Mechanism for activation of triosephosphate isomerase by phosphite dianion: the role of a ligand-driven conformational change

The L232A mutation in triosephosphate isomerase (TIM) from Trypanosoma brucei brucei results in a small 6-fold decrease in k(cat)/K(m) for the reversible enzyme-catalyzed isomerization of glyceraldehyde 3-phosphate to give dihydroxyacetone phosphate. In contrast, this mutation leads to a 17-fold increase in the second-order rate constant for the TIM-catalyzed proton transfer reaction of the truncated substrate piece [1-(13)C]glycolaldehyde ([1-(13)C]-GA) in D(2)O, a 25-fold increase in the third-order rate constant for the reaction of the substrate pieces GA and phosphite dianion (HPO(3)(2-)), and a 16-fold decrease in K(d) for binding of HPO(3)(2-) to the free enzyme. Most significantly, the mutation also results in an 11-fold decrease in the extent of activation of the enzyme toward turnover of GA by bound HPO(3)(2-). The data provide striking evidence that the L232A mutation leads to a ca. 1.7 kcal/mol stabilization of a catalytically active loop-closed form of TIM (E(c)) relative to an inactive open form (E(o)). We propose that this is due to the relief, in L232A mutant TIM, of unfavorable steric interactions between the bulky hydrophobic side chain of Leu-232 and the basic carboxylate side chain of Glu-167, the catalytic base, which destabilize E(c) relative to E(o).     

N,N'-双(苯甲酰丙酮)-1,4-丁二胺席夫碱银(I)配合物的合成及其晶体结构

以苯甲酰丙酮与1,4-丁二胺经缩合反应制得一个新的席夫碱配体——N,N'-双(苯甲酰丙酮)-1,4-丁二胺(L);L与硝酸银经配位反应合成了配合物[Ag_2(L)(NO_3)_2]_n(1),其结构经1H NMR,13C NMR,FT-IR,元素分析和X-射线单晶衍射表征。晶体结构解析表明:1(CCDC∶1 434 692)属单斜晶系,空间群P21/c,晶胞参数a=0.997 81(5)nm,b=0.778 36(4)nm,c=1.704 13(8)nm,β=106.637 0(10),V=1.261 85(11)nm3,Z=2,Dc=1.884 g·cm~(-3),R1=0.020 8,wR_2=0.054 4。1中每个银离子为扭曲四面体的配位构型,分别和相邻配体的γ-碳原子,氧原子及两个NO_3~-的氧原子配位;每个配体作为四齿配体,分别用两端的γ-碳原子,氧原子和四个银离子配位形成1D链结构,1D通过NO_3~-与银离子配位扩展形成3D网状结构。热稳定性研究结果表明:L和1的初始分解温度分别为300℃和200℃。     

Functional specificities of methylglyoxal synthase and triosephosphate isomerase: a combined QM/MM analysis

Combined SCC-DFTB/CHARMM calculations were carried out to analyze the origin for the functional specificities of triosephosphate isomerase (TIM) and methylglyoxal synthase (MGS). The two enzymes bind to the same substrate, dihydroxyacetone phosphate (DHAP), and have rather similar active sites. However, they catalyze different reactions; TIM catalyzes the isomerization of DHAP to glyceraldehyde 3-phosphate (GAP), while MGS catalyzes the elimination of phosphate from DHAP. Similar to previous suggestions, the calculations confirmed that GAP formation is prohibited in MGS due primarily to the reduced flexibility of the catalytic base (Asp 71) compared to that in TIM (Glu 165). For the suppression of phosphate elimination in TIM, the calculations show that the widely accepted stereoelectronic argument that invokes the different phosphoryl torsion angles observed in the X-ray structures of inhibitor complexes of the two enzymes is not as important as electrostatic contributions from the protein and water molecules surrounding the phosphoryl.     

Scrambling of oxygen-18 during the "borderline" solvolysis of 1-(3-nitrophenyl)ethyl tosylate

[reaction: see text] There is substantial isomerization (kiso=0.32 x 10(-3) s(-1)) of 3-NO2C6H4(13)CH(Me)OS(18O)2Tos during solvolysis (ksolv=1.04 x 10(-3) s(-1)) in 50/50 trifluoroethanol/water, even though the estimated lifetime of the putative 1-(3-nitrophenyl)ethyl carbocation intermediate of solvolysis (ca. 10(-13) s(-1)) is too short to allow rearrangement that exchanges the positions of 16O and 18O at the sulfonate leaving group. This suggests that isomerization proceeds by a mechanism that avoids formation of the carbocation-anion pair intermediate.     

