Fluorescence Intensity Of Complex Research Articles

Synthesis, structure, fluorescence and magnetic studies of two oxygen bridged polycarboxylic acid ligands and rare earth metal ion Pr, Gd, and Er complexes

In order to further enrich the research on the synthesis of complexes with polycarboxylic acid ligands and rare earth metal ion. In this study, four rare earth complexes, namely, [Gd(cpia)]n (1), [Er(cpia)]n (2), [Pr(cpna)2·2H2O]n (3) and [Gd(Hcpna)(cpna)•3H2O]n (4) have been synthesized by solvothermal method based on 5-(2-carboxyphenoxy)isophthalic acid (H3cpia) and 5-(4-carboxyphenoxy)nicotinic acid ligand (H2cpna) with rare earth metal ions Pr3+, Gd3+ and Er3+. Single crystal X-ray diffraction analyses reveal that complexes 1, 2 and 3 are two-dimensional network structure, 4 is one-dimensional chain structures. The fluorescence test results show that the fluorescence intensity of complexes 1 and 2 were lower than that of the H3cpia ligand, the fluorescence intensity of complexes 3 and 4 were lower than that of the H2cpna ligand. Magnetic results indicate complex 1 has ferromagentic behavior and weak antiferromagentic behavior in the complexes 2, 3 and 4.

The effect of adjacent double-strand DNA on the G-triplex-ThT complex fluorescence intensity enhancement and its application in TNOS and Hg2+ detection

In this paper, we have found that adjacent double-strand DNA (dsDNA) can enhance the fluorescence intensity of the G-triplex (G31)-thioflavin T (ThT) complex. By connecting the newly formed dsDNA with the G31 sequence, terminator nopaline synthase (TNOS) gene and Hg2+ were detected. The intermolecular duplex hybridization (e.g., TNOS gene and its complementary DNA), or the intramolecular mismatched thymine (T)-Hg2+-T pairs induced the formation of dsDNA with planar morphology, which resulted in the increased binding capacity of adjacent G31 to ThT, as well as the enhanced fluorescence intensity of G31-ThT complex. A versatile ‘turn-on’ fluorescence scaffold was developed for discriminating transgenic and non-transgenic soybeans and detecting Hg2+ in lake water.

Syntheses, crystal structures and fluorescent properties of imidazole based mixed-ligand nickle and cadmium complexes

Four novel mixed-ligand nickle and cadmium complexes [Cd(tolu)2(imi)3] (1) [CdCl2(imi)2]n (2), [Ni(imi)6](tolu)2 (3) and [Ni(mand)2(imi)2]·H2O (4) (imi = imidazole, Htolu = o-toluic acid, Hmand = mandelic acid) were synthesized and isolated in solid state based on nickle and cadmium salts, imidazole and different carboxylic acids. These complexes were characterized by FT-IR, elemental analyses, thermogravimetric (TG) analyses, UV–vis, X-ray structural analyses and fluorescence spectra. Complexes 1 and 4 are neutral mixed-ligand molecules. Complex 2 exhibits a 2D chain constructed by [CdCl2(imi)2] units. Complex 3 possesses [Ni(imi)6]2- anions with uncoordinated tolulate anions. In complexes 1–4, each imidazole ligand provides one nitrogen atom for coordination. Tolulate and mandelate ligands coordinate to the metal through carboxyl oxygen or hydroxyl oxygen atoms. Plenty of intramolecular hydrogen bonds as N–H⋯O and O–H⋯O interactions are observed in these complexes. Fluorescence properties of the complexes have been deeply investigated and the result reveals that Fe3+ ion has the greatest effect on fluorescence intensity of complex 3. The fluorescence intensity decreases with the increase of iron concentration.

FLUORESCENT CHARACTERISTICS OF HOECHST 33258 COMPLEXES WITH SERUM ALBUMIN AND DNA

We study the interaction of the bisbenzimodazole compound Hoechst 33258 with bovine serum albumin and calf thymus DNA by the fluorescence spectroscopy method. The fluorescence spectra of the complexes are obtained. Based on their maxima, the dependence curves of the fluorescence intensities of complexes of this ligand with protein and DNA on the ratio r = macromolecule/ligand are constructed. It is shown that the
 dependence curve in the case of albumin decreases at low protein concentrations and increases at its high concentrations. In the case of DNA, this curve increases significantly. This fact is due to the binding of the ligand to both DNA and albumin.

