Beer's law experiment, variable-temperature spectral experiment of UV-Vis absorption, 1H NMR, and measurement of magnetic moment were conducted for NiTMPyP in aqueous solution. It was found that Beer's law was obeyed in concentration range 8× 10-7-2×10-5.mol•dm-3.With the temperature increasing from 0 ℃ to 95 ℃, the isosbestic point appeared at 435 nm and the lowest downfield 1H NMR peak narrowed gradually and shifted to upfield. The magnetic moment is 2.07 BM in D2O at 30 ℃, but in the D2O-CD3COCD3 mixed solvent there was no evidence for the existance of paramagnetic species. These results show that NiTMPyP exists in aqueous solution as an equilibrium mixture of diamagnetic, four-coordinate nickel (Ⅱ) and paramagnetic, sir-coordinate nickel (Ⅱ) complexed by water molecules in the axial position. The thermodynamic parameters of the axial-coordinated reaction were △S?=-178.6 J•K-1•mol-1, △G298K?=-1.6 kJ•mol-1. 相似文献
Styrene-terminated poly(oxyethylene) macromonomers (SOE) with narrow molecular weight distribution and quantitative styrene monofunc-tionality were synthesized. In homopolymerization of SOE, conversion of monomer to polymer was shown to be low in spite of high consumption of the vinyl groups of the SOE molecules. Free-radical copolymer-ization of the macromonomer with methyl methacrylate and styrene occurred smoothly, as opposed to homopolymerization. Cumulative copolymer composition and total conversion were determined from the conversions of macromonomer and comonomer (by weight changes) and by proton NMR of the copolymer. The monomer reactivity ratios were found to be ra = 0.06 and rb = 2.0 for the copolymerization of SOE macromonomer (a) with methyl methacrylate (b). In this case the macromonomer exhibited considerably lower reactivity than predicted from its low molecular weight model compound. The monomer reactivity ratios estimated for SOE and styrene were ra = 0.86 and rb = 1.20. The reactivity of SOE was comparable to, but somewhat lower than, styrene. The graft copolymers were used as activators in the halogen displacement reaction, and it was found that their catalytic activity depends on copolymer composition and chemical structure. 相似文献
Poly(methacrylonitrile-co-styrene) (PMANS) and Poly(acrylo-nitrile- co- styrene) (PANS) having 1:1 composition were prepared with free-radical initiators. The polymers were fractionated into fractions having narrow molecular weight distribution. The dilute solution properties of the fractionated copolymers were studied by light scattering, viscometry, and osmometry in solvents (methyl ethyl ketone, dimethylformamide, and acetone), [n]-Mw and(r2)wl/2?Mw relationships have been established. The validity of the various graphical methods for the determination of Flory′s constant, Kθ were observed. From the values of the steric factors it was noticed that the copolymer coil of PANS is stiffer than that of PMANS. 相似文献
Abstract The reaction of SnCl4 with β-chlorovinyl aldehydes in anhydrous dichloromethane gave a series of octahedral complexes of the general formula SnCl4·2L (L = aldehyde). The adducts have been characterized in solution using multinuclear (1H, 13C, and 119Sn) NMR and IR spectroscopy. Solution NMR studies show that the complexes undergo rapid ligand dissociation at ambient temperature. Ligand exchange is slowed significantly at low temperature, such that, in most of the complexes, it is possible to identify both the cis and trans isomers with predominance of the cis form. The magnitude of the metal-ligand interaction was estimated on the basis of 119Sn NMR chemical shifts and used to classify the aldehydes studied according to their Lewis basicity. 相似文献
The 1H, 13C and 15N NMR spectroscopic properties of six thallium tris-(pyrazol-1-yl)borates, including a tetrakis derivative, were determined. The results in solution were necessary to understand those, more complicated, in the solid state. A collection of 205Tl-15N and 205Tl-13C couplings was measured in the latter state. Among those, a very large coupling constant (between 194 and 282 Hz) has been measured on the carbon at the position 4 of the pyrazole ring in several compounds and particularly for the cyclobutyl derivative [Tl(TpCbu)]. It has been assigned to a direct interaction of the 4-C-H ? Tl type and related to the X-ray structures, when available. 相似文献
