Group 12 Metal Complexes of Semirigid 2,6-Pyridinediylbis(3-pyridinyl)methanone:
Role of Counteranions and Solvent in Product Formation
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Abstract
In
a series of nine group 12 metal complexes of 2,6-pyridinediylbis(3-pyridinyl)methanone
(abbreviated as L), namely, [Cd(L)<sub>2</sub>Cl<sub>2</sub>] (<b>1</b>), [Cd(L)<sub>2</sub>(NO<sub>3</sub>)<sub>2</sub>]·3.5H<sub>2</sub>O (<b>2</b>), [Cd(L)<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub>](NO<sub>3</sub>)<sub>2</sub> (<b>3</b>), [Cd(L)<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub>](ClO<sub>4</sub>)<sub>2</sub>·H<sub>2</sub>O (<b>4</b>), {[Cd(L)(H<sub>2</sub>O)<sub>2</sub>](ClO<sub>4</sub>)<sub>2</sub>·1.5H<sub>2</sub>O}<sub>∞</sub> (<b>5</b>), {[Cd(L)<sub>2</sub>SO<sub>4</sub>(H<sub>2</sub>O)]·2.8H<sub>2</sub>O}<sub>∞</sub> (<b>6</b>), [Cd(L)<sub>2</sub>(CH<sub>3</sub>CO<sub>2</sub>)<sub>2</sub>]<sub>∞</sub> (<b>7</b>), [Zn(L)<sub>2</sub>(CH<sub>3</sub>CO<sub>2</sub>)<sub>2</sub>]<sub>∞</sub> (<b>8</b>), and [Hg(L)<sub>2</sub>(CH<sub>3</sub>CO<sub>2</sub>)<sub>2</sub>]<sub>∞</sub> (<b>9</b>), 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 (<b>1</b>–<b>4</b>), helical-chain
(<b>6</b>), zigzag-chain (<b>7</b>), and 3D net (<b>5</b>) coordination motifs. The presence of the ancillary aqua
ligand is essential for the crystallization of <b>3</b> and <b>5</b> by addition of deionized water to an organic mixed-solvent
medium containing <b>2</b> and <b>4</b>, respectively.
The acetate complexes <b>7</b> (Cd<sup>2+</sup>), <b>8</b> (Zn<sup>2+</sup>), and <b>9</b> (Hg<sup>2+</sup>) are isostructural.
Unconventional anion−π(pyridine), CO···CO,
O(NO<sub>3</sub><sup>–</sup>/ClO<sub>4</sub><sup>–</sup>)···CO, and cohesive nitrate···nitrate
interactions are manifested in supramolcular aggregations of the present
series of crystalline complexes