Solvent-Dependent Assemblies of Trinuclear Copper Cluster into Variable Frameworks Based on Mixed Ligands of Polyalcohol Amines and Organic Carboxylates

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A systematic investigation on solvent-dependent assembly of trinuclear copper cluhster has resulted in eight related coordination polymers: Cu3(teaH2)2(oba)2(MeOH)2 (1), Cu3(teaH2)2(oba)2(EtOH)2 (2), Cu3(teaH2)2(oba)2·(n-PrOH) (3), Cu3(teaH2)2(oba)2 (4), Cu3(teaH2)2(oba)2(H2O)2 (5), Cu3(MedeaH)2(oba)2(MeOH)2 (6), Cu[Cu3(Medea)2(oba)2]·(solvent)x (7), and [Cu3(MedeaH)2(oba)2(H2O)]·(n-PrOH)2 (8) where oba = 4,4′-oxy-bis(benzoate), teaH3 = triethanolamine, and MedeaH2 = N-methyldiethanolamine. In 1–8, the trinuclear copper secondary building units (SBUs) (Cu3) are furnished via the synergistic coordination of two organic ligands with metal centers. The structures of 1–8 exhibit two types of extensible modes (mode I for 1, 2, 3, 7, 8 and mode II for 4, 5, 6) to Cu3 SBUs. Mode I assembles Cu3 SBUs into the one-dimensional (1D) iron-chain-like structure while mode II facilitates the two-dimensional (2D) undulate rectangular (4, 4) connection. Compounds 1 and 2 feature zero-dimensional (0D) molecular structures in which two strong hydrogen-bonding interactions extend its molecular components into 1D chains. Compound 3 comprises 1D chains interspersed by free solvent molecules, whereas compound 4 consists of 2D sheets excluding any solvent molecules. Compound 5 is also made up of 0D molecular structures but uses two classic hydrogen-bonding interactions to form its 2D supramolecular connection. Compound 6 has a 2D network similar to 4. Compound 7 shows an unusual three-dimensional (3D) microporous framework in which a 1D chain is further assembled by extra CuII ions. Compound 8 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 1–8. Compounds 5 and 8 from an alcohol/H2O mixture indicate a behavior of selective coordination to the available coordination points of metal centers. The gas sorption property of compound 7 has also been investigated.