There is widespread interest in non-covalent bonding and weak interactions, such as electrostatic interactions, hydrogen bonding, solvophobic/hydrophobic interactions, metal-metal interactions, and π-π stacking, to tune the molecular assembly of planar π-conjugated organic and inorganic molecules. Inspired by the roles of metal-aromatic interaction in biological systems, such as in ion channels and metalloproteins, herein, we report the first example of the use of Hg(2+) -aromatic interactions to selectively control the assembly and disassembly of zinc-salen complexes in aqueous media; moreover, this process exhibited significant "turn on" fluorescent properties. UV/Vis and fluorescence spectroscopic analysis of the titration of Hg(2+) ions versus complex ZnL(1) revealed that the higher binding affinity of Hg(2+) ions (compared to 13 other metal ions) was ascribed to specific interactions between the Hg(2+) ions and the phenyl rings of ZnL(1); this result was also confirmed by (1)H NMR spectroscopy and HRMS (ESI). Further evidence for this type of interaction was obtained from the reaction of small-molecule analogue L(1) with Hg(2+) ions, which demonstrates the proximity of the N-alkyl group to the aromatic protons during Hg(2+)-ion binding, which led to the consequential H/D exchange reaction with D(2) O. DFT modeling of such interactions between the Hg(2+) ions and the phenyl rings afforded calculated distances between the C and Hg atoms (2.29 ?) that were indicative of C-Hg bond-formation, under the direction of the N atom of the morpholine ring. The unusual coordination of Hg(2+) ions to the phenyl ring of the metallosalen complexes not only strengthened the binding ability but also increased the steric effect to promote the disassembly of ZnL(1) in aqueous media. 相似文献
Although a variety of chemosensors as probes have been exploited for the detection of metal ions with high sensitivity and selectivity, the formed probe–metal complex was hardly suitable for separation, removal, and further recovery. This paper presents a method to detect and remove metal ions from aqueous solutions simultaneously by a fluorescence chemosensor and functional magnetic nanoparticles. A novel probe SRhB ‐Azo was synthesized based on rhodamine B (RhB ), maleic anhydride (MAH ), and azobenzene (Azo). SRhB ‐Azo showed high selectivity and sensitivity to Hg ions in aqueous solutions. Job's experiment showed the formation of a 1:2 stoichiometry complex between Hg2+ and SRhB ‐Azo. Moreover, β‐cyclodextrin (β‐CD )‐modified magnetic nanoparticles (CD‐MNPs ) were fabricated and used as host materials to form the inclusion complex CD–MNP and SRhB ‐Azo–Hg2+. Then, the SRhB ‐Azo‐Hg2+ complex could be removed by an external magnet, and subsequently recovered by UV ‐irradiation‐induced trans/cis isomerization of the Azo groups. The CD‐MNP s could be reused for nearly four times. Thus, the SRhB ‐Azo probe and CD‐MNP system has great potential application in sewage treatment. 相似文献
Non‐coordinative interactions between a metal ion and the aromatic ring of a fluorophore can act as a versatile sensing mechanism for the detection of metal ions with a large emission change of fluorophores. We report the design of fluorescent probes based on arene–metal‐ion interactions and their biological applications. This study found that various probes having different fluorophores and metal binding units displayed significant emission redshift upon complexation with metal ions, such as AgI, CdII, HgII, and PbII. X‐ray crystallography of the complexes confirmed that the metal ions were held in close proximity to the fluorophore to form an arene–metal‐ion interaction. Electronic structure calculations based on TDDFT offered a theoretical basis for the sensing mechanism, thus showing that metal ions electrostatically modulate the energy levels of the molecular orbitals of the fluorophore. A fluorescent probe was successfully applied to the ratiometric detection of the uptake of CdII ions and hydrogen sulfide (H2S) in living cells. These results highlight the utility of interactions between arene groups and metal ions in biological analyses. 相似文献
