Man-Li Cao

Ruthenium(II) 2,2′-Bibenzimidazole Complex as a Second-Sphere Receptor for Anions Interaction and Colorimeter

A ruthenium(II) complex [Ru(bpy) 2(H 2bbim)](PF 6) 2 ( 1) as anions receptor has been exploited, where Ru(II)-bpy moiety acts as a chromophore and the H 2bbim ligand as an anion binding site. A systematic study suggests that 1 interacts with the Cl (-), Br (-), I (-), NO 3 (-), HSO 4 (-), and H 2PO 4 (-) anions via the formation of hydrogen bonds. Whereas 1 undergoes a stepwise process with the addition of F (-) and OAc (-) anions: formation of the monodeprotonated complex [Ru(bpy) 2(Hbbim)] with a low anion concentration, followed by the double-deprotonated complex [Ru(bpy) 2(bbim)], in the presence of a high anion concentration. These stepwise processes concomitant with the changes of vivid colors from yellow to orange brown and then to violet can be used for probing the F (-) and OAc (-) anions by naked eye. The deprotonation processes are not only determined by the basicity of the anion but also related to the strength of hydrogen bonding, as well as the stability of the formed compounds. Moreover, a double-deprotonated complex [Ru(bpy) 2(bbim)].CH 3OH.H 2O ( 3) has been synthesized, and the structural changes induced by the deprotonation has also been investigated. In addition, complexes [Ru(bpy) 2(Hbbim)] 2(HOAc) 3Cl 2.12H 2O ( 2), [Ru(bpy) 2(Hbbim)](HCCl 3CO 2)(CCl 3CO 2).2H 2O ( 4), and [Ru(bpy) 2(H 2bbim)](CF 3CO 2) 2.4H 2O ( 5) have been synthesized to observe the second sphere coordination between the Ru(II)-H 2bbim moiety and carboxylate groups via hydrogen bonds in the solid state.

Water nanotubes confined to nanochannels of a (10,3)-b net constructed by binary building blocks via the R22(9) synthon

A (10,3)-b framework is constructed by the reaction of [Ru(H2Biim)3](PF6)2 and trimesic acid in a ratio of 1 : 1, in which the (10,3)-b net exhibits a two-fold interpenetration featuring 1D nano-sized channels. An unprecedented water nanotube consisting of the fused (H2O)28 with a double crown fashion, anchors in the channel.

Solvent-mediated crystal-to-crystal interconversion between discrete lanthanide complexes and one-dimensional coordination polymers and selective sensing for small molecules.

Two isostructural 1D coordination polymers {[Ln(OAc)2(H2O)(OBPT)]·3H2O}n (HOBPT = 4,6-bis(2-pyridyl)-1,3,5-triazin-2-ol, Ln = Eu(3+), 1; Tb(3+), 3) and two discrete complexes [Ln(OAc)2(DMF)2(OBPT)] (Ln = Eu(3+), 2; Tb(3+), 4) have been synthesized in H2O-MeOH or DMF solvents, respectively. Their structures were identified by powder X-ray diffraction. Single-crystal X-ray studies for complexes 1 and 2 revealed that the coordination geometries of the Eu(3+) ions are similar and can be described as a distorted tricapped trigonal prism with six oxygen atoms and three nitrogen atoms. The difference between them is that one aqua ligand and one oxygen atom from the OBPT ligand complete the coordination sphere in complex 1, whereas two DMF molecules complete the coordination sphere in complex 2. Interestingly, the solvent-mediated, reversible crystal-to-crystal transformation between them was achieved by immersing the crystalline samples in the corresponding solvent (H2O or DMF) or by exposing them to solvent vapor. Complex 1 shows a highly selective luminescence enhancement in response to DMF in comparison to that observed in response to other examined solvents such as acetone, ethyl acetate, ethanol, acetonitrile, methanol, and THF.

