4-Aminopyridine 4-aminopyridine Cambridge Structural Databases Chlorine compounds Cobalt Cobalt complexes Cobalt compounds Complexation Coordination reactions Crystal structure Dimers Hirshfeld analysis Horizontal displacements Hydrogen bonds Ligands Pyridine Single crystal X-ray diffraction analysis Single crystal x-ray diffraction Single crystals Supramolecular chemistry Supramolecular structure Surface analysis X ray diffraction analysis cobalt complex crystal structure fingerprint plots pyridine-pyridine dimer π-π stacking