Mono- and dinuclear Zn(II) complexes of Schiff-base ligands: syntheses, characterization and studies of photoluminescence
TL;DR: In this paper, metal mediated fluorescence enhancement is observed on complexation of HL1-HL4 with Zn(II), whereas metal mediated quenching occurs in Zn-II-complexes of L5 and L6.
Abstract: Six Schiff-bases HL1-HL4, L5 and L6 [HL1 = 2,6-bis[1-(2-aminoethyl)pyrolidine-iminomethyl]-4-methyl-phenol, HL2 = 2,6-bis[1-(2-aminoethyl)piperidine-iminomethyl]-4-methyl-phenol, HL3 = N-{1-(2-aminoethyl)pyrolidine}salicylideneimine, HL4 = N-{1-(2-aminoethyl)piperidine}salicylideneimine, L5 = 2-benzoyl pyridine-N-{1-(2-aminoethyl)pyrolidine}, L6 = 2-benzoylpyridine-N-{1-(2-aminoethyl)piperidine}] have been synthesized and characterized. Zn(II) complexes of those ligands have been prepared by conventional sequential route as well as by template synthesis. The same complexes are obtained from the two routes as evident from routine physicochemical characterizations. All the Schiff-bases exhibit photoluminescence originating from intraligand (π–π*) transitions. Metal mediated fluorescence enhancement is observed on complexation of HL1-HL4 with Zn(II), whereas metal mediated fluorescence quenching occurs in Zn(II) complexes of L5 and L6.
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TL;DR: In this paper, a new Schiff base ligand (LH2 = 2-((Pyridin-2-yl)methyleneamino)benzene-1,4-dioic acid).
34 citations
TL;DR: In this paper, a series of new photoluminescent hemidisc-shaped NiII Schiff-base complexes has been synthesized, which exhibited thermally stable rectangular columnar (Colr) mesophases at about 227 °C.
Abstract: A series of new photoluminescent hemidisc-shaped NiII Schiff-base complexes has been synthesized. The ligands and their complexes were characterized by FTIR and 1H and 13C NMR spectroscopy, FAB-MS and elemental analysis. The mesomorphic behaviour of the ligands and their complexes was probed by polarizing optical microscopy and differential scanning calorimetry. The molecular organization in the mesophase was determined by X-ray diffraction techniques. The ligands are nonmesogenic but their complexes exhibited thermally stable rectangular columnar (Colr) mesophases at about 227 °C. The complexes are blue-light emitters in solution (ca. 434 nm, Φ = 19 %) and in the solid state (ca. 469 nm, Φ = 7 %) at λex = 350 nm. A DFT study was carried out using DMol3 at the BLYP/DNP level to obtain a stable, optimized structure, which revealed a distorted square-planar geometry for the nickel complexes.
26 citations
TL;DR: In this paper, the coordination chemistry of azomethines is generalized and systematized, and the methods for targeted synthesis of five and/or six-membered chelates containing chalcogen atoms (S, Se, and Te) and nonstandard (heteroleptic, molecular, and supramolecular) structures.
Abstract: Data on the coordination chemistry of azomethines, which are based on the molecular design concept formulated and developed by V.I. Minkin and his disciples, are generalized and systematized. Particular attention is given to the methods for targeted synthesis of five- and/or six-membered chelates containing chalcogen atoms (S, Se, and Te) and nonstandard (heteroleptic, molecular, and supramolecular) structures. Achievements in the design of magnetically active and luminescent complexes and azomethine complex additives to lubricants are discussed.
20 citations
TL;DR: Zn(II) and Cu(ii) Schiff base complexes having DNA and HSA binding efficacy have been exploited as cancer therapeutic agents.
Abstract: Two new metal complexes, namely, [Zn2(LH)2(N3)4] (1) and [Cu(L)(N3)] (2), have been derived from a Schiff base ligand, (E)-2-(((2-(piperidine-2-yl)ethyl)imino)methyl)phenol (HL), employing azide as the secondary anionic residue. Single crystal structural analyses suggest the protonation of piperidine N during the crystallization of the dinuclear motif of complex 1, which is non-operative in the case of complex 2, governing the diverse denticity of the ligand backbone. After a thorough characterization, the complexes are investigated to check their bio-medical applications. Both complexes exhibit impressive binding efficacy with CT DNA as well as Human Serum Albumin (HSA) protein, as revealed from their electronic spectroscopic measurements. A sharp fluorescent quenching of the DNA-EtBr conjugate and HSA protein was encountered separately via the addition of complexes 1 and 2 with the quenching constant in the order of ∼105 M−1. A theoretical inspection through the molecular docking study has also been introduced to justify the experimental outcomes along with the determination of the interaction site and energy. Finally, both complexes are tested for anticancer activity using HeLa (cervical cancer cell) and PA1 (ovarian cancer cell) cell lines through the in vitro MTT assay, which suggests a better cancer cell killing efficacy of complex 2. The applicability of complexes 1 and 2 within the normal cell (hEG) has been concurred through the determination of much higher LD50 values, indicating significantly lower cytotoxic effect on the normal cell line. Furthermore, the haemolysis assay indicates no consequential impact of complexes (1 and 2) on the RBC. Finally, the anti proliferative activities of both the complexes towards carcinoma cell lines were analysed through various nuclear and cellular staining techniques, unveiling the cell death mechanism.
20 citations
TL;DR: DFT calculations performed by using the DMol3 program at the BLYP/DNP level of theory revealed a nine-coordinate structure for the lanthanide complexes, and different space-filling models have been proposed for the ligand and complexes to account for the columnar mesomorphism.
Abstract: A novel photoluminescent room-temperature liquid-crystalline salicylaldimine Schiff base with a short alkoxy substituent and a series of lanthanide(III) complexes of the type [Ln(LH)3(NO3)3] (Ln=La, Pr, Sm, Gd, Tb, Dy; LH=(E)-5-(hexyloxy)-2- [{2-(2-hydroxyethylamino)ethylimino]methyl}phenol) have been synthesized and characterized by FTIR, 1H and 13C NMR, UV/Vis, and FAB-MS analyses. The ligand coordinates to the metal ions in its zwitterionic form. The thermal behavior of the compounds was investigated by polarizing optical microscopy (POM) and differential scanning calorimetry (DSC). The ligand exhibits an enantiotropic hexagonal columnar (Colh) mesophase at room temperature and the complexes show an enantiotropic lamellar columnar (ColL) phase at around 120 °C with high thermal stability. Based on XRD results, different space-filling models have been proposed for the ligand and complexes to account for the columnar mesomorphism. The ligand exhibits intense blue emission both in solution and in the condensed state. The most intense emissions were observed for the samarium and terbium complexes, with the samarium complex glowing with a bright-orange light (ca. 560–644 nm) and the terbium complex emitting green light (ca. 490–622 nm) upon UV irradiation. DFT calculations performed by using the DMol3 program at the BLYP/DNP level of theory revealed a nine-coordinate structure for the lanthanide complexes.
20 citations
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TL;DR: Majors topics addressed in this review on zinc physiology are chemistry and biochemistry; interface of biochemistry and physiology of zinc; physiology and cell and molecular biology; and pathology.
Abstract: Majors topics addressed in this review on zinc physiology are ; 1) chemistry and biochemistry; 2) interface of biochemistry and physiology of zinc; 3) physiology and cell and molecular biology; 4) pathology
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