Four polymorphs of bis(phthalocyaninato)neodymium(III) were reproducibly and selectively crystallized by the slow evaporation of saturated solutions. The obtained phase depended on the initial oxidation state of the NdPc<sub>2</sub> molecule and the choice of solvent. Single-crystal X-ray diffraction studies were used to correct previous mis-identifications and provide missing coordinates for the γ-phase as well as a detailed comparison of molecular structure and crystal packing in all NdPc<sub>2</sub> polymorphs. The primary feature in all phases is columnar stacking based on parallel π π interactions, with a variety of slip angles within those stacks as well as secondary interactions between them. Chemical redox and acid-base titrations, performed on re-dissolved crystals demonstrate that NdPc<sub>2</sub><sup>+</sup> and NdPc<sub>2</sub><sup>-</sup> are easily obtained through weak oxidizing and reducing agents, respectively. Additionally, we show that the protonated form of the NdPc<sub>2</sub><sup>-</sup> complex has a nearly identical UV-Vis spectra to that of neutral NdPc<sub>2</sub>, explaining some of the confusion over chemical composition in previously published literature.<br>
The influence of secondary interactions on the [N‐I‐N]+ halogen bond
