Pressure-induced Jahn-Teller axis switching in Cu(pyz)F$_2$(H$_2$O)$_2$?

We employed infrared spectroscopy along with complementary lattice dynamics and spin density calculations to investigate local structure and magnetism through the series of pressure-driven transitions in Cu(pyz)F$_2$(H$_2$O)$_2$. Rather than frequency shifts that dovetail with the recently proposed pressure-induced Jahn-Teller switching model, we overall mode hardening, particularly in the Cu--OH$_2$ bending mode. We combine these findings with a reanalysis of the crystal structure to reveal the series of pressure-induced transitions as a combination of $a$-axis rotation, $c$-directed compression that acts to weaken O-H...F hydrogen bonds, and pyrazine ring buckling. The magnetic dimensionality crossover can be understood in terms of changes in magnetic orbital overlap.