Carboxylato Bridged Cyclic SBUs as Robust Features in a Series of Cu(II) Coordination Polymers and Halogen···Halogen Interactions in Crystal Packing
Sanobar Naaz, Bhaswati Debnath, Sakhiul Islam, Samim Khan, Faruk Ahmed, Basudeb Dutta, Atish Dipankar Jana, Mohammad Hedayetullah Mir
Abstract
Four new pyridine/meta-substituted halopyridine appended coordination polymers (CPs) {[Cu(ip)6(py)6]·2CH3OH}n (1), [Cu(ip)2(3-Clpy)2]n (2), [Cu(ip)2(3-Brpy)2]n (3), and [Cu(ip)2(3-Ipy)2]n (4) (py = pyridine, 3-Clpy = 3-chloropyridine, 3-Brpy = 3-bromopyridine, 3-Ipy = 3-iodopyridine, and H2ip = 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.