The remarkable optical properties of mer-[Cr(ddpd)2] 3+14,25 inspired us to perform an in-depth optical characterization of mer-1, mer-2 and cisfac-[3] 3+ . All three complexes under investigation show intense absorptions in the UV to green spectral region (Figure ). The lowest energy transitions in this area have mainly metal-to-ligand charge transfer 4 MLCT(Moddpd) in mer-1 and mer-2, and ligand-to-metal charge transfer 4 LMCT(ddpdMo) character in cisfac- [3] 3+ according to TD-DFT calculations and charge transfer number analyses (Figure ). Higher-energy bands are of mixed ligand-centered ( 4 LC), ligand-to-ligand charge transfer ( 4 LLCT) and LMCT(XMo) character. CASSCF(7,12)-NEVPT2 calculations place the lowest-energy 4 A2 4 T2 transitions at 308, 423 and 452 nm for cisfac-[3] 3+ , mer-1 and mer-2, respectively. This reflects the decreasing ligand field splitting in this series in agreement with the spectrochemical series Br -< Cl -< pyridine (Figure -Figure ). In the experimental absorption spectra, these formally Laporteforbidden metal-centered transitions are masked by intense LC and charge-transfer bands. Concentrated solutions of mer-1, mer-2 and cisfac- [3] 3+ in d3-MeCN revealed two sets of weak absorption bands in the red and near-infrared (NIR) spectral region that we assign to the spinflip transitions 4 A2 2 T2 and 4 A2 2 T1/ 2 E, respectively, using CASSCF(7,12)-NEVPT2 calculations (Figure , Table , see SI for details). The strong spin-orbit coupling induced by heavy atoms such as Mo and Br lifts the spin selection rule rendering these formally spin-and Laporte-forbidden transitions relatively strong ( = 0.3-4.2 M -1 cm -1 ) and most intense in mer-2. The weakest spin-forbidden absorptions were found for cisfac- [3] 3+ because the Laporte rule applies more strongly in this case due to the higher local symmetry of the [MoN6] core. In contrast to the heteroleptic complexes, cisfac- [3] 3+ features a broad absorption band at 1200-1500 nm that we assign to a more strongly distorted state of 2 T1 parentage. Overall, the energies of the spin-forbidden transitions are hardly affected by the ligand environment. While CASSCF(7,12)-NEVPT2 calculations overestimate the absolute transition energies by ca. 2000-3000 cm -1 , they correctly reflect the higher spread of 2 T1/ 2 E states in cisfac- [3] 3+ compared to mer-1 and mer-2 (Figure ). For all complexes, the multi-reference calculations on the Franck-Condon geometry place a 2 T1 state at lowest energy. The calculations also predict a minor influence of the specific configuration of the ddpd ligands in [3] 3+ (cisfac, transfac or mer) on the energies of the doublet states (Figure ). There is, however, a notable shift of the two states of 2 E parentage to higher energy in the two facial isomers (Figure ).