Spectroscopic,Computational, Antimicrobial,DNA Interaction,In Vitro Anticancer and Molecular Docking Properties of Biochemically Active Cu(II) and Zn(II) Complexes of Pyrimidine-Ligand

Biochemically active Cu(II) and Zn(II) complexes [CuL(ClO₄)₂(1) and ZnL(ClO₄)₂(2)] have been synthesized from N,N donor Schiff base ligand L derived from4,6-dichloropyrimdine-5-carboxaldehyde with 4-(2-aminoethyl)morpholine. The L, complexes 1 and 2 have been structurally characterized by elemental analysis, ¹H-NMR, FTIR, MS, UV-Visible and ESR techniques. The results obtained from the spectral studies supports the complexes 1 and 2 are coordinated with L through square planar geometry. DFT calculations results supports, the ligand to metal charge transfer mechanism can occur between L and metal(II) ions. The antimicrobial efficacy results have been recommended that, complexes 1 and 2 are good anti-pathogenic agents than ligand L. The interaction of complexes 1 and 2 with calf thymus (CT) DNA has been studied by electronic absorption, viscometric, fluorometric and cyclic voltammetric measurements. The calculated K_b values for L, complexes 1 and 2 found from absorption titrations was 4.45?×?10⁴, L; 1.92?×?10⁵, 1 and 1.65?×?10⁵, 2. The Ksv values were found to be 3.0?×?10³, 3.68?×?10³and 3.52?×?10³ for L, complexes 1 and 2 by using competitive binding with ethidium bromide (EB). These results suggest that, the compounds are interacted with DNA may be electrostatic binding. The molecular docking studies have been carried out to confirm the interaction of compounds with DNA. Consequently, in vitro anticancer activities of L, complexes 1 and 2 against selected cancer (lung cancer A549, liver cancer HepG2 and cervical carcinoma HeLa) and normal (NHDF) cell lines were assessed by MTT assay.     

A New Piperidine Derivatized-Schiff Base Based “Turn-on” Cu<Superscript>2+</Superscript>Chemo-Sensor

In this study, we report the synthesis of new Schiff base E-1-(((1-benzylpiperidin-4-yl)imino)methyl)naphthalenee-2-ol (L) and evaluation of its fluorescence response toward Cu²⁺ ion. Preliminary, solvent effect, metal selectivity and metal ligand ratio were analyzed through UV-Visible study. Fluorescence response toward Cu²⁺ was carried to assess the fluorescent property of synthesized Schiff base. The probe exhibited a higher fluorescence enhancement in the presence of Cu²⁺ over other metal ions (Ni²⁺, Zn²⁺, Hg²⁺, Co²⁺, Cd²⁺, Al³⁺, Fe²⁺, and Pb²⁺). The binding stoichiometry between L and Cu²⁺ has been investigated using Job’s plot and Benesi-Hildebrand equation and it was found that ligand L can form 1:1 L-Cu²⁺ complex with binding constant (K _a) of 4?×?10⁴ LM^?1.     

A highly Selective Fluorescent Sensor for Monitoring Cu<Superscript>2+</Superscript> Ion: Synthesis,Characterization and Photophysical Properties

A new fluorescent sensor, 4-allylamine-N-(N-salicylidene)-1,8-naphthalimide (1), anchoring a naphthalimide moiety as fluorophore and a Schiff base group as receptor, was synthesized and characterized. The photophysical properties of sensor 1 were conducted in organic solvents of different polarities. Our study revealed that, depending on the solvent polarity, the fluorescence quantum yields varied from 0.59 to 0.89. The fluorescent activity of the sensor was monitored and the sensor was consequently applied for the detection of Cu²⁺ with high selectivity over various metal ions by fluorescence quenching in Tris-HCl (pH = 7.2) buffer/DMF (1:1, v/v) solution. From the binding stoichiometry, it was indicated that a 1:1 complex was formed between Cu²⁺ and the sensor 1. The fluorescence intensity was linear with Cu²⁺ in the concentration range 0.5–5 μM. Moreso, the detection limit was calculated to be 0.32 μM, which is sufficiently low for good sensitivity of Cu²⁺ ion. The binding mode was due to the intramolecular charge transfer (ICT) and the coordination of Cu²⁺ with C = N and hydroxyl oxygen groups of the sensor 1. The sensor proved effective for Cu²⁺ monitoring in real water samples with recovery rates of 95–112.6 % obtained.     

