Synthesis and Crystal Structure of the First Guanidinate Complex of Tetravalent Cerium

Reaction of Ce（O-t-Bu）2（NO3）2 and sodium guanidinate GuaNa （Gua-=TMS2NC（NC6H11）2-） in THF affords the first guanidinate Ce（IV） complex of Ce2（O-t-Bu）7（Guaˊ） （1, Gua-=（C6H11NH）C（NC6H 11）（NH）-）. It crystallizes in monoclinic, space group P21/n with a=15.2937（14）, b=17.8409（16）, c=19.0454（16）, β=97.713（2）°, V=5149.6（8）3 , Z=4, Mr=1014.38, Dc=1.308 g/cm3 , μ=1.787 mm-1 , F（000）=2104, S=1.015, R=0.0451 and wR=0.0901 （I 〉 2σ（I））. In the reaction the cleavage of TMS-N bonds happened unexpectedly.

Synthesis and structural analysis of titanium-μ-dinitrogen complex supported by di-anionic guanidinate ligands

The synthesis,characterization,and theoretical studies of titanium-μ-N_(2) complexes with di-anionic guanidinate ligands were reported as the first example of its kind.Thus,with(Me_(3)Si)_(2)N-guanidinate ligands,the mono-anionic guanidinate-supported titanium-μ-N2complex 1 was obtained.Then,reduction of 1 with potassium afforded the di-anionic guanidinate-supported titanium-μ-N_(2) complex 2 via cleavage of one N–Si bond of the(Me3Si)2N substituents in 1,changing the guanidinate ligands automatically from mono-anionic to di-anionic and remarkably lengthening the bond length of theμ-N_(2).Characteristic studies and DFT calculations were performed to reveal that the di-anionic guanidinate ligands stabilized the geometry of 2 and increased the charge density on the bridging dinitrogen.

Chelating Guanidinates for Dysprosium(Ⅲ) Single-Molecule Magnets

Two chelating guanidinate-based dysprosium(Ⅲ)complexes,namely the monomeric{(Me_(3)Si)_(2)NC(N^(i)Pr)_(2)}_(2)Dy(μ-CI)_(2)Li(THF)_(2) 1 and the dimeric[{(Me_(3)Si)_(2)NC(N^(i)Pr)_(2)}_(2)Dy(μ-CI)]_(2) 2,have been confirmed to be single-molecule magnets.Moreover,the alteration from 1 to 2 leads to an obvious mitigated quantum tunnelling of magnetization at zero field of the hysteresis loop and much enhanced magnetic relaxation barrier(up to 312 K).5%dilution with the yttrium(Ⅲ)analogue for 2 shows no clear change for the hysteresis,indicating the single-ion nature of the magnetic behavior.

Theoretical investigation on organolanthanide guanidinate complexes

Density functional theory (DFT) calculations were carried out on the compounds Cp2Ln-guan for Ln=Y, Lu, Yb, Dy and Gd, [guan=(iPrN)2CN(iPr)2]. The results were compared with the X-ray structures that were available from the literature; the calculations reproduced quite well the experimental structural features in these complexes exhibiting distorted tetrahedron geometry. The calculated evolution of the Ln-guan bond as a function of the cation showed that lanthanide-ligand distances increased with the increa...

Synthesis and Structural Characterization of Alkali Metal Guanidinates

Reactions of 1,3-diisopropylcarbodiimide with alkali metal amides, MN（SiMe3）2 （M=Li or Na） in hexane or THF produced the alkali metal guanidinates { （i-PrN）2C [N（SiMe3）2]Li }2 （1） and { （i-PrN）2C[N（SiMe3）2]Na（THF） } 2 （2） in nearly quantitative yields. Both complexes 1 and 2 were well characterized by elemental analysis, IR spectra, ^1H and ^13C NMR spectra, and X-ray diffraction. It was found that the guanidinates adopt different coordination modes in these complexes.

Synthesis and Characterization of Bis（guanidinate） Zirconium Complexes

Addition of one equivalent of LiN（i-Pr）2 or LiN（CH2）5 to carbodiimides, RN=C=NR [R=cyclohexyl （Cy）, isopropyl （i-Pr）], generated the corresponding lithium of tetrasubstituted guanidinates {Li[RNC（N R^′2）NR]（THF）}2 [R=i-Pr, N R^′2=N（i-Pr）2 （1）, N（CH2）5 （2）; R=Cy, N R^′2=N（i-Pr）2 （3）, N（CH2）5 （4）]. Treatment of ZrCl4 with freshly prepared solutions of their lithium guanidinates provided a series of bis（guanidinate） complexes of Zr with the general formula Zr[RNC（N R^′2）NR]2Cl2 [R=i-Pr, N R^′2=N（i-Pr）2 （5）, N（CH2）5 （6）; R=Cy, N R^′2=N（i-Pr）2 （7）, N（CH2）5 （8）]. Complexes 1, 2, 5-8 were characterized by elemental analysis, IR and ^1H NMR spectra. The molecular structures of complexes 1, 7 and 8 were further determined by X-ray diffraction studies.

