Rong-Xin Yuan

Synthesis and structural and magnetic characterization of a hexadecanuclear cobalt phosphonate compound

A wheel-like hexadecanuclear cobalt phosphonate [Co(16)(OH)(6)(chp)(22)(O(3)PC(6)H(9))(2)(H(2)O)(4)] has been synthesized by reactions of cobalt perchlorate with cyclohexenephosphonic acid (H(2)O(3)PC(6)H(9)) and 6-chloro-2-hydroxypyridine (Hchp) in the presence of Et(3)N. Magnetic studies on the compound show a general decline of chi(M)T with decreasing T. The appeared maximum of chi(M)T at low temperature suggests the presence of a non-diamagnetic ground state. The alternating current susceptibilities show frequency-dependent signals.

Structural diversification and photocatalytic properties of zinc(II) polymers modified by auxiliary N-containing ligands

Four new coordination polymers, {[Zn(bismip)]·2H2O}n (1), {[Zn2(bismip)2(4,4′-bipy)]·2H2O}n (2), {Zn2(bismip)2(phen)}n (3) and {[Zn(bismip)(bimb)]2·2H2O·DMF}n (4) (H2bismip = 5-(1H-benzoimidazol-2-ylsulfanylmethyl)-isophthalic acid, 4,4′-bipy = 4,4′-bipyridine, phen = 1,10-phenanthroline, bimb = 4,4-bis(1-imidazolyl)bibenzene) were synthesized under solvothermal conditions. All these compounds were characterized by elemental analysis, IR spectroscopy, thermal analysis, powder X-ray diffraction and single-crystal X-ray diffraction. Compound 1 features a two-dimensional (2D) binodal (3,6)-connected kgd network with (43)2(46·66·83) topology. 2 exhibits two-fold interpenetrating 3D architecture with a (4·82)(42·84) Schlafli symbol in which 2D layers are interlinked by 4,4-bipy ligands. In 3, the [Zn4(bismip)4] and [ZnO4N2] units are interconnected, affording a binodal 3D (3,4)-connected network with the Schlafli symbol (83)(86). 4 is a 2D (3,4)-connected coordination network with (42·6)(42·63·8) topology. The photoluminescence properties and photocatalytic properties of these compounds were also investigated.

Efficient and green microwave-assisted multicomponent biginelli reaction for the synthesis of dihydropyrimidinones catalyzed by heteropolyanion-based ionic liquids under solvent-free conditions

Abstract An efficient and green route for the synthesis of dihydropyrimidinones via microwave-assisted Biginelli reaction catalyzed by 3 mol% of heteropolyanion-based ionic liquids under solvent-free conditions has been reported. The practical reaction was found to be compatible with different structurally diverse substrates. Good to excellent yields, short reaction times, and operational simplicity are the main highlights of this protocol. Moreover, the heteropolyanion-based ionic liquids were easily reusable for this Biginelli reaction. GRAPHICAL ABSTRACT

Structural diversity of Zn(II) coordination polymers based on bis-imidazolyl ligands and 5-R-1,3-benzenedicarboxylate and their photocatalytic properties

Eight Zn(II) coordination polymers with 5-R-1,3-benzenedicarboxylate (R = H, Br) ligands and bis-imidazolyl ligands, {[Zn(1,3-BDC)(abimb)]·H2O}n (1), {[Zn(5-Br-1,3-BDC)(abimb)]2·0.5H2O}n (2), [Zn(1,3-BDC)(nbimb)]n (3), [Zn(5-Br-1,3-BDC)(nbimb)]n (4), {[Zn(1,3-BDC)(bimpa)]·2H2O}n (5), {[Zn(5-Br-1,3-BDC)(bimpa)]·2H2O}n (6), [Zn(1,3-BDC)(bimcz)]n (7) and [Zn(5-Br-1,3-BDC)(bimcz)]n (8) (1,3-H2BDC = 1,3-benzenedicarboxylate; 5-Br-1,3-H2BDC = 5-bromo-1,3-benzenedicarboxylate; abimb = 2-amine-4,4′-bis(1-imidazolyl)-bibenzene; nbimb = 2-nitro-4,4′-bis(1-imidazolyl)-bibenzene; bimpa = bis-(4-imidazol-1-yl-phenyl)-amine; bimcz = 3,6-bis(1-imidazolyl)-carbazole), have been synthesized and structurally characterized by elemental analysis, IR and X-ray single crystal diffraction. 1 and 6 exhibit 4-connected 3D frameworks with the Schlafli symbol (65·8). 2, 7 and 8 display 3D polythreaded networks based on 2D wrinkled layers. 3 and 4 show 3D polycatenated arrays based on 2D puckered layers. 5 has a 3D supramolecular structure consisting of two-fold parallel interwoven layers through hydrogen bonding and π⋯π stacking interactions. The solid state photoluminescence and photocatalytic properties of 1–8 were also investigated.

