黄土区金盏菊幼苗对Pb/Cd次生非生物胁迫响应的红外光谱研究

植物修复法是重金属污染场地修复的重要手段,这种"绿色修复技术"得到了学者们的广泛关注和期待。在重金属胁迫条件下,植物自身会出现相应的响应反映,进而逐渐适应并有效减缓重金属的直接毒害作用。这种微尺度的调控行为往往多维度和不可见,需要借助精密仪器分析技术加以剖析。现阶段,相关方面的研究还略显欠缺。以黄土修复植物金盏菊幼苗为研究对象,分析Pb/Cd复合胁迫对其表观形貌的影响,采用傅里叶变换红外光谱法(FTIR)识别其地下和地上部分样本的官能团性质,初步推断金盏菊对Pb/Cd胁迫的响应途径和耐受机制。研究表明:随着Pb/Cd胁迫程度的加剧,金盏菊根冠弯曲萎缩,根毛数量明显减少,而其地上部分形貌差异很小。Pb/Cd胁迫对金盏菊幼苗地下和地上部分的FTIR图谱影响较大:3 573cm~(-1)附近的—OH峰强减弱且发生移动,随着Pb/Cd胁迫浓度的增加,峰形更趋复杂化;这表明Pb/Cd与—OH间存在配位结合效应,Pb/Cd胁迫干扰了有机物的合成和分泌。饱和C—H振动峰整体红移,可能与细胞膜的膜脂氧化程度有关。1 631和1 574 cm~(-1)处吸收峰强下降,说明与之关联的蛋白质组分特性可能有异。1 385 cm~(-1)处峰位有所偏移,推测金盏菊通过改变果胶质和油脂的甲基化程度,完成细胞组织对Pb/Cd胁迫的"直接排斥→逐步适应→增强抗逆性"的过程转变。FTIR对于识别土壤重金属的植物修复机制具有重要指导意义。     

金盏菊根际圈黄土溶解性有机质对Pb/Cd赋存形态原位调控机制的光谱学证据

在污染场地植物修复过程中,植物根系通过释放活性分泌物主动适应和抵御污染胁迫,直(间)接影响根际圈土壤DOM的结构组成。现阶段,植物修复的关注点主要集中于污染物的吸收、转运、累积和解毒行为,对于根际圈土壤DOM的探讨略显不足。以Pb/Cd复合污染黄土区金盏菊幼苗为研究对象,分析根际圈黄土Pb/Cd赋存形态、金盏菊生长状况等宏观差异,借助紫外可见光谱(UV)、傅里叶变换红外光谱(FTIR)和三维荧光光谱(3D-EEMs)明确Pb/Cd胁迫前后根际圈黄土DOM的微观性质。结果表明:根际圈黄土Pb/Cd以残渣态和可交换态为主,金盏菊生长周期结束后可交换态Pb/Cd含量有所升高。Pb/Cd胁迫抑制了金盏菊株高和出苗率,其生长周期有助于改善黄土理化性质。胁迫后金盏菊根部呈现细长、弯曲且萎缩的迹象;DOM紫外光谱最大吸收区间位于200~240nm,但胁迫后的图谱波峰更加尖锐,峰强更大。Pb/Cd胁迫导致DOM红外吸收峰分别从3 444和1 637cm-1移动至3 440和1 645cm-1,其中存在重金属离子与OH和C=O结合效应。DOM荧光峰集中在λex/em=240/430附近(紫外区类富里酸荧光峰),Pb/Cd胁迫对荧光峰强干扰较大,而对荧光峰位基本没有影响。金盏菊根际圈黄土DOM能够提供重要的微生态环境信息,光谱学手段能够一定程度上揭示其与Pb/Cd赋存形态的构效关系。     

Two new two‐dimensional coordination polymers based on isophthalate and a flexible N‐donor ligand containing benzimidazole and pyridine rings: synthesis,crystal structures and a solid‐state UV–Vis study

In coordination chemistry and crystal engineering, many factors influence the construction of coordination polymers and the final frameworks depend greatly on the organic ligands used. N‐Donor ligands with diverse coordination modes and conformations have been employed to assemble metal–organic frameworks. Carboxylic acid ligands can deprotonate completely or partially when bonding to metal ions and can also act as donors or acceptors of hydrogen bonds and are thus good candidates for the construction of supramolecular architectures. Two new transition metal complexes, namely poly[diaqua(μ₄‐1,4‐bis{[1‐(pyridin‐3‐ylmethyl)‐1H‐benz[d]imidazol‐2‐yl]methoxy}benzene)bis(μ₂‐isophthalato)dicobalt(II)], [Co(C₈H₄O₄)(C₃₄H₂₈N₆O₂)_0.5(H₂O)]_n, (1), and poly[diaqua(μ₄‐1,4‐bis{[1‐(pyridin‐3‐ylmethyl)‐1H‐benz[d]imidazol‐2‐yl]methoxy}benzene)bis(μ₂‐isophthalato)dicadmium(II)], [Cd(C₈H₄O₄)(C₃₄H₂₈N₆O₂)_0.5(H₂O)]_n, have been constructed using a symmetric N‐donor ligand and a carboxylate ligand under hydrothermal conditions. X‐ray crystallographic studies reveal that complexes (1) and (2) are isostructural, both of them exhibiting three‐dimensional supramolecular architectures built by hydrogen bonds in which the coordinated water molecules serve as donors, while the O atoms of the carboxylate groups act as acceptors. Furthermore, (1) and (2) have been characterized by elemental, IR spectroscopic, powder X‐ray diffraction (PXRD) and thermogravimetric analyses. The UV–Vis absorption spectrum of complex (1) has also been investigated.     

