电流型聚吡咯碘离子化学修饰电极的制备与性能研究

在玻碳电极(GCE)表面上修饰了一层导电聚合物 聚吡咯(Ppy)薄膜,用循环伏安法制备了新型的基于电流响应的掺杂碘离子的聚吡咯修饰电极;研究了电极的电化学特性。此修饰电极对碘离子的响应是基于碘离子在Ppy膜与电解质溶液中的掺杂平衡以及Ppy膜中的碘离子在修饰电极表面的氧化还原过程;制成的电流型电极对5 0×10-2mol/L～1 0×10-5mol/L的碘离子呈良好的线性响应关系,检出限为6 0×10-6mol/L。     

核黄素的微分脉冲溶出伏安分析

采用循环伏安法和微分脉冲溶出伏安法,对核黄素在裸金电极和巯基化合物分子自组装膜修饰金电极上的电化学行为进行了研究,发现在pH4.8的B-R缓冲溶液中,核黄素在裸金电极和分子自组装膜修饰金电极上均于-0.35V左右产生一对可逆的氧化还原峰。核黄素在裸金电极和谷胱甘肽、三巯基丙酸、二巯基苯丙咪唑分子自组装膜修饰金电极上,其浓度分别在3.0×10-7～2.3×10-4mol/L、1.05×10-6～2.0×10-4mol/L、2.1×10-6～2.08×10-4mol/L、1.05×10-6～2.0×10-4mol/L范围内与微分脉冲伏安峰峰电流之间有良好的线性关系,其相关系数分别为0.9932、0.9909、0.9857、0.9832,核黄素的检出限为2.1×10-7mol/L、5.2×10-7mol/L、8.6×10-7mol/L、5.2×10-7mol/L。对浓度为1.0×10-5mol/L的核黄素进行10次平行测定,所得峰电流的相对标准偏差为2.0%。将该方法用于核黄素片剂和复合维生素B片剂的测定,结果令人满意。     

盐酸吡哆辛在聚L-色氨酸修饰电极上的电化学行为及其分析测定

制备了聚L-色氨酸修饰玻碳电极(PTRP/GCE),用循环伏安法、线性单扫描伏安法、计时电量法等研究了盐酸吡哆辛(VB6)在PTRP/GCE上的电化学行为及电化学动力学性质, 实验表明：VB6在PTRP/GCE上的电极过程为1电子1质子的不可逆氧化反应,在20～400mV/s范围内,峰电流与扫速的平方根呈良好的线性关系,电极活化面积A为0.29cm2,扩散系数D为1.9612×10-4cm2/s。在pH=3的HAc-NaAc缓冲溶液中,VB6在PTRP/GCE电极上氧化峰电流与其浓度在1×10-4～5×10-6mol/L范围内呈良好的线性关系,线性回归方程为：ipa（μA） =7.7399+408.8129c (mmol/L),R=0.9931,检出限为1×10-6mol/L,VB6样品测定平均回收率为100.15%。     

L-半胱氨酸自组装膜电极对米吐尔的电催化及其分析应用

研究了米吐尔在L 半胱氨酸自组装膜修饰金电极上的电化学行为。米吐尔在该修饰电极上的CV曲线仅出现一对峰 ,其峰形对称 ,ΔEp =42mV ,氧化还原峰电流之比约等于 1,为可逆反应 ;扩散系数D =2 .2 4× 10 - 6 cm2 ·s- 1 。初步探讨了电催化机理。差分脉冲伏安法测定其氧化峰电流与米吐尔浓度在 5 .0× 10 - 7～ 2 .0× 10 - 5mol/L和 5 .0× 10 - 5～ 1.0× 10 - 3 mol/L范围内分段呈线性关系 ;相关系数分别为 0 .9987和 0 .9972 ;检测限 1.0× 10 - 8mol/L     

聚对硝基苯偶氮间苯二酚修饰电极伏安法测定多巴胺

采用循环伏安法研究了多巴胺(DA)在聚对硝基苯偶氮间苯二酚(p-nitrobenzenazo resorcinol,简称NBAR)膜修饰电极上的电化学行为,用差示脉冲伏安法对多巴胺的含量进行测定.结果表明,聚NBAR膜修饰电极对DA有明显的电催化作用.在pH4.0的磷酸盐缓冲液中,氧化峰电流与DA浓度在5.0×10-6~8.0×10-4mol/L范围内呈良好的线性关系,检测限为6.0×10-7mol/L.修饰电极可有效消除针剂中其它组分对DA测定的干扰,已用于实际样品DA含量的测定,结果令人满意.     