1H NMR and MALDI-TOF MS measurements were used to study the thermo-mechanical and thermo-oxidative degradation mechanisms of bottle-grade PET (btg-PET). In the thermo-oxidative degradation, the concentration of low molar mass compounds increased with time and the main products were cyclic and linear di-acid oligomers. In the thermo-mechanical degradation, the main-chain scission reactions affect the stability of the cyclic oligomers. One of the most important bottle-grade PET co-monomers is diethylene glycol (DEG), which is a “reactive site” in the thermal degradation of btg-PET. The DEG co-monomer was shown to be the precursor to colour changes in btg-PET, owing to the attack by molecular oxygen on the methylenic protons adjacent to the ether oxygen atoms of DEG. This behaviour was observed in the thermo-oxidative degradation process in which the degradation of DEG causes the release of hydroxyl radicals in the polymeric matrix, thereby producing mono- and di-hydroxyl substituted species. This was also observed in the thermo-mechanical degradation process. 相似文献
The radical polymerization of vinyl monomers initiated with several kinds of hydrophilic macromolecule was carried out in a magnetic field. The magnetic field promoted the polymerization; the conversion of monomers and the molecular weight of the polymers obtained increased with increasing field strength in the range of 0–0.1 T. The dependence of the composition and tacticity of the mother polymer on the magnitude of the magnetic field was studied. Using graft or block copolymers, which consisted of hard and soft segments, the effect of a magnetic field was further investigated. The degree of hardness and tightness of the hydrophobic areas (reaction areas) formed by the mother polymer in the aqueous solution was found to affect the magnetic field effect on the uncatalyzed polymerization. The overall activation energy obtained in the magnetic field was almost equal to that obtained without a magnetic field. 相似文献
The compact conformation of poly(methacrylic acid) which is observed in the unneutralized polymer has been studied using the fluorescence probes 9-methyl anthracene and Rhodamine B. Steady-state and time-resolved fluorescence anisotropy measurements have been made. The results show that this conformation contains a number of binding sites which have molecular weights in the range 9,000–10,000 and which can rotate independently of the remainder of the chain. 相似文献
Well‐defined PEO‐b‐PMMA was prepared, initiated by macroinitiator PEO‐Br, by means of ATRP, where esterification of the terminal hydroxyl group of PEO with 2‐bromoisobutyryl bromide yielded a macroinitiator PEO‐Br. Highly ordered microporous films (hexagonal pattern) were constructed by emulsion micelles of such amphiphilic diblock copolymer formed from a solution with CHCl3/H2O/THF = 100:5:10 (v/v). We also constructed the microporous films using diblock copolymer by the current water‐assisted method.
Poly(ethylene glycol)‐poly(lactide) (PEG‐PLA) block copolymers are processed to solvent cast films and solution electrospun meshes. The effect of polymer composition, architecture, and number of anchoring points for the plasticizer on swelling, degradation, and mechanical properties of these films and meshes is investigated as potential barrier device for the prevention of peritoneal adhesions. As a result, adequate properties are achieved for the massive films with a longer retention of the plasticizer PEG for star‐shaped block copolymers than for the linear triblock copolymers and consequently more endurable mechanical properties during degradation. For electrospun meshes fabricated using the same polymers, similar trends are observed, but with an earlier start of fragmentation and lower tensile strengths. To overcome the poor mechanical strengths and an occurring shrinkage during incubation, which may impair the coverage of the wound, further adaptions of the meshes and the fabrication process are necessary.
New substituted stilbenes have been prepared by reactions of (E)-4-stilbenethiole with dibromoalkanes. 1H and 13C NMR spectra of new compounds have been assigned unambiguously on the basis of a combination of homo- (1H?1H COSY) and heteronuclear (1 H?13C COSY-HETCOR) two-dimensional methods, chemical shifts, and spin-coupling constants. 相似文献
Complexes of the type [Pt R2 (dppma-PP′)] (R─Me, Et, Ph, CH2Ph, C6H4 Me-p, C6H4OMe-2, CH2CMe3, 1-naphthyl, C6H4Me-o, dppma = Ph2PNMe PPh2) have been prepared from [PtCl2, (dppma-PP′)] and the corresponding alkyl-lithium or Grignard reagents. Equilibrium constants, k, for the conversion of [PtR2 (dppma-PP′)] into cis-[PtR2(dppma-P)2] with dppma were studied using 31P NMR spectroscopy at room temperature. Equilibrium is rapidly established for R─C6H4-Me-o, at 20°C. Complex of the type cis-[PtR2 (dppma-P)2] was isolated R─C6H4 Me-o. The complexes [PtMe2(dppma-P)2] and [Pt(o-methoxyphenyl)2(dppma-P)2] were prepared, but unfortunately decomposed once isolated, the only evidence for its formation being from 31P-{1H} NMZR spectroscopy. The o-tolyl or 1-naphthyl complexes exist as syn-anti mixtures in solution, due to restricted rotation around the platinum aryl bonds. Treatment of several complexes of the type [PtR2(dppma-PP′)] with MeI gives [PtR2Me(I)(dppma-PP′)] with trans addition of MeI. Treatment of [PtR2(dppma-PP′)] with HCl gives [Pt Cl (R) (dppma-PP′)] for R─C6H2Me3-2,4,6, C6H4-CH3-2, C6H4-Me-4, Me, 1-naphthyl. The 1H, 31P NMR parameters for these complexes are discussed. Attempted preparation of complexes of the type [PtR2 (dppma-P)2M] (R─C6H4-Me-2, Me CN-C6H4-Me-4); M─Pd, Pt, Au,) are reported. 相似文献