Assembly of ZnII and CdII coordination polymers based on a flexible multicarboxylate ligand and nitrogen‐containing auxiliary ligands through a mixed‐ligand synthetic strategy: syntheses,structures and fluorescence properties

The structures of coordination polymers are strongly influenced by the organic ligands and metal ions used for their construction, so it is important to choose suitable ligands and metal ions and appropriate synthetic processes. Two novel d¹⁰ coordination polymers, namely poly[[diaquabis(2,2′‐bipyridine)[μ₄‐4,4′‐(1,4‐phenylenedioxy)bis(benzene‐1,2‐dicarboxylato)]dizinc(II)] dihydrate], {[Zn₂(C₂₂H₁₀O₁₀)(C₁₀H₈N₂)₂(H₂O)₂]·2H₂O}_n, (1), and poly[[diaquabis(1,10‐phenanthroline)[μ₄‐4,4′‐(1,4‐phenylenedioxy)bis(benzene‐1,2‐dicarboxylato)]dicadmium(II)] dimethylformamide disolvate], {[Cd₂(C₂₂H₁₀O₁₀)(C₁₂H₈N₂)₂(H₂O)₂]·2C₃H₇NO}_n, (2), have been synthesized from 4,4′‐(1,4‐phenylenedioxy)bis(benzene‐1,2‐dicarboxylic acid) (H₄L) and two different N‐containing auxiliary ligands through a mixed‐ligand synthetic strategy under a solvothermal environment. The structures were characterized by single‐crystal X‐ray diffraction, powder X‐ray diffraction, elemental analysis and IR spectroscopy. Compounds (1) and (2) both present one‐dimensional chain structures and two‐dimensional supramolecular layer structures constructed by weak hydrogen bonds. It is interesting to note that the carboxylate ligands reveal stable trans configurations in both compounds. The fluorescence properties of (1) and (2) in the solid state were also investigated.     

The crystal structure and photocatalytic properties of a three‐dimensional cadmium(II) metal–organic framework: poly[bis(μ3‐benzene‐1,2‐dicarboxylato)[μ2‐1,4‐bis(pyridin‐3‐ylmethoxy)benzene]dicadmium(II)]

Photocatalysis is a green technology for the treatment of all kinds of contaminants and has advantages over other treatment methods. Recently, much effort has been devoted to developing new photocatalytic materials based on metal–organic frameworks for use in the degradation of many kinds of organic contaminants. With the aim of searching for more effective photocatalysts, the title three‐dimensional coordination polymer, [Cd₂(C₈H₄O₄)₂(C₁₈H₁₆N₂O₂)]_n, was prepared. The asymmetric unit contains one Cd^II cation, one benzene‐1,2‐dicarboxylate anion (denoted L²⁻) and half of a centrosymmetric 1,4‐bis(pyridin‐3‐ylmethoxy)benzene ligand (denoted bpmb). Each Cd^II centre is five‐coordinated by four carboxylate O atoms from two L²⁻ ligands and by one N atom from a bpmb ligand, forming a disordered pentagonal pyramidal coordination geometry. The Cd^II centres are interlinked by L²⁻ ligands to form a one‐dimensional [Cd₂L₂]_n chain. Adjacent chains are further connected by bpmb linkers, giving rise to a two‐dimensional network, and these networks are pillared by bpmb to afford a three‐dimensional framework with a 3³.4².6³.7¹.8¹ topology. Each grid in the framework has large channels which are filled mainly by the two other equivalent frameworks to form a threefold interpenetrating net. The compound exhibits relatively good photocatalytic activity towards the degradation of methylene blue in aqueous solution under UV irradiation.     

