Reactivity of a Bis(amidinato)iron(II) Complex [Fe(MesC(NPr^<i>i</i>)₂)₂] toward Some Oxidizing Reagents

A diversified reactivity of the mononuclear bis­(amidinato)­iron­(II) complex [Fe­(MesC­(NPr^<i>i</i>)₂)₂] (<b>1</b>) toward oxidizing reagents has been disclosed. The bis­(amidinato)­iron­(II) complex was synthesized from the reaction of [Fe­(Mes)₂]₂ with 4 equiv of diisopropyl carbodiimide in good yield. Treatment of <b>1</b> with 1 equiv of benzyl chloride gives the high-spin ferric complex [FeCl­(MesC­(NPr^<i>i</i>)₂)₂] (<b>2</b>), with 0.25 equiv of S₈ affords the sulfur-insertion product [Fe­(MesC­(NPr^<i>i</i>)­(NPr^<i>i</i>S))₂] (<b>3</b>), with 1 equiv of 3,5-dimethylphenyl azide or phenyl azide yields nitrene-insertion product [Fe­(MesC­(NPr^<i>i</i>)₂)­(Pr^<i>i</i>NC­(Mes)­N­(Pr^<i>i</i>)­NAr)] (Ar = 3,5-dimethylphenyl, <b>4a</b>; phenyl, <b>4b</b>), and with 1 equiv of oxo-transfer reagent, trimethylamine oxide or 2,6-dichloropyridine oxide, generates the oxo-bridged diferric complex [(MesC­(NPr^<i>i</i>)₂)₂FeOFe­(MesC­(NPr^<i>i</i>)₂)₂] (<b>5</b>). Complexes <b>1</b>–<b>3</b>, <b>4a</b>, and <b>5</b> have been characterized by ¹H NMR, UV–vis, IR, elemental analysis, and single-crystal X-ray diffraction studies. The formations of these unusual sulfur- and nitrene-insertion products <b>3</b>, <b>4a</b>, and <b>4b</b>, can be explained by the sequential redox reaction between <b>1</b> and the oxidants, followed by migratory insertion steps

Benzo-21-crown-7-Based [1]Rotaxanes: Syntheses, X‑ray Crystal Structures, and Dynamic Characteristics

Two B21C7-based [1]rotaxanes were synthesized in high yields by means of copper(II)-mediated Eglinton coupling and a subsequent Pd/C-catalyzed reduction under H₂. X-ray single-crystal analysis shows that [1]rotaxane takes on a self-entangled conformation, wherein the macrocycle is threaded by its own tail. Moreover, it was found that [1]rotaxane with a flexible skeleton had more rotational motions than that of one with a rigid skeleton

Dynamic Softening or Stiffening a Supramolecular Hydrogel by Ultraviolet or Near-Infrared Light

The development of light-responsive hydrogels that exhibit switchable size and mechanical properties with temporal and spatial resolution is of great importance in many fields. However, it remains challenging to prepare smart hydrogels that dramatically change their properties in response to both ultraviolet (UV) and near-infrared (NIR) lights. Here, we designed a dual-light responsive supramolecular gel by integrating UV light-switchable host–guest recognition, temperature responsiveness, and NIR photothermal ability in the gel. The gel could rapidly self-heal and is capable of both softening and stiffening controlled by UV and NIR lights, respectively. Besides stiffness modulation, the bending direction of the gel can be controlled by UV or NIR light irradiation. The smart gel makes it possible to generate dynamic materials that respond to both UV and NIR lights and represents a useful tool that might be used to modulate cellular microenvironments with spatiotemporal resolution

Responsive Supramolecular Polymer Metallogel Constructed by Orthogonal Coordination-Driven Self-Assembly and Host/Guest Interactions

An emerging strategy for the fabrication of advanced supramolecular materials is the use of hierarchical self-assembly techniques wherein multiple orthogonal interactions between molecular precursors can produce new species with attractive properties. Herein, we unify the spontaneous formation of metal–ligand bonds with the host/guest chemistry of crown ethers to deliver a 3D supramolecular polymer network (SPN). Specifically, we have prepared a highly directional dipyridyl donor decorated with a benzo-21-crown-7 moiety that undergoes coordination-driven self-assembly with a complementary organoplatinum acceptor to furnish hexagonal metallacycles. These hexagons subsequently polymerize into a supramolecular network upon the addition of a bisammonium salt due to the formation of [2]­pseudorotaxane linkages between the crown ether and ammonium moieties. At high concentrations, the resulting 3D SPN becomes a gel comprising many cross-linked metallohexagons. Notably, thermo- and cation-induced gel–sol transitions are found to be completely reversible, reflecting the dynamic and tunable nature of such supramolecular materials. As such, these results demonstrate the structural complexity that can be obtained when carefully controlling multiple interactions in a hierarchical fashion, in this case coordination and host/guest chemistry, and the interesting dynamic properties associated with the materials thus obtained

Cross-Linked Supramolecular Polymer Gels Constructed from Discrete Multi-pillar[5]arene Metallacycles and Their Multiple Stimuli-Responsive Behavior