The bis(diphenylphosphino)methane (dppm)‐bridged dinuclear cycloplatinated complex {[Pt(L)]2(μ‐dppm)}2+ (Pt2 ? dppm; HL: 2‐phenyl‐6‐(1H‐pyrazol‐3‐yl)‐pyridine) demonstrates interesting reversible “pivot‐hinge”‐like intramolecular motions in response to the protonation/deprotonation of L. In its protonated “closed” configuration, the two platinum(II) centers are held in position by intramolecular d8–d8 Pt–Pt interaction. In its deprotonated “open” configuration, such Pt–Pt interaction is cleaved. To further understand the mechanism behind this hingelike motion, an analogous dinuclear cycloplatinated complex, {[Pt(L)]2(μ‐dchpm)}2+ (Pt2 ? dchpm) with bis(dicyclohexylphosphino)methane (dchpm) as the bridging ligand, was synthesized. From its protonation/deprotonation responses, it was revealed that aromatic π–π interactions between the phenyl moieties of the μ‐dppm and the deprotonated pyrazolyl rings of L was essential to the reversible cleavage of the intramolecular Pt–Pt interaction in Pt2 ? dppm. In the case of Pt2 ? dchpm, spectroscopic and spectrofluorometric titrations as well as X‐ray crystallography indicated that the distance between the two platinum(II) centers shrank upon deprotonation, thus causing a redshift in its room‐temperature triplet metal–metal‐to‐ligand charge‐transfer emission from 614 to 625 nm. Ab initio calculations revealed the presence of intramolecular hydrogen bonding between the deprotonated and negatively charged 1‐pyrazolyl‐N moiety and the methylene CH and phenyl C–H of the μ‐dppm. The “open” configuration of the deprotonated Pt2 ? dppm was estimated to be 19 kcal mol?1 more stable than its alternative “closed” configuration. On the other hand, the open configuration of the deprotonated Pt2 ? dchpm was 6 kcal mol?1 less stable than its alternative closed configuration. 相似文献
Recent work has shown that xenon chemical shifts in cryptophane‐cage sensors are affected when tethered chelators bind to metals. Here, we explore the xenon shifts in response to a wide range of metal ions binding to diastereomeric forms of 1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetic acid (DOTA) linked to cryptophane‐A. The shifts induced by the binding of Ca2+, Cu2+, Ce3+, Zn2+, Cd2+, Ni2+, Co2+, Cr2+, Fe3+, and Hg2+ are distinct. In addition, the different responses of the diastereomers for the same metal ion indicate that shifts are affected by partial folding with a correlation between the expected coordination number of the metal in the DOTA complex and the chemical shift of 129Xe. These sensors may be used to detect and quantify many important metal ions, and a better understanding of the basis for the induced shifts could enhance future designs. 相似文献
Despite several types of fluorescent sensing molecules have been proposed and examined to signal Hg2+ ion binding, the development of fluorescence‐based devices for in‐field Hg2+ detection and screening in environmental and industrial samples is still a challenging task. Herein, we report the synthesis and characterization of three new coumarin‐based fluorescent chemosensors featuring mixed thia/aza macrocyclic framework as receptors units, that is, ligands L1 – L3 . These probes revealed an OFF–ON selective response to the presence of Hg2+ ions in MeCN/H2O 4:1 (v/v), which allowed imaging of this metal ion in Cos‐7 cells in vitro. Once included in silica core–polyethylene glycol (PEG) shell nanoparticles or supported on polyvinyl chloride (PVC)‐based polymeric membranes, ligands L1 – L3 can also selectively sense Hg2+ ions in pure water. In particular we have developed an optical sensing array tacking advantage of the fluorescent properties of ligand L3 and based on the computer screen photo assisted technique (CSPT). In the device ligand L3 is dispersed into PVC membranes and it quantitatively responds to Hg2+ ions in natural water samples. 相似文献
Summary: A reversible and highly selective assay method has been developed to detect mercury(II ) (Hg2+) ions using a conjugated polymer (CP). The transduction mechanism is based on Hg2+‐mediated interpolymer π‐stacking aggregation, which results in the fluorescence self‐quenching of the CP. CPs that contain thymine moieties, poly[3‐(N‐thymin‐1‐ylacetyl)ethylamine‐thiophene] (PTT), have been synthesized and characterized. In the absence of Hg2+ ions, the PTT chains remain separated from each other and the CP exhibits strong fluorescence emission. Upon adding Hg2+ ions, the formation of interpolymer π‐stacking aggregation induced by specific thymine–Hg–thymine interactions results in the fluorescence quenching of PTT. Distinguishing aspects of this assay include the signal amplification of CPs and the specific binding of Hg2+ ions to thymine‐thymine (T–T) base pairs.
