Bonding in Low-Coordinated Organoarsenic and Organoantimony Compounds: A Threshold Photoelectron Spectroscopic Investigation

Methyl and methylene compounds of arsenic and antimony have been studied by photoelectron photoion coincidence spectroscopy to investigate their relative stability. While for As both HAs=CH2, As−CH3 and the methylene compound As=CH2 are identified in the spectrum, the only Sb compound observed is Sb−CH3. Thus, there is a step in the main group 15 between As and Sb, regarding the relative stability of the methyl compounds. Ionisation energies, vibrational frequencies and spin-orbit splittings were determined for the methyl compound from photoion mass-selected photoelectron spectra. Although the spectroscopic results for organoantimony resemble those for the previously investigated bismuth compounds, EPR spectroscopic experiments indicate a far lower tendency for methyl transfer for Sb(CH3)3 compared to Bi(CH3)3. This study concludes investigations on low-valent organopnictogen compounds

Photoelectron spectroscopy and dissociative photoionization of fulminic acid, HCNO

We report a joint experimental and computational study of the photoelectron spectroscopy and the dissociative photoionization of fulminic acid, HCNO. The molecule is of interest to astrochemistry and astrobiology as a potential precursor of prebiotic molecules. Synchrotron radiation was used as the photon source. Dispersive photoelectron spectra were recorded from 10~eV to 22~eV, covering four band systems in the HCNO cation and an ionization energy of 10.83~eV was determined. Transitions into the Renner-Teller distorted $X^+{}^2\Pi$ state of the cation were simulated using wavepacket dynamics based on a vibronic coupling Hamiltonian. Very good agreement between experiment and theory is obtained. While the first excited state of the cation shows only a broad and unstructured spectrum, the next two higher states exhibit a well-resolved vibrational progression. Transitions into the excited electronic states of \cation{HCNO}{+} were not simulated, due to the large number of electronic states that contribute to these transitions. Nevertheless, a qualitative assignment is given, based on the character of the orbitals involved in the transitions. The dissociative photoionization was investigated by photoelectron-photoion coincidence spectroscopy. The breakdown diagram shows evidence for isomerization from \cation{HCNO}{+} to \cation{HNCO}{+} on the cationic potential energy surface. Zero Kelvin appearance energies for the daughter ions \cation{HCO}{+} and \cation{NCO}{+} have been derived

X-ray induced fragmentation of fulminic acid, HCNO

Financial support by the Deutsche Forschungsgemeinschaft, Contract No. FI 575/13-2, is gratefully acknowledged. This work was performed on the PLEIADES beamline under Proposal No. 20210814. We acknowledge SOLEIL for provision of synchrotron radiation facilities and thank the PLEIADES beamline team for their assistance

Ammonia Borane, NH3_{3}BH3_{3}: A Threshold Photoelectron-Photoion Coincidence Study of a Potential Hydrogen-Storage Material

We have investigated the photoionization of ammonia borane (AB) and determined adiabatic ionization energy to be 9.26±0.03 eV for the X$^{+}$ $^{2}$E←X $^{1}$A$_{1}$ transition. Although the threshold photoelectron spectrum appears at first glance to be similar to the one of the isosteric ethane, the electronic situation differs markedly, due to different orbital energies. In addition, an appearance energy AE$_{0K}$-(NH$_{3}$BH$_{3}$, NH$_{3}$BH$_{2}$$^{+}$)= 10.00±0.03 eV has been determined, corresponding to the loss of a hydrogen atom at the BH$_{3}$-site. From the data, a 0 K bond dissociation energy for the B−H bond in the cation of 71.5±3 kJ mol$^{-1}$ was derived, whereas the one in the neutral compound has been estimated to be 419±10 kJ mol$^{-1}$

Concentration and Composition Dependent Aggregation of Pluronic- and Poly-(2-Oxazolin)-Efavirenz Formulations in Biorelevant Media

Interactions of intestinal fluids with polymer excipients, drugs and their formulations are not fully understood. Here, diffusion ordered spectroscopy (DOSY) and nuclear Overhauser effect spectroscopy (NOESY), complemented by cryo-TEM were employed to address this. Efavirenz as model drug, the triblock copolymers Pluronic F-127 (PF127) and poly(2-oxazolin) based pMeOx-b-pPrOzi-b-pMeOx (pOx/pOzi) and their respective formulations were studied in simulated fed-state intestinal fluid (FeSSIF). For the individual polymers, the bile interfering nature of PF127 was confirmed and pure pOx/pOzi was newly classified as non-interfering. A different and more complex behaviour was observed if EFV was involved. The formulations showed multi-facetted concentration and composition dependent aggregation. This demonstrates that separate evaluation of polymers or drugs in biorelevant media is not sufficient and their mixtures need to be carefully studied.<br /

Concentration and composition dependent aggregation of Pluronic- and Poly-(2-oxazolin)-Efavirenz formulations in biorelevant media.

