Solvent-driven multiply configurable on/off fluorescent indicator of the pH window: a diethylenetriamine bearing two end pyrene fragments

Fluorescence behaviors of a simple-structured molecule (L), a diethylenetriamine bearing two end pyrene fragments, have been investigated in water. Effects of adding a less-polar organic solvent (acetonitrile: MeCN) on the emission behaviors have been studied by means of steady-state and time-resolved fluorescence measurements. L dissolved in water shows dual-mode fluorescence consisting of monomer and excimer emissions. The monomer emission shows an "on-off" intensity profile against the pH window (pH 2-12), whereas the excimer emission shows an "off-on" profile. Upon MeCN addition, the monomer emission maintains the "on-off" profile. In contrast, the "off-on" profile of the excimer emission is drastically changed: L shows two more types of profiles, "off-on-off-on" and "off-on-off", along with the MeCN concentration increase, thus behaving as a multiply configurable fluorescent indicator of the pH window. The MeCN-driven excimer emission switching of L is triggered by (i) the decrease in stability of the intramolecular ground-state dimer (GSD) formed between the end pyrene fragments, which suppresses the direct photoexcitation of GSD (suppression of the "static" excimer formation), leading to a decrease in the excimer emission intensity at basic pH; and (ii) the decrease in polarity of solution, which allows formation of a "dynamic" excimer via a monomer-to-excimer transition, resulting in an enhancement of the excimer emission intensity at acidic-neutral pH.     

Synthesis of double-armed lariat ethers with pyrene moieties at each end of two sidearms and their fluorescence properties in the presence of alkali metal and alkaline earth metal cations

Two types of double-armed lariat ether derivatives having pyrene moieties at each end of two sidearms, (3x + 1)-crown-x derivatives 1 (x = 5), 2 (x = 6), and 3 (x = 4) (type A) and 3y-crown-y derivatives, 6 (y = 5) and 7 (y = 6) (type B), were synthesized, and their complexation behavior toward alkali metal and alkaline earth metal cations was examined by fluorescence spectroscopy. Pyrene excimer emission decreased accompanied by an increase in monomer emission upon metal ion complexation. This finding is ascribed to the change of the spatial distance of two pyrene rings by movement suppression of both the crown ring and one of the two sidearms based on complexation with the metal cation. The selectivity for alkaline earth metal cations was highly dependent on the fitness of the host cavity and the guest size. Although most of the fluorophores did not respond to alkali metal cations, only trans-7a containing an 18-crown-6 ring showed K(+) selectivity.     

Solvent-dependent conformational and fluorescence change of an N-phenylbenzohydroxamic acid derivative bearing two pyrene moieties

The conformation of N-phenylbenzohydroxamic acid has been reported to change depending on the solvent properties. Here, we newly synthesized N-phenylbenzohydroxamic acid derivative, which contains two pyrene moieties separated from the phenyl rings by ethylene linkers. It showed solvent-dependent conformational change, and its fluorescence was also solvent-dependent, that is, only monomer fluorescence of pyrene was observed in DMSO or DMF, whereas the excimer fluorescence was observed in CH₂Cl₂ or CHCl₃. Thus, the structural characteristics could be converted to fluorescence change as output, which would be a good candidate as a fluorescent sensor.     

Fluorescence properties of polyamines bearing two terminal quinoline fragments in water

Fluorescence properties of polyamines bearing two terminal quinoline fragments with different polyamine chain length, such as ethylenediamine (L0), diethylenetriamine (L1), and triethylenetetramine (L2), have been studied in water. These ligands show Zn²⁺-induced fluorescence enhancement, while showing almost no enhancement with other cations. However, stability constants for Zn²⁺ coordination and fluorescence response against Zn²⁺ depend strongly on the polyamine chain length. The chain length also affects the fluorescence wavelength. The Zn²⁺-L1 and Zn²⁺-L2 complexes show emission at 410 nm, while Zn²⁺-L0 complexes show a blue-shifted emission at 375 nm due to the partial charge transfer from the excited state quinoline to the Zn²⁺ center.     