The binding of Hg2+ ions causes the separate conducting polymer chains to aggregate with subsequent fluorescence self‐quenching. 相似文献
Anion–π interactions generally exist between an anion and an electron‐deficient π‐ring because of the electron‐accepting character of the ring. In this paper, we report orbital effect‐induced anomalous binding between electron‐rich π systems and F? through anion–π interactions calculated at the MP2/6‐31+G(d,p) and ωB97X‐D/6‐31+G(d,p) levels of theory. We find that anion–π interactions between F? and electron‐rich π rings increase markedly with increasing number of π electrons and size of the π rings. This is contrary to intuition because anion–π interactions would be expected to gradually decrease because of gradually increasing Coulombic repulsion between the negative charge of the anions and gradually increasing number of π electrons of the aromatic surfaces. Energy decomposition analysis showed that the key to this anomalous effect is the more effective delocalization of negative charge to the unoccupied π* orbitals of larger π rings, which is termed an “orbital effect”. 相似文献
Studies of double‐stranded‐DNA binding have been performed with three isomeric bis(2‐(n‐pyridyl)‐1H‐benzimidazole)s (n=2, 3, 4). Like the well‐known Hoechst 33258, which is a bisbenzimidazole compound, these three isomers bind to the minor groove of duplex DNA. DNA binding by the three isomers was investigated in the presence of the divalent metal ions Mg2+, Co2+, Ni2+, Cu2+, and Zn2+. Ligand–DNA interactions were probed with fluorescence and circular dichroism spectroscopy. These studies revealed that the binding of the 2‐pyridyl derivative to DNA is dramatically reduced in the presence of Co2+, Ni2+, and Cu2+ ions and is abolished completely at a ligand/metal‐cation ratio of 1:1. Control experiments done with the isomeric 3‐ and 4‐pyridyl derivatives showed that their binding to DNA is unaffected by the aforementioned transition‐metal ions. The ability of 2‐(2‐pyridyl)benzimidazole to chelate metal ions and the conformational changes of the ligand associated with ion chelation probably led to such unusual binding results for the ortho isomer. The addition of ethylenediaminetetraacetic acid (EDTA) reversed the effects completely. 相似文献
A series of isomorphic lanthanide metal–organic frameworks (MOFs) Ln(TATAB)?(DMF)4(H2O)(MeOH)0.5 (LnTATAB, Ln=Eu, Tb, Sm, Dy, Gd; H3TATAB=4,4′,4′′‐s‐triazine‐1,3,5‐triyltri‐p‐aminobenzoic acid) have been solvothermally synthesized and structurally characterized. Among these MOFs, TbTATAB exhibits good water stability and a high fluorescence quantum yield. Because mercury ions (Hg2+) have a high affinity to nitrogen atoms, and the space between multiple nitrogen atoms from triazine and imino groups is suitable for interacting with Hg2+ ions, TbTATAB shows highly selective and sensitive detection of Hg2+ in aqueous solution with a detection limit of 4.4 nm . Furthermore, it was successfully applied to detect Hg2+ ions in natural water samples. 相似文献
The reaction of [1,3‐bis(2‐ethoxy)benzene]triazene, [ HL ], with Hg(SCN)2 and Hg(CH3COO)2, resulted in the formation of the complexes [Hg L (SCN)] ( 1 ) and [Hg L 2] · CH3OH ( 2 ). They were characterized by means of X‐ray crystallography, CHN analysis, FT‐IR, 1H NMR, and 13C NMR spectroscopy. The structure of compound 1 consists of two independent complexes in which the HgII atoms are stacked along the crystallographic a axis to form infinite chains. Each HgII atom is chelated by one L ligand and one SCN ligand, whereas in compound 2 , the HgII atom is surrounded by two L ligands. In addition, 1D chains formed by metal–π interactions are connected to each other by C–H ··· π stacking interactions in the structure of 1 , which results in a 2D architecture. An interesting feature of compound 2 is the presence of C–H ··· π edge‐to‐face interactions. 相似文献
Highly selective recognition of metal ions by rational ligand design is challenging, and simple metal binding by biological ligands is often obscured by nonspecific interactions. In this work, binding‐triggered catalysis is used and metal selectivity is greatly increased by increasing the number of metal ions involved, as exemplified in a series of in vitro selected RNA‐cleaving DNAzymes. The cleavage junction is modified with a glycyl–histidine‐functionalized tertiary amine moiety to provide multiple potential metal coordination sites. DNAzymes that bind 1, 2, and 3 Zn2+ ions, increased their selectivity for Zn2+ over Co2+ ions from approximately 20‐, 1000‐, to 5000‐fold, respectively. This study offers important insights into metal recognition by combining rational ligand design and combinatorial selection, and it provides a set of new DNAzymes with excellent selectivity for Zn2+ ions. 相似文献
