铪基纳米金属有机骨架材料制备及X射线增强化学动力协同治疗应用

以铪簇作为金属有机骨架的连接点、刚性双羧基配体2,2’-联吡啶-5,5’-二羧酸作为连接器、乙酸或三氟乙酸和水作为结构调节剂,通过溶剂热法合成得到八面体结构(Hf-MOFs-1)和片状结构(Hf-MOFs-2)的铪基纳米金属有机骨架(Hf-nMOFs),再经Fe3+修饰得到多功能金属有机骨架材料(Hf-Fe-MOFs-1和Hf-Fe-MOFs-2)。模拟肿瘤微环境体系中羟基自由基检测结果表明,X射线照射能显著促进Hf-Fe-MOFs-1和Hf-Fe-MOFs-2材料产生羟基自由基,且片状Hf-Fe-MOFs-2羟基自由基产生能力高于八面体Hf-Fe-MOFs-1。进一步地,在细胞层面证实了材料能够成功被细胞摄入并实现低剂量X射线促进的化学动力学协同治疗。     

一种用于检测四环素和对硝基苯酚的高稳定性镉(Ⅱ)金属有机骨架

采用水-溶剂热法合成了 1例金属有机骨架(MOF)：{[Cd(L)_0.5(4，4''-bpy)_0.5]·H₂O}_n (1)，其中 H₄L=(1，1''∶4''，1″-三联苯)-2，2″，4，4″-四羧酸，4，4''-bpy=4，4''-联吡啶)。通过单晶 X射线衍射、元素分析、粉末 X射线衍射、热重分析以及红外光谱分析对配合物1的结构进行了表征。单晶结构分析表明1为三维结构，属于单斜晶系，C2/c空间群，Cd(Ⅱ)连接L^4-和4，4''-bpy形成二维平面结构，层与层之间通过 L^4-连接，构筑成了三维网状结构。该 MOF表现出良好的稳定性并且可以通过荧光猝灭法检测四环素(TET)和对硝基苯酚(4-NP)，四环素和对硝基苯酚的检出限分别为0.15和0.062 μmol·L^-1。此外，还研究了其荧光猝灭机理。1可成功应用于延河水样中TET和4-NP含量的测定。     

多功能Zn(Ⅱ)金属有机骨架荧光传感器检测苯甲醛、四环素、2,4,6-三硝基苯甲酸、氟啶胺、Cr2O72-和Fe3+

成功制备了新型 Zn(Ⅱ)金属有机骨架(MOF)[Zn₂(Hdepa)(dya)₂]n (1)(H₅depa=2,2'',3,4'',5-二苯醚五羧酸,dya=2,2''-二吡啶胺)。单晶 X 射线衍射分析表明 MOF 1 由 2 个 Zn²⁺离子与 1 个 Hdepa^4-离子和 2 个 dya 分子连接组成,通过氢键形成三维骨架。用粉末X射线衍射和IR表征了配合物1的相纯度。值得注意的是,配合物1具有优异的荧光特性和热稳定性,1的高灵敏度和选择性使其能够作为荧光传感器检测苯甲醛(BZH)、四环素(TC)、2,4,6-三硝基苯酚(TNP)、氟啶胺(Flu)、Cr₂O₇^2-和Fe³⁺。此外,通过荧光寿命分析了Fe³⁺、TC、BZH对MOF 1的荧光的猝灭过程,通过能量转移研究了Fe³⁺、Cr₂O₇^2-、TNP、TC、BZH和Flu的荧光猝灭机理。     

一种水中稳定的锌(Ⅱ)金属有机骨架用于检测四环素

采用溶剂热法合成1个锌(Ⅱ)金属有机骨架(Zn-MOF):[Zn (H₂L)(4,4''-bpy)]_n (1),其中H₄L=1,1''-乙烷基联苯-3,3'',5,5''-四羧酸,4,4''-bpy=4,4''-联吡啶。通过单晶X射线衍射、元素分析和热重分析等方法对其结构进行表征。单晶结构分析表明,1属于单斜晶系C2/c空间群,H₂L^2-配体采取单齿配位模式连接Zn(Ⅱ)形成一维链,4,4''-bpy连接一维链构筑成二维波浪状网。该化合物在水中表现出良好的稳定性,并且可作为高灵敏度、高选择性荧光探针检测四环素(TET),其检出限为0.17 μmol·L^-1。1可成功用于延河水中TET的测定。此外,还研究了1对TET的荧光猝灭机理。     