Catechol-Based Polymers with High Efficacy in Cytosolic Protein Delivery

Catechol-Based Polymers with High Efficacy in Cytosolic Protein Delivery

METHODS OF SYNTHESIS AND FEATURES OF USING SYSTEMS BASED ON MORIN-METAL COMPLEXES IN FLUORESCENT ANALYSIS METHODS

The review describes modern physicochemical systems based on complex compounds with organic ligands, which may have fluorescent properties when interacting with metal ions or proteins. Modern methods of synthesis of these compounds and their use in physical-chemical methods of analysis are given. Approaches to detecting the content of metals and proteins using the fluorescent properties of morin complex compounds are considered. Areas of use of the effects of amplification and quenching of fluorescence for the determination of organic compounds and metal ions, especially in the presence of DNA and RNA of different biological origin are described. The influence of surfactants on the fluorescence intensity of complexes with morin was analyzed separately.

Synthesis, optical and magnetic research of nicotinic acid ligand Zn, Cd, Mn and Co complexes

In this study, a multiple binding sites ligand, 5-(4-carboxyphenoxy)nicotinic acid ligand (H2cpna), was used to construct metal complexes with Zn2+, Cd2+, Mn2+ and Co2+ by solvothermal reaction, and four new complexes were constructed, namely, [Zn (cpna)•H2O]n (1)，[Cd (cpna) (CH3CN)·2H2O]n (2), [Mn (cpna)•2H2O]n (3) and Co(cpna)•2H2O]n (4); All the complexes were characterized by single crystal X-ray diffraction, elemental analysis and infrared analysis in the solid state; Single crystal x-ray diffraction analyses reveal that complexes 1 and 2 have two-dimensional network structures, complexes 3 and 4 have three-dimensional structures. In addition, Luminescence behavior of complex 1 and 2 was investigated and magnetic properties of complex 3 and 4 were studied. The fluorescent test results show that the fluorescence intensity of complex 1 is higher than that of ligand and emission band can be considered as LLCT emission of ligand; The Magnetic results indicate weak ferromagentic interactions in complex 3 and χmT value rises slowly and then decreases sharply from 300 ​K to 2 ​K. However, magnetic results indicate antiferromagentic interactions in complex 4 and χmT value can be divided into three parts with the change of temperature from 300 ​K to 2 ​K.

3D two-photon polymerization of smart cell gelatin – collagen matrixes with incorporated ruthenium complexes for the monitoring of local oxygen tensions

The extra cellular matrix plays a major role in the biomechanical properties of tissues that impact cell behavior and fate. It is therefore crucial to mimic these complex cell-matrix interactions in 3D cell cultures. Here, two-photon polymerization is applied to produce gelatin methacryloyl (GelMA) – collagen matrixes that further enable local pO2matrix measurement, when ruthenium complexes are used as photo-activators. The fluorescence intensity of these complexes has a direct and inverse relationship with the local pO2matrix. The 3D structures reached their maximum size in cell culture conditions after 3H with a swelling factor of ~1.5. Their shape and the ruthenium fluorescence intensity of the alveoli walls stayed constant for at least 2 weeks in the absence of cells. They were used in time series to monitor the local pO2matrix adjacent to cancer cells during their division, migration and the formation of a tumor tissue mass. At the presence of these cell activities that consume O2, a significant ~3-fold increase of the ruthenium fluorescence intensity in the alveoli walls was observed. This study demonstrates that online monitoring of the local pO2matrix is possible. The ruthenium complexes provide the bio-optical sensors that are useful for further analysis of cancer and healthy cell energy metabolism in a 3D matrix that better mimics in vivo conditions and migration paths. Unraveling the cancer cell metabolic adaptations in a changing micro-environment will help the development of new therapeutic opportunities. Statement of significanceIn 3D cell cultures, monitoring pericellular pO2 is as critical as controlling pH. This facility is currently missing. Here, we take advantage of the direct and inverse relationship between pO2 and the fluorescence intensity of ruthenium complexes to generate stable gelatin-collagen matrixes able to continuously monitoring the pO2 at the pericellular level. The ruthenium complexes, which are photo-activators in the two-photon polymerization of these matrixes, became covalently bind to the collagen fibers. Indeed, local O2 consumption by cancer cells during migration, mitosis and tumor mass formation caused a 3-fold increase of the ruthenium fluorescence. In the future, incorporating ruthenium complexes with other bio-optical sensors will create new drug screening platforms that monitor cell culture parameters at the pericellular level.