Fluorescence turn on of coumarin derivatives by metal cations: a new signaling mechanism based on C=N isomerization

[reaction: see text] A new sensing mechanism based on C=N isomerization, which shows a very significant fluorescence enhancement to the metal cations in a simple and efficient way, is demonstrated. A coumarin derivative (L) containing a C=N group was designed as an example for illustration. The free ligand L is almost nonfluorescent due to the isomerization of C=N double bond in the excited state. However, the solution of ligand shows about a 200-fold increase of fluorescence quantum yield (about 30%) upon addition of Zn(ClO4)2.     

Betaine-induced assembly of neutral infinite columns and chains of linked silver(I) polyhedra with embedded acetylenediide

Ten polymeric silver(I) double salts containing embedded acetylenediide: [(Ag2C2)2(AgCF3CO2)9(L1)3] (1), [(Ag2C2)2(AgCF3CO2)10(L2)3]H2O (2), [(Ag2C2)(AgCF3CO2)4(L3)(H2O)]0.75 H2O (3), [(Ag2C2)(1.5)(AgCF3CO2)7(L4)2] (4), [(Ag2C2)(AgCF3CO2)7(L5)2(H2O)] (5), [(Ag2C2) (AgC2F5CO2)7(L1)3(H2O)] (6), [(Ag2C2)(AgCF3CO2)7(L1)3(H2O)]2 H2O (7), [(Ag2C2)(AgC2F5CO2)6(L3)2] (8), [(Ag2C2)2(AgC2F5CO2)12(L4)2(H2O)4]H2O (9), and [(Ag2C2)(AgCF3CO2)6(L3)2(H2O)]H2O (10) have been isolated by varying the types of betaines, the perfluorocarboxylate ligands employed, and the reaction conditions. Single-crystal X-ray analysis has shown that 1-4 all have a columnar structure composed of fused silver(I) double cages, with C2(2-) species embedded in its stem and an exterior coat comprising anionic and zwitterionic carboxylates. For 5 and 6, single silver(I) cages are linked into a beaded chain through both types of carboxylate ligands. In 7, two different coordination modes of L1 connect the silver(I) polyhedra into a chain. For 8, the mu(2)-O,O' coordination mode of L3 connects the silver(I) double cages into a chain. Compound 9 exhibits a two-dimensional architecture generated from the cross-linkage of double cages by C2F5CO2-, L4, and [Ag2(C2F5CO2)2] units. Similar to 9, 10 is also a two-dimensional structure, which is formed by connecting the chains of linked double cages through [Ag2(CF3CO2)2] bridging.     

Inductive Effects on the Energetics of Prolyl Peptide Bond Isomerization: Implications for Collagen Folding and Stability

The hydroxylation of proline residues in collagen enhances the stability of the collagen triple helix. Previous X-ray diffraction analyses had demonstrated that the presence of an electron-withdrawing substituent on the pyrrolidine ring of proline residues has significant structural consequences [Panasik, N., Jr.; Eberhardt, E. S.; Edison, A. S.; Powell, D. R.; Raines, R. T. Int. J. Pept. Protein Res.1994, 44, 262-269]. Here, NMR and FTIR spectroscopy were used to ascertain kinetic and thermodynamic properties of N-acetyl-[β,γ-(13)C]D,L-proline methylester (1); N-acetyl-4(R)-hydroxy-L-proline [(13)C]methylester (2); and N-acetyl-4(R)-fluoro-L-proline methylester (3). The pK(a)'s of the nitrogen atom in the parent amino acids decrease in the order: proline (10.8) > 4(R)-hydroxy-L-proline (9.68) > 4(R)-fluoro-L-proline (9.23). In water or dioxane, amide I vibrational modes decrease in the order: 1 > 2 > 3. At 37 °C in dioxane, the rate constants for amide bond isomerization are greater for 3 than 1. Each of these results is consistent with the traditional picture of amide resonance coupled with an inductive effect that results in a higher bond order in the amide C=O bond and a lower bond order in the amide C-N bond. Further, at 37 °C in water or dioxane equilibrium concentrations of the trans isomer increase in the order: 1 < 2 < 3. Inductive effects may therefore have a significant impact on the folding and stability of collagen, which has a preponderance of hydroxyproline residues, all with peptide bonds in the trans conformation.     