多功能Zn（Ⅱ）金属有机骨架荧光传感器检测苯甲醛、四环素、2，4，6-三硝基苯甲酸、氟啶胺、Cr2O72-和Fe3+

成功制备了新型Zn（Ⅱ）金属有机骨架(MOF)[Zn₂(Hdepa)(dya)₂]_n (1)(H₅depa=2,2'',3,4'',5-二苯醚五羧酸,dya=2,2''-二吡啶胺)。单晶X射线衍射分析表明MOF 1由2个Zn²⁺离子与1个Hdepa^4-离子和2个dya分子连接组成,通过氢键形成三维骨架。用粉末X射线衍射和IR表征了配合物1的相纯度。值得注意的是,配合物1具有优异的荧光特性和热稳定性,1的高灵敏度和选择性使其能够作为荧光传感器检测苯甲醛(BZH)、四环素(TC)、2,4,6-三硝基苯酚(TNP)、氟啶胺(Flu)、Cr₂O₇^2-和Fe³⁺。此外,通过荧光寿命分析了Fe³⁺、TC、BZH对MOF 1的荧光的猝灭过程,通过能量转移研究了Fe³⁺、Cr₂O₇^2-、TNP、TC、BZH和Flu的荧光猝灭机理。     

一种水中稳定的锌(Ⅱ)金属有机骨架用于检测四环素

采用溶剂热法合成1个锌(Ⅱ)金属有机骨架（Zn-MOF）：[Zn (H₂L)(4,4''-bpy)]_n (1),其中H₄L=1,1''-乙烷基联苯-3,3'',5,5''-四羧酸,4,4''-bpy=4,4''-联吡啶。通过单晶X射线衍射、元素分析和热重分析等方法对其结构进行表征。单晶结构分析表明,1属于单斜晶系C2/c空间群,H₂L^2-配体采取单齿配位模式连接Zn (Ⅱ)形成一维链,4,4''-bpy连接一维链构筑成二维波浪状网。该化合物在水中表现出良好的稳定性,并且可作为高灵敏度、高选择性荧光探针检测四环素(TET),其检出限为0.17 μmol·L^-1。1可成功用于延河水中TET的测定。此外,还研究了1对TET的荧光猝灭机理。     

一种水中稳定的锌(Ⅱ)金属有机骨架用于检测四环素

采用溶剂热法合成1个锌(Ⅱ)金属有机骨架（Zn-MOF）：[Zn (H₂L)(4,4''-bpy)]_n (1),其中H₄L=1,1''-乙烷基联苯-3,3'',5,5''-四羧酸,4,4''-bpy=4,4''-联吡啶。通过单晶X射线衍射、元素分析和热重分析等方法对其结构进行表征。单晶结构分析表明,1属于单斜晶系C2/c空间群,H₂L^2-配体采取单齿配位模式连接Zn (Ⅱ)形成一维链,4,4''-bpy连接一维链构筑成二维波浪状网。该化合物在水中表现出良好的稳定性,并且可作为高灵敏度、高选择性荧光探针检测四环素(TET),其检出限为0.17 μmol·L^-1。1可成功用于延河水中TET的测定。此外,还研究了1对TET的荧光猝灭机理。     

刚性双(三氮唑)和羧酸混合配体构建的两种金属有机骨架材料及其在CO2环加成反应中的催化性质

通过酸碱混合配体策略合成了 2 例含刚性双三氮唑配体的金属有机骨架(MOF)材料：{[Zn₂(L)(TP)₂(H₂O)·H₂O]}_n (1)和[Zn(L)(HTMA)]_n (2),其中L=4,4''-(3,3''-dimethyl-(1,1''-biphenyl)-4,4''-diyl)bis(4H-1,2,4-triazole),H₂TP=对苯二甲酸,H₃TMA=1,3,5-均苯三甲酸。用单晶 X 射线衍射表征其结构。结构分析表明,MOF 1显示出 3,6-双节点的二维结构,其拓扑符号为(4²·6)₂(4⁸·6⁶·8),MOF 2呈现为经典的 sql二维拓扑结构。在温和条件下,2对 CO₂与环氧化物的环加成反应具有优异的催化活性,且重复使用至少3次后仍然保持其催化性能。     

