To gain insight into the nature of the electronic transitions underlying the absorption bands at the molecular level, timedependent density functional theory (TDDFT) calculations using the CAM-B3LYP range-separated functional were performed considering the first 40 electronic transitions. The calculated vertical electronic transitions for the anthranilates obtained for the S0 geometry match well with the experimentally observed photophysical data (Figures and). The strong absorption peaks seen in the visible region are calculated to result from intraligand charge transfer (ILCT) transitions, i.e., S1, S2, without the contribution ). For all four complexes in degassed toluene at room temperature, intense blue luminescence could be observed following excitation at absorption maximum wavelengths, i.e. 336 nm (for 1) or 357 nm (for 2-4). As in the UV-Vis absorption spectra, the photoluminescence maxima vary as the ligand is modified (i.e., 407, 418, 460 and 455 nm for 1, 2, 3 and 4, respectively), clearly showing the merits of the ligand modifications in photophysical behaviour (Figure , bottom). In toluene, all compounds feature a large Stokes shift, ranging from 4100-6200 cm -1 , with almost no overlap between absorption and emission. In the condensed phase, following excitation at 300 nm, all compounds exhibit intense photoluminescence, with the bands shifted to 469 -503 nm, corresponding to green emission (Figure ). The fluorescence lifetimes of 1-4 are in the range of 3.7-8.1 ns (Table and Figure ), which indicates quantum-mechanically allowed transitions. The emission wavelength in the solid is practically independent of the composition of the compound, which contrasts with the abovementioned emission behaviour in solution. Compounds 1-3, both in the solid state and solution display moderate to high photoluminescence quantum yield (PLQY) (Table ). Strikingly, in the condensed phase, the ethylaluminium derivative [(Ph-anth)AlEt]4 (4) demonstrates PLQY around unity, which, to our knowledge, is unprecedented for aluminium complexes. It is worth noting that while the a recently reported dinuclear dimethylaluminium β-oxo-δdiimine derivative achieved PLQY of 1 in a toluene solution, in the solid PLQY was reduced to 0.5-0.6 (depending whether single-crystal or powdered). Remarkably, fluorescence lifetime values for the investigated anthranilates follow a similar trend to PLQY (Table ). In the solid state, much faster non-radiative decay for 1 can be rationalized by vibrational quenching, namely high energy vibration of the N-H bond. Replacing H by a Me group (as in 2) nearly 4-fold reduces the non-radiative constant (knr), and the remaining quenching can be attributed to the folding of the parent macrocycle as arises from the optimized geometry for the S1 state of the tetramer (Figure ). For the methylaluminium derivative 3, the moderate luminescent performance arises from the speed of nonradiative energy loss through chelate ring fracture. However, when switching to the ethylaluminium derivative 4, the molecular structure is rigidified by numerous C-H•••π interactions which preserve the geometry deformation, resulting in complete blockage of the non-radiative decay pathway (knr drops to 0 s -1 ) and opening of the radiative channel. Thus, for 4 the aggregation induces stabilization of the excited states and enhances emission properties.