“…[23,24] As an element-specific technique,X -ray spectroscopy is apowerful tool to probe the electronic structure of the metal site and surrounding ligands.With the recent advent of X-ray free electron laser (XFEL) facilities with high flux and at emporal resolution better than 30 fs, [25] it has become possible to identify the nature of the excited states directly. [10,[26][27][28][29][30][31][32] In these studies,t he oxidation state,s pin, and charge-transfer character of the molecular state were identified by modeling the measured time-resolved spectra with al inear combination of measured or calculated static reference spectra. Here,w eu se ultrafast K a and K b X-ray emission spectroscopy (XES) to investigate the excited-state dynamics of one of the recently introduced Fe II carbene complexes,F e II (bpy)(btz) 2 (PF 6 ) 2 [btz = 4,4'-bis(1,2,3-triazol-5-ylidene)] with significantly altered photophysics compared to prototype polypyridyl Fe II complexes such as Fe II (bpy) 3 (Figure 1).…”