设计合成nia拓扑的金属有机骨架化合物与CO2吸附

Nia拓扑结构是由两种分别是八面体和三棱柱构型的六连接节点连接形成的三维结构.为了得到具有nia拓扑的金属有机骨架,可以通过连接具有八面体构型的配体和具有三棱柱构型的金属簇实现.常见的三棱柱构型的金属簇为M3O(M=金属,M三价)或者M3OH(M二价).本文通过设计合成的枝状的具有八面体构型的有机配体1,3,5-tris(3,5-di-(4-carboxy-phenyl-1-yl)phenyl-1-yl)benzene(TDCPB),在溶剂热条件下,利用硝酸镍合成了一种新型的具有nia拓扑结构的金属有机骨架化合物JUC-105.通过X射线单晶衍射表征,该金属有机骨架化合物是由六棱柱的Ni3OH金属簇与八面体的TDCPB共同构筑的三维骨架结构,具有较大的孔道(1.1 nm).通过粉末衍射以及热重分析,研究了这种金属有机骨架的结构稳定性.气体吸附数据表明,这种骨架没有氮气吸附能力,但是表现了一定的CO2吸附能力.     

刚性双(三氮唑)和羧酸混合配体构建的两种金属有机骨架材料及其在CO2环加成反应中的催化性质

通过酸碱混合配体策略合成了 2 例含刚性双三氮唑配体的金属有机骨架(MOF)材料：{[Zn₂(L)(TP)₂(H₂O)·H₂O]}_n (1)和[Zn(L)(HTMA)]_n (2),其中L=4,4''-(3,3''-dimethyl-(1,1''-biphenyl)-4,4''-diyl)bis(4H-1,2,4-triazole),H₂TP=对苯二甲酸,H₃TMA=1,3,5-均苯三甲酸。用单晶 X 射线衍射表征其结构。结构分析表明,MOF 1显示出 3,6-双节点的二维结构,其拓扑符号为(4²·6)2(4⁸·6⁶·8),MOF 2呈现为经典的 sql二维拓扑结构。在温和条件下,2对 CO₂与环氧化物的环加成反应具有优异的催化活性,且重复使用至少3次后仍然保持其催化性能。     

Monitoring Humic Acid Photodegradation by CUPRAC Colorimetric and HPLC Determination of Dihydroxybenzoate Isomers Produced From a Salicylate Probe

Abstract

Novel analytical methods were designed for monitoring humic acid photodegradation in environmental waters. Modified CUPric Reducing Antioxidant Capacity (CUPRAC) spectrophotometric and chromatographic methods were used for the determination of dihydroxybenzoate isomers (DHBAs) produced from a salicylate probe, which was hydroxylated by hydroxyl radicals (^?OH) produced from the photodegradation of humic acid under ultraviolet A-radiation. The combined use of CUPRAC colorimetry and HPLC was shown to effectively monitor humic acid photodegradation and ^?OH generation for the first time. The formation of 2,5-dihydroxybenzoate and 2,3-dihydroxybenzoate, as major and minor products, respectively, from the hydroxylation of a salicylate probe was demonstrated by HPLC and confirmed by a modified CUPRAC method to indicate ^?OH formation from humic acid, which acted as both a generator and absorber of hydroxyl radicals. Salicylate hydroxylation showed an increase between 30 and 50?min of illumination, and was affected by the initial concentration of humic acid up to 0.01% but not by solution pH around the neutral values. Traces of Fe(III) and Mn(II) present in natural waters decreased the ^?OH production, but EDTA partly restored the probe hydroxylation by chelating these metal cations. Since humic acid-mediated ^?OH generation may aid in natural disinfection processes, this work may extend our comprehension of concentration- and time-dependent generation of ^?OH in environmental waters and of the possible effects of other antioxidants.     

