Analysis of the Electronic Structure of Aqueous Urea and Its Derivatives: A Systematic Soft X‐Ray–TD‐DFT Approach

Abstract

Soft X-ray emission, absorption, and resonant inelastic scattering experiments have been conducted at the nitrogen K-edge of urea and its derivatives in aqueous solutions and compared with density functional theory and time-dependent density functional theory calculations. This comprehensive study provides detailed information on the occupied and unoccupied molecular orbitals of urea, thiourea, acetamide, dimethylurea and biuret at valence levels. By identifying the electronic transitions that contribute to the experimental spectral features the energy gap between the highest occupied and the lowest unoccupied molecular orbital of each molecule is determined. Moreover, a theoretical approach is introduced to simulate resonant inelastic X-ray scattering spectra by adding an extra electron to the lowest unoccupied molecular orbital mimicking the real initial state of the core electron absorption before the subsequent relaxation process.

Soft X-ray Absorption Spectroscopy of Aqueous Solutions Using a Table-Top Femtosecond Soft X-ray Source

“…These values are in line with previously reported electron-energy loss spectra on solid urea 43 and partial fluorescence yield XAS measurements of aqueous urea. 44 For aqueous NaNO 3 , we observe a narrow 1s−π* transition at 405.0 eV at the N K-edge and a broad 1sσ* transition centered at 415 eV (fwhm ≈10 eV), in agreement with previously reported data from a total electron yield XAS study on aqueous NaNO 3 . 45 Additionally, the absorption spectrum of CaCl 2 is composed of the L 3 ,L 2 -transitions at 350.5 and 353.6 eV, with relative absorption strengths in good agreement with results reported on solid CaCl 2 •H 2 O.…”

“…The nitrogen K-edge spectrum of urea is dominated by a relatively strong pre-edge feature at 402.6 eV, followed by a main-edge transition located at 403.7 eV and two postedge peaks that can be observed at 408.6 and 412.2 eV. These values are in line with previously reported electron-energy loss spectra on solid urea and partial fluorescence yield XAS measurements of aqueous urea . For aqueous NaNO 3 , we observe a narrow 1s−π* transition at 405.0 eV at the N K-edge and a broad 1s-σ* transition centered at 415 eV (fwhm ≈10 eV), in agreement with previously reported data from a total electron yield XAS study on aqueous NaNO 3 .…”

Solar light‐assisted rod‐shaped CPTF @ FACC photocatalyst: An efficient platform for oxygenation reactions and coenzymes regeneration

“…Due to this, excited electrons easily migrate to NAD + /NADP + via Rh complex and efficiently regenerate NADH/NADPH coenzyme. This mechanism theoretically confirms the presence of Z‐scheme nature 63‐66 …”

Combined Vibrational Spectroscopic and Quantum Chemical Investigations of 1,8-diaminooctane

“…The HOMO-LUMO energy gap (∆ ) value of 1,8-diaminooctane calculated as 6.18 eV. This value for Urea 6.72 eV in the literature [14]. So, 1,8-diaminooctane is very soft molecule and very stable than Urea molecule.…”