Guest-responsive excimer fluorescence of β-cyclodextrin bearing a pendant group with two pyrene moieties

β-Cyclodextrin derivative 1 , bearing a group with two pyrene moieties, exhibits predominant excimer emission in a 20% DMSO aqueous solution. In spite of the fact that pyrene is too large to be included in the β-cyclodextrin cavity and consequently both pyrene moieties are located outside the cavity, 1 varies the excimer emission intensity through the formation of inclusion complexes with guest species, thus acting as a chemosensor for molecular recognition.     

Synthesis, coordination studies and redox properties of a novel ditertiary phosphine bearing two ferrocenyl groups

The new ferrocenyl substituted ditertiary phosphine {FcCH₂N(CH₂PPh₂)CH₂}₂ [Fc = (η⁵-C₅H₄)Fe(η⁵-C₅H₅)] (1) was prepared, in 72% yield, by Mannich based condensation of the known bis secondary amine {FcCH₂N(H)CH₂}₂ with 2 equiv. of Ph₂PCH₂OH in CH₃OH. Phosphine 1 readily coordinates to various transition-metal centres including Mo⁰, Ru^II, Rh^I, Pd^II, Pt^II and Au^I to afford the heterometallic complexes {RuCl₂(p-cym)}₂(1) (2), (AuCl)₂(1) (3), cis-PtCl₂(1) (4), cis-PdCl₂(1) (5), cis-Mo(CO)₄(1) (6), trans,trans-{Pd(CH₃)Cl(1)}₂ (7) and trans,trans-{Rh(CO)Cl(1)}₂ (8). In complexes 2, 3, 7 and 8 ligand 1 displays a P,P′-bridging mode whilst for 4-6 a P,P′-chelating mode is observed. All new compounds have been fully characterised by spectroscopic and analytical methods. Furthermore the structures of 1, 2 · 2CH₂Cl₂, 3 · CH₂Cl₂, 4 · CH₂Cl₂, 6 · 0.5CHCl₃ and 8 have been elucidated by single crystal X-ray crystallography. Electrochemical measurements have been undertaken, and their redox chemistry discussed, on both noncomplexed ligand 1 and representative compounds containing this new ditertiary phosphine.     

芘衍生物发光行为的研究

本工作合成了新型的芘衍生物-芘基查尔酮(PD), 研究了其在溶液及胶束中的稳态光物理行为。结果表明: 即使在较低浓度条件下, PD分子间也容易生成基态电荷转移配合物(Inter-CT), 其荧光光谱表现为芘单体荧光、分子内电荷转移态(Intra-CT)荧光以及Inter-CT荧光, 并且具有较好的溶致变色效应、浓度效应以及温度效应, 是一良好的探针分子化合物。     

Alkali metal cation intercalation properties of titanate nanotubes

Hydrothermally synthesized titanate nanotubes show high alkali metal cation intercalation reactivity evidenced by high resolution microscopic examination, elemental mapping and profiling techniques as well as wet chemical analysis.     

四苯骈卟啉金属配合物轴向配位反应的热力学性质研究

金属卟啉在生命过程中起着重要的作用[1 - 4 ] 。CuTBP ,CoTBP与有机碱的反应,用光度法测定了轴配反应在不同温度下的速率常数和平衡常数,求得活化能及热力学参数,结果表明:它们与不同有机碱反应的活化能及平衡常数既与配体的碱性有关,也与空间位阻有关,同一温度下反应的平衡常数和速率常数的大小顺序均为:咪唑>吡啶>2 甲基吡啶>2 ,4 二甲基吡啶。1　实验部分1 .1　仪器与试剂日本产岛津UV 2 4 0G型分光光度计,上海分析仪器厂72 1型光度计(内装恒温套) ,重庆电机厂超级恒温槽。四苯骈卟啉金属配合物系自制[4] ,咪唑、吡啶、2 甲基吡…     

Crystal structures and magnetic properties of metal complexes bearing four nitronyl nitroxide moieties in the same coordination sphere