Simple and sensitive determination of hydroxyl radical in atmosphere based on an electrochemically activated glassy carbon electrode

The hydroxyl radical (?OH) plays important roles in environment and health problems. However, the short life time and low concentrations of ?OH limited its detection. In this work, a simple method has been successfully performed for the sensitive detection of hydroxyl radical based on an activated glassy carbon electrode (AGCE).4-hydroxybenzoic acid (4-HBA) was used as a trapping agent for ?OH radicals, leading to the production of electroactive 3,4-dihydroxybenzoic acid (3,4-DHBA). Different procedures including polarisation and cyclic voltammetry in acid or base solutions have been used to activate the glassy carbon electrodes. The electrochemical behaviours of 3,4-DHBA on these activated electrodes were studied and compared. Experimental results showed that the glassy carbon electrode polarised in H₂SO₄ (AGCE-P/H₂SO₄) has the greatest sensitivity and reproducibility to 3,4-DHBA. 3,4-DHBA performed a linear relationship from 1.0 × 10^?7 to 1.0 × 10^?4 M on the AGCE-P/H₂SO₄. The detection limit was down to 6.2 × 10^?8 M. This method has been successfully applied for the detection of hydroxyl radical levels in atmosphere without separation and purification process.     

Degradation of n-butylparaben and 4-tert-octylphenol in H2O2/UV system

The degradation of two endocrine disrupting compounds: n-butylparaben (BP) and 4-tert-octylphenol (OP) in the H₂O₂/UV system was studied. The effect of operating variables: initial hydrogen peroxide concentration, initial substrate concentration, pH of the reaction solution and photon fluency rate of radiation at 254 nm on reaction rate was investigated. The influence of hydroxyl radical scavengers, humic acid and nitrate anion on reaction course was also studied. A very weak scavenging effect during BP degradation was observed indicating reactions different from hydroxyl radical oxidation. The second-order rate constants of BP and OP with OH radicals were estimated to be 4.8×10⁹ and 4.2×10⁹ M^?1 s^?1, respectively. For BP the rate constant equal to 2.0×10¹⁰ M^?1 s^?1was also determined using water radiolysis as a source of hydroxyl radicals.     

Detection of active oxidative species in TiO2 photocatalysis using the fluorescence technique

The active oxidative species (mainly corresponding to hydroxyl radicals (· OH)) produced on TiO₂ film photocatalyst in aerated aqueous solution have been quantitatively investigated by measuring the fluorescence derived by the reaction with either coumarin or terephthalic acid. Upon UV light illumination, coumarin in aqueous solution and terephthalic acid in NaOH solution were converted on the TiO₂ film photocatalyst to highly fluorescent hydroxy products. Analysis of the resultant hydroxy compounds provides sensitive and specific monitoring of the generated active oxidative species. The rate of active species formation could be determined by the time dependence of the increase in concentration of the resultant hydroxy products. Using this fluorescence method, the effect of light intensity on the generation efficiency of active oxidative species was examined. The obtained results show that the efficiency of active oxidative species formation is constant at the UV intensity from 50 μW cm⁻² to 15 mW cm⁻², which is consistent with the results for · OH detection reported recently by the use of other techniques.     

DNA damage induced via independent generation of the radical resulting from formal hydrogen atom abstraction from the C1′-position of a nucleotide

Background: Deoxyribonucleotide radicals resulting from formal C1′-hydrogen atom abstraction are important reactive intermediates in a variety of DNA-damage processes. The reactivity of these radicals can be affected by the agents that generate them and the environment in which they are produced. As an initial step in determining the factors that control the reactivity of these important radical species, we developed a mild method for their generation at a defined site within a biopolymer.Results: Irradiation of oligonucleotides containing a photolabile nucleotide produced C1'-DNA radicals. In the absence of potential reactants other than O₂, approximately 90% of the damage events involve formation of alkaline-labile lesions, with the remainder resulting in direct strand breaks. The ratio of alkaline-labile lesions to direct strand breaks (∼ 9:1) is independent of whether the radical is generated in single-stranded DNA or double-stranded DNA. Strand damage is almost completely quenched under anaerobic conditions in the presence of low thiol concentrations. Competition studies with 02 indicate that the trapping rate of C1′-DNA radicals by β-mercaptoethanol is ∼ 1.1 x 10⁷ M⁻¹s⁻¹Conclusions: The mild generation of the C1'-DNA radical in the absence of exogenous oxidants makes it possible to examine their intrinsic reactivity. In the absence of other reactants, the formation of direct strand breaks from C1′-radicals is, at most, a minor pathway. Competition studies between β-mercaptoethanol and 02 indicate that significantly higher thiol concentrations than those in vivo or some means of increasing the effective thiol concentration near DNA are needed for these reagents to prevent the formation of DNA lesions arising from the C1'-radical under aerobic conditions.     