Flexible and color-tunable poly(ether ether ketone) co-coordinated with Eu(III) and Tb(III) fluorescent films: Thermal stability and luminescence property

In this work, a novel kind of carboxyl-containing poly(ether ether ketone) (PEEK-COOH) was successfully synthesized and carefully characterized. Based on PEEK-COOH as macromolecular ligands, a series of luminescent rare earth polymer complexes (PEEKn-Eux-Tb1-x) were prepared and made into flexible films. The effects of the ratio of carboxyl ligand to rare earth ions on fluorescence intensity of complexes were studied and discussed. When the molar ratio was 6:1, the fluorescence emission intensity reached a maximum. Furthermore, the relative emission intensity of Tb3+ and Eu3+ binary system depended on their ratio and the intensity of fluorescence emission peak exhibited continuous change. Because of this, the color of the prepared fluorescent films could range from bright green to fire red, and each color has high purity. The fluorescence lifetime of complexes ranged from 0.428 to 0.511 ms. Absolute quantum yield of PEEK-Eu0.4-Tb0.6 was 8.4%. Beside this, these fluorescence films exhibited a high thermal stability with 5 wt. % in the range of 240–250°C, and its tensile strength was about 28 MPa. In addition, PEEKn-Eux-Tb1-x films possessed good optical transparency. All the interesting results suggested the potential application of the luminescent rare earth polymer complexes in display devices and photo-electronic devices.

Synthesis, fluorescence properties and F− detection performance of Eu(III) complexes based on the novel coumarin Schiff base derivatives

Three novel coumarin Schiff base derivatives and corresponding Eu(III) complexes were designed and synthesized. The aggregation-induced emission (AIE) property of ligands was studied. The fluorescence properties and electrochemical properties of Eu(III) complexes were investigated by comparing different substituent groups. The ion selectivity and ion detection limits of the [EuL2(NO3)3] •H2O were also studied. The result indicates that all ligands exhibit the AIE property in CH3CN/H2O solution and emit green fluorescence with the maximum emission wavelength of 552 nm. All complexes show characteristic red fluorescence of Eu(III) and the influence of different substituents on the fluorescence intensity of Eu(III) complexes is ordered: -OCH3 > -H > -NO2, and [EuL2(NO3)3] •H2O exhibits the strongest fluorescence intensity. The density functional theory (DFT) calculations of the ligands indicate that the introduction of electron-donating groups increases the HOMO energy level and the electron cloud density, which enhance the ability to coordinate with Eu(III) and the fluorescence intensity of the corresponding complex. Besides, the electrochemical properties of Eu(III) complexes indicate that the introduction of electron-donating groups increases the energy gaps (Eg) and the conjugation of the complex, which enhances the fluorescence intensity of the complexes. Ion selectivity experiments show that [EuL2(NO3)3] •H2O has a specific recognition function for F−, and its response limit is between 1.0 × 10−5 mol·L−1 and 2.2 × 10−5 mol·L−1. Based on the above results, all the ligands and Eu(III) complexes have a promising application in optical materials due to the excellent fluorescence properties. In addition, All Eu(III) complexes also have a potential application prospects in the field of fluoride ion detection.