Many drugs and drug candidates are poorly water-soluble. Intestinal fluids play an important role in their solubilization. However, the interactions of intestinal fluids with polymer excipients, drugs and their formulations are not fully understood. Here, diffusion ordered spectroscopy (DOSY) and nuclear Overhauser effect spectroscopy (NOESY), complemented by cryo-TEM were employed to address this. Efavirenz (EFV) as model drug, the triblock copolymers Pluronic® F-127 (PF127) and poly(2-oxazoline) based pMeOx-b-pPrOzi-b-pMeOx (pOx/pOzi) and their respective formulations were studied in simulated fed-state intestinal fluid (FeSSIF). For the individual polymers, the bile interfering nature of PF127 was confirmed and pure pOx/pOzi was newly classified as non-interfering. A different and more complex behaviour was however observed if EFV was involved. PF127/EFV formulations in FeSSIF showed concentration dependent aggregation with separate colloids at low formulation concentrations, a merging of individual particles at the solubility limit of EFV in FeSSIF and joint aggregates above this concentration. In the case of pOx/pOzi/EFV formulations, coincident diffusion coefficients for pOx/pOzi, lipids and EFV indicate joint aggregates across the studied concentration range. This demonstrates that separate evaluation of polymers and drugs in biorelevant media is not sufficient and their mixtures need to be studied to learn about concentration and composition dependent behaviour

Concentration and composition dependent aggregation of Pluronic- and Poly-(2-oxazolin)-Efavirenz Formulations in Biorelevant Media

Funding Information: We thank Matthias Gr?ne for helpful discussion and his support during data collection. M. M. L?btow kindly provided the pOx/pOzi EFV formulation. We gratefully acknowledge funding by the German Research Foundation (DFG) project number 440955393. Financial support from the Verband der Chemischen Industrie (VCI) in the form of a material cost allowance as well as from the University of W?rzburg in the form of a CNC PostDoc Plus allowance (financed from Emil-Hilb-funds) is also acknowledged (A.?C.P.). Electron microscopic data were acquired at the cryo-EM facility in W?rzburg (DFG Equipment Grant INST 93/903-1 FUGG). Raw experimental data is available through the repository Zenodo via https://doi.org/10.5281/zenodo.5136465. Funding Information: We thank Matthias Grüne for helpful discussion and his support during data collection. M. M. Lübtow kindly provided the pOx/pOzi EFV formulation. We gratefully acknowledge funding by the German Research Foundation (DFG) project number 440955393. Financial support from the Verband der Chemischen Industrie (VCI) in the form of a material cost allowance as well as from the University of Würzburg in the form of a CNC PostDoc Plus allowance (financed from Emil-Hilb-funds) is also acknowledged (A.‐C.P.). Electron microscopic data were acquired at the cryo-EM facility in Würzburg (DFG Equipment Grant INST 93/903-1 FUGG). Raw experimental data is available through the repository Zenodo via https://doi.org/10.5281/zenodo.5136465 . Publisher Copyright: © 2021 The AuthorsMany drugs and drug candidates are poorly water-soluble. Intestinal fluids play an important role in their solubilization. However, the interactions of intestinal fluids with polymer excipients, drugs and their formulations are not fully understood. Here, diffusion ordered spectroscopy (DOSY) and nuclear Overhauser effect spectroscopy (NOESY), complemented by cryo-TEM were employed to address this. Efavirenz (EFV) as model drug, the triblock copolymers Pluronic® F-127 (PF127) and poly(2-oxazoline) based pMeOx-b-pPrOzi-b-pMeOx (pOx/pOzi) and their respective formulations were studied in simulated fed-state intestinal fluid (FeSSIF). For the individual polymers, the bile interfering nature of PF127 was confirmed and pure pOx/pOzi was newly classified as non-interfering. A different and more complex behaviour was however observed if EFV was involved. PF127/EFV formulations in FeSSIF showed concentration dependent aggregation with separate colloids at low formulation concentrations, a merging of individual particles at the solubility limit of EFV in FeSSIF and joint aggregates above this concentration. In the case of pOx/pOzi/EFV formulations, coincident diffusion coefficients for pOx/pOzi, lipids and EFV indicate joint aggregates across the studied concentration range. This demonstrates that separate evaluation of polymers and drugs in biorelevant media is not sufficient and their mixtures need to be studied to learn about concentration and composition dependent behaviour.Many drugs and drug candidates are poorly water-soluble. Intestinal fluids play an important role in their solubilization. However, the interactions of intestinal fluids with polymer excipients, drugs and their for-mulations are not fully understood. Here, diffusion ordered spectroscopy (DOSY) and nuclear Overhauser effect spectroscopy (NOESY), complemented by cryo-TEM were employed to address this. Efavirenz (EFV) as model drug, the triblock copolymers Pluronic (R) F-127 (PF127) and poly(2-oxazoline) based pMeOx-b-pPrOzi-b-pMeOx (pOx/pOzi) and their respective formulations were studied in simulated fed-state intestinal fluid (FeSSIF). For the individual polymers, the bile interfering nature of PF127 was confirmed and pure pOx/pOzi was newly classified as non-interfering. A different and more complex behaviour was however observed if EFV was involved. PF127/EFV formulations in FeSSIF showed concentration depen-dent aggregation with separate colloids at low formulation concentrations, a merging of individual par-ticles at the solubility limit of EFV in FeSSIF and joint aggregates above this concentration. In the case of pOx/pOzi/EFV formulations, coincident diffusion coefficients for pOx/pOzi, lipids and EFV indicate joint aggregates across the studied concentration range. This demonstrates that separate evaluation of poly-mers and drugs in biorelevant media is not sufficient and their mixtures need to be studied to learn about concentration and composition dependent behaviour. (C) 2021 The Authors. Published by Elsevier Inc.Peer reviewe