Three Distinct Equilibrium States via Self-Assembly: Simple Access to a Supramolecular Ion-Controlled NAND Logic Gate

During the past several decades, considerable effort has focused on self-assembled systems. However, most work has been directed toward understanding the equilibrium between two major chemical entities, namely the dissociated components and the corresponding associated complex. While there are quite a few examples of ‘multiresponsive’ materials, control over ‘multistate’ materials has proved difficult to achieve. Here, we report the formation and the interplay of a self-assembled calix[4]­pyrrole array that exhibits three limiting forms, namely a 1:1 self-assembled oligomer, a 2:1 capsule, and the corresponding monomers. Interconversion between these states may be controlled by using the tetraethylammonium cation (TEA⁺) and/or iodide anion (I^–) as chemical inputs. The combination of self-assembly and ion-based control may be used to create systems that display NAND logic behavior. The system outputs have been confirmed by a variety of analytic methods, including UV–vis and 2D ¹H DOSY, NOESY NMR spectroscopy, scanning electron microscopy, and single crystal X-ray diffraction analyses

Three Distinct Equilibrium States via Self-Assembly: Simple Access to a Supramolecular Ion-Controlled NAND Logic Gate

During the past several decades, considerable effort has focused on self-assembled systems. However, most work has been directed toward understanding the equilibrium between two major chemical entities, namely the dissociated components and the corresponding associated complex. While there are quite a few examples of ‘multiresponsive’ materials, control over ‘multistate’ materials has proved difficult to achieve. Here, we report the formation and the interplay of a self-assembled calix[4]­pyrrole array that exhibits three limiting forms, namely a 1:1 self-assembled oligomer, a 2:1 capsule, and the corresponding monomers. Interconversion between these states may be controlled by using the tetraethylammonium cation (TEA⁺) and/or iodide anion (I^–) as chemical inputs. The combination of self-assembly and ion-based control may be used to create systems that display NAND logic behavior. The system outputs have been confirmed by a variety of analytic methods, including UV–vis and 2D ¹H DOSY, NOESY NMR spectroscopy, scanning electron microscopy, and single crystal X-ray diffraction analyses

Three Distinct Equilibrium States via Self-Assembly: Simple Access to a Supramolecular Ion-Controlled NAND Logic Gate

During the past several decades, considerable effort has focused on self-assembled systems. However, most work has been directed toward understanding the equilibrium between two major chemical entities, namely the dissociated components and the corresponding associated complex. While there are quite a few examples of ‘multiresponsive’ materials, control over ‘multistate’ materials has proved difficult to achieve. Here, we report the formation and the interplay of a self-assembled calix[4]­pyrrole array that exhibits three limiting forms, namely a 1:1 self-assembled oligomer, a 2:1 capsule, and the corresponding monomers. Interconversion between these states may be controlled by using the tetraethylammonium cation (TEA⁺) and/or iodide anion (I^–) as chemical inputs. The combination of self-assembly and ion-based control may be used to create systems that display NAND logic behavior. The system outputs have been confirmed by a variety of analytic methods, including UV–vis and 2D ¹H DOSY, NOESY NMR spectroscopy, scanning electron microscopy, and single crystal X-ray diffraction analyses

Elucidating the Impact of Molecular Structure on the ¹⁹F NMR Dynamics and MRI Performance of Fluorinated Oligomers

To understand molecular factors that impact the performance of polymeric ¹⁹F magnetic resonance imaging (MRI) agents, a series of discrete fluorinated oligoacrylates with precisely defined structure were prepared through the combination of controlled polymerization and chromatographic separation techniques. These discrete oligomers enabled thorough elucidation of the dependence of ¹⁹F NMR and MRI properties on molecular structure, for example, the chain length. Importantly, the oligomer size and dispersity strongly influence NMR dynamics (<i>T</i>₁ and <i>T</i>₂ relaxation times) and MR imaging properties with higher signal-to-noise ratio (SNR) observed for oligomers with longer chain length and shorter <i>T</i>₁. Our approach enables an effective pathway and thus opportunities to rationally design effective polymeric ¹⁹F MR imaging agents with optimized molecular structure and NMR relaxivity