A group of para-substituted bis(acetoxy)iodoarenes has been studied by 17O and 13C NMR. Only one signal for all the oxygens of the acetoxy groups has been observed. Both 17O and 13C chemical shifts of this group show a strong invariance with para substitution. The absence of covalent I-O bonds and an ion pair structure is proposed for the title compounds. 相似文献
In the present study, the synthesis and characterization of a methacrylic-based side chain liquid crystalline monomer and its polymer were investigated with the aid of both 1-D and 2-D nuclear magnetic resonance (NMR) techniques. The mesophase characteristics of the monomer and polymer were determined by hot-stage optical polarized microscopy (HOPM). The nematic and smectic phases were observed for the monomer and polymer. Furthermore, 13C spin-lattice relaxation time measurements were performed on the above systems in order to monitor molecular dynamics. The present study provides an opportunity to carry out a systematic comparison of the evolution of structural as well as dynamical changes of the monomer and the polymer. 相似文献
Summary The reaction of 3,4-methylenedioxycinnamic acid (1) with thionyl chloride resulted in the formation of 7-chlorothieno[2,3-f]-1,3-benzodioxole-6-carbonyl chloride (2) and cinnamoyl chloride (3). Subsequent reaction of the former withp-substituted anilines led to the formation of 7-chloro-N-(p-substituted phenyl)-thieno[2,3-f]-1,3-benzodioxole-6-carboxamides (4a–c) which on photocyclization afforded 2-substituted [1,3]dioxolo[5,6][1]benzothieno[2,3-c]quinolin-6(5H)-ones (5a–c) in fairly good yields and high purity. The structures have been confirmed by IR,1H NMR, and analytical methods.Accepted for presentation at the Hong Kong International Symposium on Heterocyclic Chemistry (August 13–16, 1995) 相似文献
Using silicon tetrachloride (SiCl4), tert-butanol (t-BuOH), ethanol (EtOH) and NH3, the hybridized silicon ethoxide 3-tert-butoxide (Si(OEt)x(OBut)4-x) was synthesized and the configuration of the material was investigated by FT-IR,1 H and 13C NMR and gas chromatogram/mass spectrum (GC/MS) techniques. The results confirm that both the ethoxy and the tert-butoxy groups have been attached to silicon atoms. Furthermore, the alkoxy group types and their relative amounts in the alkoxide were also determined by 1H and 13C NMR and GC/MS. 相似文献
Abstract Poly(acryloyl-L-valine) microspheres containing peroxyester groups were prepared by copolymerization of acryloyl-L-valine with di-t-butyl peroxyfumarate in acetophenone. Graft copolymerization of some vinyl monomers onto the microspheres was carried out by photolysis or thermolysis of the peroxyester groups in the microspheres. When benzyl methacrylate (BzMA) was used as the second monomer, BzMA conversion and grafting efficiency were found to increase with time. This might be ascribed to long lifetime of the polymer radicals in the microspheres. In fact, the very stable propagating radical of BzMA was observed by ESR in the photoinduced graft copolymerization system of the microspheres and BzMA at room temperature. The copolymerization process was investigated by ESR. 相似文献
The X-ray crystal structures of series of 1-aryl-1,4-dihydro-3(2H)-isoquinolinones (1-7) have been determined. Lactame heterocyclic ring possesses more or less deformed boat conformation in all examined structures. The aryl substituent adopts the equatorial position in the structures 1-3 and the axial one in 5-7. In the structure of 4, due to extremely flattened heterocyclic ring, aryl substituent location can be named as bisectional. In all solved structures the molecules are joined into the dimers via two N-H?O hydrogen bonds. At the same time, 1H NMR studies in DMSO-d6 solutions were accomplished and profound analysis of 2J, 3J, and 5J coupling constants have shown that in isoquinolinone system the heterocyclic ring adopts the boat conformation in all investigated compounds. The stereochemical orientations of the phenyl ring at C1 do not depend on the nature of the substituent but, exclusively, on the mode of substitution. However, three forms of undulated laktam heterocyclic ring conformation in respect of 1-aryl substituent positions were confirmed by calculation (conformational analysis). 相似文献