Synthesis and crystal structure of sodium (ethane-1,2-di-yl)bis-[(3-meth-oxy-prop-yl)phosphinodi-thiol-ate] octa-hydrate.

The title compound, -poly[[tri-aqua-sodium]-di-μ-aqua-[tri-aqua-sodium]-μ-(ethane-1,2-di-yl)bis-[(3-meth-oxy-prop-yl)phosphinodi-thiol-ato]], [Na(CHOPS)(HO)] , crystallizes in the triclinic space group 1. The dianionic [CHO(CH)P(=S)(S-)CHCHP(=S)(S-)(CH)OCH] ligand fragments are joined by a dicationic [Na(HO)] cluster that includes the oxygen of the meth-oxy-propyl unit of the ligand to form infinite chains.

Intramolecular Charge Transfer in Antiaromatic Donor/Acceptor-Fused s-Indacenes.

Herein we report the synthesis and characterization of four donor/acceptor-fused s-indacenes via the late-stage oxidation of a family of unsymmetrical benzofuran/benzothiophene-s-indacene regioisomers. A thorough study of their properties through experimental and computational analysis has revealed the effect of asymmetry on the molecular properties associated with antiaromaticity, as well as a strong correlation between antiaromaticity and intramolecular charge transfer (ICT). The strength of the charge transfer depends on the fusion orientation of the donor and acceptor motifs relative to the s-indacene core.

Pinwheel-like Curved Aromatics from the Cyclotrimerization of Strained Alkyne Cycloparaphenylenes.

Carbon nanomaterials composed of curved aromatics, such as carbon nanotubes, are difficult to selectively synthesize and modify precisely. Smaller molecular fragments of curved nanomaterials, such as cycloparaphenylenes, benefit from the precision of bottom-up synthesis, however, efforts to expand the curved molecular framework into even larger structures often rely on restrictive early stage synthetic strategies or difficult to control polymerizations. In this work we report a high yielding, strain-promoted, late-stage modification of a series of [ + 1]CPPs.

Total Synthesis of Chalaniline A: An Aminofulvene Fused Chromone from Vorinostat-Treated Fungus sp. 6661.

Chalaniline A, an aminofulveno[1,2-]chromone derivative previously isolated from a vorinostat-treated ascomycete sp., was prepared in nine steps from orcinol (3,5-dihydroxytoluene). In a key transformation, the tricyclic ring system of the target was generated by a pyrrolidine-catalyzed double annulation between α-(methylsulfinyl)-2,6-dihydroxy-4-methylacetophenone and the ketaldoester, methyl 2,5-dioxopentanoate.

Probing the Influence of Alkyne Substitution on the Electronic and Magnetic Properties of Diindeno[1,2-;1',2'-]anthracenes.

To further the ability to manipulate the properties of open-shell molecules, logical and incremental modifications to molecular structure are key steps that provide fine-tuning of established diradicaloid scaffolds. We report the synthesis of an electronically "pure" diradicaloid based on a 2,6-anthroquinoidal core where the once necessary ethynyl "wings" are removed. Through the simplification of the overall electronic structure, the singlet-triplet energy gap increases by 0.

Pnictogen-Assisted Self-Assembly as a Means to Study Mediated Thiol/Disulfide Exchange in Supramolecular Dynamic Covalent Assemblies.

Thiol-disulfide interchange has been a large field of study for both biochemists and physical organic chemists alike due to its prevalence within biological systems and fundamentally interesting dynamic nature. More recently, efforts have been made to harness the power of this reversible reaction to make self-assembling systems of macrocyclic molecules. However, less effort has focused on the fundamental work of isolating these assemblies and studying the factors that control the assembly and sorting of these emerging cyclic systems.

A twist on a classic scaffold: rational design of a new bimetallic platform.

Herein, we report the synthesis of a modular family of novel bimetallic tetraamidodiamine (tada) ligands, Li-R-tada (R = MeSi, BuMeSi, and PrSi). These silylamido ligands display two distinct binding pockets whose steric profiles can be easily tuned by choice of the substituents on silicon. We also show that salt metathesis is a convenient route to install these new ligands on the early transition metals titanium(IV) and vanadium(III).

Synthesis, Characterization, and Reactivity of a Synthetic End-On Cobalt(II) Alkyl Persulfide Complex as a Model Platform for Thiolate Persulfidation.