Assembly of a Cubic Nanocage Co8L12 and a Hydrogen-Bonded 3D NbO Net Based on the [(HCO3)2]2− Synthon and Water

Two new complexes [Co(H2O)6 Co8(L1)12]X6 x n H2O (X = NO3(-), n = 12 (1); X = HCO3-, n = 24, (2); HL1 = 4,6-bis(2-pyridyl)-1,3,5-triazin-2-ol) have been synthesized and characterized by single-crystal X-ray diffraction. A [Co(H2O)6](2+) ion is encapsuled in the central cavity of the cubelike nanocage [Co(H2O)6 Co8(L1)12](6+) cation, assembled by eight cobalt ions at the corners and twelve bis-bidentate ligands L1 as the edges, via the formation of 12-fold strong hydrogen bonds between the six coordinated water molecules and the oxygen atoms of twelve L1 as a guest. Complex 1 crystallizes in a centrosymmetric space group P1, while 2 is in a very high symmetric space group Im3. In 2, a planar [(HCO3)2](2-) dimer motif R2(2)(8) synthon plus six lattice water molecules constitute a planar supramolecular synthon R8(8)(20), which acts as a four connector, generating a 3D hydrogen-bonded NbO net with cubelike host cavities of approximately 20 A diameter. Interestingly, the cubelike nanocage [Co(H2O)6 Co8(L1)12](6+) cations fill in the cavities as templates. The magnetic properties of 1 have also been studied in the temperature range of 2-300 K, and its magnetic susceptibility obeys the Curie-Weiss law, showing antiferromagnetic coupling.

pH-Dependent formation of (6,3) and (10,3) hydrogen-bonded networks based on [Ru(H2biim)3]SO4: polymorphs and topological isomers

Two polymorphs formulated as [Ru(H2biim)3]SO4 (H2biim = 2,2′-biimidazole) have been solvothermally synthesized through changing the pH value of the reaction solution in an identical solvent at 120 °C. The α-[Ru(H2biim)3]SO4 (1) crystallizes in the monoclinic space groupP21/c with a = 8.1802(9) A, b = 21.293(2) A, c = 15.2116(14) A, β = 121.357(4)°, Z = 4. The β-[Ru(H2biim)3]SO4 (2) crystallizes in a chiral space groupI41 with a = 12.6267(10) A, c = 14.244(2) A, Z = 4. Complex 1 assembles into homochiral (Δ and Λ), (6,3) honeycomb two-dimensional layers, which further alternately stack in racemic, hydrogen-bonded networks, whereas 2 is a chiral, (10,3)-b 3-D network. Thus 1 and 2 are topological isomers. Importantly, their formations are much dependent on the pH value of the reaction solution. The data observed in this study seem to suggest that the diverse hydrogen bonding modes between the sulfate and H2biim ligand identified here play a crucial role in the formation of the polymorphs and topological isomers. The powder XRD patterns and infrared spectra also provide valuable information in the diagnosis of the polymorphs.

Reversible single-crystal-to-single-crystal transformation driven by adsorption/desorption of water over organic solvents and thermal stimulation

Two new isomorphous complexes [M(OBPT)2]·0.6H2O (M = Co, (1), M = Ni, (2), HOBPT = 4,6-bis(4-pyridyl)-1,3,5-triazin-2-ol) have been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction. Each ligand bridges two metal ions and each metal ion links to four ligands, resulting in a (4,4) 2D framework with rhombic cavities. Furthermore, the uncoordinated pyridine rings are further linked to each other via forming hydrogen bonding with the lattice water molecules into 3D three-fold interpenetrated, hydrogen-bonded networks. Interestingly, they are high stable up to 450 °C and exhibit reversible single crystal to single crystal transformation triggered by thermal treatment involving dehydration and rehydration processes. Moreover, they selectively adsorb/desorb water molecules over organic solvents much depending on the strength of hydrogen bonding between water molecule and solvent.