Mononuclear transition metal complexes of the type [M(2,6-NITpy)2](ClO4)2 x solvent (2,6-NITpy = 2,6-bis-(3'-oxide-1'-oxyl-4',4',5',5'-tetramethylimidazolin-2'-yl)pyridine; M = Ni (1), Co (2), Zn (3), Mn (4), Cu (5)) have been synthesized and characterized by single-crystal X-ray diffraction studies. Crystal data: 1, monoclinic, P2(1)/c, Z = 4, a = 20.946(2) A, b = 12.0633(2) A, c = 21.173(2) A, beta = 113.55(1) degrees; 2, monoclinic, P2(1)/c, Z = 4, a = 20.902(2) A, b = 12.0981(8) A, c = 21.215(2) A, beta = 113.130(9) degrees; 3, triclinic, P1, Z = 2, a = 11.410(1) A, b = 12.932(1) A, c = 21.609(2) A, alpha = 96.040(2) degrees, beta = 102.24(1) degrees, gamma = 114.98(1); 4, monoclinic, P2(1)/n, Z = 4, a = 11.5473(8) A, b = 19.212(1) A, c = 25.236(2) A, beta = 98.772(9) degrees; 5, triclinic, P1, Z = 2, a = 12.1604(9) A, b = 12.6961(9) A, c = 18.103(2) A, alpha = 84.191(8) degrees, beta = 73.392(8) degrees, gamma = 66.072(8). The two 2,6-NITpy biradicals behave as terdentate ligands and bind almost perpendicular to each other in meridional positions. In compounds 1-4, the pyridine rings are axially ligated and four different nitronyl nitroxide radicals bind to the metal center through their O(nitroxyl) atoms, forming the equatorial plane of a distorted octahedron. On the contrary, in the copper(II) complex (5), the two N(pyridyl) atoms are found in equatorial positions. Only two nitroxide groups are then bound to the copper(II) ion in the equatorial plane, the other two being axially ligated. The two axially bound nitronyl nitroxide radicals couple ferromagnetically to the copper center (JCu-rad(ax) = + 10 K), whereas a strong antiferromagnetic coupling between this metal ion and the equatorial nitroxide groups (JCu-rad(eq) = -460 K) is observed. The other complexes exhibit strong antiferromagnetic metal-radical interactions: JNi-rad = -240 K, for 1; JMn-rad = -120 K, for 4. Interestingly, the study of the diamagnetic zinc(II) compound (3) reveals a moderate intramolecular antiferromagnetic interaction between radicals coordinated to the same metal center (Jrad-rad = -27.7 K). This interaction is transmitted through space and is also present in the other complexes: Jrad-rad = -14 K, for 1; Jrad-rad = -10 K, for 4; Jrad-rad = -20.5 K, for 5. Antiferromagnetic intermolecular interactions are also present in all the complexes herein studied.     

Highly-resolved fluorescence spectrometry of pyrene on a thin-layer chromatographic plate

Site-selection spectroscopy, by using suitable laser line excitation, gives epectra of molecules on thin-layer chromatographic plates comparable in quality to Shpol'skii spectra. Pyrene is investigated as a model compound.     

The effects of alkali cation complexation on the fluorescence properties of crown ethers

The effects of alkali metal complexation on the fluorescence properties of two crown ethers (a podand and a coronand) were investigated. Metal ion binding leads to changes in fluorescence intensity along with slight shifts in the emission maxima. This is attributed to a rigidization of the fluorophore and an interaction of the metal ion with non-bonding electrons of the crown ethers. The effects on the spectra are more pronounced in fluorescence than in absorption.Fluorescence titration with metal ions provides a simple and sensitive means for the determination of complexation constants, which were found to be highly dependent upon the water content of the methanol solution. Halide counterions, in particular iodide, act as dynamic fluorescence quenchers withStern-Volmer constants that are different for the sodium and potassium complexes, respectively.