Persulfides (RSS) are ubiquitous source of sulfides (S) in biology, and interactions between RSS and bioinorganic metal centers play critical roles in biological hydrogen sulfide (HS) biogenesis, signaling, and catabolism. Here, we report the use of contact-ion stabilized [Na(15-crown-5)][BuSS] () as a simple synthon to access rare metal alkyl persulfide complexes and to investigate the reactivity of RSS with transition metal centers to provide insights into metal thiolate persulfidation, including the fundamental difference between alkyl persulfides and alkyl thiolates. Reaction of with [Co(TPA)(OTf)] afforded the η-alkyl persulfide complex [Co(TPA)(SSBu)] (), which was characterized by X-ray crystallography, UV-vis spectroscopy, and Raman spectroscopy.

3-Position Biaryl Endochin-like Quinolones with Enhanced Antimalarial Performance.

ELQ-300 is a potent antimalarial drug with activity against blood, liver, and vector stages of the disease. A prodrug, , exhibits reduced crystallinity and improved in vivo efficacy in preclinical testing, and currently, it is in the developmental pipeline for once-a-week dosing for oral prophylaxis against malaria. Because of the high cost of developing a new drug for human use and the high risk of drug failure, it is prudent to have a back-up plan in place.

A High-Yielding Active Template Click Reaction (AT-CuAAC) for the Synthesis of Mechanically Interlocked Nanohoops.

Mechanically interlocked molecules (MIMs) represent an exciting yet underexplored area of research in the context of carbon nanoscience. Recently, work from our group and others has shown that small carbon nanotube fragments-[n]cycloparaphenylenes ([n]CPPs) and related nanohoop macrocycles-may be integrated into mechanically interlocked architectures by leveraging supramolecular interactions, covalent tethers, or metal-ion templates. Still, available synthetic methods are typically difficult and low yielding, and general methods that allow for the creation of a wide variety of these structures are limited.

Reversible Hydrosulfide (HS) Binding Using Exclusively C-H Hydrogen-Bonding Interactions in Imidazolium Hosts.

HS is a physiologically important signaling molecule with complex roles in biology and exists primarily as HS at physiological pH. Despite this anionic character, few investigations have focused on the molecular recognition and reversible binding of this important biological anion. Using a series of imidazole and imidazolium host molecules, we investigate the role of preorganization and charge on HS binding.

Synthesis and Properties of Fluorenone-Containing Cycloparaphenylenes and Their Late-Stage Transformation.

Cycloparaphenylenes (CPPs) are the smallest possible armchair carbon nanotubes, the properties of which strongly depend on their ring size. They can be further tuned by either peripheral functionalization or by replacing phenylene rings for other aromatic units. Here we show how four novel donor-acceptor chromophores were obtained by incorporating fluorenone or 2-(9H-fluoren-9-ylidene)malononitrile into the loops of two differently sized CPPs.

2-λ-Phosphaquinolin-2-ones as Non-cytotoxic, Targetable, and pH-Stable Fluorophores.

Several phosphaquinolinone derivatives have been synthesized and characterized to explore their usefulness in the realm of cell imaging. Solution-state photophysical properties in both aqueous and organic solutions were collected for these derivatives. Additionally, CCK-8 cell viability assays and fluorescent imaging in HeLa cells incubated with the new heterocyclic derivatives show evidence of favorable cell permeability, cell viability, and moderate intracellular localization when appended with the well-known morpholine targeting motif.

Benchmarking the placement of hydrosulfide in the Hofmeister series using a bambus[6]uril-based ChemFET sensor.

Hydrosulfide (HS) is the conjugate base of gasotransmitter hydrogen sulfide (HS) and is a physiologically-relevant small molecule of great interest in the anion sensing community. However, selective sensing and molecular recognition of HS in water remains difficult because, in addition to the diffuse charge and high solvation energy of anions, HS is highly nucleophilic and readily oxidizes into other reactive sulfur species. Moreover, the direct placement of HS in the Hofmeister series remains unclear.

Taming the Dichalcogenides: Isolation, Characterization, and Reactivity of Elusive Perselenide, Persulfide, Thioselenide, and Selenosulfide Anions.

Reactive sulfur species (RSS) and reactive selenium species (RSeS) play integral roles in hydrogen sulfide (HS) and hydrogen selenide (HSe) biological signaling pathways, and dichalcogenide anions are proposed transient intermediates that facilitate a variety of biochemical transformations. Herein we report the selective synthesis, isolation, spectroscopic and structural characterization, and fundamental reactivity of persulfide (RSS), perselenide (RSeSe), thioselenide (RSSe), and selenosulfide (RSeS) anions. The isolated chalcogenides do not rely on steric protection for stability and have steric profiles analogous to cysteine (Cys).

