Group 12 Metal Complexes of Semirigid 2,6-Pyridinediyl­bis(3-pyridinyl)­methanone: Role of Counteranions and Solvent in Product Formation

In
a series of nine group 12 metal complexes of 2,6-pyridine­diyl­bis­(3-pyridinyl)­methanone
(abbreviated as L), namely, [Cd­(L)2­Cl2] (1), [Cd­(L)2­(NO3)2]·3.5H2O (2), [Cd­(L)2­(H2O)2]­(NO3)2 (3), [Cd­(L)2­(H2O)2]­(ClO4)2·H2O (4), {[Cd­(L)­(H2O)2]­(ClO4)2·1.5H2O}∞ (5), {[Cd­(L)2­SO4­(H2O)]·2.8H2O}∞ (6), [Cd­(L)2­(CH3­CO2)2]∞ (7), [Zn­(L)2­(CH3­CO2)2]∞ (8), and [Hg­(L)2­(CH3­CO2)2]∞ (9), the semirigid multidentate ligand
L exhibits flexible ligation modes I–IV in response to the
cooperative effect of counteranions and solvent medium, leading to
mononuclear (1–4), helical-chain
(6), zigzag-chain (7), and 3D net (5) coordination motifs. The presence of the ancillary aqua
ligand is essential for the crystallization of 3 and 5 by addition of deionized water to an organic mixed-solvent
medium containing 2 and 4, respectively.
The acetate complexes 7 (Cd2+), 8 (Zn2+), and 9 (Hg2+) are isostructural.
Unconventional anion−π­(pyridine), CO···CO,
O­(NO3–/ClO4–)···CO, and cohesive nitrate···nitrate
interactions are manifested in supramolcular aggregations of the present
series of crystalline complexes.