Increasing structure dimensionality of copper(I) complexes by varying the flexible thioether ligand geometry and counteranions

This work focuses on the systematic investigation of the influences of pyrimidine-based thioether ligand geometries and counteranions on the overall molecular architectures. A N-containing heterocyclic dithioether ligand 2,6-bis(2-pyrimidinesulfanylmethyl)pyridine (L1) and three structurally related isomeric bis(2-pyrimidinesulfanylmethyl)benzene (L2-L4) ligands have been prepared. On the basis of the self-assembly of CuX (X = I, Br, Cl, SCN, or CN) and the four structurally related flexible dithioether ligands, we have synthesized and characterized 10 new metal-organic entities, Cu4(L1)2I4 1, Cu4(L1)2Br4 2, [Cu2(L2)2I2.CH3CN]n 3, [Cu(L3)I]n 4, [Cu(L3)Br]n 5, [Cu(L3)CN]n 6, [Cu(L4)CN]n 7, [Cu2(L4)I2]n 8, [Cu2(L4)(SCN)2]n 9, and [[Cu6I5(L4)3](BF4).H2O]n 10, by elemental analyses, IR spectroscopy, and X-ray crystallography. Single-crystal X-ray analyses show that the 10 Cu(I) complexes possess an increasing dimensionality from 0D (1 and 2) to 1D (3-5) to 2D (6-9) to 3D (10), which indicates that the ligand geometry takes an essential role in the framework formation of the Cu(I) complexes. The influence of counteranions and pi-pi weak interactions on the formation and dimensionality of these coordination polymers has also been explored. In addition, the photoluminescence properties of Cu(I) coordination polymers 4-10 in the solid state have been studied.     

Alkene isomerization catalysed with platinum hydride complexes

The mechanism of but-1-ene, pent-1-ene and 3-methylbut-1-ene isomerization catalysed with trans-[PtH(SnX₃)L₂] (I, L = PPh₃, PMePh₂, PEt₃, PPr₃; X = Cl, Br) have been studied. Stoichiometric reactions of I with the alkenes proceed even at ?90°C giving cis-[Pt(alkyI-1) (SnX₃) L₂] (II). The equilibrium amounts of II are dependent on the nature of the phosphines, halogens and alkenes. The isomerization rates, determined at +20°C, change in parallel with the relative stabilities of II as a function of phosphine (PMePh₂ > PPh₃ > PAlk₃) and halogen (Br > Cl), and decrease with methyl substitution at γ- and δ- carbons of the alkenes. 2-Substituted alk-1-enes undergo no isomerization in the reactions under investigation. When L is PPh₃ or PMePh₂, the main platinum-containing species in the course of the isomerization are trans-[Pt(alkyl-1) (SnX₃)L₂], appearing as a result of cis-trans isomerization of II. The conversion of I, L = PAlk₃ into related trans-alkyl complexes, and oxidation of I, proceed more slowly than the isomerization of alkenes. The ratio of cis- to trans-alk-2-enes is dependent on the size of L and is a maximum for L = PPh₃.     

Zum Mechanismus der α-Alkinon-Cyclisierung: Synthese und Thermolyse von 1-(1-Methylcyclopentyl)[3-13C]prop-2-inon

On the Mechanism of the α-Alkynone Cyclization: Synthesis and Thermolysis of 1-(1-Methylcyclopentyl)[3-¹³C]prop-2-ynone The relative migratory aptitude of two acetylenic substituents in the α-alkynone cyclization, a thermal conversion of α-acetylenic ketones A to 2-cyclopentenones C , was investigated by isotope-labeling experiments. The α-alkynone [β-¹³C]- 1 , specifically labeled with ¹³C at the β-acetylenic C-atom C(3), was synthesized by an intramolecular Witting reaction (230–300°) of the diacylmethylidenephosphorane [¹³C]- 7. The latter resulted from acylation of methylidenetriphenylphosphorane with the acid chloride 4 to yield the acylmethylidenephosphorane 5 , which in turn was formylated with acetic [¹³C]formic anhydride ([¹³C]- 6. ) Upon thermolysis of [β-¹³C]- 1 , its label at C(β) was transferred almost exclusively to C(β) of the 2-cyclopentenone moiety in the resulting cyclization product [¹³C]- 2. We conclude that there is a distinct preference for hydrogen migration in the acetylene → alkylidene carbene isomerization (A → B) which precedes the cyclization step (B → C). No evidence was found for a fast reversibility of this isomerization (A ? B) involving both acetylenic substituents.     

