It is shown for the first time that liquid crystal behavior can be induced through halogen bonding. Thus, mixing the nonmesomorphic components 4-alkoxystilbazole with pentafluoroiodobenzene leads to a 1:1 halogen-bonded complex whose integrity is shown by X-ray single-crystal analysis and which shows thermotropic smectic A and nematic phases.

Herein we report the photocontrol of cucurbit[8]uril (CB[8])-mediated supramolecular polymerization of azobenzene-containing monomers. The CB[8] polymers were characterized both in solution and in the solid state. These host-guest complexes can be reversibly switched between highly thermostable photostationary states. Moreover, a remarkable stabilization of Z-azobenzene was achieved by CB[8] complexation, allowing for structural characterization in the solid state.

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Scheme 1 Synthesis of dodecaalkyl iminospherand cages 6-9.

A range of ortho-metalated catalysts with alkylphosphine ligands of the general formula [Pd(X)(κ2 N,C-C6H4CH2NMe2)(PR3)] have been synthesized, and the crystal structures of five examples (R = Cy, X = TFA, OTf, Cl, I; PR3 = PCy2(o-biphenyl), X = TFA) have been determined. The crystal structures of two dimeric precursor complexes, [{Pd(μ-TFA)(κ2 N,C-C6H4CH2NMe2)}2] and [{Pd(TFA)(κ2 N,C-C6H4CHNiPr)}2], have also been determined. The application of the phosphine adducts to both Suzuki coupling and Buchwald−Hartwig amination reactions with aryl chloride substrates was examined, and the performance of these catalysts versus conventional palladium sources was evaluated. In general the palladacyclic complexes show considerably enhanced activity. Typically, the best activity is seen with tricyclohexylphosphine adducts in Suzuki coupling and tri-tert-butylphosphine analogues in amination reactions. In nearly all the amination reactions performed, small amounts of a second product species were observed, namely 4,6-bis(aryl)-3,4-dihydro-2H-[1,4]oxazines. The crystal structure of one example, 4,6-bis(4-methoxyphenyl)-3,4-dihydro-2H-[1,4]oxazine, was determined. Studies on the activation of palladacyclic precatalysts in the coupling of morpholine led to the isolation of a morpholine adduct, [Pd(TFA)(κ2 N,C-C6H5CH2NMe2){NH(CH2CH2)O}], which was structurally characterized by X-ray analysis.

In view of the range of properties required from supramolecular materials, there is clearly a need for new strong quadruple hydrogen bonded modules, which can be used in polymer or copolymer synthesis via the self- or hetero-association of complimentary units. A cytosine-based module has been prepared for supramolecular applications using a straightforward synthetic approach. The cytosine module was designed such that it does not undergo tautomeric changes observed with ureidopyrimidinones. The cytosine module was capable of forming quadruple hydrogen bonded assemblies both in solution and in the solid state, and the structure of the dimeric self-assembled unit was confirmed by single-crystal X-ray and solution NMR techniques. The dimerization constant was estimated to be greater than 9 × 106 M-1 in deuterated benzene. The capacity of the cytosine-based module to strongly hetero-associate with the ureidopyrimidinone module was demonstrated, and a supramolecular polymer of a bifunctional unit incorporating the cytosine module and PEG-based linker was described.

The synthesis of the novel seven-membered N-heterocyclic carbene (NHC) 1,3-dicyclohexyl-1,3diazepan-2-ylidene (3) and its 5,6-dioxolane derivative 4 is reported and their coordination chemistry with Rh(I), Ir(I), and Pt(0) discussed. The M(cod)(3)Cl, where M ) Rh and Ir, complexes display a high rotation barrier at room temperature about the M-C NHC bond, whereas for the M(CO) 2 ( 3)Cl and Pt-(nbe) 2 (3) complexes rapid rotation of the carbene ligand is observed at ambient temperature. The infrared ν(CO) values of the Rh(I) and Ir(I) derivatives M(CO) 2 (3)Cl give a measure of the donor ability of the new carbene ligands. The crystal structures of the amidinium salts 3‚HPF 6 and 4‚HPF 6 together with those of M(cod)(3)Cl [M ) Rh, Ir], Ir(cod)(4)Br, Ir(CO) 2 (3)Cl, and Pt(nbe) 2 (3) are reported. Both the salts and the coordinated carbene ligands exhibit extremely large NCN angles; for the complexes the angles are in the range 115.5(3)°[Pt(3)] to 122(11)°[Ir(4)].

The transport of anions across biological membranes by small molecules is a growing research field due to the potential therapeutic benefits of these compounds. However, little is known about the exact mechanism by which these drug-like molecules work and which molecular features make a good transporter. An extended series of 1-hexyl-3-phenylthioureas were synthesized, fully characterized (NMR, mass spectrometry, IR and single crystal diffraction) and their anion binding and anion transport properties were assessed using 1 H NMR titration techniques and a variety of vesicle-based experiments. Quantitative structure-activity relationship (QSAR) analysis revealed that the anion binding abilities of the mono-thioureas are dominated by the (hydrogen bond) acidity of the thiourea NH function.Furthermore, mathematical models show that the experimental transmembrane anion transport ability is mainly dependent on the lipophilicity of the transporter (partitioning into the membrane), but smaller contributions of molecular size (diffusion) and hydrogen bond acidity (anion binding) were also present.Finally, we provide the first step towards predictable anion transport by employing the QSAR equations to estimate the transmembrane transport ability of four new compounds.