Carbodicarbene-Stibenium Ion-Mediated Functionalization of C(sp3)-H and C(sp)-H Bonds.

Main-group element-mediated C-H activation remains experimentally challenging, and the development of clear concepts and design principles have been limited by the increased reactivity of relevant complexes, especially for the heavier elements. Herein, we report that the stibenium ion [(pyCDC)Sb][NTf2]3 (1) (pyCDC = bis-pyridyl carbodicarbene; NTf2 = bis(trifluoromethanesulfonyl)imide) reacts with acetonitrile in the presence of the base 2,6-di-tert--butylpyridine to enable C(sp3)-H bond breaking to generate the stiba-methylene nitrile complex [(pyCDC)Sb(CH2CN)][NTf2]2 (2). Kinetic analyses were performed to elucidate the rate dependence for all the substrates involved in the reaction. Computational studies suggest that C-H activation proceeds via a mechanism in which acetonitrile first coordinates to the Sb center through the nitrogen atom in a κ1 fashion, thereby weakening the C-H bond which can then be deprotonated by base in solution. Further, we show that 1 reacts with terminal alkynes in the presence of 2,6-di-tert--butylpyridine to enable C(sp)-H bond breaking to form stiba-alkynyl adducts of the type [(pyCDC)Sb(CCR)][NTf2]2 (3a-f). Compound 1 shows excellent specificity for the activation of the terminal C(sp)-H bond even across alkynes with diverse functionality. The resulting stiba-methylene nitrile and stiba-alkynyl adducts react with elemental iodine (I2) to produce iodoacetonitrile and iodoalkynes, while regenerating an Sb trication.

Bis(9-Boraphenanthrene) and Its Stable Biradical.

Selective and site-specific boron-doping of polycyclic aromatic hydrocarbon frameworks often give rise to redox and/or photophysical properties that are not easily accessible with the analogous all-carbon systems. Herein, we report ligand-mediated control of boraphenanthrene closed- and open-shell electronic states, which has led to the first structurally characterized examples of neutral bis(9-boraphenanthrene) (2-3) and its corresponding biradical (4). Notably, compounds 2 and 3 show intramolecular charge transfer absorption from the 9-boraphenanthrene units to p-quinodimethane, exhibiting dual (red-shifted) emission in solution due to excited state conjugation enhancement (ESCE). Moreover, while boron-centered monoradicals are ubiquitous, biradical 4 represents a rare type of open-shell singlet compound with 95% biradical character, among the highest of any reported boron-based polycyclic species with two radical sites.

Microwave-assisted extraction, separation, and chromogenic detection of laced marijuana for presumptive point-of-interdiction testing.

Presumptive drug screening enables timely procurement of search and arrest warrants and represents a crucial first step in crime scene analysis. Screening also reduces the burden on forensic laboratories which often face insurmountable backlogs. In most scenarios, on-site presumptive drug screening relies on chemical field tests for initial identification. However, even when used appropriately, these test kits remain limited to subjective colorimetric analysis, produce false positive or negative results with excessive sample quantities, and are known to cross-react with numerous innocuous substances. Previous efforts to develop microfluidic devices that incorporate these chromogenic indicator reagents address only a few of the many challenges associated with these kits. This is especially true for samples where the drug of interest is present as a lacing agent. This work describes the development of a centrifugal microfluidic device capable of integrating facile sample preparation, by way of a 3D printed snap-on cartridge amenable to microwave assisted extraction, followed by chromatographic separation and chromogenic detection on-disc. As cannabis is among the most widely used controlled substance worldwide, and displays strong interference with these indicator reagents, mock samples of laced marijuana are used for a proof-of-concept demonstration. Post extraction, the microdevice completes high throughput metering just prior to simultaneous reaction with four of the most commonly employed microchemical tests, followed by objective image analysis in CIELAB (a device-independent color model). Separation and recovery of a representative controlled substance with 93% efficiency is achieved. Correct identification, according to hierarchical cluster analysis, of three illicit drugs (e.g., heroin, phencyclidine, and cocaine) in artificially laced samples is also demonstrated on-disc. The cost effective microdevice is capable of complete automation post-extraction, with a total analysis time (including extraction) of <8 min. Finally, sample consumption is minimized, thereby preventing the complete destruction of forensic evidence.

Dielectric heating of highly corrosive and oxidizing reagents on a hybrid glass microfiber-polymer centrifugal microfluidic device.

Many assays necessitate the use of highly concentrated acids, powerful oxidizing agents, or a combination of the two. Although microfluidic devices offer vast potential for rapid analytical interrogation at the point-of-need (PON), they cannot escape the fundamental requirement for reagent compatibility. Worse, many innovative protocols have been developed that would represent a significant improvement to current field-forward practices within their respective disciplines, but adoption falters due to chemical incompatibility with challenging reagents. Polymeric centrifugal microfluidic devices meet many of the needs for accommodating complex chemical or biochemical protocols in a multiplexed and automatable format. Yet, they also struggle to accommodate highly reactive chemical components long term. In this work, we report on a simple and inexpensive reagent storage strategy that bypasses the typical complexity involved with integration of liquid reagents on microfluidic devices. Moreover, we demonstrate microdevice compatibility and operation after six months of corrosive reagent storage as well as post dielectric heating. This new strategy allows for storage of multiple highly corrosive and oxidative reagents simultaneously, enhancing the possibilities for multistep assay integration at the PON for a diverse array of applications. Successful detection after one week of corrosive reagent storage of an illicit drug and neurotransmitter metabolite, for forensic and clinical applications, is demonstrated. Furthermore, environmental sample preparation via microwave-assisted wet acid digestion is performed on-disc and integrated with downstream detection. Quantitative detection of a heavy metal in soil is achieved by way of on-disc calibration and found to be accurate within 2.4% compared to a gold standard reference (ICP-OES).