Ligand Coordination Interaction Research Articles

Engineered Mesoporous Silica-Based Core-Shell Nanoarchitectures for Synergistic Chemo-Photodynamic Therapies.

Combinatorial therapies have garnered enormous interest from researchers in efficiently devastating malignant tumors through synergistic effects. To explore the combinatorial approach, multiple therapeutic agents are typically loaded in the delivery vehicles, controlling their release profiles and executing subsequent therapeutic purposes. Herein, we report the fabrication of core (silica)-shell (mesoporous silica nanoparticles, MSNs) architectures to deliver methylene blue (MB) and cupric doxorubicin (Dox) as model drugs for synergistic photodynamic therapy (PDT), chemotherapy, and chemodynamic therapy (CDT). MB, as the photosensitizer, is initially loaded and stabilized in the silica core for efficient singlet oxygen generation under light irradiation towards PDT. The most outside shell with imidazole silane-modified MSNs is immobilized with a chemotherapeutic agent of Dox molecules through the metal (Copper, Cu)-ligand coordination interactions, achieving the pH-sensitive release and triggering the production of intracellular hydrogen peroxide and subsequent Fenton-like reaction-assisted Cu-catalyzed free radicals for CDT. Further, the designed architectures are systematically characterized using various physicochemical characterization techniques and demonstrate the potent anti-cancer efficacy against skin melanoma. Together our results demonstrated that the MSNs-based core-shell nanoarchitectures have great potential as an effective strategy in synergistically ablating cancer through chemo-, chemodynamic, and photodynamic therapies.

Synergistic Multiple Bonds Induced Dynamic Self-Assembly of Silver Nanoclusters into Lamellar Frameworks with Tailored Luminescence

Incorporating atomically precise metal nanoclusters (NCs) into ordered self-assemblies endows them with advanced photophysical properties; however, their ordered arrangement in space is difficult to achieve with only noncovalent bonds between individual clusters. Herein, we illustrate the hierarchical self-assembly of atomically precise silver NCs (NH4)6[Ag6(mna)6] (Ag6-NCs) into hexagonal two-dimensional lamellas by intercluster π···π and C-H···π interactions, which then pack into three-dimensional metal–organic frameworks (MOFs) by the metal–ligand coordination interaction. Synergistic multiple bond-induced dynamic coassembly greatly enhanced the quantum yields and lifetimes, achieving the transformation of weak fluorescence to strong thermally activated delayed fluorescence (TADF). The structure and luminescence transformation could be reversibly switched by tuning the pH values. The Ag6-NCs/Ca2+ coassemblies behaved as efficient yellow phosphors to afford white light emitting diode devices. This work demonstrates a synergistic multiple bond-induced hierarchical self-assembly to realize ordered layer-by-layer MOFs from NCs-based secondary building units with advanced TADF emission in a pH-tailored manner for potential applications in luminescent devices and sensors.

Selective Metal-Ligand Bond-Breaking Driven by Weak Intermolecular Interactions: From Metamagnetic Mn(III)-Monomer to Hexacyanoferrate(II)-Bridged Metamagnetic Mn2Fe Trimer.

Metal-ligand coordination interactions are usually much stronger than weak intermolecular interactions. Nevertheless, here, we show experimental evidence and theoretical confirmation of a very rare example where metal-ligand bonds dissociate in an irreversible way, helped by a large number of weak intermolecular interactions that surpass the energy of the metal-ligand bond. Thus, we describe the design and synthesis of trinuclear Mn2Fe complex {[Mn(L)(H2O)]2Fe(CN)6},2- starting from a mononuclear Mn(III)-Schiff base complex: [Mn(L)(H2O)Cl] (1) and [Fe(CN)6]4- anions. This reaction implies the dissociation of Mn(III)-Cl coordination bonds and the formation of Mn(III)-NC bonds with the help of several intermolecular interactions. Here, we present the synthesis, crystal structure, and magnetic characterization of the monomeric Mn(III) complex [Mn(L)(H2O)Cl] (1) and of compound (H3O)[Mn(L)(H2O)2]{[Mn(L)(H2O)]2Fe(CN)6}·4H2O (2) (H2L = 2,2'-((1E,1'E)-(ethane-1,2-diylbis(azaneylylidene))bis(methaneylylidene))bis(4-methoxyphenol)). Complex 1 is a monomer where the Schiff base ligand (L) is coordinated to the four equatorial positions of the Mn(III) center with a H2O molecule and a Cl- ion at the axial sites and the monomeric units are assembled by π-π and hydrogen-bonding interactions to build supramolecular dimers. The combination of [Fe(CN)6]4- with complex 1 leads to the formation of linear Mn-NC-Fe-CN-Mn trimers where two trans cyano groups of the [Fe(CN)6]4- anion replace the labile chloride from the coordination sphere of two [Mn(L)(H2O)Cl] complexes, giving rise to the linear anionic {[Mn(L)(H2O)]2Fe(CN)6}2- trimer. This Mn2Fe trimer crystallizes with an oxonium cation and a mononuclear [Mn(L)(H2O)2]+ cation, closely related to the precursor neutral complex [Mn(L)(H2O)Cl]. In compound 2, the Mn2Fe trimers are assembled by several hydrogen-bonding and π-π interactions to frame an extended structure similar to that of complex 1. Density functional theoretical (DFT) calculations at the PBE1PBE-D3/def2-TZVP level show that the bond dissociation energy (-29.3 kcal/mol) for the Mn(III)-Cl bond is smaller than the summation of all the weak intermolecular interactions (-30.1 kcal/mol). Variable-temperature magnetic studies imply the existence of weak intermolecular antiferromagnetic couplings in both compounds, which can be can cancelled with a critical field of ca. 2.0 and 2.5 T at 2 K for compounds 1 and 2, respectively. The magnetic properties of compound 1 have been fit with a simple S = 2 monomer with g = 1.959, a weak zero-field splitting (|D| = 1.23 cm-1), and a very weak intermolecular interaction (zJ = -0.03 cm-1). For compound 2, we have used a model with an S = 2 monomer with ZFS plus an S = 2 antiferromagnetically coupled dimer with g = 2.009, |D| = 1.21 cm-1, and J = -0.42 cm-1. The metamagnetic behavior of both compounds is attributed to the weak intermolecular π-π and hydrogen-bonding interactions.