Entanglement of individual coordination polymers having helicates as building intermediates

A series of Ag(I) coordination compounds, from one-dimensional chains to 3D porous frameworks, were achieved from N,N'-bis[1-(2-pyrazinyl)ethylidene]benzil dihydrazone, L, via self-assembly, using helicates as effective secondary building units. Compound 2 [(Ag(2.75)L)(NO(3))(2.75)] was comprised of two opposite-handed 3D frameworks formed by connecting the 4(1) helical chains into (10(3)-b) nets. The pairs of the racemic 3D frameworks were connected through additional silver(I) centers and entangled each other forming a racemic 3D net. Compound 3 [(Ag(13)L(8))(BF(4))(13)(H(2)O)(12)] was comprised of a 3D framework that was constructed from double-helical building intermediates Ag(2)L(2) with one-dimensional infinite chains being threaded into the large voids of a 3D framework to form a weave structure. The ladder-like chains in compound 4 [(Ag(3)L(2))(ClO(3))(3)(CH(3)OH)(2)(CH(3)CN)] were formed by the addition of excess NaClO(3) into the methanol solution containing AgNO(3) and the ligand L, and the zigzag chains in compound 5 [(Ag(2)L(2))(ClO(4))(2)(CH(3)CN)(2)] were constructed by the addition of excess NaClO(4) into an acetonitrile solution containing AgNO(3) and the ligand L.     

Amide-Amide and Amide-Water Hydrogen Bonds: Implications for Protein Folding and Stability

Amide-amide hydrogen bonds have been implicated in directing protein folding and enhancing protein stability. Inversion transfer (13)C NMR spectroscopy and IR spectroscopy were used to compare the ability of various amide solvents and of water to alter the rate of the cis-trans isomerization of the prolyl peptide bond of Ac-Gly-[β,δ-(13)C]Pro-OMe and the amide I vibrational mode of [(13)C=O]Ac-Pro-OMe. The results indicate that secondary amides are significantly weaker hydrogen bond donors than is formamide or water. These results are most consistent with models for protein folding in which the formation of secondary structure is a cooperative process that follows hydrophobic collapse. These results also suggest that a hydrogen bond between a main-chain oxygen and an asparagine or glutamine sidechain may contribute more to protein stability than does a main-chain-main-chain hydrogen bond.     

When does an intermediate become a transition state? Degenerate isomerization without competing racemization during solvolysis of (S)-1-(3-nitrophenyl)ethyl tosylate

(S)-1-(3-Nitrophenyl)ethyl tosylate [(S)-2-OTs] was prepared in >99% enantiomeric excess and the change in the chiral purity of this compound was monitored during solvolysis in 50:50 trifluoroethanol/water. The barely detectable formation of 0.5% (R)-2-OTs after two half times for the solvolysis reaction was used to calculate a rate constant of k(rac) approximately equal to 4 x 10-6 s-1. This is 80-fold smaller than kiso = 3.2 x 10-4 s-1 for the isomerization that exchanges oxygen-16 and oxygen-18 of 3-NO2C6H413CH(Me)OS(18O)2Tos during solvolysis and 10-fold smaller than the minimum value of k(rac) = 4.6 x 10-5 s-1 predicted if isomerization and racemization products form by partitioning of a common ion-pair intermediate of a stepwise reaction. It is concluded that the isomerization reaction proceeds mainly by a pathway that avoids formation of this putative intermediate. It is suggested that the solvolysis reaction of 2-OTs may proceed by a stepwise preassociation mechanism where solvent "reorganization" precedes substrate ionization to form an ion-pair intermediate.     

Syntheses, structures, and photoluminescence properties of metal(II) halide complexes with pyridine-containing flexible tripodal ligands