A novel organic–inorganic silica‐based fluorescent probe was designed, synthesized and characterized by different techniques such as XRD, BET, TGA, and FT‐IR. The fluorescence properties of the probe were studied in the presence of a variety of metal‐ions in water. The results revealed that various metal‐ions negligibly vary the emission intensity of the probe except for Hg2+, which quenched the intensity dramatically. The selectivity of the probe toward Hg2+ ion was further investigated in the presence of common competing metal‐ions and the results demonstrated the high selectivity of the probe toward Hg2+ ion. The fluorescence emission of the probe was also studied as a function of the concentration of Hg2+ ion. A nanomolar limit of detection was estimated for Hg2+, indicating a high sensitivity. Furthermore, the probe showed INHIBIT‐type logic behavior with Hg2+ and H+ as inputs. Also, the optimum pH range was studied in addition to reversibility and real world applicability of the probe. 相似文献
Although metal ion homeostasis in cells is often mediated through metallochaperones, there are opportunities for toxic metals to be sequestered through the existing transport apparatus. Proper trafficking of CuI in human cells is partially achieved through complexation by HAH1, the human metallochaperone responsible for copper delivery to the Wilson and Menkes ATPase located in the trans‐Golgi apparatus. In addition to binding copper, HAH1 strongly complexes HgII, with the X‐ray structure of this complex previously described. It is important to clarify the solution behavior of these systems and, therefore, the binding of HgII to HAH1 was probed over the pH range 7.5 to 9.4 using 199Hg NMR, 199mHg PAC and UV–visible spectroscopies. The metal‐dependent protein association over this pH range was examined using analytical gel‐filtration. It can be concluded that at pH 7.5, HgII is bound to a monomeric HAH1 as a two coordinate, linear complex (HgS2), like the HgII–Atx1 X‐ray structure (PDB ID: 1CC8). At pH 9.4, HgII promotes HAH1 association, leading to formation of HgS3 and HgS4 complexes, which are in exchange on the μs–ns time scale. Thus, structures that may represent central intermediates in the process of metal ion transfer, as well as their exchange kinetics have been characterized. 相似文献
Organic molecular devices for information processing applications are highly useful building blocks for constructing molecular‐level machines. The development of “intelligent” molecules capable of performing logic operations would enable molecular‐level devices and machines to be created. We designed a series of 2,5‐diaryl‐1,3,4‐oxadiazoles bearing a 2‐(para‐substituted)phenyl and a 5‐(o‐pyridyl) group (substituent X=NMe2, OEt, Me, H, and Cl; 1 a – e ) that form a bidentate chelating environment for metal ions. These compounds showed fluorescence response profiles varying in both emission intensity and wavelength toward the tested metal ions Ni2+, Cu2+, Zn2+, Cd2+, Hg2+, and Pb2+ and the responses were dependent on the substituent X, with those of 1 d being the most substantial. The 1,3,4‐oxadiazole O or N atom and pyridine N atom were identified as metal‐chelating sites. The fluorescence responses of 1 d upon metal chelation were employed for developing truth tables for OR, NOR, INHIBIT, and EnNOR logic gates as well as “ON‐OFF‐ON” and “OFF‐ON‐OFF” fluorescent switches in a single 1,3,4‐oxadiazole molecular system. 相似文献
Controlling the arrangement of different metal ions to achieve ordered heterogeneity in metal–organic frameworks (MOFs) has been a great challenge. Herein, we introduce a template‐directed approach, in which a 1D metal–organic polymer incorporating well‐defined binding pockets for the secondary metal ions used as a structural template and starting material for the preparation of well‐ordered bimetallic MOF‐74s under heterogeneous‐phase hydrothermal reaction conditions in the presence of secondary metal ions such as Ni2+ and Mg2+ in 3 h. The resulting bimetallic MOF‐74s were found to possess a nearly 1:1 metal ratio regardless of their initial stoichiometry in the reaction mixture, thus demonstrating the possibility of controlling the arrangement of metal ions within the secondary building blocks in MOFs to tune their intrinsic properties such as gas affinity. 相似文献