Influence of the guest molecules on the structural organization of the clathrates of syndiotactic poly(p‐methylstyrene)

The influence of the shape and size of guest molecules on the structural organization of the α and β class clathrates of syndiotactic poly(p‐methylstyrene) is described, through the analysis of the packing model proposed for the crystal structures of the clathrate forms containing o‐dichlorobenzene and tetrahydrofuran. Preliminary data of the crystal structure of the s‐PPMS clathrate containing benzene and a comparison with the crystal structure of the clathrate forms of syndiotactic polystyrene are also presented.     

The Photochemistry of the (Cycloalkene)(hydro)(trispyrazolylborato)iridium Complexes [Ir(η4-cod)(TpMe2)] and [Ir(η2-coe)H2(TpMe2)]: the Formation of [IrH4(TpMe2)] and [Ir(CO)H2(TpMe2)]

Photolysis of [Ir(η²-coe)H₂(Tp^Me2)] ( 1 ; Tp^Me2=hydrotris(3,5-dimethylpyrazolyl)borato, coe=(Z)-cyclooctene) in CH₃OH gives a mixture of [IrH₄(Tp^Me2)] ( 4 ) and [Ir(CO)H₂(Tp^Me2)] ( 5 ) in a ca. 1 : 1 ratio. Mass-spectral analysis of the distillate of the reaction mixture at the end of the photolysis shows the presence of coe. When pure CD₃OD is used as solvent, the deuteride complexes [IrD₄(Tp^Me2)] ((D₄)- 4 ) and [Ir(CO)D₂(Tp^Me2)] ((D₂)- 5 ) are obtained. Also the photolysis of [Ir(η⁴-cod)(Tp^Me2)] ( 3 ) (cod=cycloocta-1,5-diene) gives 4 and 5 . A key feature of this photoreaction is the intramolecular dehydrogenation of cod with formation of cycloocta-1,3,5-triene, detected by mass spectroscopy at the end of the photolysis. Labeling experiments using CD₃OD show that the hydrides in 4 originate from MeOH. When ¹³CH₃OH is used as solvent, [Ir(¹³CO)H₂(Tp^Me2)] is formed demonstrating that CH₃OH is the source of the CO ligand. The observation that the photolysis of both 1 and 3 give the same product mixture is attributed to the formation of a common intermediate, i.e., the coordinatively unsaturated 16e⁻ species {IrH₂(Tp^Me2)}.     

The Photochemistry of (Diene)(hydro)[tris(3,5-dimethylpyrazolyl)borato]rhodium Complexes,Preliminary Communication

The photochemical rearrangement of [Rh(η⁴-1,5-cod)Tp^Me2](Tp^Me2=hydrotris(3,5-dimethylpyrazolyl)borato, 1,5-cod=cycloocta-1,5-diene) to the new compound [Rh(η⁴-1,3-cod)Tp^Me2] ( 2 ) is described. The characterization of 2 was carried out using ¹H-, ¹³C-, and ¹⁰³Rh-HMQC-NMR spectroscopy. Photolysis of 2 is a versatile entry point into the organometallic chemistry of the {RhTp^Me2} fragment as it can be used to produce a) hydrido-carbonyl ([Rh(CO)H₂Tp^Me2]), b) hydrido-phenyl-phosphite ([RhH(Ph)(P(OMe)₃)Tp^Me2]), and c) ethoxide-hydrido-phosphite ([RhH(OEt)(P(OMe)₃)Tp^Me2]) complexes.     

Bioprospecting the Antibiofilm and Antimicrobial Activity of Soil and Insect Gut Bacteria

Antimicrobial resistance is a growing concern in public health and current research shows an important role for bacterial biofilms in recurrent or chronic infections. New strategies, therefore, are necessary to overcome antimicrobial resistance, through the development of new therapies that could alter or inhibit biofilm formation. In this sense, antibiofilm natural products are very promising. In this work, a bioprospection of antimicrobial and antibiofilm extracts from Uruguayan soil bacteria and insect gut bacteria was carried out. Extracts from extracellular broths were tested for their ability to inhibit planktonic cell growth and biofilm formation. Genomic analysis of Bacillus cereus ILBB55 was carried out. All extracts were able to inhibit the growth of, at least, one microorganism and several extracts showed MICs lower than 500 µg mL⁻¹ against microorganisms of clinical relevance (Staphylococcus aureus, Pseudomonas aeruginosa, and Enterobacter cloacae). Among the extracts evaluated for biofilm inhibition only ILBB55, from B. cereus, was able to inhibit, S. aureus (99%) and P. aeruginosa (62%) biofilms. Genomic analysis of this strain showed gene clusters similar to other clusters that code for known antimicrobial compounds. Our study revealed that extracts from soil bacteria and insect gut bacteria, especially from B. cereus ILBB55, could be potential candidates for drug discovery to treat infectious diseases and inhibit S. aureus and P. aeruginosa biofilms.     