Thermal and electrochemical properties of poly(butylene sulfite)-based polymer electrolyte

Poly(butylene sulfite) (poly-1) was synthesized by cationic ring-opening polymerization of butylene sulfite (1), which was prepared by the reaction of 1,4-butanediol and thionyl chloride, with trifluoromethanesulfonic acid (TfOH) in bulk. The polymer electrolytes composed of poly-1 with lithium salts such as bis(trifluoromethanesulfonyl)imide (LiN(SO₂CF₃)₂, LiTFSI) and bis(fluorosulfonyl)imide (LiN(SO₂F)₂, LiFSI) were prepared, and their ionic conductivities, thermal, and electrochemical properties were investigated. Ionic conductivities of the polymer electrolytes for the poly-1/LiTFSI system increased with lithium salt concentrations, reached maximum values at the [LiTFSI]/[repeating unit] ratio of 1/10, and then decreased in further more salt concentrations. The highest ionic conductivity values at the [LiTFSI]/[repeating unit] ratio of 1/10 were 2.36?×?10^?4 S/cm at 80 °C and 1.01?×?10^?5 S/cm at 20 °C. On the other hand, ionic conductivities of the polymer electrolytes for the poly-1/LiFSI system increased with an increase in lithium salt concentrations, and ionic conductivity values at the [LiFSI]/[repeating unit] ratio of 1/1 were 1.25?×?10^?3 S/cm at 80 °C and 5.93?×?10^?5 S/cm at 20 °C. Glass transition temperature (T _g) increased with lithium salt concentrations for the poly-1/LiTFSI system, but T _g for the poly-1/LiFSI system was almost constant regardless of lithium salt concentrations. Both polymer electrolytes showed high transference number of lithium ion: 0.57 for the poly-1/LiTFSI system and 0.56 for the poly-1/LiFSI system, respectively. The polymer electrolytes for the poly-1/LiTFSI system were thermally more stable than those for the poly-1/LiFSI system.     

Novel Fluorometric Turn On Detection of Aluminum by Chalcone-Based Chemosensor in Aqueous Phase

A novel, 100% water-soluble chalcone based chemosensing receptor {1-[3-(2-Hydroxy-phenyl)-3-oxo-propenyl]-naphthalen-2-yloxy}-acetic acid, L was synthesized and characterized. The receptor L is designed based on the chelation enhanced fluorescence (CHEF) mechanism. The chemosensing properties of L were evaluated by UV–vis and fluorescence spectrometric methods. It exhibits highly selective recognition ability towards aluminum ions in water over other metal ions. The binding stoichiometry of L? Al³⁺ complex is 2:1 by means of Job’s plot and the detection limit is 5.66?×?10^??8 M.     

A Colorimetric and Fluorescent Probe Based on Michael Acceptor Type Diketopyrrolopyrrole for Cyanide Detection

A new probe 1 was synthesized by incorporating an α,β-unsaturated ketone to a diketopyrrolopyrrole fluorophore. The probe exhibited a selective and sensitive response to cyanide against other anions. Addition of CN^? aqueous solution to 1 resulted in a rapid color change from pink to light yellow together with a blue shift from 518 to 421 nm, while other anions did not induce any significant color change. Furthermore, the Michael addition of cyanide to 1 elicited 98% fluorescence quenching at 608 nm, which constituted the fluorescence signature for cyanide detection. The detection limit was 0.67 μM using the fluorescence spectra changes, which was far lower than the WHO guideline of 1.9 μM. Moreover, 1-based test strips could successfully detect CN^? solutions.     

Coumarin Based Fluorescent Probe for Colorimetric Detection of Fe<Superscript>3+</Superscript> and Fluorescence Turn On-Off Response of Zn<Superscript>2+</Superscript> and Cu<Superscript>2+</Superscript>

