The Aryl Chlorine−Halide Ion Synthon and Its Role in the Control of the Crystal Structures of Tetrahalocuprate(II) Ions

• Published in: Crystal growth & design Vol. 7; no. 4; pp. 624 - 632
• Main Authors: Awwadi, Firas F, Willett, Roger D, Twamley, Brendan
• Format: Journal Article
• Language: English
• Published: Washington,DC American Chemical Society 01.04.2007
• Subjects: Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Methods of crystal growth; physics of crystal growth; Physics; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; Crystal growth; Crystal engineering; Weak interactions; Hydrogen bonds; Three dimensional structure; Chlorine; Supramolecular structure; Polymorphism; Crystal structure; Synthon
• ISSN: 1528-7483; 1528-7505
• DOI: 10.1021/cg060153j

The role of the arylchlorine−halide (C−Cl···X-) synthons in the development of crystal structures of the type (nCP)2CuX4·mH2O (nCP+ = n-chloropyridinium; n = 2, 3, and 4; X = Cl- and Br-; m = 0 except for (3CP)2CuBr4·H2O] are investigated. On the basis of detailed analysis of the synthonic interactions in these systems, it is concluded that the C−Cl···Cl- synthon plays a more significant role as a crystal engineering tool in these structures than the C−Cl···Br- synthon. In addition, it is shown that the C−Cl···X- interactions are weaker than the C−Br···X- synthons in the analogous (nBP)2CuX4 salts (nBP+ = n-bromopyridinium). For all of the (nCP)2CuCl4 salts, the nCP+ cations are involved in nearly linear C−Cl···Cl- interactions with Cl···Cl- distances less or equal to the sum of the van der Waals radii. Supramolecular chain networks, based on the C−Cl···Cl- and N−H···Cl- synthons, are formed with all three nCP+ cations. In addition, a polymorph of the 4CP+ salt contains two-dimensional networks based on these synthons. In contrast, the role of the linear C−Cl···Br- synthons is less well-defined. A supramolecular structure developed on the basis of the C−Cl···Br- and N−H···Br- synthons is observed only for (4CP)2CuBr4. In (2CP)2CuBr4 and (3CP)2CuBr4·H2O, formation of dimeric species occurs through a combination of hydrogen and halogen bonding. The role of a previously undescribed synthon, the N(π)···X- synthon, where the N−X vector lies roughly normal to the plane of the pyridinium ring, is explored in the further development of the three-dimensional structures.