---

Die Effekte der Komplexierung von Alkalimetallionen auf die Fluoreszenzeigenschaften von Kronenethern

Zusammenfassung Die Effekte der Komplexierung von Alkalimetallionen auf die Fluoreszenzeigenschaften zweier Kronenether (eines Podanden und eines Coronanden) wurden untersucht. Die Bindung des Metallions fürt zu Veränderungen in der Fluoreszenzintensität und zu Verschiebungen in den Emissionsmaxima. Dies wird einer gesteigerten Starrheit des Fluorophors und einer Wechselwirkung des Metallions mit nichtbindenden Elektronen des Kronenethers zugeschrieben. Die Auswirkungen auf die Spektren sind in der Fluoreszenz ausgeprägter als in der Absorption.Fluoreszenztitrationen mit Metallionen bieten eine einfache und empfindliche Möglichkeit zur Bestimmung von Komplexkonstanten, welche stark vom Wassergehalt der methanolischen Lösung abhängig befunden werden. Halogenidgegenionen, insbesonders Iodid, wirken als dynamische Fluoreszenzlöscher und weisenStern-Volmer-Konstanten auf, welche für die Natrium- bzw. Kalium-Komplexe verschieden sind.

     

Thermophysical properties of two ionic liquids based on benzyl imidazolium cation

Density, refractive index, and dynamic viscosity of two new ionic liquids involving the 1-benzyl-3-methyl imidazolium cation and the common anions chloride and methylsulfate have been determined and correlated as a function of temperature. Volumetric properties for the ionic liquids are calculated from the density and the results are also enclosed. The Lorentz–Lorenz, Dale–Gladstone, Eykman, Oster, Arago–Biot, and Newton equations, as well as a modified Eykman were used to correlate satisfactorily the relation between the densities and refractive indices of the selected ionic liquids. The influence of the benzyl group on the density was compared with other alkyl imidazolium cations and the same anions.     

Study of properties on non-protected room temperature phosphorescence and delayed excimer fluorescence of pyrene solution

A strong and stable room temperature phosphorescence (RTP) and delayed excimer fluorescence signal located at 596 and 475 nm, respectively, can be induced for pyrene solution in the absence of any protective medium only use KI or TlNO3 as a heavy atom perturber (HAP) and Na2SO3 as a deoxygenator. Both lifetimes of RTP and the delayed fluorescence are in the order of X-ms and the intensities are changed with kind and amount of HAP, but the peak positions are same and there is a iso-luminescent point in the emission spectra corresponding to emission at 475 nm and at 596 nm. The optimum conditions and the effects of kind and amount of HAP and organic solvents on luminescence properties of pyrene solution were studies in detail, and the photophysical process in the presence of KI or TlNO3 for phosphorescence and delayed excimer fluorescence emission of pyrene solution was discussed.     

Adsorptive properties of X zeolites modified by transition metal cation exchange

The ionic exchange of the NaX zeolite by Ni²⁺ and Cr³⁺ cations was progressively driven and studied by adsorption of nitrogen and carbon dioxide. For each cation-exchanged X zeolite sample, the development of characteristics such as profile of isotherms, RI criterion, isosteric adsorption heat and microporous volume using both the Dubinin–Radushkevich (DR) equation and the t-plot, was followed through the nitrogen adsorption. Results show that the cationic exchange process, in the case of Cr³⁺ introduced at middle degree, is accompanied by a textural damage for Cr(x)X, in contrast to Ni²⁺-exchanged X zeolites. This degradation occurs without significant presence of mesopores, because the RI criterion values were found to be much lower than 2.2. The CO₂ adsorption isotherms were measured at intervals of 30 K from 273 K and the equilibrium pressures ranged from 0.5 to 600 Torr. The experimental data were correlated by the Toth model. The associated three adjustable parameters were estimated by nonlinear least-squares analysis. The effect of temperature on the model parameters and the Henry’s law slope, K _H , represented by the product of Toth parameters, are discussed.     