A new family of discrete hexakis-pillar[5]­arene metallacycles with different sizes have been successfully prepared <i>via</i> coordination-driven self-assembly, which presented very few successful examples of preparation of discrete multiple pillar­[<i>n</i>]­arene derivatives. These newly designed hexakis-pillar[5]­arene metallacycles were well characterized with one-dimensional (1-D) multinuclear NMR (¹H and ³¹ P NMR), two-dimensional (2-D) ¹H–¹H COSY and NOESY, ESI-TOF-MS, elemental analysis, and PM6 semiempirical molecular orbital methods. Furthermore, the host–guest complexation of such hexakis-pillar[5]­arene hosts with a series of different neutral ditopic guests <b>G1</b>–<b>6</b> were well investigated. Through host–guest interactions of hexakis-pillar[5]­arene metallacycles <b>H2</b> or <b>H3</b> with the neutral dinitrile guest <b>G5</b>, the cross-linked supramolecular polymers <b>H2⊃(G5)</b>_<b>3</b> or <b>H3⊃(G5)</b>_<b>3</b> were successfully constructed at the high-concentration region, respectively. Interestingly, these cross-linked supramolecular polymers transformed into the stable supramolecular gels upon increasing the concentrations to a relatively high level. More importantly, by taking advantage of the dynamic nature of metal–ligand bonds and host–guest interactions, the reversible multiple stimuli-responsive gel–sol phase transitions of such polymer gels were successfully realized under different stimuli, such as temperature, halide, and competitive guest, etc. The mechanism of such multiple stimuli-responsive processes was well illustrated by <i>in situ</i> multinuclear NMR investigation. This research not only provides a highly efficient approach to the preparation of discrete multiple pillar­[<i>n</i>]­arene derivatives but also presents a new family of multiple stimuli-responsive “smart” soft matters

Additional file 1 of Combined cardiac, lung, and diaphragm ultrasound for predicting weaning failure during spontaneous breathing trial

Supplementary Material 1: The eligibility criteria for the spontaneous breathing trial (SBT) and the acquisition of images and measurement of parameters for transthoracic echocardiography (TTE), lung ultrasound (LUS), and diaphragm ultrasound

Synthesis of Triangular Metallodendrimers via Coordination-Driven Self-Assembly

A new family of 60° dendritic di-Pt­(II) acceptor tectons have been successfully designed and synthesized, from which a series of novel “three-component” triangular metallodendrimers were prepared via [3 + 3] coordination-driven self-assembly. The structures of newly designed triangular metallodendrimers are characterized by multinuclear NMR (¹H and ³¹P), ¹H DOSY NMR, mass spectrometry (CSI-TOF-MS), and elemental analysis. The shape and size of all supramolecular dendritic triangles were investigated with PM6 semiempirical molecular orbital methods

Synthesis of Triangular Metallodendrimers via Coordination-Driven Self-Assembly

A new family of 60° dendritic di-Pt­(II) acceptor tectons have been successfully designed and synthesized, from which a series of novel “three-component” triangular metallodendrimers were prepared via [3 + 3] coordination-driven self-assembly. The structures of newly designed triangular metallodendrimers are characterized by multinuclear NMR (¹H and ³¹P), ¹H DOSY NMR, mass spectrometry (CSI-TOF-MS), and elemental analysis. The shape and size of all supramolecular dendritic triangles were investigated with PM6 semiempirical molecular orbital methods

From Trigonal Bipyramidal to Platonic Solids: Self-Assembly and Self-Sorting Study of Terpyridine-Based 3D Architectures

Using a series of tritopic 2,2′:6′,2″-terpyridine (tpy) ligands constructed on adamantane, three discrete 3D metallo-supramolecular architectures were assembled, i.e., trigonal bipyramidal, tetrahedron, and cube. The self-assembly used tritopic ligands as corner directing units and metal ions as glue units at the edge. The angles of the linkers between adamantane and tpy head play a critical role in guiding the assembled structures, which have the general formula of <b>M</b>_{<b>3<i>n</i></b>}<b>L</b>_{<b>2<i>n</i></b>}, where M denotes metal ion and L denotes ligand. All complexes were fully characterized by ¹H, ¹³C NMR, diffusion-ordered NMR spectroscopy, ESI-MS, and traveling-wave ion mobility-mass spectrometry. The binary mixtures of <b>LA</b> and <b>LC</b> or <b>LB</b> and <b>LC</b> underwent a self-sorting process that led to the self-assembly of discrete 3D structures. The self-sorting behavior is solely based on the angles precoded within the arm of tritopic ligands. Moreover, kinetic study of preassembled cube and tetrahedron demonstrated a slow ligand exchange process toward a statistical mixture of hetero tetrahedrons with <b>LA</b> and <b>LB</b>

From Ring-in-Ring to Sphere-in-Sphere: Self-Assembly of Discrete 2D and 3D Architectures with Increasing Stability

Directed by increasing the density of coordination sites (DOCS) to increase the stability of assemblies, discrete 2D ring-in-rings and 3D sphere-in-sphere were designed and self-assembled by one tetratopic pyridyl-based ligand with 180° diplatinum­(II) acceptors and naked Pd­(II), respectively. The high DOCS resulted by multitopic ligand provided more geometric constraints to form discrete structures with high stability. Compared to reported supramolecular hexagons and polyhedra by ditotpic ligands, the self-assembly of such giant architectures using multitopic ligands with all rigid backbone emphasized the structural integrity with precise preorganization of entire architecture, and required elaborate synthetic operations for ligand preparation. In-depth structural characterization was conducted to support desired structures, including multinuclear NMR (¹H, ³¹P, and ¹³C) analysis, 2D NMR spectroscopy (COSY and NOESY), diffusion-ordered NMR spectroscopy (DOSY), multidimensional mass spectrometry, TEM and AFM. Furthermore, a quantitative definition of DOCS was proposed to compare 2D and 3D structures and correlate the DOCS and stability of assemblies in a quantitative manner. Finally, ring-in-rings in DMSO or DMF could undergo hierarchical self-assembly into the ordered nanostructures and generated translucent supramolecular metallogels