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Coumarins and metal ligands

Anne Kathrine R Junker, Gauthier J-P Deblonde, Rebecca J Abergel, Thomas Just Sørensen
In order to reveal subtle differences between the solution chemistries of trivalent 4f and 5f elements, the physicochemical and photophysical properties of europium(iii), terbium(iii) and curium(iii) complexes formed with a 7-methoxy-coumarin appended 1,4,7,10-tetraazadodecane-1,4,7-triacid (DO3A) ligand were studied. All three complexes were found to be kinetically inert and exhibit stability constants similar to their 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) equivalents. The Cm(iii) and Eu(iii) complexes feature strong sensitised emission, while the triplet energy of the coumarin prohibits efficient sensitisation of the Tb(iii) analogue...
May 18, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
Leili Jalili-Baleh, Hamid Forootanfar, Tuba Tüylü Küçükkılınç, Hamid Nadri, Zahra Abdolahi, Alieh Ameri, Mandana Jafari, Beyza Ayazgok, Maryam Baeeri, Mahban Rahimifard, Syed Nasir Abbas Bukhari, Mohammad Abdollahi, Mohammad Reza Ganjali, Saeed Emami, Mehdi Khoobi, Alireza Foroumadi
A novel series of coumarin-lipoic acid conjugates were synthesized via cycloaddition click reaction to find out new multi-target-directed ligands (MTDLs) for treatment of Alzheimer's disease (AD). All of synthesized compounds were screened for neuroprotective and anti-cholinesterase activities. Based on primary screening, two compounds (5 and 11) were subjected to further biological evaluations. In particular, compound 11 which was the most potent AChE inhibitor showed good inhibitory effect on Aβ-aggregation and intracellular ROS (reactive oxygen species) formation, as well as the ability of selective bio-metal chelation and neuroprotection against H2 O2 - and Aβ1-42 -induced cytotoxicity...
May 2, 2018: European Journal of Medicinal Chemistry
María S Islas, Juan J Martínez Medina, Oscar E Piro, Gustavo A Echeverría, Evelina G Ferrer, Patricia A M Williams
Coumarins (2H-chromen-2-one) are oxygen-containing heterocyclic compounds that belong to the benzopyranones family. In this work we have synthesized different coordination complexes with coumarin-3-carboxylic acid (HCCA), o-phenanthroline (phen) and zinc(II). In the reported [Zn(CCA)2 (H2 O)2 ] complex, coumarin-3-carboxylate (CCA) is acting as a bidentate ligand while in the two prepared complexes, [Zn(phen)3 ]CCA(NO3 ) (obtained as a single crystal) and [Zn(CCA)2 phen].4H2 O, CCA is acting as a counterion of the complex cation [Zn(phen)3 ]+2 or coordinated to the metal center along with phen, respectively...
March 7, 2018: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Gautam Achar, C R Shahini, Siddappa A Patil, Jan Grzegorz Małecki, Szu-Hua Pan, Albert Lan, Xuan-Ren Chen, Srinivasa Budagumpi
In this contribution, a series of sterically-encumbered coumarin substituted benzimidazole-based N-heterocyclic carbene (NHC) precursors (1-12) and their silver(I)-NHC complexes (13-24) are reported. Molecular structure of NHC precursors 8 and 12 and cationic complexes 15 and 16 was established by single crystal X-ray diffraction method. The silver(I) complexes demonstrated various significant intramolecular agostic-like interactions operating between the metal center and the hydrogen atoms of the substituents alongside a variety of feeble π-π stacking interactions...
