Laboratory Curiosities Research Articles

Guanidinium-based Integrated Peptide Dendrimers: Pioneer Nanocarrier in Cancer Therapy.

The landscape of cancer therapy has witnessed a paradigm shift with the emergence of innovative delivery systems, and Guanidinium-based Peptide Dendrimers have emerged as a vanguard in this transformative journey. With their unique molecular architecture and intrinsic biocompatibility, these dendrimers offer a promising avenue for the targeted delivery of therapeutic cargo in cancer treatment. This comprehensive review delves into the intricate world of Guanidinium- based Peptide Dendrimers, unraveling their structural intricacies, mechanisms of action, and advancements that have propelled them from laboratory curiosities to potential clinical champions. Exploiting the potent properties of guanidinium, these dendrimers exhibit unparalleled precision in encapsulating and transporting diverse cargo molecules, ranging from conventional chemotherapeutics to cutting-edge nucleic acids. The review navigates the depths of their design principles, investigating their prowess in traversing the complex terrain of cellular barriers for optimal cargo delivery. Moreover, it delves into emerging trends, such as personalized therapeutic approaches, multimodal imaging, and bioinformatics-driven design, highlighting their potential to redefine the future of cancer therapy. Crucially, the review addresses the pivotal concerns of biocompatibility and safety, examining cytotoxicity profiles, immune responses, and in vivo studies. It underscores the importance of aligning scientific marvels with the stringent demands of clinical applications. Through each section, the narrative underscores the promises and possibilities that Guanidinium-based Peptide Dendrimers hold and how they can potentially reshape the landscape of precision cancer therapy.

Counterintuitive Chemistry: Carbene Stabilization of Zero-Oxidation State Main Group Species

Carbenes have evolved from transient laboratory curiosities to a robust, diverse, and surprisingly impactful ligand class. A variety of different carbenes have significantly contributed to the development of low-oxidation state main group chemistry. This Perspective focuses upon advances in the chemistry of carbene complexes containing main group element cores in the formal oxidation state of zero, including their diverse synthetic strategies, unusual bonding and structural motifs, and utility in transition metal coordination chemistry and activation of small molecules.

Unique Phosphorus-Based Avenues for the Tuning of Functional Materials.

ConspectusRecent ground-breaking advances in synthetic chemistry have transformed main-group molecules from simple laboratory curiosities into powerful materials for a range of applications in all realms of life. Electron-accepting or -deficient materials, in particular, have been the focus of development since their generally limited availability and stability have been major hurdles in establishing new practical applications. In addition to the general requirements for the design of these materials, a deeper understanding of their inherent electronics and molecular interactions is a requirement for the successful expansion of their utility. Previously, the incorporation of electron-deficient main-group elements, such as boron, into a conjugated organic framework was considered to be an effective route toward the synthesis of high-performing electron-accepting materials. However, challenging conditions such as the need for bulky substituents for kinetic stabilization, air-free and moisture-sensitive synthesis, and restricted storage abilities have led to the investigation of other elements across the periodic table to be used in a similar vein. Lately, heavier main-group elements such as Si, Ge, P, As, Sb, Bi, S, Se, and Te have also proven to be advantageous for electron-accepting materials as they exhibit polarizable molecular orbitals that are easily accessible to electrons or nucleophiles. This has laid the foundation for materials chemistry research on a variety of applications, including optoelectronic devices such as OLEDs, organic photovoltaics, energy storage such as in batteries and capacitors, fluorescent sensors with both biological and physiological applications, organocatalysis and synthesis, and many more. Among the main-group-element-based materials, organophosphorus species are privileged as their frontier orbitals are easily altered by chemical modification or/and structural and geometrical manipulations at the phosphorus center itself, without the need for kinetic stabilization, or through electronic modification of the conjugated system. The five-membered phosphorus-based heterocycle, phosphole, is a particularly interesting motif in this context, and extensive studies on the corresponding materials have uncovered the rich fundamentals of the σ*-π* interaction that imparts intriguing accepting properties while sustaining morphological and physiological stability for utilization in real-life scenarios. Moreover, beyond the σ*-π* interaction in phospholes that is key to many of their acceptor properties as a material, the use of phosphorus also gives rise to easily accessible, low-lying antibonding orbitals. They pave the way for Lewis acid phosphorus species that, despite being considered to be electron-rich species in general, open up several possibilities for intriguing chemical reactivity through hypervalency. Herein, we representatively discuss some recent advancements through the various approaches that leverage the unique structures and electronics of organophosphorus species toward the design of materials with outstanding electronic, chemical, and structural properties and reactivities for the functional material world.

