Ionization of Decamethylmanganocene: Insights from the DFT-Assisted Laser Spectroscopy

Abstract

Metallocenes represent one of the most important classes of organometallics with wide prospects for practical use in various fields of chemistry, materials science, molecular electronics, and biomedicine. Many applications of these metal complexes are based on their ability to form molecular ions. We report the first results concerning the changes in the molecular and electronic structure of decamethylmanganocene, Cp*2Mn, upon ionization provided by the high-resolution mass-analyzed threshold ionization (MATI) spectroscopy supported by DFT calculations. The precise ionization energy of Cp*2Mn is determined as 5.349 ± 0.001 eV. The DFT modeling of the MATI spectrum shows that the main structural deformations accompanying the detachment of an electron consist in the elongation of the Mn-C bonds and a change in the Me out-of-plane bending angles. Surprisingly, the DFT calculations predict that most of the reduction in electron density (ED) upon ionization is associated with the hydrogen atoms of the substituents, despite the metal character of the ionized orbital. However, the ED difference isosurfaces reveal a complex mechanism of the charge redistribution involving also the carbon atoms of the molecule.

Effect of a single methyl substituent on the electronic structure of cobaltocene studied by computationally assisted MATI spectroscopy

“…Similarly, a nearly zero change in the metal QTAIM charge on going from a neutral sandwich molecule to a cation was calculated for nickelocene where the ionized orbital is also d xz,yz /p*. 97 On the other hand, in decamethylmanganocene, 45 bis(Z 6 -benzene)chromium, 59 and mixed sandwich complexes, 59 where an electron is detached from the non-bonding d z 2 orbital, the metal QTAIM charge increases by 0.15-0.20 a.u.…”

“…These combinations of the GGA (BPW91) or hybrid (B3PW91) functionals and triple-z split valence basis sets have demonstrated earlier good performance when modelling the MATI spectra of bisarene complexes, [46][47][48][49][50][51][52][53][54][55][56][57][58] mixed sandwiches 59 and decamethylmanganocene. 45 The 10% exact exchange TPSSh meta-type functional 69 produced high-quality results for transition-metal systems. 70 To testify the influence of diffusion functions included to the basis set as well as the role of dispersion corrections additional computations were carried out with the 6-311+G(d,p) basis set and D3 Grimme's dispersion.…”

“…DFT-supported MATI spectroscopy appeared to represent a powerful instrument for studying not only accurate ionization and vibrational energies of metallocenes, 28,45 bisarene complexes [46][47][48][49][50][51][52][53][54][55][56][57][58] or mixed sandwich systems 59 but also structural behaviors of these organometallics on ionization. 28,45,59 This opens new opportunities for investigations of substituent effects in sandwich compounds. 60 Methylation of the cobaltocene Cp rings tunes its redox properties.…”

Vibronic and Cationic Features of 2-Fluorobenzonitrile and 3-Fluorobenzonitrile Studied by REMPI and MATI Spectroscopy and Franck-Condon Simulations

“…Kwon's group built a vacuum ultraviolet single photon MATI system to study many cationic vibrational features [22][23][24][25][26][27][28][29]. Tzeng's group and Ketkov's group used two-color MATI to study the cationic spectra of many benzene derivatives and sandwich molecules [30][31][32][33][34][35][36]. Wright's group used ZEKE technology to research cationic vibrational features of many halogenated benzene and their derivatives [37][38][39][40][41][42].…”

Vibronic and Cationic Features of 2-Fluorobenzonitrile and 3-Fluorobenzonitrile Studied by REMPI and MATI Spectroscopy and Franck–Condon Simulations

“…Kwon’s group built a vacuum ultraviolet single photon MATI system to study many cationic vibrational features [ 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 ]. Tzeng’s group and Ketkov’s group used two-color MATI to study the cationic spectra of many benzene derivatives and sandwich molecules [ 30 , 31 , 32 , 33 , 34 , 35 , 36 ]. Wright’s group used ZEKE technology to research cationic vibrational features of many halogenated benzene and their derivatives [ 37 , 38 , 39 , 40 , 41 , 42 ].…”