February 22, 2018: Journal of Inorganic Biochemistry
Akop Yepremyan, Arshad Mehmood, Samantha Brewer, Madalyn M Barnett, Benjamin G Janesko, Giridhar Akkaraju, Eric E Simanek, Kayla N Green
Interests in inorganic applications of triazines is growing. In this report, metal complexes of copper(II), nickel(II), and zinc(II) and a novel class of chelates comprising a triazine ring substituted with a hydrazine group and pyralozone are evaluated using spectrophotometric methods, single crystal X-ray diffractometry, and electrochemistry. Complexes with copper(II) include a single chelate and two chloride atoms to satisfy a trigonal bipryamidal coordination sphere. The nickel(II) and zinc(II) complexes are comprised of two chelating groups that adopt an octahedral geometry around the metal ion...
2018: RSC Advances
Esther Theresa Knittl, Azza A Abou-Hussein, Wolfgang Linert
A hydrazone Schiff base ligand was synthesized by the condensation of 3-formyl-4-hydroxycoumarin and oxalyldihydrazide in the molar ratio 2:1. The Schiff base ligand acts as a mono-, bi-, tri- or even tetradentate ligand with metal cations in the molar ratios 1:1 or 2:1 ( M : L ) to yield either mono- or binuclear complexes as keto or enol isomers, where M  = Co(II), Ni(II), Cu(II), VO(IV), and Fe(III). The ligand and its metal complexes were characterized by elemental analyses, IR, 1 H NMR, mass, and UV-Vis spectroscopy...
2018: Monatshefte Für Chemie
Narayan Sinha, F Ekkehardt Hahn
Over the past two decades, self-assembly of supramolecular architectures has become a field of intensive research due to the wide range of applications for the resulting assemblies in various fields such as molecular encapsulation, supramolecular catalysis, drug delivery, metallopharmaceuticals, chemical and photochemical sensing, and light-emitting materials. For these purposes, a large number of coordination-driven metallacycles and metallacages featuring different sizes and shapes have been prepared and investigated...
August 25, 2017: Accounts of Chemical Research
Naveen Mergu, Myeongjin Kim, Young-A Son
A novel coumarin-based receptor bearing a benzohydrazide (FCBH) was developed as a fluorescent chemosensor with high selectivity toward Cu2+ . The sensor was successfully applied to the monitoring of Cu2+ in aqueous solution. After the addition of Cu2+ to FCBH, the color of the solution changed from greenish-yellow to red, and the absorption band at 457nm red-shifted to 517nm. The fluorescent green color of FCBH disappeared and the fluorescence emission was completely quenched in the presence of Cu2+ . Upon the addition of Cu2+ , deprotonation of FCBH occurred, and a 1:1 metal-ligand complex formed...
January 5, 2018: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Paulina Gonzalez, Kristof Pota, Lara Su Turan, Viviana C P da Costa, Giridhar Akkaraju, Kayla N Green
Metal-ion misregulation and oxidative stress continue to be components of the continually evolving hypothesis describing the molecular origins of Alzheimer's disease. Therefore, these features are viable targets for synthetic chemists to explore through hybridizations of metal-binding ligands and antioxidant units. To date, the metal-binding unit in potential therapeutic small molecules has largely been inspired by clioquinol with the exception of a handful of heterocyclic small molecules and open-chain systems...
August 22, 2017: ACS Chemical Neuroscience
Saman Khan, Ali Mohammed Malla, Atif Zafar, Imrana Naseem
Despite substantial research on cancer therapeutics, systemic toxicity and drug-resistance limits the clinical application of many drugs like cisplatin. Therefore, new chemotherapeutic strategies against different malignancies are needed. Targeted cancer therapy is a new paradigm for cancer therapeutics which targets pathways or chemical entities specific to cancer cells than normal ones. Unlike normal cells, cancer cells contain elevated copper which plays an integral role in angiogenesis. Copper is an important metal ion associated with chromatin DNA, particularly with guanine...
