Preparation and Characterization of Bis(μ-1,2-diaminoethane)cobalt(II) Hexavanadate: A Layered Polyoxovanadate Pillared by a Cobalt Coordination Complex

Abstract  The first example of polyoxovanadate layered framework with a cobalt coordination complex as a pillaring unit, Co^II(μ-C₂N₂H₈)₂[V₄^IVV₂^VO₁₄], was readily synthesized under hydrothermal conditions. The structure can be solved and refined in monoclinic P2 ₁ /n with a = 9.143(3) ?, b = 6.5034(11) ?, c = 15.874(4) ?, β = 101.90(2), V = 923.6(4) ?³ and Z = 2. The crystal structure comprises two-dimensional {V₄^IVV₂^VO₁₄}²⁻ layers extending parallel to [101], constructed from tetrahedral {V^VO₄} and square pyramidal {V^IVO₅} building units. Adjacent layers are linked through the octahedral {Co^IIO₂(μ-C₂N₂H₈)₂} pillars, within which the Co^II resides on an inversion center. The structure displays N–H···O and C–H···O hydrogen bonding between the ethylenediamine and vanadium oxide layers. Graphical Abstract  A new polyoxovanadate layered framework pillared with a cobalt coordination complex, Co^II(μ-C₂N₂H₈)₂[V₄^IVV₂^VO₁₄], has been prepared hydrothermally and fully characterized.      

Microwave-assisted SNAr reaction of 2,4,6-trichloro-1,3,5-triazine for the rapid synthesis of C3-symmetrical polycarboxylate ligands

The microwave-assisted S_NAr reaction of 2,4,6-trichloro-1,3,5-triazine with various unprotected amino acids was developed for the synthesis of C₃-symmetrical polycarboxylate ligands which can be used as structural directing units in metal-organic frameworks. The reactions were performed in water using a domestic microwave oven as the heating device. In comparison to the reactions performed under conventional heating, the reactions under microwave irradiation proceeded much more rapidly within 20 min to afford the desired ligands in comparative yields to those obtained by conventional heating.     

Selective synthesis of zeolitic phillipsite and hibschite hydrogarnet from lignite ash employing calcium hydroxide under mild conditions

A selective synthesis of zeolitic material, phillipsite, employing calcium hydroxide under mild chemical conditions is reported. This is to provide a potential method in reducing the amount of the waste from lignite power plant and the addition of economical value to the material. The fly ash was first activated by calcination at high temperature, and then fused with calcium hydroxide. The water was then added to the solid mixture before curing under saturated water vapour at low temperature. The treatment of as-received fly ash with either calcium hydroxide or a mixture of calcium and sodium hydroxide following as-described preparative procedure of phillipsite, but without prior calcination was also conducted, and led to the formation of Hibschite hydrogarnet, which was also evidentially selective. The following parameters, i.e. type and amount of alkali reagent, the amount of added water, fusion temperature and reaction time were investigated. Powder X-ray diffraction was used to identify type of crystalline solid products, and scanning electron microscope was employed to follow the alteration of solid morphologies. X-ray fluorescence (XRF) was used to trace the chemical composition of the solids. The heavy metal cation removal abilities toward lead ion of the prepared phillipsites were also investigated.     

Crystal structures and Hirshfeld surface analysis of transition‐metal complexes of 1,3‐azolecarboxylic acids

The crystal structures of five new transition‐metal complexes synthesized using thiazole‐2‐carboxylic acid (2‐Htza), imidazole‐2‐carboxylic acid (2‐H₂ima) or 1,3‐oxazole‐4‐carboxylic acid (4‐Hoxa), namely diaquabis(thiazole‐2‐carboxylato‐κ²N,O)cobalt(II), [Co(C₄H₂NO₂S)₂(H₂O)₂], 1 , diaquabis(thiazole‐2‐carboxylato‐κ²N,O)nickel(II), [Ni(C₄H₂NO₂S)₂(H₂O)₂], 2 , diaquabis(thiazole‐2‐carboxylato‐κ²N,O)cadmium(II), [Cd(C₄H₂NO₂S)₂(H₂O)₂], 3 , diaquabis(1H‐imidazole‐2‐carboxylato‐κ²N³,O)cobalt(II), [Co(C₄H₂N₂O₂)₂(H₂O)₂], 4 , and diaquabis(1,3‐oxazole‐4‐carboxylato‐κ²N,O⁴)cobalt(II), [Co(C₄H₂NO₃)₂(H₂O)₂], 5 , are reported. The influence of the nature of the heteroatom and the position of the carboxyl group in relation to the heteroatom on the self‐assembly process are discussed based upon Hirshfeld surface analysis and used to explain the observed differences in the single‐crystal structures and the supramolecular frameworks and topologies of complexes 1 – 5 .     

Polymorphism in metal complexes of thiazole-4-carboxylic acid

Five new molecular complexes of chemical formula [M(4-tza)₂(H₂O)₂] (M = Co, Ni, or Cu) and a complex of [Cu(4-tza)₂]·4H₂O using thiazole-4-carboxylic acid (4-tza) as the ligand have been successfully synthesized and structurally characterized by single crystal X-ray diffraction. Two district polymorphs (α and β) are found for both [Co(4-tza)₂(H₂O)₂] and [Ni(4-tza)₂(H₂O)₂]. The effects of solvent composition and temperature on the formation of these polymorphs have been investigated and phase behaviour of the polymorphs was studied through X-ray powder diffraction. Unlike the complexes of Co and Ni, [Cu(4-tza)₂(H₂O)₂] does not display polymorphism but exhibits irreversible structural transformation from [Cu(4-tza)₂(H₂O)₂] to the dehydrated form, [Cu(4-tza)₂], upon heating.     

Microwave‐Assisted Facile Synthesis and Crystal Structure of cis‐9,10,11,15‐Tetrahydro‐9,10[3′,4′]‐furanoanthracene‐12,14‐dione

A facile synthesis and crystal structure of cis‐9,10,11,15‐tetrahydro‐9,10[3′,4′]‐furanoanthracene‐12,14‐dione from the reaction of anthracene and maleic anhydride in xylene in a short time and high yield using a modified commercial domestic microwave oven is reported.     

A second crystal form of [Ni(2,2′-bipyridine)(H2O)3(NO3)](NO3) featuring a different molecular orientation

The molecular structure of a second form of [Ni(2,2′-bipyridine)(H₂O)₃(NO₃)](NO₃) is reported. The previous report is for a blue monoclinic polymorph. The second form is orthorhombic and crystallises as green blocks with unit cell parameters a = 9.1201(12) Å, b = 14.444(2) Å, c = 21.805(4) Å, V = 2872.4(8) Å³, Z = 8. The complex was characterised by elemental analysis, infrared spectroscopy, UV-Vis spectroscopy, and thermogravimetry. The bipyridine acts as a bidentate ligand to Ni²⁺ and the octahedral coordination is completed by three water molecules and one monodentate nitrate ion. A second nitrate forms hydrogen bonds to the bound water molecules. The difference between the two forms in terms of the molecular geometry is described in relation to other similar compounds. The key difference between the two forms is the orientation of the two nitrate anions, and hence the hydrogen bonding present.