Speciating volatile organic compounds in indoor air: using GC to interpret real-time PTR-MS signals.

Proton transfer reaction mass spectrometry (PTR-MS) is often employed to characterize gas-phase compounds in both indoor and outdoor environments. PTR-MS measurements are usually made without upstream chromatographic separation, so it can be challenging to differentiate between an ion of interest, its isomers, and fragmentation products from other species all detected at the same mass-to-charge ratio. These isomeric contributions and fragmentation interferences can confound the determination of accurate compound mixing ratios, the assignment of accurate chemical properties, and corresponding analyses of chemical fate.

Nanoscale Wet Etching of Molybdenum Interconnects with Organic Solutions.

Molybdenum (Mo) has emerged as a promising material for advanced semiconductor devices, especially in the design and fabrication of interconnects requiring sub-10 nm metal nanostructures. However, current wet etching methods for Mo using aqueous solutions struggle to achieve smooth etching profiles at such scales. To address this problem, we explore wet chemical etching of patterned Mo nanowires (NWs) using an organic solution: ceric ammonium nitrate (CAN) dissolved in acetonitrile (ACN).

Revisiting Isomerism in Square Planar Palladium NHC Complexes with NacAc Chelators.

Quantifying the donor ability of bidentate ligands in inorganic chemistry is not straightforward, and the Huynh electronic parameter for chelators (HEP2) presents a rare solution to the task. Aiming to extend the ligand scope in this work, the soundness and practicality of HEP2 was further scrutinized with seven stereoelectronically diverse β-ketiminato ("NacAc") chelators using palladium complexes of the type [PdBr(Pr-bimy)(NacAc)] (Pr-bimy = 1,3-diisopropylbenzimidazolin-2-ylidene). Notably, the unsymmetrical nature of this κ-, ligand family allowed for an intriguing exploration into isomerism in the square planar Pd products, which depends on the -aryl - and -substituents based on experimental and theoretical findings.

Dynamics of residential indoor gas- and particle-phase water-soluble organic carbon: measurements during the CASA experiment.

Previous time-integrated (2 h to 4 h) measurements show that total gas-phase water-soluble organic carbon (WSOC) is 10 to 20 times higher inside homes compared to outside. However, concentration dynamics of WSOC and total particle phase WSOC (WSOC)-are not well understood. During the Chemical Assessment of Surfaces and Air (CASA) experiment, we measured concentration dynamics of WSOC and WSOC inside a residential test facility in the house background and during scripted activities.

Donor Strength Determination of Buchwald-Type Phosphines.

The electronic properties of eight Buchwald-type phosphines were determined and ranked by C NMR spectroscopy, highlighting the sensitivity of the Huynh electronic parameter (HEP). Furthermore, the C NMR signals of 19 known and new P-donor complexes in CDCl (HEP values) are found to be highly correlated to those in CD. This enables the donor strength determination of P-donors even where the complexes are unstable or undergo rapid isomerization due to transphobia in CDCl.

Mesoionic Janus-Type Dicarbene: Complexes, Adducts, and Catalytic Studies.

The preparations of homo- and hetero-bimetallic complexes as well as thiourea and selenourea derivatives of a mesoionic Janus-type N-heterocyclic dicarbene (diNHC) are reported. Analogues of its monocationic intermediate NHC have also been obtained for comparison. Using the main group adducts, the π-acceptor properties of both NHCs were determined using low temperature Se NMR spectroscopy completing their stereoelectronic profiling.

The chemical assessment of surfaces and air (CASA) study: using chemical and physical perturbations in a test house to investigate indoor processes.

The Chemical Assessment of Surfaces and Air (CASA) study aimed to understand how chemicals transform in the indoor environment using perturbations (, cooking, cleaning) or additions of indoor and outdoor pollutants in a well-controlled test house. Chemical additions ranged from individual compounds (, gaseous ammonia or ozone) to more complex mixtures (, a wildfire smoke proxy and a commercial pesticide). Physical perturbations included varying temperature, ventilation rates, and relative humidity.

Electronic Profiling of -Phosphine Oxide-Substituted Imidazolin-2-ylidenes (PoxIms) and Imidazolidin-2-ylidenes (SPoxIms).

A detailed electronic study of the -phosphine oxide functionalized imidazolin-2-ylidenes (PoxIms) and imidazolidin-2-ylidenes (SPoxIms) has been performed experimentally using IR, C, and Se NMR spectroscopies. While the net donor/acceptor properties of the (S)PoxIms could not be differentiated via IR spectroscopy (TEP), NMR spectroscopic methods (HEP, Se) reveal that the (S)PoxIms are slightly weaker σ-donors but stronger π-acceptors compared to common NHCs. Moreover, backbone and substituent-effects could also be resolved by the latter, allowing for a ranking of their electronic properties.

Design of a Mesoionic Janus-type Dicarbene.

