Quantum tautomerization in porphycene and its isotopomers: Path-integral molecular dynamics simulations

Elucidating the Nuclear Quantum Dynamics of Intramolecular Double Hydrogen Transfer in Porphycene

“…In Figure 2a, we show the free energy profile projected on the two hydrogen transfer coordinates δ 1 and δ 2 defined in Figure 1 for the PIMD simulation at 290 K. As expected, the trans isomer is the most energetically stable and the free energy barrier for hydrogen transfer is around 2 k B T , in agreement with previous studies in which NQEs were also included. 32,33 For comparison, in the classical-nuclei ab initio molecular dynamics (MD) simulation at the same temperature, the hydrogen transfer reaction is a much rarer event with an effective barrier above 4 k B T , as shown in the Supporting Information.…”

Temperature dependence of the vibrational spectrum of porphycene: a qualitative failure of classical-nuclei molecular dynamics

“…These isotopologues have been the subject of previous experimental and theoretical work. 3,[30][31][32][33] Based on the linear response time-correlation formalism, we compute the vibrational density of states and infrared spectra in a wide temperature range for the different isotopologues. We analyze their similarities and differences and address the relevance of including anharmonic contributions and nuclear-quantum effects in their full-dimensional nature, especially focusing on the NH-stretch signal which is the most puzzling feature of the vibrational spectrum of this molecule.…”

Quantum localization/delocalization of muonium in the glycine–K+ complex

“…Alternatively, it has been reported that Mu can be localized in a very different region of the potential energy surface compared to hydrogen and deuterium cases due to multi-dimensional effects. In fact, it has been reported that Mu is sometimes localized around the saddle point region of the potential energy surface due to anomalously large zero-point energies at both reactant and product regions [16][17][18][19]. In this work, from a quantum mechanical point of view, we discuss localization/ delocalization of Mu in the simplest glycine-metal cation complex having an intramolecular proton-transfer pathway between amino group and carboxylic group.…”