Exploring the Properties of H₂O@C₆₀ with the Local Second‐Order Møller‐Plesset Perturbation Theory: Blue or Red Shift in C₆₀ and H₂O Fundamentals to Expect?

Abstract

The main structural, energetic and vibrational properties of H2O@C60 were computationally investigated using the density‐fitting local second‐order Møller–Plesset (DF‐LMP2) theory. Two low‐energy isomers, of C2 and C1 symmetry, were initially considered and only the latter one was identified as a true minimum with the lowest energy. The energy difference between these isomers was rather small (only 0.002 kcal/mol) and the respective interaction energy of any of the H2O@C60 isomers was −14.26 kcal/mol. These isomers were structurally similar having larger values of O−H bond lengths and angles by 0.0082 Å and 0.9 degrees, respectively, compared to a free water molecule. The calculated harmonic IR spectrum of the C1 isomer was characterized by: a) the presence of water frustrated translation frequencies at 90.5‐94.3 cm−1; b) the red shift in frequency of the first radial C60 mode (by −(1.8–2.7) cm−1) and the blue shift for the other three IR‐active C60 modes (by up to 2.2 cm−1); c) the red shift in H2O fundamentals by −19.2, −110.4 and −123.8 cm−1 for the bending, symmetric and antisymmetric mode, respectively, in excellent agreement with recently reported experimental results. The zero‐point energy contributed only 0.15 kcal/mol to the ZPE‐corrected value of H2O@C60 interaction energy which became now equal to −14.11 kcal/mol.

Improved Estimates of Host‐Guest Interaction Energies for Endohedral Fullerenes Containing Rare Gas Atoms, Small Molecules, and Cations

“…The change in the stretching frequency of 172.2 cm −1 for HF@C 60 is in excellent agreement with the experimental value (170.5 cm −1 ) [14] as well as with the earlier theoretical estimates (174.0 cm −1 ) [36] . The redshift in symmetric (94.8 cm −1 ) and asymmetric (107.8 cm −1 ) modes for H 2 O is in reasonably good agreement with the ones reported by Dolgonos [67] (110.4 cm −1 and 123.8 cm −1 , respectively). For the NH 3 molecule, Mallick et al.…”

Behavior of HF and (HF)2 inside a fullerene cage: An in silico study using different density functionals

“…The hydrogen bonding interaction between two HF molecules inside carbon nanotube was reported by Roztoczynska et al [42] The effect of confinement on hydrogen bonds is still debatable. The hydrogen bonding interaction present in XH⋯Y type of systems leads to red shift, blue shift, or even no shift depending upon the nature of X and Y as reported by Joseph et al [43] The harmonic frequencies are blue shifted for HF, H 2 O, NH 3 , and CH 4 inside C 60 as revealed by Shameema et al [44] In the case of fullerenes, the vibrational stretching frequencies of the guest molecules are reported to be either blue shifted or red shifted both experimentally and theoretically [18, 40, 44–48].…”