N-heterocyclic Carbene Silver(I) Complexes from Xanthines and Their Antimicrobial Applications

N-heterocyclic Carbene Silver(I) Complexes from Xanthines and Their Antimicrobial Applications
Author: Aysegul Kascatan Nebioglu
Publisher:
Total Pages: 261
Release: 2007
Genre: Anti-infective agents
ISBN:
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"This dissertation discusses a newly growing area of the synthesis from xanthine ligands of new silver(I) N-heterocyclic carbene (NHC) complexes and their potential antimicrobial use in cystic fibrosis lung infections. In chapter I, the ligand properties of NHCs and the synthetic methods for the formation of silver(I) NHC complexes are outlined. An overview of silver antimicrobials and previously synthesized silver(I) NHC complexes from pyridine linked and tripodal imidazolium salts for the topical applications is discussed. Furthermore, a brief summary of cystic fibrosis is given. Chapter II presents the introductory studies to explore the NHC silver(I) chemistry of caffeine. Formation and characterization of mono and dinuclear bis(NHC) silver(I) complexes from different methylated caffeine salts are given. Chapter III focuses on the formation of an NHC-silver(I) acetate complex from the iodide salt of methylated caffeine. This complex demonstrates a promising antimicrobial activity against numerous resistant respiratory pathogens including members of the Burkholderia cepacia complex which causes a high rate of mortality in patients with cystic fibrosis. Synthesis of NHC silver(I) complexes from theophylline derivatives is given in chapter IV. The antimicrobial activity of these complexes against the same pathogens used in chapter III is presented. In chapter V, the use of a bis(NHC) silver(I) complex from methylated caffeine as a carbene transfer agent is demonstrated and formation of a Rh(I) NHC complex is outlined. Furthermore, the synthesis and characterization of Pt(II) and Pd(II) NHC complexes of methylated caffeine are presented."--Abstract.

Synthesis and Antimicrobial Properties of Silver(I) N-heterocyclic Carbene Complexes

Synthesis and Antimicrobial Properties of Silver(I) N-heterocyclic Carbene Complexes
Author: Abdulkareen Modupe Melaiye
Publisher:
Total Pages: 0
Release: 2005
Genre: Anti-infective agents
ISBN:
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"New symmetric and asymmetric types of N-heterocyclic carbene (NHC) precursors, grouped into mono-dentate, bi-dentate and tri-dentate chelating ligands, were synthesized. The reaction of the carbene precursors with silver(I) oxide in methanol at room temperature affords the silver(I) N-heterocyclic carbene complexes. The solubility and stability of silver(I) NHC complexes in water depends on the ligand and counter anion. In-vitro test of water soluble silver(I) NHC complex, [AgC1--N5O2H21] [OH]− 3a shows antimicrobial activity as good as 0.5 % AgNO3 using the same amount of silver on pathogenic bacteria and fungi of clinical importance. The encapsulation of Ag(I) NHC complexes, [Ag2C34N10O4H]2 2[OH]− 6 and [Ag3C54N12O2H]3+[Br]− 2[OH]− 8a respectively by electrospinning technique, delivers bioactive nanosilver ions which improved the antimicrobial activity of the Ag(I) NHC over the un-encapsulated forms. The electrospun mat of 6 sustained the release of bioactive nanosilver ions for at least seven days. Electrospun fiber mat containing 75% of 6 showed improved antimicrobial efficacies in-vitro over silver sulfadiazine cream (SSD), with the rate of bactericidal activity six fold faster than SSD and ca. the same rate as 0.5% AgNO3. The amount of silver in the fiber mat is six times lower than SSD and 8 fold lower than 0.5% AgNO3. The size of the nanosilver ions of electrospun mat of 6 is