A new coumarin based Schiff-base chemosensor-(E)-7-(((8-hydroxyquinolin-2-yl)methylene) amino)-4-methyl-2H-chromen-2-one (H ₁₁ L) was synthesized and evaluated as a colorimetric sensor for Fe³⁺ and fluorescence “turn on-off” response of Zn²⁺ and Cu²⁺ using absorption and fluorescence spectroscopy. Upon treatment with Fe³⁺ and Zn²⁺, the absorption intensity as well as the fluorescence emission intensity increases drastically compared to other common alkali, alkaline earth and transition metal ions, with a distinct color change which provide naked eye detection. Formation of 1:1 metal to ligand complex has been evaluated using Benesi-Hildebrand relation, Job’s plot analyses, ¹H NMR titration as well as ESI-Mass spectral analysis. The complex solution of H ₁₁ L with Zn²⁺ ion exhibited reversibility with EDTA and regenerate free ligand for further Zn²⁺ sensing. H ₁₁ L exhibits two INHIBIT logic gates with two different chemical inputs (i) Zn²⁺ (IN1) and Cu²⁺ (IN2) and (ii) Zn²⁺ (IN1) and EDTA (IN2) and the emission as output. Again, an IMPLICATION logic gate is obtained with Cu²⁺ and EDTA as chemical inputs and emission as output mode. Both free ligand as well as metal-complexes was optimized using density functional theory to interpret spectral properties. The corresponding energy difference between HOMO-LUMO energy gap for H ₁₁ L, H₁₁L-Zn²⁺ and H₁₁L-Cu²⁺ are 2.193, 1.834 and 0.172 eV, respectively.     

A Carbazole-Fused-RhodamineProbe for Detection of HOCl in Living Cells

A novel fluorescent probe CR-ClO for detection of HOCl based on a carbazole fused rhodamine was designed and synthesized. The probe utilized a HOCl-promoted oxidation reaction, which lead to the ring opening of the compound with a strong enhancement of the fluorescent emission at about 587 nm.The new probe CR-ClO has excellent selectivity and high sensitivity to ClO^?,whose detection limit to ClO^? is 1.16 × 10^?6 M. Furthermore, the new probe has been successfully applied in living cells for detection of ClO^?.     

A Highly Selective and Sensitive Fluorescent Chemosensor for Aluminum Ions Based on Schiff Base

An efficient “off–on” type fluorescent chemosensor, (E)-N′-(4-(diethylamino)-2-hydroxybenzylidene)-2-hydroxybenzohydrazide (H ₂ L), based on Schiff base for the determination of Al³⁺ has been designed, synthesized, and evaluated. Upon treated with Al³⁺, the fluorescence of H ₂ L was enhanced 45-fold due to the chelation-enhanced fluorescence (CHEF) effect based on the formation of a 1:1 complex between the chemosensor and Al³⁺. Other metal ions, such as Na⁺, K⁺, Mg²⁺, Ca²⁺, Cu²⁺, Ga³⁺, Zn²⁺, Cr³⁺, Cd²⁺, Ag⁺, Fe³⁺, In³⁺, Mn²⁺, Pb²⁺, Co²⁺, and Ni²⁺ had little effect on the fluorescence. The results demonstrate that the chemosensor H ₂ L has stronger affinity with Al³⁺ than other metal ions. The detection limit of H ₂ L for sensing Al³⁺ is 3.60 × 10^?6 M in EtOH–H₂O (3:7, v/v) solution. And the recognizing behavior has been investigated both experimentally and computationally.     

Dual-Functional Fluorescein-Based Chemosensor for Chromogenic Detection of Fe<Superscript>3+</Superscript> and Fluorgenic Detection of HOCl

A novel fluorescein-based dual probe was designed and synthesized. The probe exhibited highly sensitive and selective colormetric response to Fe³⁺ and turn-on fluorescence response towards OCl^? with very low detection limits of 100 and 50 nM, respectively. It was successfully applied for quantitative detection of Fe³⁺ and OCl^? in real water samples. Moreover, probe 1 was expected to be a potentially powerful tool for studying and providing further insights into OCl^? and Fe³⁺ chemistry in the near future.     

A Ratiometric and near-Infrared Fluorescent Probe for Imaging Cu<Superscript>2+</Superscript> in Living Cells and Animals

We have rationally constructed a novel ratiometric and near-infrared Cu²⁺ fluorescent probe based on a tricarbocyanine chromophore. The new probe NIR-Cu showed a ratiometric fluorescent response to Cu²⁺ with a large emission wavelength shift (up to 142 nm) in the far-red to near-infrared region. The probe also displayed a large variation in the fluorescence ratio (I₆₃₆/I₇₇₈) to Cu²⁺ species with high sensitivity and selectivity. Additionally, the developed probe NIR-Cu was suitable for fluorescence imaging of Cu²⁺ in living cells and mice.     