A highly selective and sensitive bifunctional luminescent sensor for TNP and Iron ion based on magnesium coordination polymer

A luminescent coordination polymer [Mg3L2(H2O)6]2·12H2O (1) (H4L+Cl-= 1,3-bis(3,5-dicarboxyphenyl)imidazolium) was synthesized and systematically characterized. Complex 1 is a 0D unit constructed by L3-, water and magnesium ions, which was further assembled into 0D → 2D → 3D network constructed via various H-bondings from free/coordinated water and π···π interactions. The fluorescence intensity of complex 1 has good stabilities in acid/base conditions, photoluminescence experiments show that complex 1 has high selectivity and sensitivity for sensing nitro compounds (NCs) and metal ions by luminescence quenching effect, especially for picric acid (TNP) and Fe3+ ions, the Ksv are up to 2.6 × 104 M−1 and 5.0 × 104 M−1. Further more, their possible quenching mechanisms have been studied separately.

Synthesis, Characterization and Fluorescence Property of a New Zinc(II) Complex Based on 2,6-Bis(imino)pyridyl Ligand

A new zinc(II) complex [Zn(L1)Cl2]‧CH3CN‧1/2H2O (complex 1), where L1 stands for 2,6-Bis{[(2-ethylphenyl)imino]ethyl}pyridine, has been synthesized and characterized. Both the crystal structures of complex 1 and L1 have been determined by single-crystal X-ray diffraction. L1 crystallizes in monoclinic system P21/n space group, with a = 7.7165(5) A, b = 9.1139(7) A, c = 30.535(2) A, β = 96.037(2)° and Z = 4. Complex 1 crystallizes in the orthorhombic system, space group Pbca, and its crystallographic data are a = 14.0520(9) A, b = 14.5780(11) A, c = 26.3450(17) A, α = β = γ = 90°, and Z = 8. In complex 1, Zn1 atom is five-coordinated with a trigonal bipyramidal geometry. L1 acts as a tridentate ligand and coordinated to Zn1 with three nitrogen atoms. A two-dimensional supermolecular network is formed by hydrogen bonds, in which acetonitrile and water solvent molecules play an important role. The luminescent properties of L1 and complex 1 were investigated in the solid state. The results indicate that when coordinated with Zn atom, the fluorescence intensity of complex 1 increases accompanied by a blue-shift, which can be attributed to metal perturbed π–π* intraligand fluorescence. The single crystals of 2,6-Bis{[(2-ethylphenyl)imino]ethyl}pyridine (L1) and it’s Zinc(II) complex [Zn(L1)Cl2]‧CH3CN‧1/2H2O (1) were determined. In the crystal structure of complex 1, the acetonitrile and water solvent molecules play great role in the formation of hydrogen bonds, forming a two-dimensional supermolecular network structure.

“AIE+ESIPT” bis Schiff-base ligands with multicolor emission and their corresponding Eu(III) complexes: Synthesis and properties research

A series of bis Schiff-base ligands and their corresponding Eu(III) complexes were synthesized easily and characterized by 1H NMR,13C NMR, ESI-MS+, Elemental analysis, Molar conductivity, Thermogravimetric analysis. The AIE characteristics of all ligands (L1−4) were investigated, fluorescence and electrochemical properties of Eu(III) complexes (EuL1−4Cl3·2H2O) were also studied. The results indicate that all ligands not only possess AIE characteristics, but exhibit diverse fluorescence emission from orange to green (the emission peaks are 588 nm, 556 nm, 548 nm and 520 nm, respectively). All complexes show characteristic red fluorescence of Eu (III) ion. The effect of various substituent groups on fluorescence intensity of complexes is ordered: –N(CH2CH3)2>-OCH3>-OH > -Cl and EuL4Cl3·2H2O emits the strongest fluorescence. The results of electrochemical properties demonstrate that electron-donating groups increase the HOMO energy level and LUMO energy level of complexes, but the electron-withdrawing groups behaves contrarily. Based on the above results, all ligands and their corresponding Eu(III) complexes are promising materials in the field of optics.

Synthesis, structure, and antioxidative properties of a copper(II) complex with 1,2‐bis(benzimidazol‐2‐yl)ethane ligand

Abstract1,2‐Bis(benzimidazol‐2‐yl)ethane (bbe) and its copper(II) complex, {[Cu(bbe)Br2]2}·2DMF (1), have been synthesized and characterized by elemental analysis, ultraviolet–visible, and infrared spectra. The single crystal structure analysis of 1 shows two crystallographically independent but chemically identical [Cu(bbe)Br2] molecules. The coordination geometry of the copper atoms may best be described as a distorted tetrahedron (τ4 = 0.740 for Cu1 and 0.696 for Cu2). The cyclic voltammogram of complex 1 represents quasi‐reversible Cu2+/Cu+ pairs. in vitro antioxidant tests showed that complex 1 has significant antioxidant activity against superoxide and hydroxy radicals. Photoluminescence investigations showed that the fluorescence intensity of complex 1 is significantly weaker than that of the ligand. This may be due to the paramagnetic effect of divalent copper to cause quenching of fluorescence.

