Quantum-Mechanical Study of Lead Coordination in Sulfur-Rich Proteins: Mode and Structure Recognition in UV Resonance Raman Spectra

Abstract

Resonance Raman spectra are computed applying the weighted gradient methodology with CIS and DFT gradients to determine the characteristic spectral patterns for Hg(II) and Pb(II) loaded sulfur-rich proteins while excited to a characteristic LMCT electronic transition band. A framework of structure-spectrum relationships is established to assess lead coordination modes via vibrational spectroscopy. Illustrative calculations on Hg(II) complexes agree with experimental data demonstrating reliability and accuracy of the applied methodology. In contrast to Hg(II) complexes, a unique 3-center-4-electron hypervalent CβH---S interaction present in lead-sulfur complexes was established and suggested to play a key role in the strong preference for lead versus other metal ions in lead specific proteins such as PbrR691. The characteristic Pb-S symmetric stretching bands, predicted without additional refinements such as scaling of a force field or frequencies, are found around 238 cm−1 for 3-coordinated lead-sulfur domains, and around 228 cm−1 for 4-coordinated lead-sulfur domains. These results present an experimental challenge for clear detection of lead coordination via solely UVRR spectroscopy. In addition to predicted UVRR spectra, UVRR excitation profiles for relevant vibrational bands of lead-sulfur domains are presented.

Decreased surface defects and non-radiative recombination via the passivation of the halide perovskite film by 2-thiophenecarboxylic acid in triple-cation perovskite solar cells

“…2a, one new weak Raman band at 225 cm −1 can be observed, which is related to Pb–S stretching in comparison with unpassivated perovskite surface. 32 This band is proof of the Lewis adduct formation between the S atoms in 2TiCOOH and the uncoordinated Pb atoms in the perovskite film. The assignment of the broadband ranging from 271 to 310 cm −1 represents methylammonium (MA) torsional modes, which is predict the tetragonal structure.…”

High‐Mobility p‐Type Organic Semiconducting Interlayer Enhancing Efficiency and Stability of Perovskite Solar Cells

“…Raman spectroscopy is further employed to analyze the interaction between BDTS‐2DPP and perovskite (Figure c). One new weak Raman band at 226 cm −1 is assigned to PbS stretching, which is a direct evidence of the formation of Lewis adduct between the under‐coordinated Pb in perovskite film and S in BDTS‐2DPP . It should be noted that the samples for FTIR and Raman spectra measurements were prepared at room temperature, indicating that the passivation of perovskite by BDTS‐2DPP is still efficient without thermal treatment.…”