Orthogonal non-covalent binding forces in solid state supramolecular herringbone-shaped "interlocked dimers"....

The crystal structures of [(ppy)Pd(mu-pz)](2) (ppy = 2-(2-pyridyl)phenyl, pz = pyrazol-1-yl) (1) and two different solvatomorphs of it, [(ppy)Pd(mu-pz)](2) x 1/2 CH(2)Cl(2) (2) and [(ppy)Pd(mu-pz)](2) x 1/2 CHCl(3) (3) have been elucidated by powder (1 and 2) and single crystal (3) X-ray diffraction. In all of them two molecules fit together following a very similar pattern forming a "dimer". All neutral dinuclear square-planar complexes having mu-pz or related bridges and planar aromatic ligands completing the coordination spheres found in the CSD show a similar arrangement to those observed in compounds 1-3, consisting of "interlocked dimers" following a herringbone-like pattern. A DFT study reveals the simultaneous action of pi,pi- and T-stacking interactions occurring as two sets of orthogonally oriented binding forces, as well as anagostic bonds overlapped with the latter.