Temperature dependent vibrational dynamics in crystalline para-terphenyl under high pressure

► High-resolution homogeneously broadened IR bands under simultaneous high-pressure and low-temperature. ► High-pressure measurements examined the effect of conformation changes on vibrational dynamics. ► Increased planarity of p-terphenyl under pressure decreased couplings of out-of-plane vibrations. ► Increased intramolecular interactions at high-pressure yield increased couplings of in-plane vibrations.