The importance of spodium bonds, H-bonds and pi-stacking interactions in the solid state structures of four zinc complexes with tetradentate secondary diamine ligands

In this manuscript we report the preparation of four new zinc complexes, [{(mu-CH3COO)ZnL1}(2)Zn]center dot 2DMSO (1), [{(DMF)ZnL1(mu-CH3COO)(ZnLZn)-Zn-1(N-3)}]center dot 0.64DMSO center dot 0.36EtOH (2), [(mu-CH3COO)(2)Zn2L1](n)(3) and [(Zn2LCl2)-Cl-2] (4), and their characterization by elemental and spectral analyses, where H2L1 is 1,3-propanediylbis(iminomethylene)bis(4-chlorophenol) and H2L2 is 1,3-propanediylbis(iminomethylene)bis(6-methoxyphenol). The structures have been confirmed by single crystal X-ray diffraction analysis. The synthetic strategy for complexes 1 and 2 involves the use of drops of DMSO, which is essential to stabilize the crystals of 1 and 2, respectively, indicating the importance of DMSO in the stabilization of the complexes. A thorough DFT calculation using the quantum theory of atoms-in-molecules and the non-covalent interaction plot (NCI plot) indicates the formation of strong H-bonds, CH...pi and ancillary SpBs in complexes 1 and 2. DMSO has not been added during the synthesis of complexes 3 and 4, where no spodium bonds have been observed. Strong self-assembled (pi-pi stacked or H-bonded) dimers have been found in the solid state structures of 3 and 4.