2017: PloS One
Esther S Areas, Bruna Juliana da S Bronsato, Thiago M Pereira, Guilherme P Guedes, Fábio da S Miranda, Arthur E Kümmerle, Antônio G B da Cruz, Amanda P Neves
A series of new CoIII complexes of the type [Co(dien)(L1-L3)]ClO4 (1-3), containing fluorescent coumarin-N-acylhydrazonate hybrid ligands, (E)-N'-(1-(7-oxido-2-oxo-2H-chromen-3-yl)ethylidene)-4-R-benzohydrazonate [where R=H (L12- ), OCH3 (L22- ) or Cl (L32- )], were obtained and isolated in the low spin CoIII configuration. Single-crystal X-ray diffraction showed that the coumarin-N-acylhydrazones act as tridentate ligands in their deprotonated form (L2- ). The cation (+1) complexes contain a diethylenetriamine (dien) as auxiliary ligand and their structures were calculated by DFT studies which were also performed for the CoII (S=1/2 and S=3/2) configurations...
December 5, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Peng Wang, Yu Fang, Jun Jiang, Yujin Ji, Youyong Li, Junwei Zheng, Qingfeng Xu, Jianmei Lu
Owing to the demands of state-of-the-art information technologies that are suitable for vast data storage, the necessity for organic memory device (OMD) materials is highlighted. However, OMDs based on metal complexes are limited to several types of transition-metal complex systems containing nitrogen-donor ligands. Herein, attempts are made to introduce novel alkynylgold(III) materials into memory devices with superior performance. In this respect, an alkynyl-containing coumarin gold(III) complex, [(C19 N5 H11 )Au-C≡C-C9 H5 O], has been synthesized and integrated into a sandwiched Al/[(C19 N5 H11 )Au-C≡C-C9 H5 O]/indium tin oxide device...
July 18, 2017: Chemistry, An Asian Journal
Nayan Roy, Abhijit Dutta, Paritosh Mondal, Pradip C Paul, T Sanjoy Singh
A new coumarin based Schiff-base chemosensor-(E)-7-(((8-hydroxyquinolin-2-yl)methylene) amino)-4-methyl-2H-chromen-2-one (H11 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...
July 2017: Journal of Fluorescence
Jingjing Deng, Guoyue Shi, Tianshu Zhou
This study demonstrates a new strategy for colorimetric detection of alcoholic strength (AS) in spirit samples based on dual-responsive lanthanide infinite coordination polymer (Ln-ICP) particles with ratiometric fluorescence. The ICP used in this study are composed of two components: one is the supramolecular Ln-ICP network formed by the coordination between the ligand 2,2'-thiodiacetic acid (TDA) and central metal ion Eu3+ ; and the other is a fluorescent dye, i.e., coumarin 343 (C343), both as the cofactor ligand and as the sensitizer, doped into the Ln-ICP network through self-adaptive chemistry...
October 26, 2016: Analytica Chimica Acta
Muhammad Saleem, Muhammad Rafiq, Muhammad Hanif
Due to the deleterious effects of mercury on human health and natural ecosystems, high reactivity, non-degradability, extreme volatility and relative water and tissue solubility, it would consider as one of the most toxic environmental pollutants among the transition metals. In the present investigation, we have tried to summarized the several organic material based fluorescent sensor including rhodamine, boron-dipyrromethene (BODIPYs), thiourea, crown-ether, coumarine, squaraines, pyrene, imidazole, triazole, anthracene, dansyl, naphthalenedimide/ naphthalene/ naphthalimide, naphthyridine, iridium (III) complexes, polymeric materials, cyclodextrin, phthalic anhydride, indole, calix [4]arene, chromenone, 1,8-naphthalimides, lysine, styrylindolium, phenothiazine, thiocarbonyl quinacridone, oxadiazole, triphenylamine-triazines, tetraphenylethene, peptidyl and semicarbazone for the trace mercury detection in the aqueous, aqueous-organic and cellular media...