Development of supramolecular shape-memory polyurethanes based on Cu(II)–pyridine coordination interactions

Shape-memory polymers with supramolecular switch have received increasing attention. This study reports the synthesis and characterization of supramolecular shape-memory polyurethane based on Cu(II)–pyridine coordination, obtained by mixing pyridine containing polyurethane with CuCl2. The results show that there are strong metal–ligand coordination interactions formed between Cu(II) and the pyridine ring in a series of CuCl2-doped polyurethane samples. The Cu(II)–pyridine coordination plays a crucial role in the enhanced physical netpoints for outstanding shape-memory properties. Indeed, the so-synthesized CuCl2-doped polyurethane exhibits not only a rapid tensile shape recovery but also excellent crimp shape recovery. The CuCl2-doped polyurethane containing suitable metal–ligand coordination interactions shows more than 99% shape fixation and more than 95% shape recovery. Our findings promote further applications of shape-memory polymers in multiple engineering fields.

Role of Synergistic C–H···N and C–H···O H-Bonding Interactions in Self-Assemblies of a Phthalocyanine Derivative and Several Pyridine Derivatives

Phthalocyanine (Pc)-based fused derivatives are widely used materials in many nanotechnology fields, such as photovoltaic devices, pigments, and sensors, because of their excellent physical and chemical properties. It has been proven that most Pc molecules can self-assemble with ligands by the metal–ligand coordination interaction or π–π stacking interaction, yet little is known about the supramolecular packing of H-bonded Pc derivatives. Herein, we report the self-assembly of rylene-annulated Pc (ZnPcPDI4) with a series of pyridine derivatives at the solid/liquid interface via synergistic C–H···N and C–H···O H-bonding interactions. We use scanning tunneling microscopy combined with theoretical simulations to demonstrate the interactions in the self-assembled process. The intermolecular binding modes of Pcs with ligands and their thermodynamics stability are revealed by the combination of density functional theory and molecular dynamics simulations with the modified force field parameters. This study prov...

Room Temperature Self‐Healing Methyl Phenyl Silicone Rubbers Based on the Metal–Ligand Cross‐Link: Synthesis and Characterization

Novel self‐healing silicone rubbers are prepared by a two‐step procedure: aminopropyl methyl phenyl polysiloxanes is first reacted with salicylaldehyde and then with copper acetate. The reversible nature of the metal–ligand coordination interaction between polysiloxanes with pendent Schiff‐base groups and Cu2+ has endowed silicone rubbers with superior self‐healing properties. As compared with other self‐healing silicone rubbers based on hydrogen bonds or Diels–Alder reaction, this cross‐linked system shows high healing power. The materials are cut into two parts and put together in a mold for 1 h at 30 °C, observing a macroscopic healing and a strength recovery up to 87.0%. image

Complexation Enhancement Drives Water-to-Oil Ion Transport: A Simulation Study.

