To compare the results of our solid-state calculations to the gas phase ansatz, we also calculated the spin-phonon coupling coefficients and magnetic relaxation rates for a gas-phase molecule of 1. For this, we optimise the geometry and calculate the vibrational modes of 1, with Dy replaced by Y, with Gaussian09d 43 using PBE-D3, the Stuttgart RSC 1997 ECP for Y and the cc-pVDZ basis sets for all other atoms. We found a root-mean-square-deviation (RMSD) for all the atomic positions compared to the experimental crystal structure of 0.13 Å.