Chengbing Ma

Structural transformation mediated by o-, m-, and p-phthalates from two to three dimensions for manganese/phthalate/4,4′-bpy complexes (4,4′-bpy = 4,4′-bipyridine)

Three isomers of o-, m-, and p-phthalate are used to link together Mn centres, resulting in [Mn(phth)(H2O)x]n moieties (phth = phthalate dianion) with single-chain, double-chain and sheet structures, respectively, which predetermine the extended structures derived from the crosslinkage of 4,4′-bipyridine, and show the influence of isomerism of the phthalate on topological changes of the final polymers from two dimensional (2D) single-layer, double-layer to 3D network architectures. These structural changes in topology are correlated with the differences in the magnetic and optical properties of the polymers.

Framework variations in Mn(II)–organic coordination polymers: solvent templated formation and characterisation of 1D zigzag and straight chain network isomers

Hydrothermal reaction of manganese carbonate with 4,4′-biphenyldicarboxylic acid (H2bda) and 1,10-phenanthroline (phen) affords coordination polymers, [Mn(bda)(phen)(H2O)]n·npy·nH2O (1·npy·nH2O, 1a), [Mn(bda)(phen)(H2O)]n·2npip (1·2npip, 1b) and [Mn(bda)(phen)]n (2). The polymer 1 crystallizes into either 1D zigzag chain or straight chain structures depending on the crystallisation solvents used, and both of them stack into a 3D guest-filled porous framework via inter-chain interactions, whereas the polymer 2 organizes into a 3D ligand-filled porous coordination framework in the absence of suitable guests. The polymer 1 represents an unusual example of network isomers formed via the templating of structurally dissimilar but closely related organic guests.

The first heterometallic examples of 3d–4f heptanuclear [MnII3LnIII4] complexes with planar disc-like cores and diverse magnetic properties

A family of heptanuclear [Mn(II)(3)Ln(III)(4)] clusters with planar disc-like cores have been synthesized by a solvothermal route, where Ln = La, Pr, Nd, and Gd, and such fascinating topology is unprecedented in 3d-4f complexes. Dc magnetic susceptibility data show different magnetic behaviors derived from the difference in Ln ions.

Aggregation of tetranuclear Mn building blocks with alkali ion. Syntheses, crystal structures and chemical behaviors of monomer, dimer and polymer containing [Mn4(µ3-O)2]8+ units

Aggregation of tetranuclear Mn(4)O(2) building blocks with alkali ion was studied. Several Mn(iii) complexes containing [Mn(4)O(2)(AcO)(7)(pyz)(2)](-) (pyz = pyrazinate) anion(s) were obtained from an assembly system containing Mn(ii), MnO(4)(-), HOAc and Hpyz (Napyz or Kpyz). These [Mn(4)O(2)](8+) complexes have monomeric (1 and 2), dimeric (4 and 5) and one-dimensional chain () structures of which alkali metal ion connects the Mn ions of adjacent [Mn(4)O(2)](8+) units through mu(1,1)- and mu(1,3)-carboxylate bridges. Complexes 2 or 3 were converted into [Mn(12)O(12)(AcO)(16)(H(2)O)(4)] in EtOH solution in the presence of HOAc. However, in MeOH solution, a coordination polymer [Mn(2)(HCOO)(4)(H(2)O)(4)](n) was obtained accompanying the oxidation of MeOH to become HCHO and HCOOH. Tracing the (1)H NMR spectra of 2 or 3 in CD(3)OD, the disappearance of the resonance signals in 3 h indicated the decomposition of the [Mn(4)O(2)](8+) cores. Complex 2 exhibits its proton NMR signals in CDCl(3) which are similar to those of its pic analogue but accompany downfield shift to various extents for all the corresponding signals. Variable-temperature magnetic susceptibilities of complexes 2-5 in the range 5-300 K were recorded and were fitted for an Mn(4)O(2) butterfly core, giving the fitting parameters J(bb) = -2.67 to -3.76 cm(-1) and J(wb) = -1.16 to -3.14 cm(-1). Small J values indicate weak antiferromagnetic coupling interactions of the Mn(iii) sites and the spin ground states are considered as S(T) = 0 based on the J(bb)/J(wb) ratio approximately 1 for these complexes. The ESR spectra were recorded for complex 2 in dual-mode at liquid-helium temperatures and no obvious signal could be found. The addition of p-cresol gives rise to the reduction of the [Mn(4)O(2)](8+), resulting in observable signals.

A trimanganese cluster-based 2D layer framework with facile single-crystal-to-single-crystal transformation to afford a 1D chain structure

A new isophthalate manganese(II) coordination polymer, [Mn3(ip)3(bipy)2]n·2nH2O (1) (H2ip = isophthalic acid and bipy = 2,2′-bipyridine), with a 2D layer structure built up from isophthalato-linking trimanganese clusters, is obtained by refluxing a weakly basic solution containing bipy, Mn(OAc)2·4H2O, H2ip, and triethylamine. Both the complex and the dehydrated materials show irreversible water adsorption at room temperature, accompanied by facile single-crystal-to-single-crystal structural transformation forming a 1D chain-like coordination polymer upon rehydration, [Mn(ip)(bipy)(H2O)2]n·nH2O (2). The thermogravimetric behavior and magnetic properties of both the complexes are examined.