We address the structures and energetics of ion solvation in aqueous and organic solutions to understand liquid-liquid ion transport. Atomistic molecular dynamics (MD) simulations with polarizable force field are performed to study the coordination transformations driving lanthanide (LnIII ) and nitrate ion transport between aqueous and an alkylamide-oil solution. An enhancement of the coordination behavior in the organic phase is achieved in contrast with the aqueous solution. In particular, the coordination number of Ce3+ increases from 8.9 in the aqueous to 9.9 in the organic solutions (from 8 in the aqueous to 8.8 in the organic systems for Yb3+ ). Moreover, the local coordination environment changes dramatically. Potential of mean force calculations show that the LnIII -ligand coordination interaction strengths follow the order of LnIII -nitrate>LnIII -water>LnIII -DMDBTDMA. They increase 2-fold in the lipophilic environment in comparison to the aqueous phase, and we attribute this to the shedding of the outer solvation shell. Our findings highlight the importance of outer sphere interactions on the competitive solvation energetics that cause ions to migrate between immiscible phases; an essential ingredient for advancing important applications such as rare earth metal separations. Some open questions in simulating the coordination behavior of heavy metals are also addressed.

ChemInform Abstract: Self‐assembly of Metal‐organic Coordination Structures on Surfaces

AbstractReview: 240 refs.

Synthesis, characterization, monolayer assembly and 2D lanthanide coordination of a linear terphenyl-di(propiolonitrile) linker on Ag(111).

As a continuation of our work employing polyphenylene-dicarbonitrile molecules and in particular the terphenyl derivative 1 (TDCN), we have synthesized a novel ditopic terphenyl-4,4"-di(propiolonitrile) (2) linker for the self-assembly of organic monolayers and metal coordination at interfaces. The structure of the organic linker 2 was confirmed by single crystal X-ray diffraction analysis (XRD). On the densely packed Ag(111) surface, the terphenyl-4,4"-di(propiolonitrile) linkers self-assemble in a regular, molecular chevron arrangement exhibiting a Moiré pattern. After the exposure of the molecular monolayer to a beam of Gd atoms, the propiolonitrile groups get readily involved in metal–ligand coordination interactions. Distinct coordination motifs evolve with coordination numbers varying between three and six for the laterally-bound Gd centers. The linker molecules retain an overall flat adsorption geometry. However, only networks with restricted local order were obtained, in marked contrast to previously employed, simpler polyphenylene-dicarbonitrile 1 linkers.

Tetraphenylethene-based Zn complexes for the highly sensitive detection of single-stranded DNA

Metal–ligand coordination interactions were utilized to develop tetraphenylethene-based DNA probes, which exhibited a higher fluorescent on/off ratio than ethidium bromide.

Preparation and performance of antibacterial layer-by-layer polyelectrolyte nanofiltration membranes based on metal–ligand coordination interactions

Coordinative nanofiltration membranes with commendable antibacterial property and hydrophilicity are prepared and investigated extensively by alternating LBL assembly of polyethyleneimine and polystyrene sulfonate using Cu2+ as coordination agent.

Metal-ions directed self-assembly of hybrid diblock copolymers

Abstract

Self-assembly of low dimensional nanostructures and materials via supramolecular interactions at interfaces

Low dimensional inorganic–organic heterostructure nanomaterials with multiple different functional components attaching at interface have drawn considerable attention over the last decades, due to their excellent optical and electronic properties in comparison with their individual components. Supramolecular self-assembly of disordered building blocks has played an essential role in constructing well-defined functionalized structures. Solid–liquid interfaces are known as ideal platforms in the self-assembly process, thus providing a series of novel and attractive strategies to construct low dimensional inorganic–organic heterostructure nanomaterials with different sizes and shapes. In this review, we summarized low dimensional inorganic–organic heterostructure nanomaterials on the basis of self-assembly that is driven by synergistically metal–ligand coordination and other intermolecular interactions. Both stepwise self-assembly on the inorganic (or organic) solid surface and self-assembly of inorganic–organic building block through hydrogen bond, metal–ligand coordination interaction, π–π stacking, hydrophobic interaction, and covalently bonding were discussed.

Editorial of the PCCP themed issue “Scanning tunneling microscopy: revealing new physical chemistry insight”

