Analysis of supramolecular interactions directing crystal packing of novel mononuclear chloranilate-based complexes: Different types of hydrogen bonding and π-stacking

Abstract

Three novel mononuclear chloranilate complexes, {[Cu(bpy)(H2O)(C6O4Cl2)]·H2O}6 (2; bpy = 2,2′-bipyridine), [Cu(bpy)(C6O4Cl2)]·0·5H2O (3) and [(n-Bu)4N][Fe(H2O)2(C6O4Cl2)2]·2H2O (4) have been prepared using building blocks [MIII(C6O4Cl2)3]3− (MIII = Fe and Cr), which proved to be a source of the chloranilate groups. Namely, by applying layering technique an unexpected partial decomposition of used metalate anions leads to the release of the chloranilate ligand from the coordination sphere of chromium(III) and iron(III) ions. During crystallization process, the released group is consequently coordinated to copper(II) ion in the reaction mixtures, yielding crystals of 2 or 3. Crystals of compound 4 have been formed as a result of the ligand exchange process. Also, it appears that slow diffusion and the solvent mixture used herein causes formation of the crystals of the quality needed for X-ray analysis of the starting building block [(n-Bu)4N]3[Cr(C6O4Cl2)3] (1), whose crystal structure has not been known. Interestingly, compound {[Cu(bpy)(C6O4Cl2)(H2O)]·H2O}6 (2) displays an unusual case of hypersymmetry with Z' = 6. Analysis of crystal structures and intermolecular interactions of 1–4 revealed role of hydrogen bonding and π-interactions in stabilization of crystal lattices, further characterized by fingerprint plots derived from the Hirshfeld surfaces (HS). Two phases of compound 4 were identified: at low-temperature (100 K) 4-LT and at room-temperature 4-RT, with similar unit-cell parameters. However, different positions and orientations of water molecules result in completely different hydrogen-bonding patterns.