Structure solution and refinement of Ni(PyC-m-NH 2 ) 2 was carried out using the program TOPAS 6.0. [ ] Reflections in the powder pattern were indexed by an iterative use of singular value decomposition to determine the unit cell and possible space group symmetries. [ ] More precise lattice parameters and the instrumental profile were determined by constrained Pawley refinement, [ ] applying the fundamental parameters approach [ ] along with Gaussian and Lorentzian strain and crystalline size broadening. The background was modeled by employing Chebychev polynomials of th order along with an additional Pseudo-Voigt peak. A zero error correction was used, and the Lorentz-Polarization factor was set to . for the Ge( ) monochromator. The crystal structure was solved by applying the global optimization method of simulated annealing in real space. [ ] The PyC-m-NH 2 molecules were defined as rigid bodies in point-for-site notation using the conformation of the Ni(PyC-m-NH 2 ) 2 crystal structure model in our library and allowed to translate and rotate freely. The obtained structure model was refined by the Rietveld method, with two isotropic atomic displacement parameters used for Ni and for the linker atoms respectively. A final refinement was performed with all parameters freed. Starting unit cell parameters for Ni(PyC-m-NH 2 ) 2 (H 2 O) 4 were determined by starting with the structure model for Ni(PyC) 2 (H 2 O) 4 , fixing the entire complex as a rigid body, and then running simulated annealing on the lattice parameters using reasonable bounds. The rest of the structure solution process was as described above.