配合物构型、配体结构及反式效应对Ru(Ⅱ)吡啶类配合物中NO2配体在酸催化下反应机理的影响

顺-Ru(bpy)2(NO2)2和反-Ru(bpy)2(NO2)2(bpy=2,2-联吡啶)组成完全相同,但配合物的构型不同.反-Ru(bpy)2(NO2)2和反-Ru(py)4(NO2)2(PY=吡啶)两个配合物构型相同,辅助配体相同,但主配体有差异.本文通过在不同或相似条件下,上述三个配合物中辅助配体NO2-在酸催化下的反应结果的对比,探讨了配合物中的NO2-在酸催化下的反应机理(缔合或解离)与配合物构型、配体结构以及配体反式效应性质之间的关系.当反应配体对位为NO2-等反式效应较强的基团时,反应倾向于以解离机理发生配体取代反应.若对位为OH-等反式效应较弱的基团时,倾向于发生No2-配体的分解反应.在顺式联吡啶二硝基化合物中.酸催化下只发生配体分解反应.通过对比得出,处于反应配体(No2-)反位的配体的性质,特别是反式效应性质的强弱,会明显影响或改变配体取代反应的机理(解离或缔合)或反应类型(取代或分解),有时甚至是影响反应机理或反应方式的主要因素.无论在反式还是在顺式构型的配合物中,bpy的约束构型会影响过渡态的稳定性,进而影响反应发生的机理.     

Ru(bpy)32+配合物及bpy上双取代基效应的DFT法研究

报道Ru(bpy)32+配合物取代基效应的量子化学密度泛函(DFT)法研究的结果。探讨Ru(bpy)32+的三个配体bpy(2,2′-联二吡啶)被取代基(-NH2,-OH,-NO2)对位双取代后对配合物电子结构及相关性质,如配位键长、光谱性质等的影响规律,为该类配合物的合成及性质分析提供理论参考。     

齐聚苯胺修饰的三联吡啶铁配合物的合成及其光谱和电化学性质

合成了一系列齐聚苯胺修饰的三联吡啶铁配合物,研究了齐聚苯胺链长、不同取代基等对配合物光谱性质和氧化还原性质的影响。 结果表明,相对于配合物[Fe(TPY)₂]²⁺(TPY:三联吡啶),供电子齐聚苯胺单元的引入,使得修饰基团与配合物中心核[Fe(TPY)₂]²⁺之间形成了强的D-A体系,导致配合物¹MLCT吸收波长显著红移至594 nm,且摩尔吸光系数增加近5倍。 配合物同时具有基于金属中心、三联吡啶配体和齐聚苯胺单元的多个氧化还原过程,强拉电子取代基使齐聚苯胺单元氧化还原峰简并且峰电势明显正移,而正丁基取代基对氧化还原峰电势的影响较小。     

钌多吡啶配合物的合成及插入配体的位阻效应对键合DNA的影响

合成了2,3-二甲基-1,4,8,9-四氮三联苯(dmtatp)和2,3-二苯基-1,4,8,9-四氮三联苯(dptatp)两种新配体及它们与2,2′-联吡啶和钌(Ⅱ)的混配物[Ru(bpy)₂dmtatp]²⁺(1)和[Ru(bpy)₂dptatp]²⁺(2),用电子吸收光谱、稳态荧光、粘度测定和圆二色谱研究了配合物与小牛胸腺DNA的相互作用。结合我们以前对配合物[Ru(bpy)₂tatp]²⁺(3)(tatp为1,4,8,9-四氮三联苯)与小牛胸腺DNA的作用研究,得出配合物与DNA的键合强度顺序为:[Ru(bpy)₂tatp]²⁺>[Ru(bpy)₂dptatp]²⁺>[Ru(bpy)₂dmtatp]²⁺,这与插入配体的位阻效应的减少趋势相一致。同时,还测定了配合物与DNA的键合常数。     

利用静电吸引作用提高光催化放氢效率

本文设计合成了两个分别带正电荷和负电荷的Ir(Ⅲ)配合物[Ir(ppy)₂(bpy)]⁺(ppy=2-苯基吡啶,bpy=2,2′-联吡啶)和[Ir(ppy)₂(pbs)]^-(pbs=1,10-菲啰啉-4,7-二苯磺酸钠)作为光敏剂,以[Co(bpy)₃]²⁺为放氢催化剂,比较了Ir(Ⅲ)配合物的光催化放氢效率.发现带负电荷的Ir(Ⅲ)配合物具有更高的光催化放氢效率,带负电荷光敏剂和带正电荷催化剂间的静电吸引可能对放氢效率的提高起到了重要作用.     