January 2017: Journal of Fluorescence
Qiongqiong Zhang, Cankun Zhang, Lingyun Cao, Zi Wang, Bing An, Zekai Lin, Ruiyun Huang, Zhiming Zhang, Cheng Wang, Wenbin Lin
Metal-organic frameworks (MOFs) with light-harvesting building blocks designed to mimic photosynthetic chromophore arrays in green plants provide an excellent platform to study exciton transport in networks with well-defined structures. A step-by-step exciton random hopping model made of the elementary steps of energy transfer between only the nearest neighbors is usually used to describe the transport dynamics. Although such a nearest neighbor approximation is valid in describing the energy transfer of triplet states via the Dexter mechanism, we found it inadequate in evaluating singlet exciton migration that occurs through the Förster mechanism, which involves one-step jumping over longer distance...
April 27, 2016: Journal of the American Chemical Society
Chetan T Prabhakara, Sangamesh A Patil, Shivakumar S Toragalmath, Shivashankar M Kinnal, Prema S Badami
The impregnation of halogen atoms in a molecule is an emerging trend in pharmaceutical chemistry. The presence of halogens (Cl, Br, I and F) increases the lipophilic nature of molecule and improves the penetration of lipid membrane. The presence of electronegative halogen atoms increases the bio- activity of core moiety. In the present study, Co(II), Ni(II) and Cu(II) complexes are synthesised using Schiff bases (HL(I) and HL(II)), derived from 8-formyl-7-hydroxy-4-methylcoumarin/3-chloro-8-formyl-7-hydroxy-4-methylcoumarin with 2,4-difluoroaniline/o-toluidine respectively...
April 2016: Journal of Photochemistry and Photobiology. B, Biology
Pablo Rivera-Fuentes, Stephen J Lippard
Nitroxyl (HNO) is a biological signaling agent that displays distinctive reactivity compared to nitric oxide (NO). As a consequence, these two reactive nitrogen species trigger different physiological responses. Selective detection of HNO over NO has been a challenge for chemists, and several fluorogenic molecular probes have been recently developed with that goal in mind. Common constructs take advantage of the HNO-induced reduction of Cu(II) to Cu(I). The sensing mechanism of such probes relies on the ability of the unpaired electron in a d orbital of the Cu(II) center to quench the fluorescence of a photoemissive ligand by either an electron or energy transfer mechanism...
November 17, 2015: Accounts of Chemical Research
Muhammad Mujahid, Agnieszka Foltyn-Arfa Kia, Brian Duff, Denise A Egan, Michael Devereux, Siobhán McClean, Maureen Walsh, Natasha Trendafilova, Ivelina Georgieva, Bernadette S Creaven
Silver(I) complexes of coumarin-based ligands and one of their phenanthroline (phen) adducts have been prepared and characterized using microanalytical data, molar conductivity, IR, (1)H and (13)C NMR, UV-Vis, and atomic absorption (AAS) spectroscopies. The binding modes of the coumarin-based ligands and the most probable structure of their Ag(I) complexes were predicted by means of molecular modeling and calculations of their IR, NMR, and absorption spectra using density functional theory (DFT). The cytotoxicity of the compounds studied against human-derived hepatic carcinoma cells (Hep-G2) and a renal cancer cell line (A498) showed that the complexes were more cytotoxic than the clinically used chemotherapeutic, mitoxantrone...
December 2015: Journal of Inorganic Biochemistry
Qingtao Meng, Hongmin Jia, Peter Succar, Liang Zhao, Run Zhang, Chunying Duan, Zhiqiang Zhang
A new complex between coumarin-based ligand (CL) and copper ion has been prepared and applied to be an ON-OFF-ON reversible fluorescence chemosensor for the detection of Cys with high sensitivity and specificity. In HEPES buffer, CL displayed high affinity towards Cu(2+) ion over other physiological and environmental metal ions, accompanied with a 98.4% of fluorescence quenching. In the presence of Cys, the detachment of Cu(2+) ion of CL-Cu(2+) ensemble led to the liberation of the fluorophore, CL, and thus fluorescence was recovered...
December 15, 2015: Biosensors & Bioelectronics
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