Edwin Weber

Host Guest Complex Chemistry III

The solvent extraction of metal ions by crown compounds.- Crown compounds as alkali and alkaline earth metal ion selective chromogenic reagents.- Photocontrol of ion extraction and ion transport by photofunctional crown ethers.- Macroheterocyclic ligands on polymers.- Synthesis and metal complexes of aza-macrocycles with pendant arms having additional ligating groups.- Bridged, capped and fenced porphyrins.

Design of Organic Solids

Directional Aspects of Intermolecular Interactions.- Supramolecular Synthons and Pattern Recognition.- Hydrogen-Bonded Ribbons, Tapes and Sheets as Motifs for Crystal Engineering.- Functional Organic Zeolite Analogues.- Crystalline Polymorphism of Organic Compounds.

A proposal for the classification and nomenclature of host-guest-type compounds

We suggest a system of classification and naming of general application to host-guest-type compounds. The classification is based on several criteria, including the host-guest type and the host-guest interaction, but also on topological and numerical considerations. The application of this concept to the classification of any host-guest situation is illustrated by several examples.

Molecular recognition: designed crystalline inclusion complexes of carboxylic hosts

Abstract Recently there has heen a gradual drift of organic chemists into research relevant to biology. This has resulted in a rich array of sophisticated model systems. Ultimately, such models are intended to imitate the specific recognition of substrates. The lattice-type inclusions are expected to be particularly useful in this respect. This paper explains the basic ideas of a new strategy for directed lattice inclusion called “coordination-assisted clathrate formation.” Besides matching sizes and shapes, this strategy makes extensive use of functional group interactions between a host and a guest molecule, allowing molecular recognition in the solid state. In particular, the carboxylic group is demonstrated as a sensitive site of host molecules for interaction (multicontact binding) with guest molecules o f different H-bond donor and/or acceptor strength involving alcohols, carboxamides, dimethyl sulfoxide and carboxylic acids. Hosts refer to molecules of different geometric shapes (scissor-type, roof-shaped and small-ring acids). We will look at structural aspects of the H-bonded supramolecular aggregates formed between host and guest that are responsible for the mutual recognition properties.

High‐Separation Performance of Chromatographic Capillaries Coated with MOF‐5 by the Controlled SBU Approach

Recently developed MOF surface-coating techniques, the controlled SBU approach (CSA) for the generation of MOF-5, and the use of self-assembled monolayers have been combined to generate a wall-bonded, crosslinked stationary phase for gas chromatographic capillary columns displaying excellent performance in the separation of natural gas components. The chromatographic performance of this new type of column has been compared to the state-of-the-art solution for this separation problem, namely a coated silica column of the porous layer open tubular (PLOT) type. Chromatographic parameters such as separation, resolution, and tailing factors, as well as plate numbers and heights in the case of isothermal operation, have been determined. Kinetic and thermodynamic parameters characterizing the analyte-stationary phase interaction have been determined for various C1-C4 analytes.

New trigonal lattice hosts: stoicheiometric crystal inclusions of laterally trisubstituted benzenes—X-ray crystal structure of 1,3,5-tris-(4-carboxyphenyl)benzene·dimethylformamide

New host molecules with a central 1,3,5-trisubstituted benzene ring and rigidly attached lateral arms composed of aryl or arylethynyl and extra functional groups are reported. They are shown to give more than thirty clathrates with a wide variety of organic solvents comprising alicyclic, aromatic, heterocyclic, dipolar aprotic, and protic molecules. Inclusion selectivities and stoicheiometries of the different clathrates are discussed. The crystal structure of (2a)·dimethylformamide (DMF)(1:3) inclusion compound has been determined from single-crystal X-ray diffraction. The crystals show R symmetry. There are six host and eighteen guest molecules in the hexagonal unit cell with a=b= 23.160(9) and c= 11.812(3)A. The final linear R is 0.082 for 1 518 unique reflections. The host molecules adopts a propeller conformation with perfect three-fold symmetry and acts as a donor in hydrogen bonds to three DMF molecules. In the crystal structure the host–guest units are arranged stack-wise.

Flexible Low‐Voltage Organic Complementary Circuits: Finding the Optimum Combination of Semiconductors and Monolayer Gate Dielectrics

Low-voltage p-channel and n-channel organic transistors with channel lengths down to 0.5 μm using four small-molecule semiconductors and ultra-thin dielectrics based on two different phosphonic acid monolayers are fabricated on plastic substrates and studied in terms of effective mobility, intrinsic mobility and contact resistance. For the optimum materials combination, flexible complementary circuits have signal delays of 3.1 μs at 5 V.

Functional group assisted clathrate formation — Scissor-like and roof-shaped host molecules

A strategy has been developed for the design, synthesis, and testing of new clathrate hosts that possess relationship complementarity to specific guest-compounds.

Inclusion Compounds of Diol Hosts Featuring Two 9-Hydroxy-9-fluorenyl or Analogous Groups Attached to Linear Spacer Units

A series of new clathrate host molecules 1−15, each containing two 9-hydroxy-9-fluorenyl or analogous terminal groups attached to linear central units of different lengths and structural compositions, has been synthesized. Their crystalline inclusion compounds with a variety of organic guests − including amines, alcohols, ketones, and other dipolar aprotic compounds or aromatic hydrocarbons − are reported (229 examples of clathrates) and their properties are compared. The crystal structures of a free host compound and of six selected clathrates of different compound classes have been determined by X-ray diffraction, showing varied modes of supramolecular interaction.

A new organic nanoporous architecture: Dumb-bell-shaped molecules with guests in parallel channels

A new type of dumb-bell-shaped host molecule (6-8) has been synthesised, of which 1,8-bis((1)-adamantyl)-1,3,5,7-octatetrayne (8 = BAOT) forms an open porous architecture when cocrystallised with a number of typical solvent molecules. Adamantyl substituents attached to a tetraalkyne spacer build up the walls of parallel channels wherein guest molecules are aligned. Surprisingly, the tetraalkyne unit is significantly bent. Desolvation experiments provide evidence for a reversible inclusion of guests. In the case of the inclusion of 2-butanone, a partial substitution by symmetrical and asymmetrical long-chain chromophores during crystallisation was possible. Stained crystals showed optical frequency doubling. The crystal structure analysis revealed a centric space group, although considerable translational and orientational disorder was present. Application of scanning pyroelectric microscopy revealed that the growth of inclusion compounds with 2-butanone produced polar ordering of guest molecules, which were aligned in two macro-domains of opposing polarity. The resulting orientation of the carbonyl dipoles is in agreement with the theoretical prediction of a Markov model of spontaneous polarity formation based on molecular recognition processes on growing crystal faces. The present case represents a new example of a property-driven supramolecular synthesis.