Nanocrystalline Apatites: Post-Immersion Acidification and How to Avoid It—Application to Antibacterial Bone Substitutes

Biomimetic nanocrystalline apatites analogous to bone mineral can be prepared using soft chemistry. Due to their high similarity to bone apatite, as opposed to stoichiometric hydroxyapatite for example, they now represent an appealing class of compounds to produce bioactive ceramics for which drug delivery and ion exchange abilities have been described extensively. However, immersion in aqueous media of dried non-carbonated biomimetic apatite crystals may generate an acidification event, which is often disregarded and not been clarified to-date. Yet, this acidification process could limit their further development if it is not understood and overcome if necessary. This may, for example, alter biological test outcomes, during their evaluation as bone repair materials, due to potentially deleterious effects of the acidic environment on cells, especially in in vitro static conditions. In this study, we explore the origins of this acidification phenomenon based on complementary experimental data and we point out the central role of the hydrated ionic layer present on apatite nanocrystals. We then propose a practical strategy to circumvent this acidification effect using an adequate post-precipitation equilibration step that was optimized. Using this enutralization protocol, we then showed the possibility of performing (micro)biological assessments on such compounds and provide an illustration with the examples of post-equilibrated Cu2+- and Ag+-doped nanocrystalline apatites. We demonstrate their non-cytotoxicity to osteoblast cells and their antibacterial features as tested versus five major pathogens involved in bone infections, therefore pointing to their relevance in the field of antibacterial bone substitutes. The preliminary in vivo implantation of a relevant sample in a rat's calvarial defect confirmed its biocompatibility and the absence of adverse reaction. Understanding and eliminating this technical barrier should help promoting biomimetic apatites as a genuine new class of biomaterial-producing compounds for bone regeneration applications, e.g., with antibacterial features, far from being solely considered as "laboratory curiosities".

An Air-Stable "Masked" Bis(imino)carbene: A Carbon-Based Dual Ambiphile.

Carbenes, once considered laboratory curiosities, now serve as powerful tools in the chemical and material sciences. To date, all stable singlet carbenes are single-site ambiphiles. Here we describe the synthesis of a carbene which is a carbon-based dual ambiphile (both single-site and dual-site). The key is to employ imino substituents derived from a cyclic (alkyl)(amino)carbene (CAAC), which imparts a 1,3-dipolar character to the carbene. Its dual ambiphilic nature is consistent with the ability to activate simple organic molecules in both 1,1- and 1,3-fashion. Furthermore, its 1,3-ambiphilicity facilitates an unprecedented reversible intramolecular dearomative [3 + 2] cycloaddition with a proximal arene substituent, giving the carbene the ability to "mask" itself as an air-stable cycloadduct. We perceive that the concept of dual ambiphilicity opens a new dimension for future carbene chemistry, expanding the repertoire of applications beyond that known for classical single-site ambiphilic carbenes.

Air-Stable Thermoluminescent Carbodicarbene-Borafluorenium Ions.