Seven coordination compounds, [Zn(L3)Cl2] . MeOH . H2O (1), [Mn(L3)2Cl2] . 0.5EtOH . 0.5H2O (2), [Cu3(L2)2Cl6] . 2DMF (3), [Cu3(L2)2Br6] . 4MeOH (4), [Hg2(L4)Cl4] (5), [Hg2(L4)Br4] (6), and [Hg3(L4)2I6] . H2O (7), were synthesized by the reactions of ligands 1,3,5-tris(3-pyridylmethoxyl)benzene (L3), 1,3,5-tris(2-pyridylmethoxyl)benzene (L2), and 1,3,5-tris(4-pyridylmethoxyl)benzene (L4) with the corresponding metal halides. All the structures were established by single-crystal X-ray diffraction analysis. In complexes 1 and 2, L3 acts as a bidentate ligand using two of three pyridyl arms to link two metal atoms to result in two different 1D chain structures. In complexes 3 and 4, each L2 serves as tridentate ligand and connects three Cu(II) atoms to form a 2D network structure. Complexes 5 and 6 have the same framework structure, and L4 acts as a three-connecting ligand to connect Hg(II) atoms to generate a 3D 4-fold interpenetrated framework, while the structure of complex 7 is an infinite 1D chain. The results indicate that the flexible ligands can adopt different conformations and thus can form complexes with varied structures. In addition, the coordination geometry of the metal atom and the species of the halide were found to have great impact on the structure of the complexes. The photoluminescence properties of the complexes were investigated, and the Zn(II), Mn(II) and Hg(II) complexes showed blue emissions in solid state at room temperature.     

Vapochromic behavior of {Ag2(Et2O)2[Au(C6F5)2]2}n with volatile organic compounds

The vapochromic behaviors of {Ag2L2[Au(C6F5)2]2}n (L = Et2O (1), Me2CO (2), THF (3), CH3CN (4)) were studied. {Ag2L2[Au(C6F5)2]2}n (L = Et2O (1)) was synthesized by the reaction of [Bu4N][Au(C6F5)2] with AgOClO3 in 1:1 molar ratio in CH2Cl2/Et2O (1:2). 1 was used as starting material with THF to form {Ag2L2[Au(C6F5)2]2}n (L = THF (3)). 3 crystallizes in the monoclinic space group C2/c and consists of tetranuclear units linked together via aurophilic contacts resulting in the formation of a 1D polymer that runs parallel to the crystallographic z axis. The gold(I) atoms are linearly coordinated to two pentafluorophenyl groups and display additional Au...Ag close contacts within the tetranuclear units with distances of 2.7582(3) and 2.7709(3) A. Each silver(I) center is bonded to the two oxygen atoms of the THF molecules with a Ag-O bond distance of 2.307(3) A. TGA analysis showed that 1 loses two molecules of the coordinated solvent per molecular unit (1st one: 75-100 degrees, second one: 150-175 degrees C), whereas 2, 3, and 4 lose both volatile organic compounds (VOCs) and fluorinated ligands in a less well defined manner. Each complex loses both the fluorinated ligands and the VOCs by a temperature of about 325 degrees C to give a 1:1 gold/silver product. X-ray powder diffraction studies confirm that the reaction of vapors of VOCs with 1 in the solid state produce complete substitution of the ether molecules by the new VOC. The VOCs are replaced in the order CH3CN > Me2CO > THF > Et2O, with the ether being the easiest to replace. {Ag2(Et2O)2[Au(C6F5)2]2}n and {Ag2(THF)2[Au(C6F5)2]2} n both luminesce at room temperature and at 77 K in the solid state. Emission maxima are independent of the excitation wavelength used below about 500 nm. Emission maxima are obtained at 585 nm (ether) and 544 nm (THF) at room temperature and at 605 nm (ether) and 567 nm (THF) at 77 K.     

Haloacyl complexes of boron, [(CF3)3BC(O)Hal]- (Hal=F, Cl, Br, I)

The haloacyltris(trifluoromethyl)borate anions [(CF3)3BC(O)Hal]- (Hal=F, Cl, Br, I) have been synthesized by reacting (CF3)3BCO with either MHal (M=K, Cs; Hal=F) in SO2 or MHal (M=[nBu4N]+, [Et4N]+, [Ph4P]+; Hal=Cl, Br, I) in dichloromethane. Metathesis reactions of the fluoroacyl complex with Me3SiHal (Hal=Cl, Br, I) led to the formation of its higher homologues. The thermal stabilities of the haloacyltris(trifluoromethyl)borates decrease from the fluorine to the iodine derivative. The chemical reactivities decrease in the same order as demonstrated by a series of selected reactions. The new [(CF3)3BC(O)Hal]- (Hal=F, Cl, Br) salts are used as starting materials in the syntheses of novel compounds that contain the (CF3)3B-C fragment. All borate anions [(CF3)3BC(O)Hal]- (Hal=F, Cl, Br, I) have been characterized by multinuclear NMR spectroscopy (11B, 13C, 17O, 19F) and vibrational spectroscopy. [PPh4][(CF3)3BC(O)Br] crystallizes in the monoclinic space group P2/c (no. 13) and the bond parameters are compared with those of (CF3)3BCO and K[(CF3)3BC(O)F]. The interpretation of the spectroscopic and structural data are supported by DFT calculations [B3LYP/6-311+G(d)].     

