Taming Molecular Folding: Anion-Templated Foldamers with Tunable Quaternary Structures.

Higher-order foldamers represent a unique class of supramolecules at the forefront of molecular design. Herein we control quaternary folding using a novel approach that combines halogen bonding (XBing) and hydrogen bonding (HBing). We present the first anion-templated double helices induced by halogen bonds (XBs) and stabilized by "hydrogen bond enhanced halogen bonds" (HBeXBs).

Absolute structure determination of Berkecoumarin by X-ray and electron diffraction.

X-ray and electron diffraction methods independently identify the S-enantiomer of Berkecoumarin [systematic name: (S)-8-hydroxy-3-(2-hydroxypropyl)-6-methoxy-2H-chromen-2-one]. Isolated from Berkeley Pit Lake Penicillium sp., Berkecoumarin is a natural product with a light-atom composition (CHO) that challenges in-house absolute structure determination by anomalous scattering.

Cucurbit[8]uril Binds Nonterminal Dipeptide Sites with High Affinity and Induces a Type II β-Turn.

In an effort to target polypeptides at nonterminal sites, we screened the binding of the synthetic receptor cucurbit[8]uril (Q8) to a small library of tetrapeptides, each containing a nonterminal dipeptide binding site. The resulting leads were characterized in detail using a combination of isothermal titration calorimetry, H NMR spectroscopy, electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS), and X-ray crystallography. The equilibrium dissociation constant values determined for the binding of Q8 to nonterminal dipeptide sites Lys-Phe (KF) and Phe-Lys (FK) were 60 and 86 nm, respectively.

Chelation chemistry of manganese-52 for PET imaging applications.

Introduction: Due to its decay and chemical properties, interest in manganese-52 has increased for development of long-lived PET radiopharmaceuticals. Its long half-life of 5.6 days, low average positron energy (242 keV), and sufficient positron decay branching ratio make it suitable for radiolabeling macromolecules for investigating slow biological processes.

The interplay between hydrogen and halogen bonding: substituent effects and their role in the hydrogen bond enhanced halogen bond.

The hydrogen bond enhanced halogen bond (HBeXB) has recently been used to effectively improve anion binding, organocatalysis, and protein structure/function. In this study, we present the first systematic investigation of substituent effects in the HBeXB. NMR analysis confirmed intramolecular HBing between the amine and the electron-rich belt of the XB donor (N-H⋯I).

Pushing the limits of the hydrogen bond enhanced halogen bond-the case of the C-H hydrogen bond.

C-H hydrogen bonds have remarkable impacts on various chemical systems. Here we consider the influence of C-H hydrogen bonds to iodine atoms. Positioning a methyl group between two iodine halogen bond donors of the receptor engendered intramolecular C-H hydrogen bonding (HBing) to the electron-rich belt of both halogen bond donors.

Halogen bonding organocatalysis enhanced through intramolecular hydrogen bonds.

Recent results indicate a halogen bond donor is strengthened through direct interaction with a hydrogen bond to the electron-rich belt of the halogen. Here, this Hydrogen Bond enhanced Halogen Bond (HBeXB) plays a clear role in a catalyst. Our HBeXB catalyst improves product conversion in a halide abstraction reaction over a traditional halogen bonding derivative.

Cryptic Biosynthesis of the Berkeleypenostatins from Coculture of Extremophilic sp.

Coculture fermentation of and yielded berkeleypenostatins A-G (-) as well as the previously reported berkeleylactones A-H, the known macrolide A26771B, citrinin, and patulin. As was true with the berkeleylactones, there was no evidence of the berkeleypenostatins in either axenic culture. The structures were deduced from analyses of spectral data, and the absolute configuration of berkeleypenostatin A () was determined by single-crystal X-ray crystallography.

Theoretical, Solid-State, and Solution Quantification of the Hydrogen Bond-Enhanced Halogen Bond.

Proximal noncovalent forces are commonplace in natural systems and understanding the consequences of their juxtaposition is critical. This paper experimentally quantifies for the first time a Hydrogen Bond-Enhanced Halogen Bond (HBeXB) without the complexities of protein structure or preorganization. An HBeXB is a halogen bond that has been strengthened when the halogen donor simultaneously accepts a hydrogen bond.

Influence and Substituent Effects on the HOMO-LUMO Energy Gap and Stokes Shift in Ru Mono-Diimine Derivatives.

The ground (S) and excited triplet (T) electronic states and corresponding optical spectra of a series of cationic complexes [RuH(CO)L(PPh)] (L=2,2´-bipyridyl) (Rubpy), 4,4´-dicarboxylic-2,2´-bipyridyl (Rudcbpy), bis-4,4'-(N-methylamide)-2,2´-bipyridyl (Rudamidebpy), bis-4,4'-(methyl)-2,2´-bipyridyl (RudMebpy), [Ru(CO)dcbpy(PPh)] (Ru(2CO)dcbpy), and [Ru(H)dcbpy(PPh)] (Ru(2H)dcbpy) have been studied by combined Density Functional/Time-Dependent Density Functional (DFT/TDDFT) techniques using different combinations of DFT exchange-correlation functionals and basis sets. PBE0/LANL2DZ provided more accurate geometries to describe S whereas B3LYP/LANL2DZ predicted spectral energies that correlated better with the available experiment data. The Ru (II) complexes with different substituents emit photons ranging from 560-610 nm in the series RudMebpy, Rubpy, Rudamidebpy, Rudcbpy.