A New Half-Salamo-Based Homo-Trinuclear Nickel(II) Complex: Crystal Structure, Hirshfeld Surface Analysis, and Fluorescence Properties

A new homo-trinuclear Ni(II) half-salamo-based complex [Ni3(L)2(μ-OAc)2(OAc)2(CH3OH)2]·2CH3OH was synthesized via the reaction of a tridentate ligand HL (2-[O-(1-ethyloxyamide)]oxime-4-bromophenol) and Ni(OAc)2·4H2O, and characterized using elemental analyses, IR spectra, UV-Vis absorption spectra, X-ray crystallography, and Hirshfeld analysis. Interestingly, single-crystal X-ray analysis showed that the two acetate molecules were bonded simultaneously with the Ni(II) atoms by mono-dentate chelating and bidentate bridging coordination modes, respectively, and the resulting hexa-coordinate geometries were ultimately formed. Furthermore, the Hirshfeld analysis of the complex was studied. Compared with HL, the complex fluorescence intensity was significantly lowered, indicating that the Ni(II) ions have fluorescence quenching characteristics.

A novel fluorescent sensing platform for insulin detection based on competitive recognition of cationic pillar[6]arene

Competitive host-guest recognition has been utilized to determine small molecules using macrocyclic supramolecular host, while less studies focused on the specific recognition and sensing of protein. In the present work, we are the first time to report a label-free fluorescent assay for insulin determination based on the supramolecular recognition between cationic pillar[6]arene (CP6) and insulin. The approach is based on fluorescence resonance energy transfer (FRET) through competitive recognition between CP6 functionalized reduced graphene oxide (CP6@rGO) and probe/insulin molecules. Probe molecule (RhB) has strong fluorescent signal, and its fluorescent is quenched by rGO based on FRET. When target protein molecule (insulin) is added to CP6@rGO, the probe is displaced by insulin and a host-guest complex CP6@rGO/insulin is formed, resulting in a “turn-on” fluorescence signal. The fluorescence intensity of complex increased linearly with the increase of insulin concentration ranging 0.01–0.50 and 1.0–16.0 μM, respectively with a detection limit of 3 nM. The sensor was successfully utilized to determine insulin in artificial serum. The molecular docking result showed that the N-terminal Phe of insulin's B chain was included in the CP6 cavity through electrostatic interaction and formed a stable host-guest complex.

In vitro and in vivo phasor analysis of stoichiometry and pharmacokinetics using short-lifetime near-infrared dyes and time-gated imaging.

We introduce a simple new approach for time-resolved multiplexed analysis of complex systems using near-infrared (NIR) dyes, applicable to in vitro and in vivo studies. We show that fast and precise in vitro quantification of NIR fluorophores' short (subnanosecond) lifetime and stoichiometry can be done using phasor analysis, a computationally efficient and user-friendly representation of complex fluorescence intensity decays obtained with pulsed laser excitation and time-gated camera imaging. We apply this approach to the study of binding equilibria by Förster resonant energy transfer using two different model systems: primary/secondary antibody binding in vitro and ligand/receptor binding in cell cultures. We then extend it to dynamic imaging of the pharmacokinetics of transferrin engagement with the transferrin receptor in live mice, elucidating the kinetics of differential transferrin accumulation in specific organs, straightforwardly differentiating specific from nonspecific binding. Our method, implemented in a freely-available software, has the advantage of time-resolved NIR imaging, including better tissue penetration and background-free imaging, but simplifies and considerably speeds up data processing and interpretation, while remaining quantitative. These advances make this method attractive and of broad applicability for in vitro and in vivo molecular imaging and could be extended to applications as diverse as image-guided surgery or optical tomography.

