Furthermore, the presence of multiple reflections where just one is expected (e.g., at 15.4° in 2θ, corresponding to the (006) plane; Figure ) suggests the coexistence of at least two phases with different interlayer spacing. Extending the ligand exchange incubation time of bza and amch led to samples exhibiting poor crystallinity and no increase in LEY. Analysis by DART-MS also reveals non-negligible signal intensity attributable to the presence of ba in these samples, consistent with only partial exchange. We posit that the larger footprint of bza and amch on the surface of the ZnSe slab limits the extent to which these ligands can substitute ba. Between these two ligands, the planarity of the aromatic bza enables somewhat greater LEY for this ligand compared to the non-planar amch. Models of fully substituted ZnSe(bza) and ZnSe(amch) exhibit different extents of distortion in the ZnSe layer (Figure ). The Zn-Zn distance within the basal plane, a descriptor of the distance between ligands on the plane surface, increases by 9% for both models. Changes in Zn-Se-Zn bond angles deviate an average of 4% in ZnSe(bza) from those of ZnSe(ba); the corresponding deviation in ZnSe(amch) is a much greater 14%. These models are consistent with the observation of low LEY in ZnSe(bza) and lower LEY in ZnSe(amch), and illustrate that unfavourable basal plane distortion prevents complete transformation of ZnSe(ba) to pure ZnSe(bza) or ZnSe(amch).