新型环状金属Pt(Ⅱ)配合物:合成、晶体结构及光谱性质

合成了一种新的环状金属配体4-甲氧甲酰基-6-(4-甲基苯基)-2,2’-联吡啶(HL)及它的单核与双核Pt(Ⅱ)配合物[Pt(L)PPh₃](ClO₄)(1)与[Pt₂L₂(μ-dppm)](ClO₄)₂(2)(dppm=二(二苯基磷)-甲烷),并研究了它们的结构及光物理性质.配合物2的晶体结构分析表明,中心金属离子Pt(Ⅱ)呈扭曲平面正方形构型,桥配体dppm连接两个金属中心,0.3375 nm的Pt——Pt距离表明双核配合物中存在金属-金属相互作用.两配合物在～450 nm处的肩峰归属于金属到配体的电荷转移(MLCT)吸收,在固体及溶液中均观测到强烈的光致磷光发射.配合物1在固态时620 nm的低能发射归属为³(π-π)跃迁,并暗示配合物1晶体结构中存在分子间配体-配体相互作用,然而在溶液中仅观察到³MLCT发射光谱,但配合物2在固态及溶液中都观察到明显的金属和金属相互作用到配体的电荷转移(³MMLCT)发射.     

双过氧钒配合物与吡啶类配体相互作用的NMR研究

为探讨单齿/双齿吡啶类配体对反应平衡的影响,在模拟生理条件下(0.15mol·L-1NaCl溶液),应用多核(1H、13C和51V)多维(COSY,HSQC和HMBC)以及变温NMR技术研究双过氧钒配合物[OV(O2)2(D2O)]-/[OV(O2)2(HOD)]-(简写为bpV)与系列吡啶类配体的相互作用,研究结果表明bpV与有机配体的反应性从强到弱的顺序为:2,2′-联吡啶2,2′-联吡啶-4,4′-二甲酸根吡啶异烟酸根,这说明双齿吡啶类配体配位能力强于单齿配体,而不带羧基的吡啶类配体(单齿或双齿)配位能力强于所对应的带羧基的取代吡啶,竞争配位导致一系列新的6配位(配体为吡啶或异烟酸根)或7配位(配体为2,2′-联吡啶或2,2′-联吡啶-4,4′-二甲酸根)的过氧钒物种[OV(O2)2LL′]n-(LL′=吡啶类配体,n=1,2,3)生成。     

平面四方金属苯配合物的二阶超极化率的量子化学计算

反位平面四方型过渡金属有机配合物[XM(PEt₃)₂-C₆H₄-A] (M＝Pd, Pt; X＝Br, I; A＝NO₂, CHO), 具有较高的二阶超极化率. 采用从头算方法对该配合物的二阶超极化率进行了研究. 构型在MP2/Lanl2DZ水平优化. 基组采用赝势价分裂基Lanl2DZ添加弥散函数和极化函数. HF水平计算(个别情况用MP2计算验证)表明, 苯的对位取代基A的吸电子能力越强, 金属对位配体X的供电子能力越强, 则配合物的二阶超极化率越大.     

吲哚咪唑基钌(Ⅱ)联吡啶配合物与酵母RNA的相互作用

通过紫外-可见光谱和荧光光谱滴定、稳态荧光猝灭和溴化乙啶竞争键合实验研究了Ru(Ⅱ)配合物[Ru(bpy)(H₂iip)₂](ClO₄)₂{bpy=2,2′-联吡啶, H₂iip=2-(吲哚-3-基)-咪唑[4,5-f][1,10]-邻菲罗啉}的酵母RNA键合性质. 结果表明, 二者键合模式为嵌入键合, 其键合常数为7.09×10⁶ L/mol, 比小牛胸腺DNA的键合常数大, 且比同类配合物[Ru(bpy)₂(H₂iip)](ClO₄)₂的酵母RNA键合常数大.     

铀酰与羧酸和肟基类配体相互作用的理论研究

深入了解各种功能基团与铀酰离子的络合行为有助于设计和开发高效海水提铀吸附剂. 本工作通过密度泛函理论(DFT)方法系统地研究了两种典型铀酰络合配体吡啶-2,6-二羧酸(H₂DPA)和戊二酰偕亚胺二肟(H₂A)与铀酰离子及碳酸根离子形成的配合物的结构、成键性质以及热力学稳定性. 研究结果表明, 所有配合物中, 配体与铀酰离子之间具有不同强度的共价相互作用. 由于H₂A配位时发生了质子重排, 而且配体的解离能较高, 使其更难与[UO₂(CO₃)₃]^4-发生取代反应, 因此H₂DPA配体是海水提铀中一种潜在的有效配体. 本工作的相关研究结果为海水提铀中高效吸附基团的设计和开发提供了理论线索.     

