Excited State Dynamics of the Carbazolato‐Carbene Chromium(III) Complex [Cr(bimca) ₂ ] ⁺

Efficient near‐infrared spin‐flip luminescence from molecular chromium(III) complexes is challenging to achieve due to the presence of various nonradiative excited state decay pathways. General design principles for efficient spin‐flip emission, especially in the near‐infrared spectral region, are not yet well established. Small structural modifications can unexpectedly suppress spin‐flip luminescence completely, as found for the amido/carbene complex [Cr(bimca) 2 ] + (bimca – = 1,8‐bis(3‐methylimidazolin‐2‐ylidene‐1‐yl)carbazolido). To better understand these apparently unforeseeable effects, static and time‐resolved spectroscopy with quantum chemical calculations is combined to elucidate the excited state dynamics of [Cr(bimca) 2 ] + . Weak high‐energy fluorescence is observed, yet low‐energy spin‐flip emission is not detected. In this particular N ‐heterocyclic carbene complex, efficient nonradiative decay via CH overtones of the carbene's N ‐methyl substituents impedes the spin‐flip phosphorescence.