A versatile synthetic strategy for the preparation of homo- and heterobimetallic complexes bearing an unprecedented mesoionic Janus-type diNHC is presented. Moreover, its electronic property is evaluated, and a preliminary catalytic application in the direct diarylation of 1-methylpyrrole is demonstrated.

Diverse Post-Metathesis Reactivities of Mixed Amido-Isothiocyanato Molybdenum Complexes.

Attempts to prepare mixed isothiocyanato-bis(imido) Mo complexes led to the discovery of post-metathesis rearrangements toward three distinct products (-), which feature the NCS-derived chelators [N(NMe)CS] ( in dinuclear and ) and [N(SiMe)(NMe)CS] ( in mononuclear ). Notably, the preparation of bidentate ligand and its coordination chemistry are unprecedented. Together with computational studies, it is proposed that the putative "mono-substituted" intermediate [Mo(NBu)(NMe)(NCS)] serves as the common starting point for the observed molecular transformations.

Ventilation in a Residential Building Brings Outdoor NO Indoors with Limited Implications for VOC Oxidation from NO Radicals.

Energy-efficient residential building standards require the use of mechanical ventilation systems that replace indoor air with outdoor air. Transient outdoor pollution events can be transported indoors via the mechanical ventilation system and other outdoor air entry pathways and impact indoor air chemistry. In the spring of 2022, we observed elevated levels of NO (NO + NO) that originated outdoors, entering the National Institute of Standards and Technology (NIST) Net-Zero Energy Residential Test Facility through the mechanical ventilation system.

Kinetics of hypochlorous acid reactions with organic and chloride-containing tropospheric aerosol.

Chlorine plays an important role in tropospheric oxidation processes, in both marine and continental environments. Although modeling studies have explored the importance of halogen chemistry, uncertainty remains in associated chemical mechanisms and fundamental kinetics parameters. Prior kinetics measurements of multiphase halogen recycling reactions have been largely performed with dilute, bulk solutions, leaving unexplored more realistic chemical systems which have high solute concentrations and are internally mixed with both halide and organic components.

Donor Strength Determination of Anionic Ligands.

14 new gold(I) NHC complexes of the type [AuX(Pr-bimy)] (Pr-bimy = 1,3-diisopropylbenzimidazolin-2-ylidene) have been prepared and fully characterized. These complexes and their reported analogues were used to systematically compare and rank the donating abilities of overall 34 anionic X-type donors by C NMR spectroscopy. Specifically, the carbene chemical shift of the Pr-bimy ligand was found to be responsive to the ligand X spanning an overall range Δδ > 37 ppm between the strongest and weakest donor in this study.

Stereoelectronic Profiling of Neutral and Monoanionic Biimidazoles and Mixed Diimines.

14 mono-, di-, and tetranuclear palladium complexes were prepared to study the coordination chemistry of symmetrical and unsymmetrical azole-derived diimines and their anions. The diverse range of complexes obtained highlights the structural and electronic diversities imposed by these ligands. Using the monopalladium species, the electronic properties of selected bidentate ligands were determined, ranked, and compared by C NMR spectroscopy, extending the scope of the HEP2 (Huynh electronic parameter 2) scale, which can detect even subtle differences.

Versatile halogenation a C^C palladacycle intermediate.

Stable cyclopalladated complexes containing an (sp)C-Pd bond were synthesized α-CH deprotonation and palladation of -alkyl groups of carbene ligands bearing electron-withdrawing substituents. The strong electron donating strengths of the resulting C^C chelators were experimentally identified, and the palladacycle underwent template-directed, versatile C-halogenation with X.

Stereoelectronic Mapping of Dithiocarbamates and Xanthates.

A library of 12 palladium(II) complexes of the type [PdBr(Pr-bimy)(L∧X)] comprising 10 dithiocarbamato (RNCS) and two xanthato (ROCS) ligands have been prepared and fully characterized. With these complexes in hand, the electronic and steric properties of the bidentate, monoanionic ligands were evaluated using the HEP2 and % methodologies. Moreover, the construction of the first stereoelectronic map for dithiocarbamates enabled the in-principle identification of optimal ligand parameters for enhanced cytotoxic activities of their gold(III) complexes.

Controlled Access to Four- and Six-Membered Palladacycles Modifying Donor Abilities of β-Ketiminato Ligands ("NacAcs").

The synthesis of Pd complexes of the type [PdBr(Pr-bimy)(NacAc)] (NacAc = β-ketiminate, Pr-bimy = 1,3-diisopropylbenzimidazolin-2-ylidene) was attempted, in a continuing effort to quantify donor abilities of chelating β-ketiminate ligands using the Huynh electronic parameter for bidentate donors (HEP2). Subtle variation of N-substituents on the NacAc backbone was discovered to induce a drastic change in the preferred chelating mode, in that the commonly encountered κ-,-six-membered palladacycles were observed with R = Me and Et, while the unusual κ-,-four-membered palladacycles were isolated with R = Pr, Cy, and Bu. Computational studies subsequently corroborated these findings, in the form of an overall exergonic six-to-four-membered ring contraction process and a lower associated activation energy for the three more electron-donating alkyl moieties.