Anion Influence on the Packing of 1,3-Bis(4-Ethynyl-3-Iodopyridinium)-Benzene Halogen Bond Receptors.

Rigid and directional arylethynyl scaffolds have been widely successful across diverse areas of chemistry. Utilizing this platform, we present three new structures of a dicationic 1,3-bis(4-ethynyl-3-iodopyridinium)-benzene halogen bonding receptor with tetrafluoroborate, nitrate, and hydrogen sulfate. Structural analysis focuses on receptor conformation, anion shape, solvation, and long range packing of these systems.

Structural and Computational Characterization of a Bridging Zwitterionic-Amidoxime Uranyl Complex.

A bridging (μ) neutral zwitterionic amidoxime binding mode previously unobserved between amidoximes and uranyl is reported and compared to other uranyl amidoxime complexes. Density functional theory computations show the dinuclear complex exhibits a shallow potential energy surface allowing for facile inclusion of a nonbonding water molecule in the solid-state.

A Long-Lived Halogen-Bonding Anion Triple Helicate Accommodates Rapid Guest Exchange.

Anion-templated helical structures are emerging as a dynamic and tractable class of supramolecules that exhibit anion-switchable self-assembly. We present the first kinetic studies of an anion helicate by utilizing halogen-bonding m-arylene-ethynylene oligomers. These ligands formed high-fidelity triple helicates in solution with surprisingly long lifetimes on the order of seconds even at elevated temperatures.

Correction: The intramolecular hydrogen bonded-halogen bond: a new strategy for preorganization and enhanced binding.

[This corrects the article DOI: 10.1039/C8SC01973H.].

The intramolecular hydrogen bonded-halogen bond: a new strategy for preorganization and enhanced binding.

Natural and synthetic molecules use weak noncovalent forces to preorganize structure and enable remarkable function. Herein, we introduce the intramolecular hydrogen bonded-halogen bond (HB-XB) as a novel method to preorganize halogen bonding (XBing) molecules, while generating a polarization-enhanced XB. Positioning a fluoroaniline between two iodopyridinium XB donors engendered intramolecular hydrogen bonding (HBing) to the electron-rich belt of both XB donors.

The synthesis of lactone-bridged 1,3,5-triphenylbenzene derivatives as pi-expanded coumarin triskelions.

Two triply lactone-bridged 1,3,5-triphenylbenzene derivatives with solubilizing moieties have been synthesized in five and six steps from commercially available starting materials. Compounds containing the 1,3,5-triphenylbenzene core with two atom bridges are relatively unknown. This new class of pi-expanded coumarins contain triskelion architectures and X-ray crystallographic studies of one of the triskelions indicates that the 1,3,5-triphenylbenzene core adopts a near-planar geometry.

Steric Effects of pH Switchable, Substituted (2-pyridinium)urea Organocatalysts: a Solution and Solid Phase Study.

The study of hydrogen bonding organocatalysis is rapidly expanding. Much research has been directed at making catalysts more active and selective, with less attention on fundamental design strategies. This study systematically increases steric hindrance at the active site of pH switchable urea organocatalysts.

Experimental investigation of halogen-bond hard-soft acid-base complementarity.

The halogen bond (XB) is a topical noncovalent interaction of rapidly increasing importance. The XB employs a `soft' donor atom in comparison to the `hard' proton of the hydrogen bond (HB). This difference has led to the hypothesis that XBs can form more favorable interactions with `soft' bases than HBs.

The Berkeleylactones, Antibiotic Macrolides from Fungal Coculture.

A carefully timed coculture fermentation of Penicillium fuscum and P. camembertii/clavigerum yielded eight new 16-membered-ring macrolides, berkeleylactones A-H (1, 4, 6-9, 12, 13), as well as the known antibiotic macrolide A26771B (5), patulin, and citrinin. There was no evidence of the production of the berkeleylactones or A26771B (5) by either fungus when grown as axenic cultures.

Structural and Energetic Properties of Haloacetonitrile - GeF Complexes.

The 1:1 and 2:1 complexes of FCHCN and ClCHCN with GeF have been investigated by M06/aug-cc-pVTZ calculations, low-temperature, thin-film IR spectroscopy, and an x-ray structure has been obtained for (FCHCN)-GeF. Theoretical structures and binding energies for FCHCN-GeF and ClCHCN-GeF demonstrate that halogen substitution significantly weakens the Ge-N dative bonds. The Ge-N distances for the F-and Cl-complexes (2.

A Halogen-Bond-Induced Triple Helicate Encapsulates Iodide.

The self-assembly of higher-order anion helicates in solution remains an elusive goal. Herein, we present the first triple helicate to encapsulate iodide in organic and aqueous media as well as the solid state. The triple helicate self-assembles from three tricationic arylethynyl strands and resembles a tubular anion channel lined with nine halogen bond donors.

Protonation and Alkylation Induced Multidentate C-H•••Anion Binding to Perrhenate.

A family of pyridyl functionalized arylacetylene C-H HB receptors were synthesized and binding interactions to perrhenate (ReO ) studied in the solid state. The protonation and alkylation state of the pyridine nitrogen dictate the location and denticity of the interactions. X-ray structures of neutral and singly charged reveal the formation of favorable self-complimentary dimers, owning to the presence of nitrogen HB acceptor sites.

Advantages of Organic Halogen Bonding for Halide Recognition.

The study of hydrogen bonding organocatalysis is rapidly expanding. Much research has been directed at making catalysts more active and selective, with less attention on fundamental design strategies. This study systematically increases steric hindrance at the active site of pH switchable urea organocatalysts.