Front Cover: Critical Assessment of pH-Dependent Lipophilicity Profiles of Small Molecules: Which One Should We Use and In Which Cases? (ChemPhysChem 24/2023)

Lipophilicity is a physicochemical property with wide relevance in drug design, computational biology, food, environmental and medicinal chemistry. Lipophilicity is commonly expressed as the partition coefficient for neutral molecules, whereas for molecules with ionizable groups, the distribution coefficient (D) at a given pH is used. The logD_pH is usually predicted using a pH correction over the logP_N using the pK_a of ionizable molecules, while often ignoring the apparent ion pair partitioning . In this work, we studied the impact of on the prediction of both the experimental lipophilicity of small molecules and experimental lipophilicity-based applications and metrics such as lipophilic efficiency (LipE), distribution of spiked drugs in milk products, and pH-dependent partition of water contaminants in synthetic passive samples such as silicones. Our findings show that better predictions are obtained by considering the apparent ion pair partitioning. In this context, we developed machine learning algorithms to determine the cases that should be considered. The results indicate that small, rigid, and unsaturated molecules with logP_N close to zero, which present a significant proportion of ionic species in the aqueous phase, were better modeled using the apparent ion pair partitioning . Finally, our findings can serve as guidance to the scientific community working in early-stage drug design, food, and environmental chemistry.     

ChemInform Abstract: Identification of Novel Cu,Ag, and Au Ternary Oxides from Global Structural Prediction.

Ab initio global structural prediction and specifically, the minima hopping method combined with high‐throughput calculations are used to explore the periodic table in search of novel oxide phases.     

Rechargeable sodium-ion battery based on a cathode of copper hexacyanoferrate

Journal of Solid State Electrochemistry - In this work, the performance of copper (II) hexacyanoferrate(III) (CuHCF) as a cathode material for sodium-ion batteries was studied. The compound was...     

Cation Co-intercalation in Potassium Copper(II) Hexacyanoferrates

The cation-insertion solid state electrochemistry of a potassium copper(II) hexacyanoferrate in contact with LiClO₄/DMSO, NaPF₆/DMSO, and KPF₆/DMSO electrolytes has been theoretically and experimentally studied using the voltammetry of immobilized particles methodology. Voltammetric data, combined with SEM/EDS analysis permit to determine a K_0.876Cu^II_1.328Fe^III_0.049[Fe^III_0.318Fe^II_0.682(CN)₆] stoichiometry for the synthesized solid. Separation of electronic and ionic contributions to Gibbs energy changes can be made based on cyclic voltammetric and open circuit potential measurements. These parameters can be combined to measure values of the Gibbs energy of cation-independent electron transfer of 7.2±0.4 (K⁺), 7.1±0.5 (Na⁺) kJ mol⁻¹, in close agreement with the expected independence of this parameter on the electrolyte cation. The reduction Fe(III) centers bound to cyano groups exhibit a cation-dependent, essentially Nernstian character which can be described in terms of Na⁺ and K⁺ insertion/deinsertion while in the case of Li⁺ electrolytes there is significant co-cation diffusion. Chronoamperometric data provide estimates of the diffusion coefficients of Na⁺, and K⁺ ions through the solid around 10⁻⁹ cm² s⁻¹.     

Ring-opening polymerization of lactones by mono(cyclopentadienyl)titanium complexes

Mono(cyclopentadienyl)titanium complexes of the general formula Ti(η⁵-C₅R₅)X₂OR' were designed as structurally well-defined mononuclear initiators for the ring-opening polymerization of four-, six-, and seven-membered lactones. Living pseudo-anionic mechanism with acyl-oxygen cleavage is suggested by various NMR spectroscopic studies as well as the isolation of the mono(insertion) products. The nature of the ancillary ligands lead to significant changes in the polymerization activity and is discussed in terms of electronic and steric effects.