Molecular Dynamics Simulations of Heterogeneous Hydrogen Bond Environment in Hydrophobic Deep Eutectic Solvents

Hydrophobic deep eutectic solvents (DESs) have emerged as excellent extractants. Their performance depends on the heterogeneous hydrogen bond environment formed by multiple hydrogen bond donors and acceptors. An understanding of this heterogeneous hydrogen bond environment can be used to develop principles for designing high-performance DESs for extraction and other separation applications. We investigate the structure and dynamics of hydrogen bonds in eight hydrophobic DESs formed by decanoic acid, menthol, thymol, and Lidocaine using molecular dynamics simulations. The results show the diversity of hydrogen bonds in the eight DESs and their impact on diffusivity and molecular association. Each DES possesses four-six types of hydrogen bonds and one or two of them overwhelm the others in quantity and lifetime. The dominating hydrogen bonds determine whether the DESs are governed by intra- or inter-component associations. The component diffusivity presents an inverse relationship with the hydrogen bond strength.

A Many-Faced Alkaloid: Polymorphism of (–)-Monophyllidin

The synthesis of the alkaloid (–)-monophyllidin is described. The molecule is a hybrid of xanthoxyline and (S)-proline, accessible in one-step through a Mannich reaction. In the solid-state, defined structural arrangements with different physical properties are formed. Single crystal X-ray diffraction revealed structures of six distinct polymorphs. In the crystalline state, the alkaloid can host small polar molecules (preferably water), while the (S)-proline moiety is present in the zwitterionic state. Combined with the chelate, which is already present in the xanthoxyline substructure, an ideal disposition for multiple hydrogen bond networks evolve. Therefore, highly water-soluble polymorphs of monophyllidin can form. This structural flexibility explains the many faces of the molecule in terms of structure as well as analytical data. Furthermore, speculations about the biological role of the molecule, with regard to the manifold interactions with water, are presented.

Conductive zigzag Pd(iii)–Br chain complex realized by a multiple-hydrogen-bond approach

Coexistence of zigzag structure and the uncommon Pd(iii) oxidation state in quasi-1D halogen-bridged metal complexes was realized in a conductive Br-bridged Pd chain complex, [Pd(dabdOH)2Br]SO4·3H2O (2), for the first time.

Excellent performance of aromatic polyguanamines induced by multiple hydrogen bondable tetraazacalix[2]arene[2]-triazine ring in their main chain

Poly(guanamine)s containing tetraazacalix[2]arene[2]triazine ring within the polymer main-chain show outstanding thermal and mechanical properties arisen from the multiple-hydrogen bond.

Complementary multiple hydrogen-bond-based magnetic composite microspheres for high coverage and efficient phosphopeptide enrichment in bio-samples

A novel smart polymer functionalized magnetic nanocomposite microsphere as an ideal platform to efficiently enrich both mono-phosphopeptides and multiple-phosphopeptides without distinction from complex biological samples.

Molecular Engineering of β-Substituted Oxoporphyrinogens for Hydrogen-Bond Donor Catalysis

<p>A new class of bifunctional hydrogen-bond donor organocatalyst using oxoporphyrinogens with increased intramolecular hydrogen-bond donor distances is reported. Oxoporphyrinogens are highly non-planar rigid macrocycles containing a multiple hydrogen bond forming binding site. In this work we report the first example of non-planar OxPs as hydrogen-bond donor catalysts. The introduction of β-substituents is key to the catalytic activity and the catalysts are able to catalyze 1,4-conjugate additions and sulfa-Michael additions, as well as, Henry and aza-Henry reactions at low catalyst loadings (≤ 1 mol%) under mild conditions. Preliminary mechanistic studies have been carried out and a possible reaction mechanism has been proposed based on the bi-functional activation of both substrates through hydrogen-bonding interactions.</p>