Synthesis and Crystal Structure of Bis(N,N'- cyclohexyl-N''-bis(trimethylsilyl)samarium Chloride

The reaction of [(SiMe3)2NC(NC6H11)2]Li with SmCl3 in 2:1 molar ratio in THF gave bis(N,N-cyclohexyl-N创-bis(trimethylsilyl)samarium chloride, [(SiMe3)2NC(NC6H11)2]Sm(m- Cl)2Li(THF)2 1 in 85% isolated yield as pale-yellow crystals. Complex 1 was structurally characte- rized by single-crystal X-ray diffraction analysis at 289(2) K. It crystallizes in monoclinic, space group C2/c with a = 26.886(3), b = 13.677(2), c = 19.465(3) ? b = 120.26(1), V = 6182(2) ?, Z = 4, Mr = 1105.84, Dc = 1.188 g/cm3, F(000) = 2340 and m(MoKa) = 1.150 mm-1. The structure was refined to R = 0.0378 and wR = 0.0885 for 4342 observed reflections with I > 2s(I). The coordination geometry of samarium ion can be best described as a distorted pseudooctahedron.

One New Schiff Base Complex with One in Situ Synthesized Ligand:Synthesis and Structure

One new Ni（Ⅱ） complex [Ni（H2L）]Cl（H2O）3 based on one in-situ synthesized Schiff base ligand H3L （H3L = bis（benzyl-2-pyridylidene）-diaminoguanidine） was prepared and structurally characterized by single-crystal X-ray diffraction method. The complex crystallizes in the monoclinic system, space group C2/c with a = 27.944（7）, b = 7.7405（19）, c = 25.999（7） ,A, β = 115.545（2）°, V = 5074（2） A^3, Mr = 566.69, Z = 8, Dc = 1.484 g/cm^3, F（000） = 2352,μ（MoKα） = 0.912 mm^-1, R = 0.0594 and wR = 0.1477 for 5145 observed reflections （1 〉 2σ（I））. The complex exhibits one mononuclear structure in which the Ni（Ⅱ） atom adopts a [NiN4] pseudo-planar square geometry. Interestingly, along the b axis, each two neighboring [Ni（H2L）]^＋ units by an inverse center form pairs of molecules through the intermolecular benzene-pyridine π…π interactions.

Guanidine分子在燃料电池用阴离子交换膜中的应用

以壳聚糖(CS)和2,3-环氧丙基三甲基氯化铵(GTA)为原料,制备季铵化壳聚糖(QCS),将其与小分子游离胍(Guanidine)共混,借助戊二醛(GA)的化学交联作用,将季铵化壳聚糖中的氨基以及胍中的氨基交联,形成网状结构,由此制得含有不同含量Guanidine分子的交联QCS-G阴离子交换膜。实验过程中,对该膜的含水率、溶胀度、力学强度、电导率及耐碱稳定性等进行了详细的考察。结果表明,游离胍的引入可有效地提高膜的电导率和耐碱稳定性,同时降低了膜的溶胀度及含水率。其中小分子游离胍质量分数为2.5%的膜(QCS-G2.5%)在70℃时的电导率可达到6.58×10^(-2)S/cm;在10 mol/L NaOH溶液中浸渍72 h后该膜70℃测得的电导率损失仅为3.8%,离子交换量损失仅为3.82%,表明该膜的耐碱性能较好。

Denaturing Effects of Urea and Guanidine Hydrochloride on Hyperthermophilic Esterase from Aeropyrum pernix K1

The changes in the activity and the conformation of the hyperthermophilic esterase derived from aerobic thermophilic Aeropyrum pernix K1 （ APE1547 ） were studied during denaturation by guanidine hydrochlofide （ GdnHC1 ） and urea. The denaturation course of APE1547 was followed by the steady-state and time resolved fluorescence methods. An increase in the denaturant concentration in the denatured system can significantly enhance the inactivation and unfolding of APE1547. The enzyme can be completely inactivated with a urea concentration of 2.7 mol/L or a GdnHCl concentration of 7.5 mol/L. The fluorescence emission maximum of the enzyme protein red shifts in magnitude to a maximum value（355 nm） when the concentration of GdnHCl is 5.1 mol/L. The experimental results indicate that APE1547 has a high resistance to urea. Unfolding of APE1547 in GdnHCI（4. 2-6.0 mol/L） was shown to be an irreversible process. The present results indicate that the ion pairs in this protein may be a key factor for the stability of this esterase.

Synthesis and NHE1 inhibitory activity of ligustrazine derivatives

A series of novel derivatives of ligustrazine linked with substituted benzoyl guanidine were synthesized. These compounds have not been reported in literature, and their chemical structures were confirmed by IR, ^1H NMR and MS. The results of NHE1 inhibitory activity test showed that compounds I2, I3, I4, I6, and I7 possess more potent NHE1 inhibitory activity than cariporide.