Binding of a coordinatively unsaturated mercury(II) thiolate compound by carboxylate anions.

Reactions of [Hg(Tab)2](PF6)2 (TabH = 4-(trimethylammonio)benzenethiol) (1) with acetic acid (HAc), propanoic acid (HPro), salicylic acid (HSal), benzoic acid (HBez), malonic acid (H2Mal), oxalic acid (H2Oxa), adipic acid (H2Adi), or methylimindiacetic acid (H2Meida) in the presence of Et3N gave rise to a family of mercury(II)-thiolate-carboxylate compounds, [Hg(Tab)2(Ac)](PF6) · 0.5H2O (2 · 0.5H2O), [Hg(Tab)2(Pro)](PF6) (3), [Hg(Tab)2(Sal)](PF6) · MeOH (4 · MeOH), [Hg(Tab)2(Sal)](Sal) · MeOH (5 · MeOH), [Hg(Tab)2(Bez)](PF6) · H2O (6 · H2O), [Hg(Tab)2(HMal)](Mal)0.5 H2O (7 · H2O), [{Hg(Tab)2}2(μ-Oxa)](PF6)2 H2O (8·2H2O), [{Hg(Tab)2}2(μ-Adi)](PF6)2 (9), [Hg(μ-Tab)(μ-Adi)]2n (10), and [Hg(Tab)2(Meida)] · 2.5H2O (11 · 2.5H2O). These compounds were characterized by elemental analysis, IR spectra, UV-vis spectra, (1)H NMR, and single-crystal X-ray crystallography. Each mercury(II) atom in [Hg(Tab)2](2+) dication of 2-7 is further coordinated by two oxygen atoms from one Ac(-), Pro(-), Sal(-), Bez(-), Mal(2-) or HMal(-) anion, forming a unique seesaw-shaped coordination geometry. In 8 or 9, two [Hg(Tab)2](2+) dications are connected by one bridging oxalate or adipate dianion to generate a dimeric structure with each mercury(II) center adopting a seesaw-shaped geometry. In 10, a pair of octahedrally coordinated mercury(II) atoms are bridged by two sulfur atoms of two Tab ligands to form a [Hg(μ-Tab)2Hg](4+) fragment, which is further connected to its equivalent ones via four adipate dianions, thereby forming a rare two-dimensional network. In 11, the mercury(II) atom in the [Hg(Tab)2](2+) dication is coordinated by one nitrogen and two oxygen atoms from one Meida(2-) dianion to have a rare square pyramidal geometry. The formation of 2-11 from 1 may be applicable to mimicking the interactions of the mercury(II) sites of Hg-MerR and Hg-MT with various amino acids encountered in nature.

A Convenient Strategy for Designing a Soft Nanospace: An Atomic Exchange in a Ligand with Isostructural Frameworks

Direct observation of gas molecules confined in the nanospace of porous materials by single-crystal X-ray diffraction (SXRD) technique is significant because it leads to deep insight into the adsorption mechanism and the actual state of the adsorbents in molecular level. A recent study revealed that flexibility is one of the important factors to achieve periodic guest accommodation in the nanospace enabling direct observation of gas molecules. Here, we report a convenient strategy to tune the framework flexibility by just an atomic exchange in a ligand, which enables us to easily construct a soft nanospace as the best platform to study gas adsorption. Indeed, we succeeded to observe C2H2 and CO2 molecules confined in the pores of a flexible porous coordination polymer (PCP-N) in different configurations using SXRD measurement, whereas gas molecules in a rigid framework (PCP-C) isostructural to PCP-N were not seen crystallographically. The result of the coincident in situ powder X-ray diffraction and adsorption measurement for PCP-N unambiguously showed that the framework could flexibly transform to trap gas molecules with a commensurate fashion. In addition, for PCP-N, we found that the adsorbed gas molecules induced significant structural change involving dimensional change of the pore from one-dimensional to three-dimensional, and subsequently, additional gas molecules formed periodic molecular clusters in the nanospace.