A new one‐dimensional cadmium(II) coordination polymer incorporating 4‐[4‐(1H‐imidazol‐1‐yl)phenyl]pyridine and 5‐hydroxybenzene‐1,3‐dicarboxylate ligands

The design and synthesis of new organic lgands is important to the rapid development of coordination polymers (CPs). However, CPs based on asymmetric ligands are still rare, mainly because such ligands are usually expensive and more difficult to synthesize. The new asymmetric ligand 4‐[4‐(1H‐imidazol‐1‐yl)phenyl]pyridine (IPP) has been used to construct the title one‐dimensional coordination polymer, catena‐poly[[[aqua{4‐[4‐(1H‐imidazol‐1‐yl‐κN³)phenyl]pyridine}cadmium(II)]‐μ‐5‐hydroxybenzene‐1,3‐dicarboxylato‐κ³O¹,O^1′:O³] monohydrate], {[Cd(C₈H₄O₅)(C₁₄H₁₁N₃)₂(H₂O)]·H₂O}_n, under hydrothermal reaction of IPP with Cd^II in the presence of 5‐hydroxyisophthalic acid (5‐OH‐H₂bdc). The Cd^II cation is coordinated by two N atoms from two distinct IPP ligands, three carboxylate O atoms from two different 5‐OH‐bdc²⁻ dianionic ligands and one water O atom in a distorted octahedral geometry. The cationic [Cd(IPP)₂]²⁺ nodes are linked by 5‐OH‐bdc²⁻ ligands to generate a one‐dimensional chain. These chains are extended into a two‐dimensional layer structure via O—H…O and O—H…N hydrogen bonds and π–π interactions.     

双吡啶化合物3，7-di(3-pyridyl)-1，5-dioxa-3，7-diazacyclooctane构建的四个过渡金属配合物的合成、结构及热稳定性

采用准刚性的双吡啶化合物3,7-di(3-pyridyl)-1,5-dioxa-3,7-diazacyclooctane(L),合成了4个过渡金属配合物[Co(NO3)(H2O)2(L)2]NO3(1)、[Co2Cl4(L)2]·CH2Cl2(2)、[Cd2(AcO)4(L)2]·4CH3OH(3)和[Cd2(NO3)2(CH3OH)2(H2O)2(L)2](NO3)2·2H2O(4)。单晶衍射分析表明,配合物1是单核结构,配合物2是24-元环状双核结构,而配合物3和4为多边形双核结构。在这些配合物中,双吡啶配体分别采用了单齿、trans-和cis-桥连3种不同配位方式。配合物经过了元素分析、红外、热重和X射线单晶结构分析表征。     

Suppression of Rice Cryptochrome 1b Decreases Both Melatonin and Expression of Brassinosteroid Biosynthetic Genes Resulting in Salt Tolerance

We investigated the relationship between the blue-light photoreceptor cryptochrome (CRY) and melatonin biosynthesis by generating RNA interference (RNAi) transgenic rice plants that suppress the cryptochrome 1b gene (CRY1b). The resulting CRY1b RNAi rice lines expressed less CRY1b mRNA, but not CRY1a or CRY2 mRNA, suggesting that the suppression is specific to CRY1b. The growth of CRY1b RNAi rice seedlings was enhanced under blue light compared to wild-type growth, providing phenotypic evidence for impaired CRY function. When these CRY1b RNAi rice plants were challenged with cadmium to induce melatonin, wild-type plants produced 100 ng/g fresh weight (FW) melatonin, whereas CRY1b RNAi lines produced 60 ng/g FW melatonin on average, indicating that melatonin biosynthesis requires the CRY photoreceptor. Due to possible feedback regulation, the expression of melatonin biosynthesis genes such as T5H, SNAT1, SNAT2, and COMT was elevated in the CRY1b RNAi lines compared to the wild-type plants. In addition, laminar angles decreased in the CRY1b RNAi lines via the suppression of brassinosteroid (BR) biosynthesis genes such as DWARF. The main cause of the BR decrease in the CRY1b RNAi lines seems to be the suppression of CRY rather than decreased melatonin because the melatonin decrease suppressed DWARF4 rather than DWARF.     

Synthesis and Crystal Structure of a Two-dimensional Cadmium(Ⅱ)Coordination Polymer:[Cd(AIP)(Bpy)]n·nBpy(H2AIP=5-Aminoisophthalic Acid,Bpy=2,2'-Bipyridyl)

A two-dimensional coordination polymer,[Cd(AIP)(Bpy)]n·nBpy,Was hydrother-mally synthesized by the reaction of hydrate cadmium acetate with 5-aminoisophthalic acid,lithium hydroxide,vanadiumpentoxide,sodium chloride and 2,2'-bipyridyl in water solution.It crystallizes in orthorhombic,space group C2221,absolute structure parameter 0.00(7),with a=15.336(4),b=22.390(6),C=14.257(3)(A),v=4896(2)(A)3,C28H21CdN5O4,Mr=603.90,Z=8,F(000)=2432,Dc=1.639 g/cm3,μ=0.939 mm-1,T=298(2)K,S=1.001,R=0.0296 and wR=0.08 13 for 5522 observed reflections(I＞2o(I)).In the title complex,each 5-aminoisophthalate ligand bridges three cadmium(Ⅱ)ions to form a two-dimensional layer structure.