A Dansyl-Rhodamine Ratiometric Fluorescent Probe for Hg<Superscript>2+</Superscript> Based on FRET Mechanism

Based on resonance energy transfer (FRET) from dansyl to rhodamine 101, a new fluorescent probe (compound 1) containing rhodamine 101 and a dansyl unit was synthesized for detecting Hg²⁺ through ratiometric sensing in DMSO aqueous solutions. This probe shows a fast, reversible and selective response toward Hg²⁺ in a wide pH range. Hg²⁺ induced ring-opening reactions of the spirolactam rhodamine moiety of 1, leading to the formation of fluorescent derivatives that can serve as the FRET acceptors. Very large stokes shift (220 nm) was observed in this case. About 97-fold increase in fluorescence intensity ratio was observed upon its binding with Hg²⁺.     

A New Fluorescent “Turn-Off” Coumarin-Based Chemosensor: Synthesis,Structure and Cu-Selective Fluorescent Sensing in Water Samples

We report the synthesis and characterization two coumarin-based fluorescence probes, N′-{[7-(diethylamino)-2-oxo-2H-chromen-3-yl]carbonyl}pyridine-3-carbohydrazide (3) and N′-benzoyl-7-(diethylamino)-2-oxo-2H-chromene-3-carbohydrazide (4), proposed as a novel fluorescent chemosensor. The two probes designed showed an instant turn-off fluorescence response to Cu²⁺ over other metal ions in ethanol-water mixture based on intramolecular charge transfer (ICT). It was found that pyridine-analogue coumarin is highly selective and sensitive sensor for Cu²⁺. The 3 sensor coordinates Cu²⁺ in 1:1 stoichiometry with a binding constant, K_a = 5.22 M^?1 and the detection limit was calculated 1.97 × 10^?9 M.     

A Dual-Target Fluorescent Probe with Response-Time Dependent Selectivity for Cd<Superscript>2+</Superscript> and Cu<Superscript>2+</Superscript>

A novel fluorescent probe (NT) was developed by merging 2-hydrazinylbenzothiazole with 2-hydroxy-1-naphthaldehyde for the detection of Cd²⁺ and Cu²⁺. The probe alone is almost nonfluorescent due to the isomerization of C=N in the excited state. The addition of Cd²⁺ can cause an immediate strong green fluorescence owing to the suppression of C=N isomerization by Cd²⁺-coordination. Furthermore, NT gives a delayed turn-on fluorescence response to Cu²⁺ although it is a vigorous fluorescence quencher, which was thanks to the inhibition of the electron transfer between excited fluorophore and paramagnetic Cu²⁺ by sulfur donor. Based on fluorescence spectra and ESI-MS analysis, the binding modes between NT and Cd²⁺/Cu²⁺ were proposed.     

Ni(II) and Zn(II) Complexes Containing Alkynyl Functionalized Salicylaldimine Ligand and Heterocyclic Coligand: Synthesis,Characterization and Luminescence Properties

Some nickel(II) and zinc(II) complexes of the type [Ni(L)(phen/bipy)]X (1a–6a) and [Zn(L) (phen/bipy)]X (1b–6b) (where L = 2-{(E)-[(4-trimethylsilylethynylphenyl)imino]methyl}-4-(4-nitro phenylethynyl)phenol; phen = 1, 10-phenanthroline, bipy = 2, 2´-bipyridine; X = ClO₄ ^?, BF₄ ^?, PF₆ ^?) have been prepared and characterized on the basis of elemental analyses, FTIR, ¹H NMR and mass spectral studies. The molecular structure of L was determined by single crystal X-ray diffraction studies. The electrochemical behaviour of the Ni(II) complexes indicate that the phen complexes appears at more positive potential as compared to those for bipy complexes, as a consequence of its strong π-acidic character. TGA was carried out to study the thermal behavior of the complexes. Room temperature luminescence is observed for all complexes corresponds to π → π* ILCT transition. The size of the counter anion and heterocyclic coligands phen and bipy shows marked effect on emission properties of the complexes.     

Synthesis and Properties of a Novel FRET-Based Ratiometric Fluorescent Sensor for Cu<Superscript>2+</Superscript>

A novel FRET-based probe LS3 was designed and synthesized. As expected, it exhibited high selectivity and sensitivity for detecting Cu²⁺ over other commonly coexistent metal ions. The detection limit was measured to be 0.0423 μM for Cu²⁺, which can meet the selective requirements for practical application. In addition, the newly synthesized compound 3a/b have potential value of further synthesizing more analogous FRET-based probes.     