U(VI) and Zn(II) coordination complexes with 5-(N-acetato(4-pyridyl))tetrazolate anions

A U(VI) mononuclear coordination complex [UO2(a4-ptz)2·(H2O)3] (1) and a Zn(II) 1-D coordination polymer [Zn(a4-ptz)2·(H2O)2]·2H2O (2) have been synthesized with 5-[N-acetato(4-pyridyl)]tetrazolate (a4-ptz) as ligand. Complex 1 has a slightly distorted pentagonal bipyramid around each U center. Complex 2 is octahedral with four a4-ptz and two water ligands. Each Zn center is linked by carboxylate-O(1) and tetrazolate-N(2) of a4-ptz forming a 1-D polymeric chain. Complexes 1 and 2 are self-assembled to form 3-D supramolecular structures through hydrogen bonds. The luminescence properties of 1 and 2 were investigated at room temperature in the solid state. The results suggest that 1 and 2 may be useful as photoactive materials.

Bis(5-aminotetrazole-1-acetato-kappaO)tetraaquacobalt(II) and catena-poly[[cadmium(II)]-bis(mu-5-aminotetrazole-1-acetato-kappa3N4:O,O')].

The Co(II) atom in bis(5-aminotetrazole-1-acetato)tetraaquacobalt(II), [Co(C3H4N5O2)2(H2O)4], (I), is octahedrally coordinated by six O atoms from two 5-aminotetrazole-1-acetate (atza) ligands and four water molecules. The molecule has a crystallographic centre of symmetry located at the Co(II) atom. The molecules of (I) are interlinked by hydrogen-bond interactions, forming a two-dimensional supramolecular network structure in the ac plane. The Cd(II) atom in catena-poly[[cadmium(II)]-bis(mu-5-aminotetrazole-1-acetato], [Cd(C3H4N5O2)2]n, (II), lies on a twofold axis and is coordinated by two N atoms and four O atoms from four atza ligands to form a distorted octahedral coordination environment. The Cd(II) centres are connected through tridentate atza bridging ligands to form a two-dimensional layered structure extending along the ab plane, which is further linked into a three-dimensional structure through hydrogen-bond interactions.

Four coordination clusters using fluorenyl and carbazyl phosphonates as ligands

Four polynuclear complexes, [Co4(FluPO3)2(FluPO3H)2(CH3CO2)2(py)6(H2O)2] (1), [Mn5O3(FluPO3)2(PhCO2)5(CH3OH)(phen)2] (2), [Mn5O3(CarbPO3)2(PhCO2)5(CH3OH)(phen)2] (3) and [MnII4MnIII6O2(OH)2(CarbPO3)8(PhCO2)4(py)6] (4) (FluPO3H2 = (9-methyl-9H-fluoren-9-yl)phosphonic acid, CarbPO3H2 = N-carbazolylmethylphosphonic acid), were synthesized and characterized. In compound 1, the cobalt centers are bridged by phosphonate ligands into a circle. Both the cores of complexes 2 and 3 feature three μ3-O and two capping FluPO32− or CarbPO32− groups bridging five MnIII atoms to form a basket-like cage structure. Complex 4 contains divalent and trivalent ions and has a butterfly-like [MnII4MnIII6O2(OH)2(CarbPO3)4]12+ core with four phosphonate ligands in the body position and five Mn atoms on each wing side. Magnetic susceptibility measurements reveal the existence of antiferromagnetic interactions in 1, 2·4CH3CN·2H2O, 3·PhCO2H·6CH3CN·2H2O and 4·py·8H2O. Fitting the experimental data led to the following parameters: J1 = −10.1 cm−1, J2 = −18.0 cm−1, J3 = −8.0 cm−1, J4 = −5.9 cm−1, J5 = −2.8 cm−1, g = 2.0 for 2·4CH3CN·2H2O, and J1 = −7.4 cm−1, J2 = −22.8 cm−1, J3 = −6.9 cm−1, J4 = −4.8 cm−1, J5 = −0.3 cm−1, g = 2.0 for 3·PhCO2H·6CH3CN·2H2O.

Syntheses and characterization of 2-D lanthanide complexes based on and isonicotinate N-oxide ligand

The lanthanide complexes [Ln2(INO)2(SO4)2(H2O)4] · H2O 1 · Ln (Ln = Ce, Pr, and Nd; INO = isonicotinate N-oxide) were synthesized under hydrothermal conditions. The compounds are isostructural and crystallized in monoclinic space group C2/c. Ln(III) is nine-coordinate in a mono-capped square antiprism coordination environment. Ln(III) ions are linked by , N-oxide groups and carboxylates from INO to give an inorganic chain. These chains are connected by INO ligands into a 2-D layer. These layers are joined through hydrogen bonding interactions into a 3-D crystal structure.