Study of the complexation of 5,17-bis-(N-tolyliminomethyl)-25,27-dipropoxycalix[4]arene with pyridine carboxylic acids by RP HPLC and molecular modelling

Host–guest complexation process of 5,17-bis-(N-tolyliminomethyl)-25,27-dipropoxycalix[4]arene with pyridine carboxylic acids by RP HPLC method (mobile phase – MeCN/H₂O, 86/14 by volume, LiChrosorb RP 18, UV detector, λ = 254 nm) had been studied. The binding constants and Gibbs free energies of the complexes 5,17-bis(N-tolyliminomethyl)-25,27-dipropoxycalix[4]arene with the pyridine carboxylic acids are within 584 to 1914 M^? 1 and ? 15.76 to ? 18.69 kJ/mol, respectively. It was shown by the molecular modelling that the complexes are stabilised by hydrogen bonds between carboxylic groups of the acids and nitrogen atoms of imino groups at the upper rim or oxygen atoms of the hydroxyl groups at the lower rim of the macrocycle. Linear dependence of the binding constants from the acid lipophilicity log P indicates the role of solvophobic interactions during the complexation process.     

The Formation of Luminescent Supramolecular Ternary Complexes in Water: Delayed Luminescence Sensing of Aromatic Carboxylates Using Coordinated Unsaturated Cationic Heptadentate Lanthanide Ion Complexes

The synthesis of four lanthanide ion complexes Eu?1, Eu?2, Tb?1 and Tb?2, from the heptadentate tri-arm cyclen (1,4,7,10-tetraazacyclododecane) ligands 1 and 2 that were made in one-pot syntheses is described. These coordinatively unsaturated complexes have two labile metal-bound water molecules, as demonstrated by X-ray crystallography. This was also confirmed by evaluating their hydration state (q～2) by measuring their lifetimes in D²O and H²O, respectively. The above complexes were all designed as being “photophysically silent” prior to the recognition of the anion, since they do not possess antenna that can participate in sensitisation of the Eu(III) or the Tb(III) excited state. However, the two water molecules can be displaced upon anion binding by the appropriate aromatic carboxylates to give ternary complexes in water, through either four- or six-member ring chelates (q～0), or possibly via a monodentate binding. In the case of Tb?1 and Tb?2, large luminescence enhancements were observed upon the formation of such ternary complexes with N,N-dimethylaminobenzoic acid at ambient pH. Such binding and luminescent enhancements were also observed for Tb?1 in the presence of salicylic acid. On all occasions, the anion recognition “switched” the emission “on” over two logarithmic units. At higher concentrations, the emission is reduced possibly due to quenching. In the case of aspirin, the binding was too weak to be measured, indicating that Tb?1 selectively detects salicylic acid, the active form of aspirin in water. In the case of Eu?1 and Eu?2, the affinity of these complexes towards such aromatic carboxylates was too weak for efficient ternary complex formation.     

含取代基苯基羧酸与柔性含氮配体构筑的三个过渡配位化合物的合成、晶体结构与物理性质

利用3,5-二硝基苯甲酸（3,5-DNBH）,1,2-双咪唑亚甲苯（1,2-bimb）与3种过渡金属盐通过水热反应成功地构筑3个过渡金属配位化合物,即[M（3,5-DNB）₂（1,2-bimb）]（M=Co（Ⅱ） （1）,Cd（Ⅱ）（3））和[Zn（3,5-DNB）₂（1,2-bimb）]_n （2）。通过红外光谱、元素分析、单晶和粉末X射线衍射表征了这三个化合物。化合物1和3是同构的,含有一个双核单元[M₂（COO）₂],该双核单元由金属离子、3,5-二硝基苯甲酸根以及1,2-bimb分子构成。双核单元再通过O…π弱相互作用形成超分子结构,该弱相互作用是通过3,5-二硝基苯甲酸根上的硝基氧原子与1,2-bimb上的苯环所形成。化合物2是一维链结构,链与链之间再通过3,5-二硝基苯甲酸根和1,2-双咪唑亚甲苯配体上苯环之间的π…π相互作用,形成了一个超分子结构。室温条件下研究了化合物2和3分散在甲醇中的荧光性质。热重测试结果显示3个化合物具有相对较高的热稳定性。可见光照射条件下化合物1对罗丹明B具有一定的催化降解能力。此外,直流磁化率结果显示化合物1中金属离子之间存在反铁磁相互作用。     

3,4,5,6-四氟邻苯二甲酸与含氮配体的过渡金属配合物的合成、晶体结构及对Fe3+的荧光传感

利用过渡金属盐与3,4,5,6-四氟邻苯二甲酸（TFPT）、1,3-二（4-吡啶基）-丙烷（DPP）和1,4-二（1,2,4-三氮唑）-1-丁烷（BTB）经水热法合成了3个新的配合物：{[M（TFPT）（DPP）]·H₂O}_n（M=Cd（1）,Ni（2））,{[Cd（TFPT）（BTB）_0.5]·2H₂O}_n（3）。通过X射线单晶衍射分析测定了它们的结构。配合物1和2具有相似的一维链结构。中心金属离子表现为扭曲的[MO₄N₂]八面体构型。配合物3具有二维结构。中心金属离子表现为扭曲的[CdO₅N]八面体构型。配合物1和3分别在424 nm、442 nm处出现来自于配体的荧光发射,对应于配体的π^*-π的跃迁,配合物2在356 nm处有非常弱的荧光发射。不同金属阳离子对配合物1和3的荧光强度有不同程度的影响,并且通过荧光的猝灭机理,它们都能选择性检测Fe³⁺离子。     

Syntheses and structures of tetranuclear Zn（Ⅱ） complexes with in situ generated macrocyclic Schiff base ligands:Applications in Zn2+ sensing

Three novel Zn（II） complexes,[Zn₄L¹Cl₄]-3H₂O（1）,[Zn₄L²Cl₄]-2DMF（2） and[Zn₄L³Cl₄]H₂O（3）,have been synthesized and structurally characterized.In these complexes,interesting 32-membered dodecadentate macrocyclic ligands were generated in situ by ’2 + 2’ type condensation reactions between a tetraamine and various dialdehydes.All the complexes are isostructurally tetranuclear Zn（Ⅱ） complexes,containing endogenous alkoxo and phenoxo bridges.Applications of the macrocyclic ligands as Zn²⁺ sensors have been investigated.Take H₄L¹ for example,it exhibits a 4-fold fluorescence enhancement upon the addition of 2 equiv.of Zn²⁺ in MeOH.