The output of a Ti:Sapphire oscillator/regenerative amplifier system (Coherent Astrella, 800 nm, 1 kHz, 35 fs, 3.6 mJ/pulse) was used to pump a commercial OPA system (Light Conversion, TOPAS Prime) to generate tunable near-IR signal (1.2-1.7 μm) and idler (1.7-2.4 μm) pulses. The signal and idler beams were then mixed in a home-built difference frequency generation (DFG) set up with a type I AgGaS2 crystal to generate tunable mid-infrared pulses between 3 to 7 μm (>25 μJ/pulse, >200 cm -1 bandwidth, 80-100 fs pulse durations). To collect 2D spectra for Re(CO)3(CH3CN)3 + ions, the laser center frequency was set to around 2050 cm -1 with pulse energies ~35 μJ/pulse. The DFG output was sent to a mid-infrared acousto-optic pulse shaper (PhaseTech, Quickshape+) and shaped into a train of four pulses with desired delay, phase, and rotating frame frequency. Dispersion and Bragg corrections were applied to compress the pulse in time and optimize output power. The amplitude of the acoustic wave was reduced to avoid signal saturation, and approximately 3 µJ/pulse train of energy entered the ion trap. For protonated caffeine, the DFG output was tuned to 1750 cm -1 with pulse energies ~27 μJ/pulse. The maximum output from the shaper at this frequency range was ~ 9 μJ/pulse. The full power was used to interact with protonated caffeine due to its smaller IR response compared to the metal carbonyl species.