ChemInform Abstract: VIBRATIONAL SPECTRA OF SOME GROUP VB HALIDES PART 2, A RAMAN SPECTROSCOPIC STUDY OF HALOBISMUTHATE(III) AND HALOANTIMONATE(III) COMPLEXES IN HALOGEN ACID SOLUTIONS

Abstract

Die Raman‐Spektren der HBr‐ und HCl‐Lösungen von Bi(III) und Sb(III) werden aufgenommen und die bei verschiedenen Halogen‐Metall‐Verhältnissen gebildeten Spezies untersucht.

Ultrafast Solution-Phase Photophysical and Photochemical Dynamics of Hexaiodobismuthate(III), the Heart of Bismuth Halide Perovskite Solar Cells

“…Short-wavelength Δ A kinetic traces show modulations with a 121 cm –1 frequency (FFT) and a several picosecond decoherence lifetime (Figure c). These modulations can be assigned to the solute’s impulsive stimulated Raman scattering (ISRS) because they start at negative delay times as soon as excitation and probe pulses begin to temporally overlap and exhibit the frequency close to a 114 cm –1 a 1g Raman frequency of BiI 6 3– . , The long decoherence time also agrees with these modulations taking place in the BiI 6 3– electronic ground state. Different modulations with a frequency of ν 1 = 89 ± 2 cm –1 (FFT, 94 ± 12 cm –1 ; Figure S7 and Table S3) occur in-phase in the blue and red wings of the 625 nm Δ A band (from 535 to 625 and 760 nm; Figure d).…”

“…This rules out coherent vibrational motion taking place on the product PES because in this case the oscillations in the blue and red wings of the product absorption band should exhibit a sharp π-phase shift. , The constant phase of the oscillations suggests stepwise coherent population of the 3 π LMCT product state: coherent vibrational motion with a ∼92 cm –1 frequency (period, 360 fs) makes BiI 6 3– to revisit the coupling region between the 3 T 1u and 3 π LMCT states in an oscillatory, time-dependent fashion (Figure ). Tetragonal distortion and/or totally symmetric stretching are likely the motions involved in the 92 cm –1 reaction mode because the corresponding nuclear displacements, being Raman- and JT-active, are the earliest to occur following the excitation event and the observed frequency is close to the e g and a 1g frequencies in BiI 6 3– (96 and 114 cm –1 , , and the t 2g frequency is ∼2 times lower). It takes two approaches of the coupling zone for coherent transfer of the population into the 3 π LMCT, the first at ∼190 fs and the second at ∼550 fs; the oscillation maxima (∼4:1 ratio; Figure d) are related to the population fractions being transferred.…”

“…The 395 and 895 nm Δ A kinetic traces (symbols), their fits (red) with pump-probe CCF deconvolution (CCF fwhm, 125 and 100 fs), and the fit residuals (green, bottom), (a) and (b). In (c), several picosecond long oscillations (inset, the green curve represents the 395 nm residue and the red curve represents a damped cosine fit) begin at negative delay times, display the 121 cm –1 (FFT) frequency, which is close to a 114 cm –1 a 1g Raman frequency of BiI 6 3– , , and therefore are assigned to ISRS-induced wavepacket motion in the ground state BiI 6 3– . In­( d), the fits (red) to the fit residues (symbols) in the 535–620 nm blue (top) and 620–760 nm red (bottom) wings of the 625 nm Δ A band show modulations with ν 1 = 89 cm –1 and a decoherence time constant τ c 1 = 275 fs (blue) superimposed with fast-damped high-frequency modulations ( ν 2 = 317 cm –1 and a decoherence time constant τ c 2 = 55 fs, cyan).…”

“…The ground-state geometry of BiI 6 3– ,,, (as well as the other two halides, BiBr 6 3– and BiCl 6 3– ,,,− ) is considered to be of O h symmetry in the condensed phase, including room-temperature liquid solutions, on the basis of resonance Raman spectra, which exhibit only three Raman-active modes (t 2g , e g , and a 1g at 54, 96, and 114 cm –1 , respectively). , The asymmetry of the 96 cm –1 Raman band was attributed to a slight distortion of BiI 6 3– to C 4v due to the 6s 2 electron pair effect …”