Four new pyridine/meta-substituted halopyridine appended coordination polymers (CPs) {[Cu(ip) 6 (py and [Cu(ip) 2 (3-Ipy) 2 ] n (4) (py = pyridine, 3-Clpy = 3chloropyridine, 3-Brpy = 3-bromopyridine, 3-Ipy = 3-iodopyridine, and H 2 ip = isophthalic acid) have been synthesized by a diffusion method. The compounds are structurally characterized by the single crystal X-ray diffraction technique, and supramolecular interactions are studied by geometrical and density functional theory calculations. The study reveals that the compounds 1−3 form a two-dimensional (2D) coordination polymeric structure with carboxylato bridged dimeric Cu(II) cyclic secondary building units. However, a cyclic supramolecular synthon involving four halogen (X = Cl, Br) atoms has been observed in 2 and 3. This cyclic halogen synthon combined with a pyridine ring forms a (π•••π)+X•••X+(π•••π) mega-synthon, which dictates the dimensionality of 2D CPs into a three-dimensional (3D) network. However, compound 4 with a larger I atom does not show such interactions and forms a 1D tape structure.

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