Showing papers in "Advances in Inorganic Chemistry in 2020"

Antimony and bismuth as antimicrobial agents

Abstract: There is an emerging interest in the application of metal complexes in the treatment of microbial infections and colonization. Their unique modes of action and the difficulty that microbes face in evolving mechanisms for resistance toward metal complexes, makes them attractive. Metal complexes offer a way to incorporate a diverse range of ligands and therefore easily tune physico-chemical properties, which in turn can affect the overall behavior of the complex in a biological system. For more than a decade, we have synthesized and characterized a range of bismuth and antimony complexes in the + III and + V oxidation states and evaluated their efficacy toward the treatment of Leishmania or bacteria, including but not limited to: Helicobacter pylori, methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus and Escherichia coli. In many cases these novel complexes outperform the current medicinal compounds employed. There is still work to be done to understand the relationship between the chemical structure of metal complexes and their corresponding antimicrobial activity. We have compiled recent results in the area of metal complexes against microbes, to uncover some of the trends related to antimicrobial activity.

The role of defects in the properties of functional coordination polymers

Abstract: Coordination Polymers (CPs) are periodic architectures defined by the assembly of metal entities and ligands through coordination bonds. They can be designed to present porous architectures, known as Metal-Organic Frameworks (MOFs). They can be prepared as bulk materials and at the nanoscale using bottom-up synthesis or top-down approaches. Nanoscale CPs are a subject of high current interest due to the new physico-chemical properties that they can show because of confinement effects as well as their material process-ability. We present several selected CP samples with different electronic properties, electrical conductivity and/or emission, as well as ways to down-size their scale to obtain CP nanostructures. Studies on their physical properties at the nanoscale show the relevance of the confinement effects and the presence of defects, which can be controlled during the preparation process. Indeed, defect engineering is an extremely relevant tool to manipulate the material crystal quality and its specific properties. Therefore, engineered defects are gaining attention in both CPs and their porous version, MOFs, because of their implications for both physical properties and properties affecting catalysis and sorption. However, this is still a very poorly developed field. The main scope of this chapter is to provide a general overview of the impact that defects may have on the chemical, physical, electrical and/or optical properties, as well as in catalysis and sorption capabilities of some CPs, and the way to gain control of the defect production. We have selected two relevant types of 1D CP families, MMX and Cu2I2 double chains, to discuss their electronic properties and the influence that the incorporation of defects has on them. MMX chains based on the assembly of two dimetallic entities: [Pt2(dta)4] (dta = ditiocarboxylate) and [Pt2(dta)4I2], behave as metallic conductors at room temperature in bulk and at the nanoscale, but the weakness of the Pt I coordination bonds facilitates the occurrence of defects such as iodine vacancies, which significantly alter their conductivity. Their preparation at the nanoscale is feasible based on the reversible process between [Pt2(dta)4] and [Pt2(dta)4I2]. Thus, the polymer [Pt2(dta)4I2]n can be solubilized or sublimated to produce [Pt2(dta)4] and [Pt2(dta)4I2] and rearrange back to [Pt2(dta)4I2]n even on-surfaces. The exquisite control of the assembling process gives rise to a number of structural defects present along the MMX chains. In any case, electrical measurements in single chains of [Pt2(dta)4I2]n currently postulated these CPs among the best molecular wires. We also describe several examples of Cu2I2 double chains grafted with N-aromatic terminal ligands. They show interesting electronic properties as emission and semi-conductivity. The general structural core of these 1D-CPs is based on a Cu2I2 double chain which is very sensitive to chemical and physical stimuli. We discuss the use of these CPs as stimuli-response materials, their bottom-up preparation using fast precipitation and the use of these nanostructures to prepare novel composites as multifunctional ultra-thin films. Moreover, we also show the possibility of modulating their physical properties upon the creation of structural defects. Finally, we describe different synthetic pathways (pre- and post-synthesis) to harness the incorporation of both local- and long-range defects in MOFs, resulting in altered chemistry and structures without compromising the porous scaffold. The role of defects in MOF properties related to catalysis, sorption and conductivity is widely discussed in this chapter, highlighting the importance of using advanced scanning probe microscopy, synchrotron X-rays and neutron techniques to achieve a better understanding of these functional nanomaterials.

Nano-architectonics for Coordination Assemblies at Interfacial Media

Abstract: As compared with self-assembly of lipids and surfactants, coordination-based assemblies are conducted through well-defined geometry to produce designable internal nano-structures of the assembled materials. Coordination would be a powerful tool in the nano-architectonics approach for functional materials. Another key term, interface, also has crucial roles in the nano-architectonics approaches. Interfacial environments provide anisotropic media for material associations. From the viewpoints of possible applications such as device usages and dominant contributions of surfaces in nano-sized objects, it is important to investigate fabrication and properties of the coordination assemblies at the interfacial media. In this chapter, fabrication and properties of metal complexes and coordination compounds are reviewed, focusing on their interfacial effects especially in interfacial thin films. Based on this background, some typical examples and recent examples in nano-architectonics for coordination assemblies at interfacial media are shortly introduced in this chapter. The introduced examples are categorized according to interfacial film types: (i) self-assembled monolayer (SAM) method; (ii) Langmuir-Blodgett (LB) technique; (iii) layer-by-layer (LbL) assembly; (iv) lipid bilayer membrane.

Nanoscale coordination polymers for medicine and sensors

Abstract: Miniaturization of coordination polymers to the nanoscale represents a unique opportunity to assemble a novel class of highly customizable functional materials that marry the rich diversity, chemistry and properties of coordination complexes to the advantages of nanomaterials. The new structures, which exhibit well-defined and dispersed morphologies, can allow for a proper correlation with their functionality, and therefore, enable the rational design of new generations of these nanostructures targeting specific desired properties. In this chapter we will give a brief introduction to the rational fabrication of such functional nanostructures following different coordination polymerization mechanisms. The novel “smart” nanoscale coordination polymer particles (NCPs) exhibit interesting properties of relevance for different fields and applications, worth to mention nanomedicine and sensors. Herein we make a summary of the main results obtained in both areas that evidence the significance of this novel family of materials. For this, the review has been divided into two main sections. In the first part we revise general methodologies for cargo loading and delivery, including the design of stimuli-responsive systems. In the second section we will review the latest advances in the use of NCPs as chemical sensing platforms. These results open new avenues for all the possible applications that can be derived from the implications of CPPs on surfaces. Finally, a brief introduction to the new research line on 2D-coordination polymers will be outlined.

Selected polyazole based coordination polymers displaying functional properties

Abstract: In this account, we present recent on-going developments on the design and synthesis of transition metal (M(II) = Fe, Cu, Zn, Cd, Hg) coordination networks built from 1,2,4-triazole, tetrazole, benzimidazole or pyrazole building blocks. Special focus is placed on the use of a high energetic material made of a dissymmetric 1,2,4-triazole-tetrazole ligand, able to provide coordination polymers of alkali metals and alkaline earth metals, as well as salts. These materials, apart from their structural diversity and appeal, present some potential applications in gas or metallic storage, molecular electronics (spin crossover), gas sensing, toxic metal sensing and capture, as well as in medicinal applications.