Effects of transition metal ion coordination on the collision-induced dissociation of polyalanines

Transition metal-polyalanine complexes were analyzed in a high-capacity quadrupole ion trap after electrospray ionization. Polyalanines have no polar amino acid side chains to coordinate metal ions, thus allowing the effects metal ion interaction with the peptide backbone to be explored. Positive mode mass spectra produced from peptides mixed with salts of the first row transition metals Cr(III), Fe(II), Fe(III), Co(II), Ni(II), Cu(I), and Cu(II) yield singly and doubly charged metallated ions. These precursor ions undergo collision-induced dissociation (CID) to give almost exclusively metallated N-terminal product ions whose types and relative abundances depend on the identity of the transition metal. For example, Cr(III)-cationized peptides yield CID spectra that are complex and have several neutral losses, whereas Fe(III)-cationized peptides dissociate to give intense non-metallated products. The addition of Cu(II) shows the most promise for sequencing. Spectra obtained from the CID of singly and doubly charged Cu-heptaalanine ions, [M + Cu - H](+) and [M + Cu](2+) , are complimentary and together provide cleavage at every residue and no neutral losses. (This contrasts with [M + H](+) of heptaalanine, where CID does not provide backbone ions to sequence the first three residues.) Transition metal cationization produces abundant metallated a-ions by CID, unlike protonated peptides that produce primarily b- and y-ions. The prominence of metallated a-ions is interesting because they do not always form from b-ions. Tandem mass spectrometry on metallated (Met = metal) a- and b-ions indicate that [b(n) + Met - H](2+) lose CO to form [a(n) + Met - H](2+), mimicking protonated structures. In contrast, [a(n) + Met - H](2+) eliminate an amino acid residue to form [a(n-1) + Met - H](2+), which may be useful in sequencing.     

Effects of metal coordination on the reactivity of 1,3,4-triphenyl-1,2-dihydrophosphete

Nucleophilicity dominates the reaction chemistry of 1,3,4-triphenyl-1,2-dihydrophosphete even when it is coordinated to electrophilic metal centers, but coordination dramatically alters the course of its reactions. Deoxygenation of carbonyl-containing substrates is effected by both the W(CO)₅ complex, which reductively couples benzaldehyde, and the HgCl₂ complex, which converts benzaldehyde to α,α-dichlorotoluene. Metal coordination appears to decrease the tendency of the dihydrophosphete to undergo electrocyclic ring opening to the corresponding 1-phosphabutadiene, and the HgCl₂ complex reacts with dimethyl acetylenedicarboxylate to afford a cyclopentadienyl ylide containing an intact dihydrophosphete unit. By reducing the nucleophilicity of the dihydrophosphete and/or the availability of the highly nucleophilic uncoordinated dihydrophosphete, coordination to HgCl₂ and W(CO)₅ makes accessible new mechanistic pathways. Dihydrooxaphosphinines, although unavailable through the reactions of the dihydrophosphete, may be synthesized by exploitation of the reactivity of organotitanium metallacycles. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:21–28, 1998     

Highly selective ratiometric fluorescence determination of Ag+ based on a molecular motif with one pyrene and two adenine moieties

A highly selective ratiometric fluorescence sensor for Ag+ was developed with a molecular motif containing one pyrene and two adenine moieties.     

Three main group metal coordination polymers bearing imidazole-based dicarboxylates: Hydro(solvo)thermal syntheses, crystal structures and properties

Three coordination polymers [Pb(HMIDC)]_n (1), [Ba(H₂MIDC)₂]_n (2) and {[Mg(HMIDC)(H₂O)₂]·H₂O}_n (3) (H₃MIDC = 2-methyl-1H-imidazole-4,5-dicarboxylic acid) have been yielded under different hydro(solvo)thermal conditions. X-ray diffraction analysis reveals that compound 1 exhibits a 3-D framework constructed by 2-D networks joined by μ₄-HMIDC²⁻ bridges. Compound 2 also presents a 3-D structure, which is generated from 2-D layers pillared by 1-D chains along the c-axis. Compound 3 is a 1-D infinite chain and forms supramolecular layers through hydrogen bonds. The thermal and solid-state photoluminescence properties of polymers 1-3 have been determined as well. The theoretical predication of the methyl substituent effect of the ligand H₃MIDC has been investigated.