Supramolecular co-ordination networks constructed via pi-stacking interactions and charge-assisted hydrogen bonds

Abstract

The diprotic acid 3,4-dihydroxy-3-cyclobutene-1,2-dione (squaric acid, H 2 SQA) reacts with [(η 5 -C 5 H 5 ) 2 Co] in THF to form a hydrogen bonded co-ordination network in crystalline {[Co II (HSQA-HSQA) 2 (H 2 O) 4 ] 2-}{[(η 5 -C 5 H 5 ) 2 Co III ] + } 2 (1) which contains Co II and Co III metal centres and the supramolecular salt {[(η 5 -C 5 H 5 ) 2 Co III ] + }{[(HSQA)(H 2 SQA)] -} (2) depending on the solvent and on the stoichiometric ratio. The diprotic acid pyridine-2,6-dicarboxylic acid (dipicolinic acid, H 2 DPA) reacts with [(η 5 -C 5 H 5 ) 2 Co] and [(η 6 -C 6 H 6 ) 2 Cr] in THF or water to form the supersalt {[(η 5 -C 5 H 5 ) 2 Co] + }{ [(HDPA)(H 2 DPA)] -} (3) and the coordination complex {[(η 6 -C 6 H 6 ) 2 Cr I ] + } 2 {[(DPA) 2 Cr III ] -}•2H 2 O (4), respectively. All compounds have been structurally characterised by single-crystal X-ray diffraction. The metal centres in the mixed valence species 4 are the paramagnetic 17 electrons Cr I and 15 electrons Cr III , respectively. The crystalline edifices in all compounds are held together by π-stacking interactions involving the flat organic moieties and by hydrogen bonding interactions of the O-H•••O and/or O-H•••O (-) type between the acid moieties, whether as metal co-ordinated ligands or as free ions and by charge assisted C-H δ+ •••O δbonds between cations and anions.

Linear hydrogen-bonded molecular tapes in the cocrystals of squaric acid with 4,4′-dipyridylacetylene and 1,2-bis(4-pyridyl)ethylene

“…3 and 4. The squarate monoanion dimer is rare, and we have found only eight examples in the CSD (Angelova et al, 1996;Bernardinelli et al, 1989;Bock et al, 1998;Braga et al, 1999;Braga & Grepioni, 1998;Kanters et al, 1991;Karle et al, 1996;MacLean et al, 1999). In all other squarate structures, the squarate monoanions are linked by a single intermolecular OÐHÁ Á ÁO hydrogen bond and no tenmembered rings are formed.…”

“…Squaric acid (3,4-dihydroxy-3-cyclobutene-1,2-dione) is a very strong dibasic acid and has been studied for potential application to xerographic photoreceptors, organic solar cells and optical recording (Seitz & Imming, 1992;Liebeskind et al, 1993). From the viewpoint of crystal engineering, squaric acid is also a useful tool for constructing crystalline architectures, because of its rigid and¯at four-membered ring framework, and its proton donating and accepting capabilities for hydrogen bonding (Braga et al, 1999;Reetz et al, 1994). We have recently shown that the simple combination of chloranilic acid and various dipyridyl-type ligands can create a variety of supramolecular architectures involving an in®nite one-dimensional molecular tape structure (Zaman et al, 1999(Zaman et al, , 2000.…”

Chromium(III) Complex Obtained from Dipicolinic Acid: Synthesis, Characterization, X-Ray Crystal Structure and Electrochemical Studies

“…[8][9][10][11][12][13][14] The first [Cr(dipic) 2 ] − complex containing inorganic cationic counter ion, has been NH 4 [Cr(dipic) 2 ].…”

Synthesis, crystal structure, DFT studies, and Hirshfeld surface analysis of N,N'-bis(3-quinolyl-methylene)diphenylethanedione dihydrazone

“…hydrogen bonding, ionic interactions and π-π stacking interactions have fascinated increasing attention in crystal engineering. In particular, hydrogen bonding π-π stacking interactions which is a powerful organizing force in designing various supramolecular and solid-state architectures [8][9][10], is extensively used not only for networking numerous organic and organometallic compounds [11,12], but also for generating interesting supramolecular properties, such as electrical, optical and magnetic [13,14] properties. Quinoline groups, with effective sites for coordination to transition metal ions, have been used for the construction of supramolecular coordination compounds [15][16][17][18].…”