Mixed Ligand Complexes of Palladium (II) with Diethylenetriamine as Primary Ligand and Peptides as Secondary Ligand

Solution equilibria of the system palladium (II)-diethylenetriamine (dien) and peptides have been studied. The pH-metric titration of the reaction mixture containing equimolar solutions of palladium (II), dien and peptide have shown the formation of 1:1:1 mixed ligand complex. The pK_e of the peptides studied and formation constants of the resulting complexes have been determined at 25°C. The mode of chelation has been deduced from the conductivity measurements.     

Evolution of the Ligand Shell Morphology during Ligand Exchange Reactions on Gold Nanoparticles

Ligand exchange reactions are used to achieve nanoparticles coated with a mixture of ligand molecules. Currently, nothing is known on the evolution of the morphology of the ligand shell during the reaction. Here, we use a recently developed method (based on MALDI‐TOF) to follow the evolution of the ligand shell composition and morphology during the reaction. We observe the expected evolution in composition and we find that the ligand shell starts as a random mixture and gradually evolves towards a patchy morphology. When the composition has reached a plateau (i.e. when the reaction is generally assumed to be finished), the ligand shell morphology keeps evolving for days, slowly approaching its equilibrium configuration.     

混配络合物中配位体最佳浓度比的理论研究

我们认为,如金属离子M能与配位体A和B形成二元络合物,那么在配位数允许和不存在空间障碍的情况下,总有三元络合物形成.但由于两种配位体之间的浓度比例调节不当,会造成三元络合物在溶液里的所有组份中占很小的比例,这样,往往给人们一个错觉,即没有三元络合物形成,三元混配络合物在溶液里所有组份中所占的比例达到极大时,两配位体之间的浓度比例是可以通过计算得到的。     

Morpholin als ambidenter Ligand

Morpholine as Ambident Ligand The reaction of MeInCl₂ with Li‐morpholinate [Li(Morph)] at 20 °C in THF gave after work‐up and recrystallization from diglyme the salt [Li(Diglyme){In₃Me₂Cl₄(Morph)₄}]·Diglyme ( 1 ). The treatment of the reaction mixture of MesInCl₂/Li(Morph) with wet THF yield as only isolated compound the coordination polymer [Li₆Cl₆(HMorph)₃] ( 2 ). Under similar conditions the reaction of InCl₃ with Li(Morph) led after work‐up in wet THF to [Li(Diglyme)₂][InCl₄(HMorph)₂] ( 3 ). 1 – 3 were characterized by NMR and IR spectroscopy as well as by X‐ray analysis. According to this, 1 contains the trinuclear anion [In₃Me₂Cl₄(Morph)₄]^? in which one of the morpholinate ligands is coordinated via N atom to the In³⁺ ions, while the O atom belongs to the coordination sphere of the Li⁺ ion. In 2 , LiCl forms a hexagonal heteroprismn, in which the morpholine molecules are responsible for a 3d network via coordination of both Lewis‐basic heteroatoms. 3 contains trans‐[InCl₄(Hmorph)₂]^? ions, connected by hydrogen bonding along [011].     

Ligand binding properties of cobalamins

The main goal of the present density functional theory calculations is a comparative study of NO, O₂, ${{\rm NO}_{2}^{-}}$ , and H₂O binding to different forms of cob(II)alamins and cob(III)alamins. The comparison of binding energies of small ligands enables one to draw conclusions regarding the stability of the studied derivatives of cobalamins as well as to define the preferred form of cobalamin for each ligand. Ligands such as NO and O₂ favor cob(II)alamins, while H₂O and ${{\rm NO}_{2}^{-}}$ cob(III)alamins. The obtained results are confronted with available experimental data. Finally, our findings allow one to divide the studied small ligands into two groups: NO and O₂ for which the coordination to cobalamins significantly weakens their internal bonds, and ${{\rm NO}_{2}^{-}}$ and H₂O for which the effect is not observed.     

Ligand field-actuated redox-activity of acetylacetonate

The quest for simple ligands that enable multi-electron metal–ligand redox chemistry is driven by a desire to replace noble metals in catalysis and to discover novel chemical reactivity. The vast majority of simple ligand systems display electrochemical potentials impractical for catalytic cycles, illustrating the importance of creating new strategies towards energetically aligned ligand frontier and transition metal d orbitals. We herein demonstrate the ability to chemically control the redox-activity of the ubiquitous acetylacetonate (acac) ligand. By employing the ligand field of high-spin Cr(ii) as a switch, we were able to chemically tailor the occurrence of metal–ligand redox events via simple coordination or decoordination of the labile auxiliary ligands. The mechanism of ligand field actuation can be viewed as a destabilization of the d_z² orbital relative to the π* LUMO of acac, which proffers a generalizable strategy to synthetically engineer redox-activity with seemingly redox-inactive ligands.

Tailoring the chemical surroundings of chromium(ii) allows reversible electron-transfer to the ubiquitous, purportedly redox-inactive acetylacetonate.