The development of METAL-WRF Regional Model for the description of dust mineralogy in the atmosphere

The mineralogical composition of airborne dust particles is an important but often neglected parameter for several physiochemical processes, such as atmospheric radiative transfer and ocean biochemistry. We present the development of the METAL-WRF module for the simulation of the composition of desert dust minerals in atmospheric aerosols. The new development is based on the GOCART-AFWA dust module of WRF-Chem. A new wet deposition scheme has been implemented in the dust module alongside the existing dry deposition scheme. The new model includes separate prognostic fields for nine (9) minerals: illite, kaolinite, smectite, calcite, quartz, feldspar, hematite, gypsum, and phosphorus, derived from the GMINER30 database and also iron derived from the FERRUM30 database. Two regional model sensitivity studies are presented for dust events that occurred in August and December 2017, which include a comparison of the model versus elemental dust composition measurements performed in the North Atlantic (at Izaña Observatory, Tenerife Island) and in the eastern Mediterranean (at Agia Marina Xyliatos station, Cyprus Island). The results indicate the important role of dust minerals, as dominant aerosols, for the greater region of North Africa, South Europe, the North Atlantic, and the Middle East, including the dry and wet depositions away from desert sources. Overall, METAL-WRF was found to be capable of reproducing the relative abundances of the different dust minerals in the atmosphere. In particular, the concentration of iron (Fe), which is an important element for ocean biochemistry and solar absorption, was modeled in good agreement with the corresponding measurements at Izaña Observatory (22% overestimation) and at Agia Marina Xyliatos site (4% overestimation). Further model developments, including the implementation of newer surface mineralogical datasets, e.g., from the NASA-EMIT satellite mission, can be implemented in the model to improve its accuracy.This study was supported by the Hellenic Foundation for Research and Innovation project Mineralogy of Dust Emissions and Impacts on Environment and Health (MegDeth - HFRI no. 703). Part of this study was conducted within the framing of the AERO-EXTREME (PID2021-125669NB-I00) project funded by the State Research Agency/Agencia Estatal de Investigación of Spain and the European Regional Development Funds

Predicting Cocrystallization Based on Heterodimer Energies: Part II

Many crystal engineering studies employ urea functionalities for their predictable association into one-dimensional hydrogen bonded chains. Previously, we showed (<i>Cryst. Growth Des.</i>, <b>2015</b>, <i>15</i> (10), 5068–5074) that the urea chain motif usually seen in structures of diphenylureas (PUs) with meta-substituents could be disrupted in several cases by cocrystallization with the strong hydrogen bond acceptor triphenylphosphine oxide (TPPO). Computed differences in the urea···urea and urea···TPPO dimer energies of ∼5.3–6 kcal/mol were a reasonably accurate indicator for cocrystallization success. The current study attempts to reassess the limits of this computational approach using a larger set of 16 <i>ortho</i>- and <i>para</i>-substituted PUs. Seven of the 10 PU systems predicted to cocrystallize on the basis of dimer energy calculations were experimentally realized, along with an eighth whose difference in homo/heterodimer energies fell below the threshold. The absence of cocrystallization in two of the predicted systems is likely due to preferred urea···substituent hydrogen bonding over both urea···urea and urea···TPPO interactions, a factor that was not considered in the homo/heterodimer energy comparisons. When taken in combination with the previous study, energy predictions were 87% accurate over the 30 systems investigated

Ortho-Substituent Effects on Diphenylurea Packing Motifs

Hydrogen bonding between urea groups is a widely used motif in crystal engineering and supramolecular chemistry studies. In an effort to discern how the steric and electronic properties of substituents affect the molecular conformation and crystal packing of ortho-substituted <i>N</i>,<i>N</i>′-diphenylureas (<i>o</i>PUs), herein we report the synthesis, characterization, and polymorph screening of eight members of this family. Of the 16 total <i>o</i>PU structures known (including nine structures from this study and seven previously reported), only two are isostructural. These 16 structures are sorted into three general architecture types based on their hydrogen bond topologies. In Type I, urea molecules related by translation form linear one-dimensional (1D) hydrogen bonded chains. In Type II, urea molecules rotate about a 1D hydrogen bond axis forming twisted chains. Urea groups do not hydrogen bond to one another in Type III. Energy calculations performed at the B3LYP/6-31G­(d,p) level show a higher rotational barrier about the amide bond in <i>o</i>PUs compared to meta-substituted diphenylureas (<i>m</i>PUs), which may explain the smaller range of torsion angles observed in <i>o</i>PUs compared to <i>m</i>PUs. Although ortho-substitution does not seem to limit the hydrogen bonding between urea groups in most cases, a notably higher percentage of <i>o</i>PU phases are polar compared to PUs with other substitution patterns. This suggests restricted conformations might offer some advantage in achieving acentric materials