Polymer electrolytes based on vinyl ethers with various EO chain length and their polymer electrolytes cross-linked by electron beam irradiation

Polymer electrolytes based on vinyl ethers with various ethyleneoxy (EO) chain length (poly-1a (m?=?3), poly-1b (m?=?6), poly-1c (m?=?10), and poly-1d (m?=?23.5)) with lithium bis(trifluoromethanesulfonimide) (LiTFSI) were prepared, and effect of pendant EO chain length in the polymers on electrochemical and thermal properties was investigated. Glass transition temperature (T _g) of all polymer electrolytes increased linearly with an increase in salt concentrations. Ionic conductivities of the polymer electrolytes increased with an increase in the pendant EO chain length of the polymers at the constant [Li]/[O] ratio, but in the polymer electrolyte of the poly-1d (m?=?23.5) with the longest pendant EO chain length, ionic conductivity decreased in the low temperature range of ?20 to 10 °C due to the crystallization of the pendant EO chain. The highest ionic conductivity, 1.23?×?10^?4 S/cm at 30 °C, was obtained in the polymer electrolyte of the poly-1c (m?=?10) with pendant EO chain length of 10 at the [Li]/[O] ratio of 1/20. It was found that the cross-linking of the polymer electrolyte, composed of poly-1c (m?=?10) with LiTFSI at the [Li]/[O] ratio of 1/28, by electron beam (EB) irradiation may improve the mechanical property without affecting ionic conductivity, thermal property, and oxidation stability. Polymer electrolytes based on poly-1a (m?=?3), poly-1b (m?=?6), poly-1c (m?=?10), and poly-1d (m?=?23.5) and cross-linked polymer electrolytes were electrochemically stable until 4 V and thermally stable around 300 °C.     

A Novel Colorimetric and Fluorescent “Off-On” Chemosensor for Cu2+ Based on a Rhodamine Derivative Bearing Naphthyridine Group

A new rhodamine-based derivative bearing a naphthyridine group (compound 1) was synthesized as a colorimetric and fluorescent “off-on” chemosensor for Cu²⁺ in aqueous solutions. The sensing behaviors of 1 toward various metal ions in neutral aqueous solutions were investigated by absorption and fluorescence spectroscopies. Compound 1 is found to exhibit a significant increase in absorbance at 561 nm and an amplified fluorescence at 590 nm toward Cu²⁺ in a selective, sensitive and rapid manner. The quantification of Cu²⁺ by 1 using an absorption spectroscopy method was satisfactory in the linear working range 0.9–10 μM, with a detection limit of 5.4?×?10^?8?M for Cu²⁺ and good tolerance of other metal ions. Upon addition of Cu²⁺, the spirolactam ring (colorless and nonfluorescent) of 1 was opened to ring-opened amide (red color and fluorescent) and a 1:1 stoichiochemetry for the 1-Cu²⁺ complex was formed with an association constant of 1.57?×?10⁴?M^?1.     

A Novel Fluorescent Probe for the Highly Selective and Sensitive Detection of Palladium in Aqueous Medium

Based on the Pd⁰-catalyzed Tsuji-Trost allylic oxidative insertion reaction, we developed a fluorescent probe PdL1 for sensing Pd⁰. As expected, probe PdL1 exhibited high selectivity and excellent sensitivity in both absorbance and fluorescence detection of Pd⁰ in CH₃CH₂OH/PBS (10 mM, pH = 7.4, 6:4, v/v) solution. The detection limit was calculated to be as low as 15 nM, which can meet the selective requirements for practical application.     

Calix[4]arene Based Dual Fluorescent Sensor for Al<Superscript>3+</Superscript> and S<Subscript>2</Subscript>O<Subscript>7</Subscript><Superscript>2−</Superscript>

Specific functionalized calix[4]arene based fluorescent chemosensor was synthesized for cations and anions binding efficiency examination. Receptor C4MA displayed strong affinity for Al³⁺and S₂O₇ ^2? with enhanced fluorescence intensity. The selective response of C4MA was investigated in the presence of different co-existing competing ions. The limit of detection (LOD) of Al³⁺and S₂O₇ ^2? was calculated as 2.8?×?10^?6 M and 2.6?×?10^?7 M respectively. Sensor C4MA forms (1:1) stoichiometric complex with both Al³⁺ and S₂O₇ ^2? and their binding constants were calculated as 12.1?×?10⁴ and 8.3?×?10³ respectively. Complexes were also characterized through FT-IR spectroscopy.

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