I-123 metaiodobenzylguanidine imaging for predicting ventricular arrhythmia in heart failure patients

Compared to antiarrhythmic drugs, implantable cardioverter defibrillator （ICD） leads to a more significant im- provement in preventing ventricular arrhythmia in heart failure patients. However, an important question has been raised that how to select appropriate patients for ICD therapy. 1-123 metaiodobenzylguanidine （MIBG） planar and SPECT imaging have shown great potentials to predict ventricular arrhythmia in heart failure patients by as- sessing the abnormalities of the sympathetic nervous system. Clinical trials demonstrated that several parameters measured from 1-123 MIBG planar and SPECT imaging, such as heart-to-mediastinum ratio, washout rate, defect score, and innervation/perfusion mismatch, predicted ventricular arrhythmias in heart failure patients. This paper introduces the current practice of ICD therapy and reviews the technical background of 1-123 MIBG planar and SPECT imaging and their clinical data in predicting ventricular arrhythmia.

FLAME RETARDANT OF GUANIDINE CONDENSED PHOSPHATE (GCP) FOR WOOD

GCP and APP were used as flame retardants for poplar wood and larch wood,and their flame retardancy(OI), permeability (Surface electron spectroscopy), water-re pellency and corrosion toward nail evaluated. The results showed that GCP is in advance of APP. From the thermal analysis and char composition analysis, it is concluded that GCP mainly functions in condensed phase.

Polymer Supported Synthesis of Multi-substituted Pyrimidine-4-one Derivatives via Pbf-activated Thiourea

Efficient polymer supported synthesis of multi-substituted pyrimidine-4-one derivatives was described. Target products were produced from fluorenylmethoxycarbonyl（Fmoc） protected β-amino acid loaded on hydro- xymethyl resin through deprotection, N-alkylation, guanidine formation, and cleavage of 2,2,4,6,7-pentamethyl dihy-drobenzofuran-sulfonyl（Pbf） by trifluoracetic acid（TFA） followed with cyclization. The procedure has the advantages of easy operation, mild reaction conditions, and forming multiple substituents.

Simple and Mild Syntheses of Optically Active 2-(N,N-Dialkylamino)oxazolines

Chloroamidinium salts and a-amino alcohols derived from commercially available tetraalkyl ureas and α-amino acids, respectively, can be used for the syntheses of optically active 2-（N,N-dialkylamino）oxazolines in moderate to excellent yields without any catalyst. It is a simple and mild method for the syntheses of optically active oxazolines

Thermal Behavior, Specific Heat Capacity and Adiabatic Time-to-explosion of GDN

A new compound, [（NH2）2C=NH2]＋N（NO2）2-（GDN）, was prepared by mixing ammonium dinitramide （ADN） and guanidine hydrochloride in water. The thermal behavior of GDN was studied under the non-isothermal conditions with DSC and TG/DTG methods. The apparent activation energy（E） and pre-exponential constant（A） of the exothermic decomposition stage of GDN were 118.75 kJ/mol and 10^10.86 s^-1, respectively. The critical temperature of the thermal explosion（Tb） of GDN was 164.09 ℃. The specific heat capacity of GDN was determined with the Micro-DSC method and the theoretical calculation method, and the standard molar specific heat capacity was 234.76 J·mol^-1·K^-1 at 298.15 K. The adiabatic time-to-explosion of GDN was also calculated to be a certain value between 404.80 and 454.95 s.

Rheological Behavior of the Guanidio Polyelectrolytes

The rheological behavior of polyhexamethylene guanidine hydrochloride (PHGC) and polyethylene guanidine stearate (PHGS) has been investigated using the capillary rheometer. It is shown that the polyelectrolyte melts are non-Newtonian of shear. thinning fluid. The melt viscosity, the flow activation energy and the flow temperature are high even if the molecular weight is not high. The melting viscosity of PHGC is higher than that of PHGS at the same experimental conditions. By comparison with the case of PHGS the non-Newtonian index of PHGC is smaller, the flow activation energy and the flow temperature of PHGC are higher, which was caused by the difference in their molecular structure.

Facile Synthesis of [1,2,4]Triazolo[4,3-a]pyrazin-3-amines via Oxidative Cyclization of 1-(Pyrazin-2-yl)guanidine Derivatives

In this study, we applied a novel, mild, and convenient synthetic method involving the oxidative cyclization of 1-(pyrazin-2-yl)guanidine derivatives to produce [1,2,4]triazolo[4,3-a ]pyrazin-3-amines. We optimized the reaction procedure to easily obtain 5-chloro-[1,2,4]triazolo[4,3-a ]pyrazin-3-amine. Various types of halogenated pyrazines can successfully undergo this process. We synthesized a series of 1-(pyrazin-2-yl)guanidines and [1,2,4]triazolo[4,3-a ]pyrazin-3-amines, and then elucidated their structures based on their ~1H-NMR, ^(13)C-NMR, ESI-HRMS, and nuclear Overhauser effect spectra.

A NEW GUANIDINE DERIVATIVE FROM ASTRAGALUS COMPLANATUS R.Br.

A new guanidine derivative,complanatin has been isolated from the seeds of Chinese traditional medicine Astragalus complanatus R.Br..Its structure was established on the basis of spectral data and X-ray crystallographic analysis to be N-[3-carboxypropyl]-N-[3-methyl-2-butenyl]guanidine.