It has been 30 years since the invention of Scanning Tunnelling Microscopy (STM). STM allows scientists to directly image the nano-world at atomic resolution and has stimulated the development of a large family of probe-based microscopy. More importantly, STM has opened new avenues to explore the fascinating properties associated with nano-sized objects, and has fueled the growth of nanoscience and nanotechnology. As a powerful surface characterization technique, STM is particularly important for physical chemistry research of surfaces and interfaces. The aim of the ‘‘Scanning tunneling microscopy: revealing new physical chemistry insight’’ themed issue, is to highlight the role of STM techniques at the interface of chemistry, physics, and material sciences, focusing especially on surface physical chemistry. The topics covered by the issue include single molecule science, surface physics and chemistry, supramolecular assembly on surfaces and interfaces, and molecular electronics. One of the most fascinating features of STM is not only its ability to obtain the ultimate single molecular resolution, but also to locally probe the electronic properties of the atoms and molecules. It goes without saying that STM has motivated the development of single molecule science. In the perspective article by Wang, Hou, and coworkers (DOI: 10.1039/C3CP51446C), an overview of tip-assisted single molecule chemistry, such as the identification of specific orbitals or states of molecules on surfaces, tipinduced single-molecule manipulation, atomically resolved chemical reactions in photochemistry and tip-induced electroluminescence, has been given. One hot topic in single molecule science is molecular electronics and quantum transport through metallic nanocontacts. By employing the STM-based break junction technique, Mao et al. reported the observation of a multiple subatomic steplength when stretching single atom contacts (DOI: 10.1039/C3CP50473E). Fundamental understanding of surface physical chemistry is of great importance for catalysis, electrochemistry, and many other application fields. The emergence of STM and other advanced surface characterization techniques provides powerful tools to understand surface and interface science. In this collection, Yang and Magnussen present quantitative studies of the diffusion process of adsorbates at electrodes under electrochemical control, using an in situ video STM at a temporal resolution of tens of milliseconds (DOI: 10.1039/ C3CP51027A). Rosei et al. reported the structural characterization of submonolayer Zn on a Pd(111) surface, which is technically important for near-surface alloy heterogeneous catalysis (DOI: 10. 1039/C3CP50793A). The engineering of highly ordered molecular patterns on surfaces represents a prominent bottom-up approach for the fabrication of well-defined molecular architectures at surfaces, which is considered to be an important step towards next-generation molecule-based electronics. Chen et al. present a comprehensive review of supramolecular assemblies of binary nanostructures on graphite surfaces (DOI: 10.1039/ C3CP00023K). Significant attention has been devoted to understanding and tailoring weak but appreciable noncovalent intermolecular interactions, such as hydrogen bonding (DOI: 10.1039/ C3CP50891A), dipole–dipole interaction (DOI: 10.1039/C3CP50808K), and metal– ligand coordination interactions (DOI: 10.1039/C3CP50779C), in order to fabricate sophisticated 2D supramolecular assemblies. On the other hand, the phase transition of cobalt porphyrin adlayers on Au(100) surfaces highlights the important role of substrate structure and substrate–adsorbate interactions for supramolecular assembly (DOI: 10.1039/C3CP50797A). The delicate balance between different weak interactions may result in complicated polymorphs in the adlayers (DOI: 10.1039/C3CP50829C and DOI: 10.1039/C3CP51074C), which on the other hand, provides a great opportunity to understand the underlying driving forces of the self-assembly process. Institute of Chemistry, Chinese Academy of Sciences, and Beijing National Laboratory for Molecular Sciences, Beijing 100190, P. R. China DOI: 10.1039/c3cp90096g

CdCl2·H2O nanorods oriented parallel on the Langmuir film of (phthalocyaninato) [tetrakis(4-pyridyl)porphyrinato] cerium complex

Highly ordered nanorods of CdCl2·H2O were found to grow on the Langmuir film surface of the sandwich-type (phthalocyaninato) [tetrakis(4-pyridyl)porphryrinato] cerium double-decker complex [Ce(Pc)(TPyP)]. Experimental results revealed the important template role the Langmuir monolayer of [Ce(Pc)(TPyP)] played during the formation of well orientated CdCl2·H2O nanorods because of the metal–ligand coordination interaction between the Cd2+ cations in the subphase solution and the pyridyl groups of the double-decker molecules. The CdCl2·H2O nanorods formed were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), atomic force microscopic (AFM) and X-ray photoelectron spectroscopy (XPS).

A Chromo‐Fluorogenic Tetrazole‐Based CoBr2 Coordination Polymer Gel as a Highly Sensitive and Selective Chemosensor for Volatile Gases Containing Chloride

Crystalline coordination polymers are a newer class of organic–inorganic hybrid nanomaterials created by infinitely extending metal–ligand coordination interactions. These polymers show promise in a broad range of applications, including gas storage, molecular sieves, ion exchange, sensing, magnetism, and catalysis. [1, 2] Recently, a rational-design strategy for supramolecular gels based on the concept of coordination polymers is attracting interest. [3–6] In particular, recent studies have demonstrated that simple bridging organic units can facilitate the formation of coordination polymer gels in the absence of auxiliary moieties (e.g., urea, sugar, cholesterol, long alkyl chains), offering new possibilities to produce functional soft materials from structurally

Controlling the Secondary Structure of Nonbiological Oligomers with Solvophobic and Coordination Interactions

Making use of a combination of metal–ligand coordination interactions and solvophobic forces, an oligomer based on phenylacetylene incorporates Ag+ ions to form a highly ordered helical structure. The space-filling model shown makes clear the trigonal-planar coordination environment at silver.