A Molecular Helix: Self-Assembly of Coordination Polymers from d10 Metal Ions and 1,10-Phenanthroline-5,6-dione (pdon) with the Bridges of SCN- and Cl- Anions

Novel complexes of (half)-filled d-configurations, including [Zn(pdon)(SCN)(mu-Cl)(H2O)](n) (1), [Cd-2(pdon)(2)(mu(1,3)-SCN)(4)](n) (2), [Hg(pdon)(2)Cl-2] (3), and [Mn(pdon)(2)(SCN)(2)] (4) (pdon = 1,10-phenanthroline-5,6-dione), were synthesized and structurally characterized by single crystal X-ray diffraction. Self-assembly behaviors of these metal ions with anions are essentially different, although some of them are elements of the same group. Various supramolecular interactions of H-bonding, pi center dot center dot center dot pi stacking, and C-X center dot center dot center dot pi (X = H, O, and S) are observed in the structures. In 1, central Zn2+ cations are connected to form an infinite one-dimensional (1D) zigzag chain by bridged Cl- and further extended to two-dimensional layers via weak interactions. Complex 2 consists of dinuclear units doubly bridged by two end-to-end (EE) SCN- anions and linked to 1D molecular helix along the b-axis with a long pitch of 13.077 angstrom. The helix displays racemic mixtures in the crystal. Complexes 3 and 4 are six-coordinated with distorted octahedron geometry. pdon serves as a terminal ligand in complexes. Spectroscopic and electrochemical properties of pdon and the complexes are studied in dimethyl sulfoxide (DMSO) solution at room temperature. Circular dichroism (CD) spectral results suggest that there is phenomenon of spontaneous resolution in the DMSO solution for the spiral structure 2.