Borenium ions, originally synthesized as fundamentally important laboratory curiosities, have attracted significant attention due to their applications in catalysis and frustrated Lewis pair chemistry. However, investigations of the materials properties of these types of compounds are exceptionally rare. Herein, we report the synthesis, molecular structures, and optical properties of a new class of air-stable borenium ions, stabilized by the strongly donating carbodicarbene (CDC) ligand (2, 3, 6). Notably, CDC-borafluorenium ions exhibit thermoluminescence in solution, a result of a twisted intramolecular charge transfer process. The temperature responsiveness, which is observable by the naked eye, is assessed over a 20 to -60 °C range. Significantly, compound 2 emits white light at lower temperatures. In the solid state, these borocations exhibit increased quantum yields due to aggregation-induced emission. CDC-borafluorenium ions with two different counteranions (Br-, BPh4-) were investigated to evaluate the effect of anion size on the solution and solid-state optical properties. In addition, CDCs containing both symmetrical and unsymmetrical N-heterocycles (bis(1-isopropyl-3-methylbenzimidazol-2-ylidene)methane and bis(1,3-dimethyl-1,3-dihydro-2H-benzo[d]imidazol-2-ylidene)methane) were tested to understand the implications of free rotation about the CDC ligand carbon-carbon bonds. The experimental work is complemented by a comprehensive theoretical analysis of the excited-state dynamics.

Bicyclobutanes: from curiosities to versatile reagents and covalent warheads.

The unique chemistry of small, strained carbocyclic systems has long captivated organic chemists from a theoretical and fundamental standpoint. A resurgence of interest in strained carbocyclic species has been prompted by their potential as bioisosteres, high fraction of sp3 carbons, and limited appearance in the patent literature. Among strained ring systems, bicyclo[1.1.0]butane (BCB) stands apart as the smallest bicyclic carbocycle and is amongst the most strained carbocycles known. Despite the fact that BCBs have been synthesized and studied for well over 50 years, they have long been regarded as laboratory curiosities. However, new approaches for preparing, functionalizing, and using BCBs in "strain-release" transformations have positioned BCBs to be powerful synthetic workhorses. Further, the olefinic character of the bridgehead bond enables BCBs to be elaborated into various other ring systems and function as covalent warheads for bioconjugation. This review will discuss the recent developments in the synthesis and functionalization of BCBs as well as the applications of these strained rings in synthesis and drug discovery. An overview of the properties and the historical context of this interesting structure will be provided.

Stability of nanocrystalline metals: The role of grain-boundary chemistry and structure

Nanocrystalline metals are transitioning from laboratory curiosities to engineering materials, in large part due to advances in improving their stability, making their exceptional properties more predictable and accessible. Nanoscale grains typically have a very strong innate tendency to coarsen, but the grain-boundary structure can be designed and tuned to lower its excess energy, reducing both the driving force for coarsening and the grain-boundary mobility. This article reviews two major strategies for achieving low-energy grain boundaries in nanocrystalline structures. First, grain-boundary alloying is discussed, including grain-boundary segregation and its energetic competition with the formation of second phases; with sufficient grain-boundary segregation tendency it is possible to stabilize nanostructures to high temperatures. Second, methods of achieving low-energy crystallographic grain-boundary structures are discussed, including the formation of nanotwinned structures and relaxing grain boundaries into low-energy structures through their interactions with partial dislocations. Both of these strategies have led to effective and implementable stable nanocrystalline materials, and point to many directions for future advancements.

Solid Acid Electrochemical Cell for the Production of Hydrogen from Ammonia

Summary Production of high-purity hydrogen by thermal-electrochemical decomposition of ammonia at an intermediate temperature of 250°C is demonstrated. The process is enabled by use of a solid-acid-based electrochemical cell (SAEC) in combination with a bilayered anode, comprising a thermal-cracking catalyst layer and a hydrogen electrooxidation catalyst layer. Cs-promoted Ru on carbon nanotubes (Ru/CNT) serves as the thermal decomposition catalyst, and Pt on carbon black mixed with CsH2PO4 is used to catalyze hydrogen electrooxidation. Cells were operated at 250°C with humidified dilute ammonia supplied to the anode and humidified hydrogen supplied to the counter electrode. A current density of 435 mA/cm2 was achieved at a potential of 0.4 V and ammonia flow rate of 30 sccm. With a demonstrated faradic efficiency for hydrogen production of 100%, the process yields hydrogen at a rate of 1.48 m o l H 2 / g c a t h .

