Abstract
In a series of nine group 12 metal complexes of 2,6-pyridinediylbis(3-pyridinyl)-methanone (abbreviated as L), namely, [Cd(L)(2)Cl-2] (1), [Cd(L)(2)(NO3)(2)]center dot 3.5H(2)O (2), [Cd(L)(2)-(H2O)(2)](NO3)(2) (3), [Cd(L)(2)(H2O)(2)](ClO4)(2)center dot H2O (4), {[C(L)(H2O)(2)](ClO4)(2)center dot 1.5H(2)O}(infinity) (5), {[Cd(L)(2)SO4(H2O)]center dot 2.8H(2)O}(infinity) (6), [Cd(L)(2)(CH3CO2)(2)](infinity) (7), [zn(L)(2)(CH3CO2)(2)](infinity) (8), and [Hg(L)(2)(CH3CO2)(2)](infinity) (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-pi(pyridine), C=O center dot center dot center dot C=O, O(NO3-/ClO4-)center dot center dot center dot C=O, and cohesive nitrate center dot center dot center dot nitrate interactions are manifested in supramolcular aggregations of the present series of crystalline complexes.