Synthesis and characterization of a family of tetranuclear manganese(III) phosphonate complexes

Four tetranuclear manganese(III) complexes containing phosphonate ligands (RPO32−, R = Me, Et and n-Bu), [Mn4O2(MePO3)2(O2CMe)4(bpy)2]·4MeCOOH (1), [Mn4O2(EtPO3)2(O2CMe)4(bpy)2]·7H2O (2), [Mn4O2(n-BuPO3)2(O2CMe)4(bpy)2]·4H2O·(COOH)2 (3) and [Mn4O2(MePO3)2(O2CPh)4(phen)2]·4PhCOOH·2MeCN (4), have been synthesized and characterized by IR spectroscopy, ESI-MS spectrometry, electrochemical analysis, magnetic measurements and TGA. The X-ray analysis shows that the four complexes all have one [Mn4(μ3-O)2]8+ core with four coplanar Mn atoms disposed in an extended “butterfly-like” arrangement and two O atoms triply bridging each “wing”, and the peripheral ligation is provided by four μ2-MeCO2− or four μ2-PhCO2−, two terminal bpy or phen (bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline) groups at both ends of the molecule, and two bicapping μ3-phosphonate ligands, which each binds to three manganese centers above and below the plane. The cyclic voltammetry of 1 and 3 each displays four reduction and one oxidation processes, of which the four reduction processes are possibly attributed to the reduction of four MnIII of the compounds to MnII. The ESI-MS data indicate that the family of complexes are stable in solution. Magnetic susceptibility measurements reveal that compounds 1 and 3 display antiferromagnetic interactions between the adjacent MnIII ions mediated through the μ3-O, O–C–O and O–P–O bridges.

(N-CnH2n-1)-1,3-Azapropanedithiolate (n=5, 6, 7)-bridged diiron complexes as mimics for the active site of FeFe -hydrogenases: the influence of the bridge on the diiron complex

To further understand the effects of 1,3-azadithiolate (ADT) bridges on the structures and properties of diiron complexes, a novel family of (N-CnH2n−1)-1,3-azapropanedithiolate-bridged diiron complexes [Fe2(CO)6(CH2S)2N–CnH2n−1] (n = 5, 6, 7) and their PMe3-disubstituted complexes [Fe2(CO)4(PMe3)2(CH2S)2N–CnH2n−1] (n = 5, 6, 7) were synthesized as mimics of [FeFe]-hydrogenases. Our studies suggest that the coordination configurations, CO stretching frequencies, 1H and 31P NMR signals, redox potentials and electrocatalytic H2-production processes of diiron complexes are closely pertinent to the electron-donating abilities and steric chemistry of the ADT bridges.

Novel Ag(I) complexes with propeller-like structure of tripodal ligand: syntheses and structures of two- and three-coordinate silver (I) complexes

Abstract Two mononuclear Ag(I) complexes, [Ag(tbsb)](NO3)·DMF (1) and [Ag(tbsb)](NO3)·4.5H2O (2) {tbsb=1,3,5-tris(2-benzimidazol)sulfanylmethyl)-2,4,6-trimethylbenzene}, have been synthesized by self-assembly reaction of AgNO3 with tbsb and characterized structurally. The silver atoms of both the complexes are coordinated by the imine nitrogen atoms from a tripodal ligand (tbsb) to form two- and three-coordinate structures, respectively. Complex 1 presents the first example of silver (I) compound of the tripodal ligand possessing propeller-like structure.

Phenanthroline–manganese inclusion complexes of dicarboxylic acid containing extensive hydrogen-bonding interactions

Abstract Two phenanthroline–manganese inclusion complexes with [MnCl(H2O)(phen)2]+ core were prepared in the presence of dicarboxylic acid and their structures were determined. Uncoordinated adipic acid and phthalic acid as guest molecules are included in the complexes with formulas {[MnCl(H2O)(phen)2]Cl}2·C6H10O4·8H2O (1) and {[MnCl(H2O)(phen)2]Cl}4·2C8H6O4·4H2O (2). The dicarboxylic acid molecules together with aqua and Cl− ligands, Cl− anions and solvate H2O molecules form extensive hydrogen-bonding interactions, building up supramolecule-like aggregate structure.

Hydrogen photogeneration catalyzed by a cobalt complex of a pentadentate aminopyridine-based ligand

A pentadentate aminopyridine ligand [(9-methyl-1,10-phenanthrolin-2-yl)methyl]bis-(pyridin-2-ylmethyl)amine (DPA-Dmphen) has been prepared and characterized. This ligand readily accommodates Co(II) or Ni(II) bearing a coordinated apical water ligand, and the resulting complexes of general formula [M(Dmphen-DPA)(H2O)](ClO4)2 (MCo (1) and MNi (2)) have been investigated for photo- and electrocatalytic proton reduction in CH3CN–H2O (1/3, v/v) mixed solvent and CH3CN, respectively. Under visible-light irradiation (λ > 400 nm), complex 1 shows hydrogen evolution activity in the presence of [Ir(ppy)2(bpy)]PF6 as a photosensitizer and TEA as an electron donor, whereas 2 displays much lower catalytic activity under the same conditions. The highest turnover number (TON) of 210 is achieved for H2 evolution from an optimized system containing 1 (0.1 mM), [Ir(ppy)2(bpy)](PF6) (0.5 mM), and 10 vol% TEA in CH3CN–H2O (1/3, v/v) mixed solvents at pH 10. Under those conditions catalytic hydrogen production is mainly limited by photosensitizer and catalyst stability. Furthermore, electrochemical studies reveal that both complexes are active for electrocatalytic proton reduction in acetonitrile, when using acetic acid as a proton source with overpotentials of (0.48 V vs. Fc+/Fc) for 1 and (0.46 V vs. Fc+/Fc) for 2.