Solvent-Dependent Assemblies
of Trinuclear Copper Cluster into Variable Frameworks Based on Mixed
Ligands of Polyalcohol Amines and Organic Carboxylates
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Abstract
A systematic investigation on solvent-dependent assembly
of trinuclear copper cluhster has resulted in eight related coordination
polymers: Cu<sub>3</sub>(teaH<sub>2</sub>)<sub>2</sub>(oba)<sub>2</sub>(MeOH)<sub>2</sub> (<b>1</b>), Cu<sub>3</sub>(teaH<sub>2</sub>)<sub>2</sub>(oba)<sub>2</sub>(EtOH)<sub>2</sub> (<b>2</b>),
Cu<sub>3</sub>(teaH<sub>2</sub>)<sub>2</sub>(oba)<sub>2</sub>·(<i>n</i>-PrOH) (<b>3</b>), Cu<sub>3</sub>(teaH<sub>2</sub>)<sub>2</sub>(oba)<sub>2</sub> (<b>4</b>), Cu<sub>3</sub>(teaH<sub>2</sub>)<sub>2</sub>(oba)<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub> (<b>5</b>), Cu<sub>3</sub>(MedeaH)<sub>2</sub>(oba)<sub>2</sub>(MeOH)<sub>2</sub> (<b>6</b>), Cu[Cu<sub>3</sub>(Medea)<sub>2</sub>(oba)<sub>2</sub>]·(solvent)<sub><i>x</i></sub> (<b>7</b>), and [Cu<sub>3</sub>(MedeaH)<sub>2</sub>(oba)<sub>2</sub>(H<sub>2</sub>O)]·(<i>n</i>-PrOH)<sub>2</sub> (<b>8</b>) where oba = 4,4′-oxy-bis(benzoate), teaH<sub>3</sub> = triethanolamine, and MedeaH<sub>2</sub> = <i>N</i>-methyldiethanolamine. In <b>1</b>–<b>8</b>, the
trinuclear copper secondary building units (SBUs) (Cu<sub>3</sub>)
are furnished via the synergistic coordination of two organic ligands
with metal centers. The structures of <b>1</b>–<b>8</b> exhibit two types of extensible modes (mode <b>I</b> for <b>1</b>, <b>2</b>, <b>3</b>, <b>7</b>, <b>8</b> and mode <b>II</b> for <b>4</b>, <b>5</b>, <b>6</b>) to Cu<sub>3</sub> SBUs. Mode <b>I</b> assembles Cu<sub>3</sub> SBUs into the one-dimensional (1D) iron-chain-like
structure while mode <b>II</b> facilitates the two-dimensional
(2D) undulate rectangular (4, 4) connection. Compounds <b>1</b> and <b>2</b> feature zero-dimensional (0D) molecular structures
in which two strong hydrogen-bonding interactions extend its molecular
components into 1D chains. Compound <b>3</b> comprises 1D chains
interspersed by free solvent molecules, whereas compound <b>4</b> consists of 2D sheets excluding any solvent molecules. Compound <b>5</b> is also made up of 0D molecular structures but uses two
classic hydrogen-bonding interactions to form its 2D supramolecular
connection. Compound <b>6</b> has a 2D network similar to <b>4</b>. Compound <b>7</b> shows an unusual three-dimensional
(3D) microporous framework in which a 1D chain is further assembled
by extra Cu<sup>II</sup> ions. Compound <b>8</b> provides 1D
solvated structures with the voids occupied by lattice solvent molecules.
The coordination ability of solvent molecules has been established
for the underlying factor behind the different assemblies of compounds <b>1</b>–<b>8</b>. Compounds <b>5</b> and <b>8</b> from an alcohol/H<sub>2</sub>O mixture indicate a behavior
of selective coordination to the available coordination points of
metal centers. The gas sorption property of compound <b>7</b> has also been investigated
