Synthesis, crystal structure, and topology of a polycatenated bismuth coordination polymer

Solvothermal reaction of Bi(NO3)3·5H2O with the flexible ligand 1,3,5-tris[4-(carboxyphenyl)oxamethyl]-2,4,6-trimethylbenzene (H3TBTC) in methanol at 120 °C for 1 h led to the formation of a novel coordination polymer (CP) with the composition of Bi(TBTC). The structure of the microcrystalline material was determined through three-dimensional electron diffraction (3DED) measurements and phase purity was confirmed by a Pawley refinement, elemental analysis, and thermal analysis. The compound crystallizes in the triclinic space group <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?P%5Coverset%7B-%7D%7B1%7D" data-classname="equation" /> with one Bi3+ cation and one TBTC3− trianion in the asymmetric unit. Edge-sharing of BiO7 polyhedra leads to the formation of dinuclear Bi2O12 units, which through coordination to six TBTC3− ions form a layered two-periodic structure. Upon heating the material in air, the unit cell volume contracts by 9%, which is attributed to a shift in the inter-layer arrangement and to the flexibility of the building units of the structure. The compound starts to decompose at ∼300 °C. Topological analysis revealed layers consisting of 3-c and 6-c nodes, consistent with the two-periodic kgd net – the dual of the Kagome net (kgm). However, due to the non-planar nature of the Bi(TBTC) layers, adjacent layers are interlaced by polycatenation.