1,2-(Benz)Azaphospholes: A Slow Beginning to a Bright Future

ABSTRACTWhile initially laboratory curiosities, the chemistry of phospholes evolved as a better understanding of their structure, reactivity, and electronic properties was established. With their potential as building blocks for new electronic materials emerging, researchers started to investigate phospholes that maximized π-conjugation. Subsequently, numerous heteroatom-substituted derivatives with a σ2,λ3 P-center were reported, but one particular analog, 1,2-(benz)azaphospholes was noticeably absent, likely due to unusual/impractical synthetic methods. A serendipitous synthetic discovery in 2016 provided straightforward access to these highly aromatic 6π-electron (10π if the fused benzene ring is included) heterocycles. Early reactivity studies have shown that the functionalized products of these rare heterocycles have unusual structures and may find application as catalysts for hydrofunctionalization, as new types of transmetallation agents, or as reactive centers for strong bond activation.

Isolable Silylene Ligands Can Boost Efficiencies and Selectivities in Metal‐Mediated Catalysis

AbstractA significant number of isolable silylenes are currently known. They have quickly developed from laboratory curiosities to useful ligands in metal‐mediated homogeneous catalysis. This includes their utilization in various catalytic transformations, such as C−C cross‐coupling, cyclotrimerization, hydroformylation, borylation, deuteration, hydrosilylation, amination, hydrogenation, and transfer semi‐hydrogenation reactions. Recent studies suggest that the silylene ligands surpass the steering properties of their phosphine and N‐heterocyclic carbene (NHC) analogues and provide excellent chemo‐, regio‐, and stereoselectivites. Mechanistic studies suggest that their promoted performance of metal‐mediated catalytic transformations results from a strong σ‐donor character along with cooperative effects of their SiII centers. This Minireview covers the most recent advances in the field.

Isolable Silylene Ligands Can Boost Efficiencies and Selectivities in Metal-Mediated Catalysis.

A significant number of isolable silylenes are currently known. They have quickly developed from laboratory curiosities to useful ligands in metal-mediated homogeneous catalysis. This includes their utilization in various catalytic transformations, such as C-C cross-coupling, cyclotrimerization, hydroformylation, borylation, deuteration, hydrosilylation, amination, hydrogenation, and transfer semi-hydrogenation reactions. Recent studies suggest that the silylene ligands surpass the steering properties of their phosphine and N-heterocyclic carbene (NHC) analogues and provide excellent chemo-, regio-, and stereoselectivites. Mechanistic studies suggest that their promoted performance of metal-mediated catalytic transformations results from a strong σ-donor character along with cooperative effects of their SiII centers. This Minireview covers the most recent advances in the field.

Nanothermites: A short Review. Factsheet for Experimenters, Present and Future Challenges

AbstractNanothermites are the most important family of energetic materials in contemporary pyrotechnics. This article traces the main research which was carried out in this still recent domain and the challenges that remain to be overcome. The academic effort of past two decades has brought nanothermites from the status of laboratory curiosities to the one of pre‐industrial materials. Different aspects of nanothermites are discussed in order to provide valuable information to scientists experimenting in this domain. Experimental details on the preparation and the disposal of nanothermites are reported. The current research on nanothermites deals with: (i) the development of new aluminothermic mixtures; (ii) the preparation of hybrid compositions by combining nanothermites with explosive nanopowders and (iii) the study of reactive properties. From an academic standpoint, the future challenges are to find new compositions and effects. From a practical standpoint, the effort must focus on the integration of nanothermites and their derivatives in pyrotechnic systems. Toxicological concerns are expected to become increasingly important over the next decade.

Quadruplex nucleic acids as targets for anticancer therapeutics

Quadruplex nucleic acids — helical four-stranded structures known to form from guanine-rich nucleic acid sequences through Hoogsteen-type hydrogen bonding — were once just laboratory curiosities. However, they are now emerging from this rather obscure status to become important targets for small-molecule drugs, which can stabilize the quadruplex structures and thereby promote selective downregulation of gene expression and telomerase inhibition, and also activate DNA damage responses. Most of these quadruplex-binding small molecules can stabilize a range of cellular quadruplexes, as well as clusters of quadruplexes within a single gene or telomere, which could be an advantage. This widespread stabilization can generate a polygene response, and thus is able to simultaneously affect several key driver genes in human cancers, with potential therapeutic benefit. Quadruplex DNA structures were first observed more than 50 years ago, but have only relatively recently attracted interest for their role in the development of cancer. This Perspective considers attempts to selectively bind and stabilize these structures using small molecules, with the aim of developing anticancer therapeutics.