Comparison of Antiaromatic Properties in a Series of Structurally Isomeric Naphthothiophene-Fused s-Indacenes.

Fusion of aromatic subunits to stabilize an antiaromatic core allows the isolation and study of otherwise unstable paratropic systems. A complete study of a series of six naphthothiophene-fused s-indacene isomers is herein described. Additionally, the structural modifications resulted in increased π-π overlap in the solid state, which was further explored through changing the sterically blocking mesityl group to (triisopropylsilyl)ethynyl in three derivatives.

Tunable Macrocyclic Polyparaphenylene Nanolassos via Copper-Free Click Chemistry.

Deriving diverse compound libraries from a single substrate in high yields remains to be a challenge in cycloparaphenylene chemistry. In here, a strategy for the late-stage functionalization of shape-persistent alkyne-containing cycloparaphenylene has been explored using readily available azides. The copper-free [3+2]azide-alkyne cycloaddition provided high yields (>90 %) in a single reaction step.

Active template strategy for the preparation of π-conjugated interlocked nanocarbons.

Mechanically interlocked carbon nanostructures represent a relatively unexplored frontier in carbon nanoscience due to the difficulty in preparing these unusual topological materials. Here we illustrate an active-template method in which a [n]cycloparaphenylene precursor macrocycle is decorated with two convergent pyridine donors that coordinate to a metal ion. The metal ion catalyses alkyne-alkyne cross-coupling reactions within the central cavity of the macrocycle, and the resultant interlocked products can be converted into fully π-conjugated structures in subsequent synthetic steps.

Impact of Internal Charge Transfer on the Photophysical Properties of Pyridine-Fused Phosphorus-Nitrogen Heterocycles.

The phosphaquinolinone scaffold has been previously studied as a modular core for a variety of fluorescent species where use of substituent effects has focused on increasing or decreasing electron density in the core rings. We now report the synthesis and analysis of several pyridine-containing phosphaquinolinone species exhibiting notable linear conjugation from the aryl-substituent to electron-withdrawing pyridyl nitrogen. Varying the nature of the aryl substituent from electron-withdrawing to electron-donating leads to the generation of an internal charge-transfer (ICT) band in the absorbance spectrum, which becomes the dominant absorbance in terms of intensity in the most electron-rich -NMe example.

Synthesis and reactivity of a tris(carbene) zinc chloride complex.

The [B(BuIm)] ligand has gained increased attention since it was first reported in 2006 due to its ability to stabilize highly reactive first row transition metal complexes. In this work, we investigate the coordination chemistry of this ligand with redox-inert zinc to understand how a zinc metal center behaves in such a strong coordinating environment. The B(BuIm)ZnCl (1) complex can be formed deprotonation of [B(BuIm)][OTf] followed by the addition of ZnCl.

Supramolecular Activation of S by Cucurbiturils in Water and Mechanism of Reduction to HS by Thiols: Insights into Biological Sulfane Sulfur Trafficking.

Reactive sulfur species (RSS) play critical roles in diverse chemical environments. Molecules containing sulfane sulfur (S) have emerged as key species involved in cellular redox buffering as well as RSS generation, translocation, and action. Using cucurbit[7]uril (CB[7]) as a model hydrophobic host, we demonstrate here that S can be encapsulated to form a 1:1 host guest complex, which was confirmed by solution state experiments, mass spectrometry, and X-ray crystallography.

Thionitrite (SNO ) and Perthionitrite (SSNO ) are Simple Synthons for Nitrosylated Iron Sulfur Clusters.

S/N crosstalk species derived from the interconnected reactivity of H S and NO facilitate the transport of reactive sulfur and nitrogen species in signaling, transport, and regulatory processes. We report here that simple Fe ions, such as those that are bioavailable in the labile iron pool (LIP), react with thionitrite (SNO ) and perthionitrite (SSNO ) to yield the dinitrosyl iron complex [Fe(NO) (S )] . In the reaction of FeCl with SNO we were able to isolate the unstable intermediate hydrosulfido mononitrosyl iron complex [FeCl (NO)(SH)] , which was characterized by X-ray crystallography.

Hydrolysis-Based Small-Molecule Hydrogen Selenide (HSe) Donors for Intracellular HSe Delivery.

Hydrogen selenide (HSe) is a central metabolite in the biological processing of selenium for incorporation into selenoproteins, which play crucial antioxidant roles in biological systems. Despite being integral to proper physiological function, this reactive selenium species (RSeS) has received limited attention. We recently reported an early example of a HSe donor (TDN1042) that exhibited slow, sustained release through hydrolysis.