Structural and electronic switching of a single crystal 2D metal-organic framework prepared by chemical vapor deposition.

The incorporation of metal-organic frameworks into advanced devices remains a desirable goal, but progress is hindered by difficulties in preparing large crystalline metal-organic framework films with suitable electronic performance. We demonstrate the direct growth of large-area, high quality, and phase pure single metal-organic framework crystals through chemical vapor deposition of a dimolybdenum paddlewheel precursor, Mo2(INA)4. These exceptionally uniform, high quality crystals cover areas up to 8600 µm2 and can be grown down to thicknesses of 30 nm. Moreover, scanning tunneling microscopy indicates that the Mo2(INA)4 clusters assemble into a two-dimensional, single-layer framework. Devices are readily fabricated from single vapor-phase grown crystals and exhibit reversible 8-fold changes in conductivity upon illumination at modest powers. Moreover, we identify vapor-induced single crystal transitions that are reversible and responsible for 30-fold changes in conductivity of the metal-organic framework as monitored by in situ device measurements. Gas-phase methods, including chemical vapor deposition, show broader promise for the preparation of high-quality molecular frameworks, and may enable their integration into devices, including detectors and actuators

Structural Diversity in 1,3-Bis(<i>m</i>‑cyanophenyl)urea

Hydrogen bonding between 1,3-bis ureas is a commonly used motif in the assembly of supramolecular structures such as gels, capsules and crystals. The title compound, 1,3-bis­(<i>m</i>-cyanophenyl)­urea (<b>mCyPU</b>), has previously been shown to crystallize in both an anhydrous and monohydrate phase (α and H–I). An expanded search for polymorphs and cocrystals of <b>mCyPU</b> revealed a much greater diversity of solid forms including three additional polymorphs (β, δ, ε), a second hydrate (H–II) and two cocrystal phases with dimethyl sulfoxide and triphenylphosphine oxide. Analysis of the single crystal structures obtained in this study shows that the typical 1-dimensional H-bonding between 1,3-bis urea groups is disrupted by the presence of other H-bond acceptors including cyano, water, sulfoxide and phosphine oxide functionalities. Re-examination of <b>α-mCyPU</b> additionally showed both blade and plate-like morphologies could be obtained from different growth solvents, with crystals of the latter morphology exhibiting a grain boundary migration prior to melting

Predicting Cocrystallization Based on Heterodimer Energies: The Case of <i>N</i>,<i>N</i>′‑Diphenylureas and Triphenylphosphine Oxide

Diarylureas frequently assemble into structures with one-dimensional H-bonded chain motifs. Herein, we examine the ability of triphenylphosphine oxide (TPPO) to disrupt the H-bonding motif in 14 different <i>meta</i>-substituted <i>N</i>,<i>N</i>′-diphenylureas (mXPU) and form cocrystals; 1:1 mXPU:TPPO cocrystals were obtained in 9 of 14 cases examined (64% success rate). Cocrystals adopt five different lattice types, all of which show unsymmetrical H-bonded [R₂¹(6)] dimers between the urea hydrogens and the phosphine oxygen. Heterodimer (mXPU···TPPO) and homodimer (mXPU···mXPU) interaction energies, Δ<i>E</i>_int, calculated using density functional theory at the B3LYP/6-31G­(d,p) level were used to rationalize the experimental results. A clear trend was observed in which cocrystals were experimentally realized only in cases in which the differences in heterodimer versus homodimer energy, ΔΔ<i>E</i>_int, were greater than ∼5.3–6 kcal/mol. Although calculated interaction energies are a simplified measure of the system thermodynamics, these results suggest that the relative ΔΔ<i>E</i>_int between heterodimers and homodimers is a good predictor of cocrystal formation in this system