Structure and Optical Properties of Plane-Type And Z-Type Topology Triazole Quinoxaline Cd(II) Complexes

Two coordination polymers are obtained by self-assembly reactions of Cd2+ with 2,3-bis((1H-1,2,4-triazol-1-yl)methyl)quinoxaline (BTMQ) and terephthalic acid at room temperature. Complex 1 exhibits a two-dimensional planar structure, which crystallizes in the monoclinic space group P21/c with unit cell parameters: a = 12.752(4) A, b = 9.416(3) A, c = 16.069(5) A, α = 90, β = 102.146(5), γ = 90°, V = 1886.4(10) A3, Z = 2. Complex 2 shows a Z-type two-dimensional network structure, and crystallizes in the triclinic space group P-1 with unit cell parameters: a = 6.917(4) A, b = 10.338(5) A, c = 16.156(8) A, α = 96.889(7), β = 93.421(8), γ = 96.161(7)°, V = 1137.2(10) A3, Z = 1. Fluorescence spectral studies of BTMQ and the two complexes are also investigated, and the results show that the fluorescence intensity of complex 1 is stronger than that of the ligand, but the fluorescence intensity of complex 2 is weaker than that of the ligand.

Construction and optical properties of infinite Cd and finite Cu molecules stairs

Two coordination complexes, namely [(hpdq)(pta)Cd]n (1) and [(pptp)(pta)Cu2Cl] (2) have been synthesized by solvothermal method based on two polypyridyl ligands, 2,3,6,7,10,11-hexakis- (2-pyridyl)dipyrazino[2,3-f:2′,3′-h]quinoxaline) (hpdq), 4′-(4- (3H-pyrrol-3-yl)phenyl)- 2,2′:6′,2″- terpyridine (pptp) and auxiliary ligand p-phthalic acid (pta), respectively. Single crystal x-ray diffraction analyses reveal that complexes 1 and 2 assembled based on distinct asymmetric unit comprising one and two respective polypyridyl ligands but one Cd(II) and two Cu(I)ions, respectively. Among them, The asymmetric units in 1 was extended to one dimensional chain via the link of auxiliary ligand pta, just like infinite layers of stairs that connected by cadmium ions as the node. While that in 2 to Zero dimensional tetranuclear structure via the link of auxiliary ligand pta, just like finite four layers of stairs that Copper ion as the node connection. Furthermore, solid fluorescence spectra properties of two complexes were also investigated, and the result shows the fluorescence intensity of complex 1 is stronger than that of the hpdq ligand, but the fluorescence intensity of complex 2 is weaker than that of the pptp ligand. CCDC number of 1and 2 are 1483301 and 1483302.

Determination of phenformin hydrochloride employing a sensitive fluorescent probe

A complexation of non-fluorescent phenformin hydrochloride (PFH) with cucurbit [7]uril (CB [7]) in aqueous solution was investigated using the fluorescent probe of palmatine (PAL) coupled with CB [7]. The fluorescent probe of CB [7]–PAL exhibited strong fluorescence in aqueous solution, which was quenched gradually with the increase of PFH. This effect is observed because when PFH was added to the host–guest system of CB [7]–PAL, PFH and PAL competed to occupy the CB [7] cavity. Portions of the PAL molecule were expelled from the CB [7] cavity owing to the introduction of PFH. Based on the significant quenching of the supramolecular complex fluorescence intensity, a fluorescence method of high sensitivity and selectivity was developed to determine PFH with good precision and accuracy for the first time. The linear range of the method was 0.005–1.9μgmL−1 with a detection limit of 0.003μgmL−1. In this work, association constants (K) of PFH with CB [7] were also determined. KCB [7]–PFH=(2.52±0.05)×105Lmol−1. The ability of PFH to bind with CB [7] is stronger than that of PAL. The results of a density functional theory calculation authenticated that the moiety of PFH was embedded in the hydrophobic cavity of CB [7] tightly, and the nitrogen atom is located in the vicinity of a carbonyl-laced portal in the energy-minimized structure. The molecular modelling of the interaction between PFH and CB [7] was also confirmed by 1H NMR spectra (Bruker 600MHz).