Photoinduced degradation by iron(III): removal of triphenyltin chloride from water

The photoredox process taking place in iron(III) aquacomplexes was used to cause the complete degradation of triphenyltin (TPT). TPT elimination was proved to come only from attack by hydroxyl radicals generated upon irradiation at 365 nm of Fe(H₂O)₅OH²⁺, the iron(III) species present under the experimental conditions ([Fe(III)] in the range (3–6) × 10^?4 mol l^?1). The first step is the formation of an adduct between hydroxyl radicals and the benzene ring. The main process is a stepwise dephenylation of the starting TPT. Hydroxylated phenyltin derivatives were also formed, but only as minor photoproducts. The process was shown to be efficient with artificial light as well as with solar light. Copyright © 2001 John Wiley & Sons, Ltd.     

THE GENERATION OF HYDROXYL RADICALS IN BIOLOGIC SYSTEMS: TOXICOLOGICAL ASPECTS

Abstract— The formation of hydroxyl radicals in vitro was studied through their reaction with 2-keto-4-thiomethylbutyric acid to form ethylene gas. The autoxidation reaction of 6-aminodopamine served as a model source of hydroxyl radicals. Ethylene production was suppressed by catalase and by superoxide dismutase, indicating that both hydrogen peroxide and superoxide were involved in the reaction. Hydroxyl radical scavengers (thiourea > benzoate > ethanol) suppressed ethylene production in good agreement with their respective rate constants for reaction with hydroxyl radicals. Urea served as a negative control. Several substituted thiourea derivatives also suppressed ethylene production to a similar degree as thiourea itself. Biologic studies centered on several cytotoxic agents whose mechanisms of action are thought to involve hydroxyl radicals. These agents included alloxan, which destroys the beta cells of the pancreas, and 6-hydroxy- and 6-aminodopamine, which destroy sympathetic nerves. Damage to tissues in vivo was blocked to varying degrees by pretreatment of animals with hydroxyl radical scavengers such as ethanol or the thiourea derivatives. In addition, hydroxyl radical scavengers blocked the action of 5,7-dihydroxytryptamine, a neurotoxin whose effects on noradrenaline neurons were previously shown to be blocked by inhibitors of monoamine oxidase. The data indicate that these cell toxins produce their damaging actions on specific target cells through the intracellular generation of hydroxyl radicals.     

The roles of hydroxyl radicals, photo-generated holes and oxygen in the photocatalytic degradation of humic acid

This article is aimed at studying on the roles of the hydroxyl radicals, photo-generated holes, and oxygen in the photocatalytic degradation of humic acid (HA) in acid and alkaline conditions. The results indicate that hydroxyl radicals?? scavenger alone can inhibit the photocatalytic degradation process completely in alkaline condition, which implies that photo-generated holes cannot directly degrade the organic matter in alkaline condition. Moreover, the reaction sites between hydroxyl radicals and HA is on the TiO₂ surface in acid condition. But in alkaline condition, hydroxyl radicals diffuse and react with HA in the solution. The generation of hydroxyl radicals almost stops and the photocatalytic degradation is inhibited seriously without oxygen, which illustrates that oxygen plays an important role in the photocatalytic degradation of HA.     

A New CoII Complex as a Bulge-Specific Probe for DNA

Bulge cleavage of two or three bases occurs when a DNA substrate is specifically cleaved oxidatively by [Co^II(tfa)₂(happ)] (see picture). Hydrogen peroxide is necessary for the activation of this octahedral complex, which suggests that hydroxyl radicals are the reactive species. The complex has no significant reactivity towards the corresponding sequence in a single-stranded DNA region, and it exhibits only a low affinity towards double-stranded DNA. happ=macrocyclic ligand based on 1,10-phenanthroline, tfa=trifluoroacetate.