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Figure 1
(a) Three types of connectivities of bdc in the chelating and bridging modes. Two structural isomers in the double-pillared-layer structure [M2(di­carboxyl­ate)2(pillar)2]. (b) The (4,4) `rectangular' net has an idealized local mm symmetry with type-I and type-II linkages. (c) The (4,4) `square' net has an idealized local fourfold rotational symmetry with type-III connectivity of di­carboxyl­ates. A rhombus-shaped net is also possible for type-III linkages. The axial positions are occupied by di­pyridyl pillar ligands, which have been omitted for clarity.

IUCrJ
Volume 5| Part 2| March 2018| Pages 182-189
ISSN: 2052-2525
https://doi.org/10.1107/S2052252518001379