functional and 6-31G(d,p) basis set. Vertical excited state calculations were performed within the Tamm-Dancoff approximation (TDA) at the same level of theory as the ground state optimization. Optimized singlet excited states were obtained using TDA-PBE0/6-31G(d,p) in the gas phase. The attachment/detachment formalism was employed to calculate 𝛷s values for each of the excited states using the NANCY package, 21 with a value of 0.00 -0.32 representing a pure charge transfer state (CT), 0.33 -0.66 representing a mixed state, coined Mix, and 0.67 -1.00 representing a locally excited state (LE). Molecular orbitals were visualized using GaussView 6.0. Intensity data were collected at 173 K, using either just ω steps or both ω and φ steps, accumulating area detector images spanning at least a hemisphere of reciprocal space. Data for both compounds were collected using CrystalClear and processed (including correction for Lorentz, polarization and absorption) using CrysAlisPro. Structures were solved by direct methods (SIR2011) and refined by fullmatrix least-squares against F 2 (SHELXL-2018/3). Non-hydrogen atoms were refined anisotropically, and hydrogen atoms were refined using a riding model. Both structures structure showed void space containing poorly ordered solvent molecules (4TABN1: 727 Å 3 , toluene; 5TABN2: 1068 Å 3 , acetone) and the SQUEEZE 27 routine implemented in PLATON was used to remove the contribution to the diffraction pattern of the electron density in the void spaces. All calculations except SQUEEZE were performed using the CrystalStructure 29 interface. Selected crystallographic data are presented in Table . CCDC 2218300-2218301 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/structures. and 5TABN2 both possess highly twisted conformations in the solid state (Figure ). There are no intermolecular π-stacking interactions in the unit cell.