Redox- and pH-Responsive Orthogonal Supramolecular Self-Assembly: An Ensemble Displaying Molecular Switching Characteristics

Two heteroditopic monomers, namely a thiopropyl-functionalized tetrathiafulvalene-annulated calix[4]­pyrrole (SPr-TTF-C[4]P <b>1</b>) and phenyl C₆₁ butyric acid (PCBA <b>2</b>), have been used to assemble a chemically and electrochemically responsive supramolecular ensemble. Addition of an organic base initiates self-assembly of the monomers via a molecular switching event. This results in the formation of materials that may be disaggregated via the addition of an organic acid or electrolysis

A Versatile and Efficient Strategy to Discrete Conjugated Oligomers

An efficient and scalable strategy to prepare libraries of discrete conjugated oligomers (<i><i>Đ</i></i> = 1.0) using the combination of controlled polymerization and automated flash chromatography is reported. From this two-step process, a series of discrete conjugated materials from dimers to tetradecamers could be isolated in high yield with excellent structural control. Facile and scalable access to monodisperse libraries of different conjugated oligomers opens pathways to designer mixtures with precise composition and monomer sequence, allowing exquisite control over their physical, optical, and electronic properties

Expanded Porphyrin-Anion Supramolecular Assemblies: Environmentally Responsive Sensors for Organic Solvents and Anions

Porphyrins have been used frequently to construct supramolecular assemblies. In contrast, noncovalent ensembles derived from expanded porphyrins, larger congeners of naturally occurring tetrapyrrole macrocycles, are all but unknown. Here we report a series of expanded porphyrin-anion supramolecular assemblies. These systems display unique environmentally responsive behavior. Addition of polar organic solvents or common anions to the ensembles leads to either a visible color change, a change in the fluorescence emission features, or differences in solubility. The actual response, which could be followed easily by the naked eye, was found to depend on the specifics of the assembly, as well as the choice of analyte. Using the ensembles of this study, it proved possible to differentiate between common solvents, such as diethyl ether, THF, ethyl acetate, acetone, alcohol, acetonitrile, DMF, and DMSO, identify complex solvent systems, as well as distinguish between the fluoride, chloride, bromide, nitrate, and sulfate anions

Ion-Regulated Allosteric Binding of Fullerenes (C₆₀ and C₇₀) by Tetrathiafulvalene-Calix[4]pyrroles

The effect of ionic species on the binding of fullerenes (C₆₀ and C₇₀) by tetrathiafulvalene-calix[4]­pyrrole (TTF-C4P) receptors and the nature of the resulting supramolecular complexes (TTF-C4P + fullerene + halide anion + tetraalkylammonium cation) was studied in the solid state through single crystal X-ray diffraction methods and in dichloromethane solution by means of continuous variation plots and UV–vis spectroscopic titrations. These analyses revealed a 1:1 stoichiometry between the anion-bound TTF-C4Ps and the complexed fullerenes. The latter guests are bound within the bowl-like cup of the C4P in a ball-and-socket binding mode. The interactions between the TTF-C4P receptors and the fullerene guests are highly influenced by both the nature of halide anions and their counter tetraalkylammonium cations. Three halides (F^–, Cl^–, and Br^–) were studied. All three potentiate the binding of the two test fullerenes by inducing a conformational change from the 1,3-alternate to the cone conformer of the TTF-C4Ps, thus acting as positive heterotropic allosteric effectors. For a particular halide anion, the choice of tetraalkylammonium salts serves to modulate the strength of the TTF-C4P-fullerene host–guest binding interactions and, in conjunction with variations in the halide anion, can be exploited to alter the inherent selectivity of the host for a given fullerene. Differences in binding are reflected in the excited state optical properties. Overall, the present four-component system provides an illustration of how host–guest binding events involving appropriately designed artificial receptors can be fine-tuned via the addition of simple ionic species as allosteric modulators