalenediimide core, and an electron‐rich aromatic crown ether, 1,5‐dinaphtho[38]crown‐10. The highest order species in the library is the tetrahedral [7]catenane.WILEY-VCH

Guest‐Induced Transformation of a Porphyrin‐Edged FeII4L6 Capsule into a CuIFeII2L4 Fullerene Receptor

The combination of a bent diamino(nickel(II) porphyrin) with 2-formylpyridine and Fe(II) yielded an Fe(II) 4 L6 cage. Upon treatment with the fullerenes C60 or C70 , this cage was found to transform into a new host-guest complex incorporating three Fe(II) centers and four porphyrin ligands, in an arrangement that is hypothesized to maximize π interactions between the porphyrin units of the host and the fullerene guest bound within its central cavity. The new complex shows coordinative unsaturation at one of the Fe(II) centers as the result of the incommensurate metal-to-ligand ratio, which enabled the preparation of a heterometallic cone-shaped Cu(I) Fe(II) 2 L4 adduct of C60 or C70 .

Template-directed synthesis of multi-component organic cages in water

We describe here the discovery of a new class of organic cages assembled from simple tri- and dithiol building blocks using dynamic combinatorial chemistry (DCC). These water-soluble disulfide-linked architectures containing up to eleven components are only generated upon templation by positively charged polyamine guests of appropriate shape and length such as spermine and spermidine. The overall response of the system as expressed in the pattern of peaks in an HPLC trace provides an unusual tool for the identification of the templating analyte.

Proton‐Driven Switching Between Receptors for C60 and C70

Buckybinding: The selective binding of either C60 and C 70 in a mixture of the two fullerenes occurs by proton-induced, reversible, and controllable morphological switching between receptors for different fullerenes (see picture). Using hydrogen bonding as the exchange reaction, the response of the naphthalenediimide (NDI) building blocks to the presence of fullerene guests depends on the concentration of protons as a third component.

Highly Sensitive Magnetic Effects Induced by Hydrogen-Bonding Interactions in a High-Spin Metallosupramolecular Fe4II [2×2] Grid-Type Complex

A sensitive magnetic nanoprobe: Hydrogen-bonding interactions are reflected with great sensitivity in the (1)H NMR spectra of a high-spin multinuclear Fe(4) (II) [2x2] grid-type complex (see scheme) and the measured shifts can be used to evaluate the hydrogen-bond donating ability. The grid complex also represents a prototype of a very sensitive magnetic nanoreceptor for the detection of very small changes around a magnetic center.

Self-ordering of metallogrid complexes via directed hydrogen-bonding

Reaction of imidazole aldehydes with dihydrazino derivatives of 2-phenylpyrimidine provides a family of bis(acylhydrazone) ligands which form [2 × 2] metallogrid complexes with transition metal ions including Fe(II), Co(II), Cu(II) and Zn(II). The free ligands show H-bonding interactions, both donor and acceptor, largely involving the imidazole units, while binding of the metal ions occupies all the acceptor sites and leaves only the pyrrolic-NH site as an H-bond donor, although its deprotonation by a strong base can regenerate an acceptor. These H-bonding interactions have been studied by (1)H NMR spectroscopy in solution and in the solid state by means of several crystal structure determinations. The Fe(II) grids appear to be exclusively high-spin species over a wide temperature range in solution. In the solid state various forms of spin-crossover behaviour can be observed between 1.8 and 300 K, which has been rationalised in terms of the varied forms of hydrogen-bonding possible in the crystalline state.

Self-assembly of alkoxy-substituted bis(hydrazone)-based organic ligands and of a metallosupramolecular grid on graphite.

Self-assembly of a bis(hydrazone) chelating ligand functionalized with octadecyloxy substituents is described, as well as the reproducible thermally activated self-assembly of its metallosupramolecular cationic Co(II) [2x2] grid-type complex, on a highly oriented pyrolitic graphite (HOPG) substrate. Scanning tunnelling microscopy measurements at the solid/liquid interface reveal that the grid units of the annealed films are oriented edge-on to the basal plane of the HOPG, which indicates that the influence of the octadecyl chains is not sufficient to tie the grids into a face-on orientation. To gain a detailed understanding of the self-assembly behaviour of the grid on HOPG, the results for the grid itself have been compared to those of its constituent ligands.

Rigid Dimers Formed through Strong Interdigitated H‐Bonds Yield Compact 1D Supramolecular Helical Polymers

Hierarchical self-assembly of small abiotic molecular modules interacting through noncovalent forces is increasingly being used to generate functional structures and materials for electronic, catalytic, and biomedical applications. The greatest control over the geometry in H-bond supramolecular architectures, especially in H-bonded supramolecular polymers, can be achieved by using conformationally rigid molecular modules undergoing self-assembly through strong H-bonds. Their binding strength depends on the multiplicity of the H-bonds, the nature of donor/acceptor pairs and their secondary attractive/repulsive interactions. Here a functionalized molecular module is described, which is capable of self-associating through self-complementary H-bonding patterns comprising four strong and two medium-strength H-bonds to form dimers. The self-association of these phenylpyrimidine-based dimers through directional H-bonding between two lateral pyridin-2(1H)-one units of neighboring molecules allows the formation of highly compact 1D supramolecular polymers by self-assembly on graphite. A concentration-dependent study by scanning tunneling microscopy at the solid-liquid interface, corroborated by dispersion-corrected density functional studies, reveals the controlled generation of either linear supramolecular 2D arrays, or long helical supramolecular polymers with a high shape persistence.

Association of quaterpyridine complex cations with polyanionometallates

Reactions in CH3CN:CH2Cl2 (2:1) under Ar of the dimethyl-quaterpyridine ligand C22H18N4 (L) with Mn(ClO4)2, Fe(BF4)2, CoCl2, Co(NO3)2, Zn(NO3)2, Cd(CH3COO)2 and HgCl2 give complexes of the type [ML(H2O) m X n ]2[MX p ], where X denotes the initial counterions, with m = 1, n = 1, p = 4 or m = 2, n = 0, p = 6. The complexes have been characterised by spectroscopic techniques and elemental analysis. The solid-state structures of two forms of the CoCl2 complex have been established by X-ray crystallography, enabling an analysis of the interactions occurring in crystals of this type.

Generation of a Multicomponent Library of Disulfide Donor-Acceptor Architectures Using Dynamic Combinatorial Chemistry.

We describe here the generation of new donor-acceptor disulfide architectures obtained in aqueous solution at physiological pH. The application of a dynamic combinatorial chemistry approach allowed us to generate a large number of new disulfide macrocyclic architectures together with a new type of [2]catenanes consisting of four distinct components. Up to fifteen types of structurally-distinct dynamic architectures have been generated through one-pot disulfide exchange reactions between four thiol-functionalized aqueous components. The distribution of disulfide products formed was found to be strongly dependent on the structural features of the thiol components employed. This work not only constitutes a success in the synthesis of topologically- and morphologically-complex targets, but it may also open new horizons for the use of this methodology in the construction of molecular machines.