Self-assembly of tetrabromoterephthalic acid with different metal system: Diversity in dimensionalities, structures and gas adsorption

A new series of coordination compounds of different dimensionalities, {Cd2(TBTH)2(TBT)(DMF)6} (1), {Cu(TBT)(DMF)2}n (2), {Ni(TBT)(DMF)2(EtOH)2}n (3) and {Mn(TBT)(DMF)}n (4) have been synthesized under similar reaction conditions and stoichiometry using tetrabromoterephthalic acid (TBTH2) as a building block. Single crystal X-ray diffraction study reveals 1 is a dimeric discrete complex whereas 2 and 3 are found to be 1D coordination polymers and all the three compounds extend to three dimensions by non-covalent (H-bonding and O⋯Br) interactions. Compound 4 has a 3D framework structure where {Mn(CO2)}n chains are cross-linked by TBT linkers and DMF molecule also acts as a bidentate bridging ligand. The difference in dimensionalities can be correlated to the metal ions (CdII, CuII, NiII and MnII) having different ionic radius. Compound 4 does not contain any guest solvent molecule but removal of bridging DMF molecules creates a 1D channel with dimension of 2.1 × 4.2 Å2. Adsorption studies reveal that the desolvated compound 4 (4′) with unsaturated MnII sites can uptake an appreciable amount of CO2 at 195 K (15 wt.%), and H2 at 77 K (∼0.4 wt.%) although surface area is not significant.

Graphical abstractA new series of coordination compounds of different dimensionalities, {Cd2(TBTH)2(TBT)(DMF)6} (1), {Cu(TBT)(DMF)2}n (2), {Ni(TBT)(DMF)2(EtOH)2}n (3) and {Mn(TBT)(DMF)}n (4) have been synthesized under similar reaction conditions and stoichiometry using tetrabromoterephthalic acid (TBTH2) as a building block. Structure determination reveals 1 is a dimeric discrete complex whereas 2 and 3 are found to be 1D coordination polymers and compound 4 is a 3D porous coordination framework.Figure optionsDownload full-size imageDownload as PowerPoint slide