Crystal structure of bis[(hydrogen 5-methylisophthalato)-(2,5-bis(4- pyridyl)-1,3,4-thiadiazole)]zinc(II) dihydrate, Zn(C9H7O4)2(C12H8N4S)2 · 2H2O

Abstract

Source of materialDirect mixing of the starting materials in solution leads to immediate fine precipitate formation. In order to obtain crystals, suitable for X-ray diffraction analysis, the hydrothermal methods were applied. Amixture of 5-methylisophthalic acid (CH 3H2ip, 0.1 mmol), 2,5-bis(4-pyridyl)-1,3,4-thiadiazole (bpt, 0.1 mmol), Zn(OAc) 2 · 4H 2 O( 0.1 mmol), KOH (0.10 mmol) and H 2 O (15 mL) was placed in aTeflon-lined stainless steel vessel, heated to 140°Cfor 4days, and then cooled to room temperature over 24 h. Colorless block-shaped crystals of the title compound were obtained. DiscussionThe rational design and assembly of inorganic coordination polymers or metal-organic frameworks have received remarkable attention and have been developed rapidly in recent years. Being easily and efficiently synthesized from relatively simple subunits, these complexes exhibit fascinating structural topologies and potential applications as functional materials [1][2][3][4][5][6][7][8]. To build these molecular architectures, researchers often employ bridging poly-carboxylate and bipyridyl ligands to construct coordination polymers because of their versatile coordination modes and high structural stability. Exo-bidentate rod-like N,N'-donor ligands, such as 4,4-bipyridine, can have significant influence on the assembly systems of multicarboxylate ligands and metal centers. Its derivatives dpe (1,2-bi(4-pyridyl)ethene), bpa (1,2-bi(4-pyridyl) ethane) and bpp (1,3-di(4-pyridyl)propane) with certain spacers between the two 4-pyridyl rings may also lead to fascinating architectures with interesting properties. Unlike the more commonly used 4,4-bipyridine-like ligands, 2,5-bis(4-pyridyl)-1,3,4-thiadiazole possesses an angular disposition of its terminal pyridyl spacers. Its central thiadiazole ring and two more potential N-donor atoms inducing flexible coordination modes, which favours the construction of unexpected, unpredictable and interesting frameworks. The asymmetric unit contains one Zn(II) cation, two bpt ligands, two CH 3Hip anions and two lattice water molecules. The Zn II ion is four-coordinated with adistorted tetrahedral environment, provided by two pyridyl Natoms from two different bpt molecules, two carboxylate Oa toms from two CH3Hip molecules. The Zn-Nb ond length is 2.046(2) Å and the Zn-Od istances is 1.950(2) Å.5-Methylisophthalate acts as amonodentate ligand in an mono-anion mode. 2,5-Bis(4-pyridyl)-1,3,4-thiadiazole acts as amono-dentate ligand. Several kinds of hydrogen bonding are observed in the crystal structure: (a) hydrogen bonding between water oxygen atoms and uncoordinated oxygen atoms of carboxylate group O5-H1W···O2 with the bond distance of 3.082(3) Å and bond angle of 135.6°;(b) hydrogen bonding between water oxygen atoms and coordinated oxygen atoms of carboxylate unit (O5-H2W···O1, 2.784(3) Å,163.3°); (c) hydrogen bonding between uncoordinated oxygen atoms of carboxylate group and uncoordinated nitrogen atoms of pyridyl group (O3-H3···N4, 2.677(2) Å,174.2°). These weak hydrogen bonds f...