Formation of One-Dimensional Metal−Water Chain Containing Cyclic Water Hexamers

Formation of H-bonding networks in the solid state structure of a trinuclear cobalt(iii/ii/iii) complex with N2O2 donor Schiff base ligand and glutaric acid as bridging co-ligand: synthesis, structure and DFT study

A trinuclear linear mixed-valence centrosymmetric cobalt(iii)-cobalt(ii)-cobalt(iii) complex, [CoII{(μ-L)(μ-Hglu)CoIII(OH2)}2](ClO4)2·6H2O has been synthesized during tetradentate N2O2 donor 'Schiff base' ligand, H2L {N,N'-bis(salicylidene)-1,3-diaminopropane} and glutaric acid (H2glu) as anionic co-ligand. The complex has been characterized by spectroscopic measurements and its solid state structure has been determined by single crystal X-ray diffraction analysis. The supra-molecular assembly formed by the hydrogen bonding interactions in the solid state of the complex has been analysed using DFT calculations.

A novel three-dimensional tetranuclear CoII coordination polymer with water hexamers based on the V-shaped tetracarboxylate ligand 4-(2,4-dicarboxylatophenoxy)phthalate

A new coordination polymer (CP), namely, poly[[diaquatris[μ₂-1,4-bis(1H-imidazol-1-yl)benzene]bis[μ₆-4-(2,4-dicarboxylatophenoxy)phthalato]tetracobalt(II)] hexahydrate], {[Co₄(C₁₆H₆O₉)₂(C₁₂H₁₀N₄)₃(H₂O)₂]·6H₂O}_n, has been synthesized by solvothermal reaction. The CP was fully characterized by IR spectroscopy, elemental analysis, thermogravimetric analysis, and powder and single-crystal X-ray diffraction. It presents a three-dimensional (3D) structure based on tetranuclear Co^II secondary building units (SBUs) with a tfz-d net and point symbol (4³)₂(4⁶·6¹⁸·8⁴). The 4-(2,4-dicarboxyphenoxy)phthalic acid (H₄dcppa) ligands are completely deprotonated and link {Co₄(COO)₄}^4- SBUs into two-dimensional (2D) layers. Furthermore, adjacent layers are connected by 1,4-bis(1H-imidazol-1-yl)benzene (bib) ligands, giving rise to a 3D supramolecular architecture. Interestingly, there are numerous elliptical cavities in the CP where isolated unique discrete hexameric water clusters have been observed. The results of thermogravimetric and magnetic analyses are described in detail.

A Water Cluster Conduit in Crystal

The crystal structure of compound (1), [CuCl(phen)(H₂NCH₂COO)]∙4H₂O, reveals an unusual hydrogen-bond water cluster aggregate T6(2)6(2). Four water molecules in (1) form an isolated water cluster, [(H₂O)₁₄]_n, resembling a “phenanthro-[1,2]phenanthrene polymer structure shape” along the ac plane. The two face-face parallel [(H₂O)₁₄]_n planes are bridged by Cl atoms in [CuCl(phen) (H₂NCH₂COO)] with a strong O-H∙∙∙Cl hydrogen bond to form a water cluster conduit.

One-dimensional water cages with repeat units of (H2O)24resembling pagodane trapped in a 3D coordination polymer: proton conduction and tunable luminescence emission by adsorption of anionic dyes

A 3D-coordination polymer was shown to trap one-dimensional polyhedral water cages consisting of repeat units of (H₂O)₂₄, the geometry of which resembles the exotic organic molecule pagodane.

Monometallic and bimetallic ruthenium(II) complexes derived from 4,5-bis(benzimidazol-2-yl)imidazole (H3Imbzim) and 2,2'-bipyridine as colorimetric sensors for anions: synthesis, characterization, and binding studies

Mixed-ligand monometallic and bimetallic ruthenium(II) complexes of compositions [(bpy)(2)Ru(H(3)Imbzim)](ClO(4))(2) x 2 H(2)O (1) and [(bpy)(2)Ru(H(2)Imbzim)Ru(bpy)(2)](ClO(4))(3) x CH(2)Cl(2) (2), where H(3)Imbzim = 4,5-bis(benzimidazol-2-yl)imidazole and bpy = 2,2'-bipyridine, have been synthesized and characterized using standard analytical and spectroscopic techniques. The X-ray crystal structures of both compounds have been determined and showed that 1 crystallized in the triclinic form with space group P1 and 2 is in the monoclinic form with space group P2(1)/m. The anion binding properties of complexes 1 and 2, as well as those of the parent H(3)Imbzim, were thoroughly investigated in an acetonitrile solution using absorption, emission, and (1)H NMR spectral studies, which revealed that both of the metalloreceptors act as sensors for F(-), for AcO(-), and, to some extent, for H(2)PO(4)(-). At a relatively lower concentration of anions, a 1:1 hydrogen-bonded adduct was formed; however, in the presence of an excess of anions, stepwise deprotonation of the two benzimidazole NH fragments occurred, an event that was signaled by the development of vivid colors visible with the naked eye. Double deprotonation was also observed in the presence of hydroxide. Less basic anions (AcO(-) and H(2)PO(4)(-)) induce deprotonation of only one NH. The effect of solvents on the absorption and emission spectral behavior has also been studied in detail. The binding affinities of different anions toward the receptors were evaluated and showed that the binding constants of 1 and 2 are substantially enhanced relative to free H(3)Imbzim because upon coordination to the Ru(II) center(s), H(3)Imbzim/H(2)Imbzim(-) becomes electron-deficient, thereby rendering the imidazole NH protons more available for hydrogen bonding to the anions. Cyclic voltammetry studies carried out in acetonitrile provided evidence of an anion-dependent electrochemical response with F(-) and AcO(-). Anion-induced lifetime shortening makes complex 2 a suitable lifetime-based sensor for anions.

An ice-like water hexamer with 3 symmetry in the hydrogen-bonded structure of 2,3,5,6-tetrafluoro-1,4-bis(imidazol-1-ylmethyl)benzene dihydrate

An ice-like hexameric water cluster, stabilized by the flexible bis-imidazolyl compound 2,3,5,6-tetrafluoro-1,4-bis(imidazol-1-ylmethyl)benzene (Fbix), is found in the trigonal R3 crystal structure of the title compound, C(14)H(10)F(4)N(4).2H(2)O or Fbix.2H(2)O. The Fbix molecule lies about an inversion centre with one water molecule in the asymmetric unit in a general position. A cyclic chair-like hexameric water cluster with 3 symmetry is generated with a hydrogen-bonded O...O distance within the hexamer of 2.786 (3) A. The Fbix molecule adopts a trans conformation, where the imidazole ring makes a dihedral angle of 70.24 (11) degrees with the central tetrafluorinated aromatic ring. Each water hexamer is connected by six Fbix molecules through intermolecular O-H...N hydrogen bonds [N...O = 2.868 (3) A] to yield a three-dimensional supramolecular network with primitive cubic (pcu) topology. Large voids in each single pcu network lead to fourfold interpenetrated aggregates of Fbix.2H(2)O.