Syntheses, crystal structures and supramolecular assemblies of two Cu(II) complexes based on a new heterocyclic ligand: Insights through C─H•••Cl and π•••π interactions

A heterocyclic ligand, N3L [4-(1-methylimidazole)-2,6-di(pyrazinyl)pyridine] has been synthesized and characterized by several spectroscopic methods. The ligand (N3L) was then used for the preparation of two complexes, namely, [Cu(N3L)Cl2] (complex 1)...

Halloysite Nanoclay with High Content of Sulfonic Acid-Based Ionic Liquid: A Novel Catalyst for the Synthesis of Tetrahydrobenzo[b]pyrans

One of the main drawbacks of supported ionic liquids is their low loading and consequently, low activity of the resultant catalysts. To furnish a solution to this issue, a novel heterocyclic ligand with multi imine sites was introduced on the surface of amino-functionalized halloysite support via successive reactions with 2,4,6-trichloro-1,3,5-triazine and 2-aminopyrimidine. Subsequently, the imine sites were transformed to sulfonic acid-based ionic liquids via reaction with 1,4-butanesultone. Using this strategy, high loading of ionic liquid was loaded on halloysite nanoclay. The supported ionic liquid was then characterized with XRD, SEM, TEM, EDS, FTIR, BET, TGA and elemental mapping analysis and utilized as a metal-free Brønsted acid catalyst for promoting one-pot reaction of aldehydes, dimedone and malononitrile to furnish tetrahydrobenzo[b]pyrans. The catalytic tests confirmed high performance of the catalyst. Moreover, the catalyst was stable upon recycling.

In-Vitro Cytotoxicity, Antimicrobial activities and DNA binding studies, of Novel Copper (II) complex with Heterocyclic base

A novel ternary copper (II) complex have been synthesized by the addition of N, N-heterocyclic ligand with L-amino acid. The copper (II) complex, [Cu(1,10-phen) (L-Thr) Br] (where phen=1,10-phenanthroline and Threo=Threonine) characterized by various spectroscopic method. The intense UV band around 271nm was due to π-π* transition. The DNA binding study of these copper (II) complex are examined by UV–Visible, Emission spectroscopic, cyclic voltammetric and viscosity method. The results revealed that complex shown to be a intercalation mode of binding into DNA. The anticancer activity of Cu (II) complexes has capability to the kill HepG2 liver cancer cell as assessed by the MTT method, The Ic50value was found 21.50µg/ml The biological activity of the complex tested against certain pathogenic bacteria and fungi results revealed it was found to be potent antibacterial agent.

Biomolecular Interaction, Antibacterial and Anticancer Activities of Organometallic Re(I) Complexes with 5-(2-butyl-5-chloro-1H-imidazol-4-yl)-1,3-diaryl-4,5-dihydro-1H-pyrazole

Organometallic rhenium(I) complexes (I-VI) using substituted 5-(2-butyl-5-chloro-1H-imidazol-4-yl)-1,3-diaryl-4,5-dihydro-1H-pyrazole have been synthesized and characterised by spectroscopic method. For evaluation of HOMO-LUMO energy gap, estimation of bond angle, bond length data and Mulliken charge analysis DFT studies were performed. The complexes (I-VI) can be generated by bis-heterocyclic ligand followed by metal chelation. The interactions between synthesised compounds and double stranded DNA (HS DNA) was carried out by viscosity measurements, absorption titration, and gel electrophoresis gives information about modes of binding and the nucleolytic efficiency of compounds. Groove binding was suggested as the most possible mode and the DNA-binding (Kb) constants of the complexes were calculated. Electronic spectra and conductivity measurement confirm the different transition, and non-electrolytic nature of the metal complexes. Thermodynamic parameter ΔG0 value ranging from -7227.0 to -9463.0 J/moleoK. According to the thermodynamic parameter, the main binding force could be judged. In vivo and In vitro cytotoxicity against the eukaryotic and prokaryotic cells gives toxic nature of the synthesised compounds. An antimicrobial study was carried out by estimating MIC (Minimum Inhibitory Concentration) against two Gram-positive and three Gram-negative bacteria. All compounds found effective against S. cerevisiae which is confirmed by enhancing ROS production and DNA damage show by gel electrophoresis as compared to untreated yeast cell culture and DMSO.

Design, synthesis and biological evaluation of heterocyclic methyl substituted pyridine Schiff base transition metal complexes

In recent years heterocyclic Schiff base metal complexes attract more attention in biological application and also showing interesting co-ordination chemistry. In this research article a novel heterocyclic methyl-substituted pyridine Schiff base transition metal complexes of Fe(III), Co(III), Cu(II), and Ni(II) have been design and synthesized by reacting metal acetate or metal salts (FeCl3, CoOAc, CuOAc, NiOAc), with substituted heterocyclic ligand. All newly synthesized metalcomplexes were characterized by spectroscopic data and screened for elemental analysis, FT-IR, ESR, Magnetic susceptibility and TGA. The Electronic spectra and magnetic susceptibility measurements indicates that square planer and octahedral geometry of these complexes also suggest their structure in which (N, O) group acts as bidentate ligand. The thermal stability, decomposition rate and thermodynamic parameters of synthesized metal complexes were calculated by Freeman Carroll method. Also the biostatistical data of antimicrobial and anti-oxidant activities of synthesized metal complexes indicates moderate to good results. Graphic abstract

Rollover Cyclometalation as a Valuable Tool for Regioselective C–H Bond Activation and Functionalization

Rollover cyclometalation constitutes a particular case of cyclometallation reaction. This reaction occurs when a chelated heterocyclic ligand loses its bidentate coordination mode and undergoes an internal rotation, after which a remote C–H bond is regioselectively activated, affording an uncommon cyclometalated complex, called “rollover cyclometalated complex”. The key of the process is the internal rotation of the ligand, which occurs before the C−H bond activation and releases from coordination a donor atom. The new “rollover” ligand has peculiar properties, being a ligand with multiple personalities, no more a spectator in the reactivity of the complex. The main reason of this peculiarity is the presence of an uncoordinated donor atom (the one initially involved in the chelation), able to promote a series of reactions not available for classic cyclometalated complexes. The rollover reaction is highly regioselective, because the activated C–H bond is usually in a symmetric position with respect to the donor atom which detaches from the metal stating the rollover process. Due to this novel behavior, a series of potential applications have appeared in the literature, in fields such as catalysis, organic synthesis, and advanced materials.