磷酸可待因在Nafion修饰玻碳电极上的伏安行为研究及测定

用循环伏安法和微分脉冲吸附伏安法对磷酸可待因在Nafion修饰玻碳电极上的伏安行为进行了研究。结果表明在 0 .1mol/LHCl底液中 ,磷酸可待因在 + 1 .0 6V处 (vs.SCE)产生一良好的氧化峰 ,磷酸可待因浓度在 5 .0× 1 0 - 7～2 .5× 1 0 - 5mol/L范围内与峰电流呈线性关系 ,检出限为 1 .3× 1 0 - 7mol/L。并分别对其单方药和复方药制剂进行了测定     

聚5-磺基水杨酸修饰电极上对苯二酚的电化学行为

用循环伏安法将 5 磺基水杨酸修饰于玻碳电极表面 ,制备出对对苯二酚具有电催化作用的聚合物膜修饰电极。研究了对苯二酚 (HQ)在该聚合物薄膜修饰电极上的电化学行为。在 0 5mmol/LH2 SO4底液中 ,HQ在该电极上的线性范围为 2 0× 1 0 - 6～ 1 0× 1 0 - 4 mol/L。该修饰电极可将对苯二酚和邻苯二酚(CC)的氧化峰分开约 1 0 5mV     

聚对氨基苯磺酸修饰电极对桑枝中桑色素的灵敏测定

采用电聚合的方法制备了聚对氨基苯磺酸(PABSA)修饰电极,以循环伏安法和差分脉冲伏安法研究了桑色素在该修饰电极上的电化学行为。PABSA和黄酮类药物桑色素的π-π共轭作用使得桑色素在该修饰电极上产生的氧化峰更加灵敏。实验发现,在pH 7.0的磷酸盐缓冲介质中,桑色素在0.214 V处产生灵敏的氧化峰。在优化实验条件下,采用差分脉冲伏安法对桑色素进行定量测定,桑色素的氧化峰电流与其浓度呈良好的线性关系,线性范围为5.0×10-7~1.0×10-3 mol/L,检出限为1.0×10-7 mol/L。将该修饰电极用于桑枝生物样品中桑色素含量的测定,结果满意。该方法具有灵敏度高、重现性好的特点,且该修饰电极稳定性高,可重复使用。     

聚吖啶橙修饰电极伏安法测定黄嘌呤

报道了聚吖啶橙 (POAO)修饰电极多阶半微分伏安法测定黄嘌呤 (Xa)。在pH 5 .3的磷酸盐缓冲溶液中 ,Xa在POAO电极上于 0 .8V处产生一灵敏的氧化峰 ,峰电流与其浓度在 7.8× 1 0 - 8～ 1 .1× 1 0 - 6mol/L和 1 .1× 1 0 - 6～ 1 .0×1 0 - 5mol/L范围内呈良好的线性关系 ,检出限为 7.8× 1 0 - 9mol/L。方法可用于人尿中Xa的测定     

尿酸在普鲁士蓝修饰电极上的电化学行为及其分析应用

用恒电位电解法制备了普鲁士蓝修饰玻碳电极,研究了尿酸(UA)在该电极上的电化学行为,并提出了一种新的用于检测UA的方法。在 0. 1mol/L(pH5. 0 )的醋酸缓冲溶液中, 0. 100mol/LKCl作为支持电解质,UA在普鲁士蓝修饰电极上于 0. 470V处产生一灵敏的氧化峰,方波伏安法测定其氧化峰电流与UA浓度在 2. 5×10-6 ~2. 0×10-4 mol/L范围内呈良好的线性关系,相关系数为 0. 9986,检出限为 1. 1×10-6 mol/L。该电极制作简单,重现性良好,可用于UA的测定。     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.     

Synthesis of N-substituted carbazolones from α-iodo enaminones via Pd(0)-catalyzed intramolecular coupling under microwave irradiation

A variety of N-aryl and N-alkyl carbazolones were conveniently achieved in good to high yields via Pd₂(dba)₃-mediated intramolecular coupling of N-substituted α-iodo enaminones under microwave irradiation. The Pd(0)-catalyzed cyclization was found to proceed favorably with the more electron-deficient phenyl ring during the reactions involving unsymmetrical N,N-diaryl α-iodo enaminones. This unique property enables the construction of carbazolone skeleton containing nitro substituted benzenoid ring.     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Synthesis of substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles by intramolecular nitrilimine cycloaddition

Both substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles have been synthesized by the 3+2 intramolecular dipolar cycloaddition of nitrilimines to alkynes. This cyclization has been extended to more versatile 3-bromo derivatives by the use of alkynylbromides as dipolarophiles.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.