A New Metal-organic Framework Constructed from Flexible Polycarboxylate Acid and Rigid Imidazole-based Ligands

A new complex, [Ni3(L)2(BTA)2]·2H2O (1, L=1,4-di(1H-imidazol-4-yl)benzene, H3BTA=benzene-1,3,5-triacetic acid), has been hydrothermally prepared and characterized by single-crystal X-ray diffraction, IR spectroscopy, elemental analysis, TG and PXRD. The complex crystallizes in monoclinic, space group P1 with a=9.0303(12), b=10.0796(13), c=12.7966(17) , α=99.268(2), β=94.490(2), γ=103.722(3)o, V=1108.5(3) 3 , Z=2, C48H38N8O14Ni3 , Mr=1126.99, Dc=1.688 g/cm3 , μ=1.344 mm-1 , S=1.001, F(000)=578, the final R=0.0389 and wR=0.0895 for 3083 observed reflections (I > 2σ(I)). In the title complex, the flexible BTA3- ligands utilize oxygen atoms of carboxylate groups to coordinate with Ni(II) ions to form two-dimensional double-layer networks which are further pillared into a three-dimension framework via the rigid ditopic ligand L. Topological analysis revealed that complex 1 is a typical (3,8)-connected tfz-d 3D network based on the trinuclear [Ni3(CO2)6N4] subunits.     

Synthesis and Crystal Structure of a Novel Bimetallic Porphyrin Complex Salt {[MnTPP(CH3OH)2]3Fe(CN)6}·13H2O

A novel bimetallic porphyrin complex salt, {[MnTPP(CH3OH)2]3Fe(CN)6}·13H2O (TPP = tetraphenylporphyrin), has been synthesized and structurally characterized by X-ray diffraction analysis. The crystal is of trigonal, space group R-3 with a = b = 31.0618(10), c = 11.8366(8) (A), Z = 3, V = 9890.3(8) (A)3, C144H134FeMn3N18O19, Mr = 2641.36, Dc = 1.330 g/cm3, μ(MoΚα) = 0.463 mm-1, F(000) = 4131, R = 0.0525 and wR = 0.1382 for 3045 observed reflections (I ＞ 2((I)). The title complex is composed of one [Fe(CN)6]3- anion, three [MnTPP(CH3OH)2] cations and thirteen water molecules, which are connected by multiform hydrogen bonds leading to a 3D supramolecular network structure.     

Amidinate bromogermylene resulting from carbodiimide insertion into Ar–GeBr bond

The reaction of diaryldibromodigermene Tbb(Be)Ge = Ge(Br)Tbb (Tbb = 4-Bu^t-2,6-[CH(SiMe₃)₂]₂C₆H₂) with N,N'-diisopropyl-carbodiimide afforded the corresponding amidinato-supported bromogermylene via the insertion of the C=N moiety into the Ge–C(Tbb) sss-bond. The formation mechanism of the amidinato-supported bromogermylene was revealed by DFT calculations. This type of insertion reaction toward a metal–carbon bond can be interpreted in analogy to the reactivity of transition-metal complexes.     

A One-dimensional Metallic Oxide Constructed from Molybdenum Clusters and Mn（Ⅱ）-[3-（2-pyridyl） pyrazole] Cationic Coordination Components

A new polyoxomolybdate compound [Mn II (L) 2 (Mo 8 O 26) 0.5 ] 2n (1,L=3-(2-pyridyl)pyrazole) has been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction,elemental analyses,TG and IR spectroscopy.The compound crystallizes in the triclinic system,space group P1 with a=10.063(4),b=11.554(5),c=11.554(5),α=88.89,β=74.839(4),γ=74.839(4)o,V=1249.8(9) 3,C 16 H 14 MnMo 4 N 6 O 13,M r=937.03,D c=2.490 g/cm 3,μ(MoKα)=2.521 mm 1,F(000)=898,Z=2,the final R=0.0390 and wR=0.0970 for 4000 observed reflections (I > 2σ(Ⅰ)).Single-crystal X-ray diffraction analysis results reveal that compound 1 owns a chain structure based on β-[Mo 8 O 26 ] 4anions,which are linked by Mn II (L) 2 units via the terminal oxygen atoms.