Synthesis, structure and photophysical properties of two tetranuclear copper(I) iodide complexes based on acetylpyridine and diphosphine mixed ligands

Two copper(I) iodide tetramers, namely, [μ2-1,3-bis(diphenylphosphanyl)propane-κ2 P:P′]di-μ3-iodido-di-μ2-iodido-[1-(pyridin-3-yl)ethan-1-one-κN]tetracopper(I) dichloromethane disolvate, [Cu4I4(C6H7NO)2(C27H26P2)2]·2CH2Cl2 (Cu L 3 ), and [μ2-1,3-bis(diphenylphosphanyl)propane-κ2 P:P′]di-μ3-iodido-di-μ2-iodido-[1-(pyridin-4-yl)ethan-1-one-κN]tetracopper(I), [Cu4I4(C6H7NO)2(C27H26P2)2] (Cu L 4 ), have been synthesized from reactions of CuI, 1,3-bis(diphenylphosphanyl)propane (dppp) and 3- or 4-acetylpyridine (3/4-acepy). The complexes were characterized by elemental analysis, IR spectroscopy, single-crystal X-ray diffraction (XRD), powder XRD and photoluminescence spectroscopy. Both complexes possess a stair-step [Cu4I4] cluster structure with a crystallographic inversion centre located in the middle of a Cu2I2 ring (Z′ = 1 \over 2). The dppp ligands each adopt a bidentate coordination mode that bridges two CuI centres on one side of the [Cu4I4] cluster and the acepy ligands act as terminal ligands. The solid-state samples of similar complexes show highly efficiency thermally activated delayed fluorescence (TADF) at room temperature. At ambient temperature, both Cu L 3 and Cu L 4 exhibit photoluminescence, with a maximum emission in the region 560–580 nm and with short emissive decay times, but only phosphorescence was observed at 77 K. The narrow gaps between the higher lying singlet state and the triplet state, ΔE(S 1 − T 1), also confirm the presence of TADF. Structure analysis and consideration of photoluminescence indicates that the position of the acetyl group on the heterocyclic ligand has an obvious influence on the structural arrangement, on intermolecular interactions and on the observed photophysical properties.

Novel Heterocyclic Transition Metal Complexes: Synthesis, Characterization, Antimicrobial and Anticancer Activity

A heterocyclic ligand, 5-(2-(4-chlorophenyl)-1H-benzo[d]imidazol-1-yl)quinolin-8-ol and its Co(II), Ni(II), Cu(II) and Zn(II) complexes were synthesized and characterized by elemental analysis and spectroscopic techniques. According to the spectral analysis, the ligand acts as a bidentate ligand and coordinating through the nitrogen and deprotonated oxygen atoms. For Cu(II) and Ni(II) complexes, spectral analysis reveals square planer geometry, whereas Co(II) and Zn(II) complexes have tetrahedral geometry. The antibacterial results show that Zn(II) complex is more effective than the other metal(II) complexes examined. The ligand and its metal complexes were tested for anticancer activity using the MTT assay with cisplatin as the reference drug against A549, MCF7, and HCT116 cancer cell lines. Results showed that the metal(II) complexes were shown to be more active than the ligand, especially Zn(II) complex being the most potent among this series.

Mechanistic Insight of Sensing Hydrogen Phosphate in Aqueous Medium by Using Lanthanide(III)-Based Luminescent Probes

The development of synthetic lanthanide luminescent probes for selective sensing or binding anions in aqueous medium requires an understanding of how these anions interact with synthetic lanthanide probes. Synthetic lanthanide probes designed to differentiate anions in aqueous medium could underpin exciting new sensing tools for biomedical research and drug discovery. In this direction, we present three mononuclear lanthanide-based complexes, EuLCl3 (1), SmLCl3 (2), and TbLCl3 (3), incorporating a hexadentate aminomethylpiperidine-based nitrogen-rich heterocyclic ligand L for sensing anion and establishing mechanistic insight on their binding activities in aqueous medium. All these complexes are meticulously studied for their preferential selectivities towards different anions such as HPO42−, SO42−, CH3COO−, I−, Br−, Cl−, F−, NO3−, CO32−/HCO3−, and HSO4− at pH 7.4 in aqueous HEPES (2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid) buffer. Among the anions scanned, HPO42− showed an excellent luminescence change with all three complexes. Job’s plot and ESI-MS support the 1:2 association between the receptors and HPO42−. Systematic spectrophotometric titrations of 1–3 against HPO42− demonstrates that the emission intensities of 1 and 2 were enhanced slightly upon the addition of HPO42− in the range 0.01–1 equiv and 0.01–2 equiv., respectively. Among the three complexes, complex 3 showed a steady quenching of luminescence throughout the titration of hydrogen phosphate. The lower and higher detection limits of HPO42− by complexes 1 and 2 were determined as 0.1–4 mM and 0.4–3.2 mM, respectively, while complex 3 covered 0.2–100 μM. This concludes that all complexes demonstrated a high degree of sensitivity and selectivity towards HPO42−.