Gauging the donor strength of iron(0) complexes their N-heterocyclic carbene gold(I) adducts.

We isolate and characterize the gold(I)-iron(0) adducts [(Pr-bimy)Au-Fe(CO)(PMe)][BAr] and [Au-{Fe(CO)(PMe)}][BAr] (Pr-bimy = 1,3-diisopropylbenzimidazolin-2-ylidene, BAr = tetrakis(pentafluorophenyl)borate). DFT analysis reveals that the gold-iron interaction in [(Pr-bimy)Au-Fe(CO)(PMe)][BAr] is predominantly a σ-donation from iron to gold. We further extend this class of compounds to include [(Pr-bimy)Au-Fe(CO)(PR)][BAr] (PR = PPh, PCy, PCyPh, PMePh, PMePh, P(4-CHF)) and [(Pr-bimy)Au-Fe(CO)(PPh)][BAr] and correlate the Pr-bimy carbenic C NMR signal with the relative donor strength of the iron(0) ligand.

Mixed NHC-thiolato complexes of palladium: understanding the formation of di- mononuclear complexes.

The preference for the formation of mono- dinuclear mixed carbene/thiolato complexes of Pd has been studied with three types of N-heterocyclic carbenes derived from benzimidazole, imidazole and 1,2,4-triazole. The complexes were prepared by treatment of halido/NHC precursors with sodium isopropylthiolate in a salt metathesis reaction. Mononuclear complexes are formed when the sulfur and carbon donors are exclusively to each other, while their arrangement preferably leads to dinuclear complexes with μ-bridging thiolato ligands.

Exploring Aurone Derivatives as Potential Human Pancreatic Lipase Inhibitors through Molecular Docking and Molecular Dynamics Simulations.

Inhibition of human pancreatic lipase, a crucial enzyme in dietary fat digestion and absorption, is a potent therapeutic approach for obesity treatment. In this study, human pancreatic lipase inhibitory activity of aurone derivatives was explored by molecular modeling approaches. The target protein was human pancreatic lipase (PDB ID: 1LPB).

Donor Strength Determination of Pyridinylidene-amide Ligands using Their Palladium-NHC Complexes.

Pyridinylidene-amides (PYAs) are a relatively new type of N-donor ligands that can exist in three isomeric forms and adopt various resonance structures. This makes them electronically flexible, and in order to evaluate their electronic profile using the Huynh electronic parameter (HEP), seven structurally diverse mixed -heterocyclic carbenes (NHCs)/PYA palladium complexes of the type -[PdBr(Pr-bimy)(PYA)] were prepared and fully characterized by various spectroscopic and spectrometric methods. This study shows that PYAs are among the strongest, formally neutral N-donors, but they are still weaker than phosphines and organometallic ligands such as NHCs.

Stereoelectronic Profiling of Acyclic Diamino Carbenes (ADCs).

A library of 14 heterobis(carbene) complexes of the general formula [Au(Pr-bimy)(ADC)]BF (-) containing the N-heterocyclic carbene reporter Pr-bimy and various protic acyclic diaminocarbenes (ADCs) have been prepared to estimate their stereoelectronic properties by C NMR spectroscopy and percentage buried volume (%) determinations. Their preparation was achieved by nucleophilic attack of five secondary amines on six mixed NHC/isocyanide complexes of the type [Au(Pr-bimy)(CN-R)]BF (-). Analyses of the Pr-bimy carbene signals reveal that protic ADCs are stronger donors than classical and expanded-ring NHCs.

Heterogeneous Chemistry of CaCO Aerosols with HNO and HCl.

Calcite (CaCO) aerosols often serve as an idealized proxy for calcium-rich mineral dust. Their use has also previously been proposed for stratospheric solar radiation management (SSRM). Little is known about the heterogeneous chemistry of calcite aerosols with trace gases HNO and HCl and therefore their potential impact on stratospheric ozone (O).

Fused azole-thiazolines via one-pot cyclization of functionalized N-heterocyclic carbene precursors.

A one-pot two-step methodology was exploited to synthesize fused thiazoline-azolium salts via reactions of bromoalkyl-azolium salts with KSCN and NaOH. The synthetic feasibility and versatility was demonstrated by the high yield (>80%) preparation of 13 salts with different backbones, linkers and substituents. Using methylpropionato as an N-protecting group, the resulting salts could be further derivatized to their neutral azole-thiazolines.

Donor Strengths Determination of Pnictogen and Chalcogen Ligands by the Huynh Electronic Parameter and Its Correlation to Sigma Hammett Constants.

The suitability and accuracy of the Huynh electronic parameter (HEP) was further tested to reveal remote substituent effects in pyridines, which are located five or six bonds away from the reporter probe. These values show an excellent correlation to Hammett σ-constants of the respective substituents with coefficients of R =0.9856 (σ ) and R =0.