Coordination polymers and metal-organic frameworks: materials by design.

The field of coordination polymers and metal–organic frameworks (MOFs) has evolved over a period of approximately 25 years to a stage where it is one of the most widely investigated areas of materials chemistry. The field has impacted many areas of science including commercial applications from

Industry and Academia Continue Working on Big Ideas for Nanotechnology

The nanotechnologies enjoying commercial success in the oil field today are small in number, and for the most part, can be categorized as single-well applications. Examples include the dissolvable ball-drop systems used in horizontal well completions and the specialty additives operators are using to enhance drilling fluids. The next big leap for this area of emerging technology will be the development of nanoparticles that work on larger scales, either in production operations or for fluid treatment. Counted among the industry’s nanopioneers, Saudi Aramco is getting closer to the deployment of nanoparticles for a number of reservoir-wide applications. Others are working on creating nanoparticles that will improve the performance of waterflooding, and university researchers in Texas are developing a magnetic nanoparticle that aims to make offshore water treatment more efficient, and possibly more economic. These concepts were presented at SPE’s Annual Technology Conference and Exhibition held last year in Dubai. Taken together, they offer a small, yet compelling, sample of the ideas still working their way through the pipeline. Kirk Rainey, the vice president of A&I Ventures in Houston and a former chemical-enhanced oil recovery expert at Shell, has been involved with nanotechnology consortiums for more than 7 years. Speaking generally, he explained that the oil and gas industry is interested in nanoparticles partly because of the potential efficiencies they offer. It helps to think of nanoparticles from a chemical perspective; their collectively high-surface-area—typically where chemical reactions take place—means even relatively small volumes can make a big impact. “The negatives include the fact that in many cases engineering these nanoparticles, or nanostructures, can be very costly,” said Rainey. “And while it may be easy to do on a small scale, learning how to scale something up to the oil field is going to take a lot of effort, and the ability to do that is sometimes unknown.” That point about scale is very important, especially when discussing reservoir applications. Rainey emphasized that if large doses of nanoparticles are needed, then their cost must be relatively low to justify their use. He said the ability to strike such a balance will separate “laboratory curiosities” from viable commercial products.

The abandoned controversy surrounding universal white blood cell reduction.

The abandoned controversy surrounding universal white blood cell reduction.

Sodium Phosphaethynolate as a Building Block for Heterocycles

AbstractPhosphorus‐containing heterocycles have evolved from laboratory curiosities to functional components, such as ligands in catalytically active metal complexes or molecular constituents in electronic devices. The straightforward synthesis of functionalized heterocycles on a larger scale remains a challenge. Herein, we report the use of the phosphaethynolate (OCP)− anion as a building block for various sterically unprotected and functionalized hydroxy substituted phosphorus heterocycles. Because the resulting heterocycles are themselves anions, they are building blocks in their own right and allow further facile functionalization. This property may be of interest in coordination chemistry and material science.

ChemInform Abstract: Stable Carbenes: From “Laboratory Curiosities” to Catalysis Mainstays

AbstractReview: 19 refs.

Stable Carbenes: From ‘Laboratory Curiosities' to Catalysis Mainstays

The past 20 years have witnessed an explosion in research in the area of stable carbenes. From laboratory curiosities, they have emerged as a front-line alternative to phosphines in metal catalysis. The range of reactivity that they enable in organocatalysis, much of it through their capability to render functional groups umpolung, is enviable. Of course, their unique properties enable them to outperform both phosphines and more traditional Lewis bases in specific transformations. This Cluster assembles leaders in the field that provide a brief introduction to the unique chemistry afforded by these species.