Redox-active Silver N-heterocyclic Carbene Complexes

Redox-active Silver N-heterocyclic Carbene Complexes
Author: Kotiba Malek
Publisher:
Total Pages: 55
Release: 2018
Genre: Antibacterial agents
ISBN:
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Bacterial resistance to current ß-lactam antibiotics necessitates new therapeutic approaches. Silver-based drugs offer a promising alternative because of their antibacterial properties and minimal bacterial resistance. However, many silver-based antibacterial drugs rapidly release silver ions, limiting the bioavailability of silver ions for a longer period of time. Recently, N-heterocyclic carbenes (NHC) containing silver complexes have become a popular subject of research due to their versatility and the slow release of silver ions under biological conditions. To further enhance the efficacy of silver-NHC drugs, we fused redox-active substituents such as naphthoquinone and ferrocenes to NHCs. Both naphthoquinone and ferrocenes have been shown to increase reactive oxygen species (ROS) under biological conditions that may augment the antibacterial action of redox-active silver-NHC complexes. Herein, we report synthesis and characterization of several redox-active silver-NHC complexes, 1-(ferrocenylmethyl)-3-mesityl-imidazol-2-ylidene silver chloride [(2)AgCl] (compound 6), 1,3-di (ferrocenylmethyl)imidazol-2-ylidene silver chloride [(3)AgCl] (compound 7), bis (1-benzyl-3-mesitylimidazol-2-ylidene) silver chloride [(1)2Ag][Cl], (compound 9), Bis (1-(ferrocenylmethyl)-3-mesityl-imidazol-2-ylidene) silver chloride [(2)2Ag][Cl] (compound 10), Bis (1,3 di(ferrocenylmethyl)imidazole-2-ylidene) silver chloride [(3)2Ag][Cl] (compound 11), and bis (1,3-dimesityl-4,5-naphthoquino-imidazol-2-ylidene) silver chloride [(4)2Ag][Cl] (compound 12). Complexes were identified and confirmed via various analytical techniques, including 1H NMR, 13C NMR, infrared spectroscopy, UV-vis spectroscopy, and single crystal X-ray crystallography.A series of cyclic and differential pulse voltammetry experiments were conducted on the complexes to investigate their electrochemical properties. Complexes [(2)AgCl], [(3)AgCl], [(2)2Ag][Cl], [(2)2Ag][Cl], [(3)2Ag][Cl], and [(4)2Ag][Cl] exhibited redox activity attributed to the presence of ferrocene and naphthoquinone moiety. Their antibacterial properties were tested against gram-negative bacterial strains (Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa) and showed excellent antibacterial properties that are comparable to previously reported silver-NHC complexes. All silver-NHC complexes detailed in this report exhibit MIC and MBC values in the range of 2-12.5 æg/mL. Further mechanistic studies are necessary to elucidate the manner in which these complexes affect bacterial cells.

A Stability Comparison and Antimicrobial Evaluation of Gold N-heterocyclic Carbenes and Their Silver Percursors

A Stability Comparison and Antimicrobial Evaluation of Gold N-heterocyclic Carbenes and Their Silver Percursors
Author: Tammy J. Siciliano
Publisher:
Total Pages: 266
Release: 2008
Genre: Anti-infective agents
ISBN:
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The synthesis of the first metal N-heterocyclic carbene (NHC) complexes by Öfele and Wanzlick started an exciting new class of coordination chemistry. The isolation of the first free carbene by Arduengo provided a novel route from which numerous NHC metal complexes have been made. Among their many applications, the potential for therapeutic use has been an area of growing interest and a topic of this review. The first gold NHC complex synthesized from its silver NHC precursor by Lin revolutionized the frontier for simple gold NHC generation to which this review is rooted. Chapter 1 provides a review on past and current routes by which gold(I) and gold(III) NHC complexes have been synthesized. The discussion focuses on their structural comparisons and a detailed history of the medicinal use of gold is presented before exploring their current role in the field. In Chapter 2, the stability of gold-(bis)NHC complexes in aqueous and physiological solution is discussed in comparison to their silver-(bis)NHC precursors. Silver has been used as an antimicrobial agent for thousands of years and the antimicrobial properties of both are explored. Chapter 3 focuses further on water stability and antimicrobial properties as it is applied to silver acetate NHC complexes in comparison to silver- and gold-(bis)NHC analogues. Imidazolium salts, NHC precursors, have been shown to possess antimicrobial properties. Chapter 4 investigates these properties on synthesized imidazolium salts with a variety of functional groups on varying positions of the imidazole ring. There are several different types of silver dressings commercially available. Chapter 5 evaluates the antimicrobial effectiveness of eight such dressings and comparisons are made.

N-heterocyclic Carbenes

N-heterocyclic Carbenes
Author: Silvia Díez-González
Publisher: Royal Society of Chemistry
Total Pages: 469
Release: 2011
Genre: Science
ISBN: 1849730423
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Over the last fifteen years, N-heterocyclic carbenes (NHCs) have mostly been used as ancillary ligands for the preparation of transition metal-based catalysts. Compared to phosphorus-containing ligands, NHCs tend to bind more strongly to metal centres, avoiding the necessity for the use of excess ligand in catalytic reactions. The corresponding complexes are often less sensitive to air and moisture, and have proven remarkably resistant to oxidation. Recent developments in catalysis applications have been facilitated by the availability of carbenes stable enough to be bottled, particularly for their use as organocatalysts. This book shows how N-heterocyclic carbenes can be useful in various fields of chemistry and not merely laboratory curiosities or simple phosphine mimics. NHCs are best known for their contribution to ruthenium and palladium-catalysed reactions but the scope of this book is much broader. The synthesis of NHC ligands and their corresponding metal complexes are covered in depth. Moreover, the biological activity of NHC-containing complexes, as well as an overview of their theoretical aspects are included. Such metal species are further examined, not only in terms of their catalytic applications, but also of their stereoelectronic parameters and reactivity/stability. Finally, special attention is given to the hot topic of organocatalysis. The book will be of interest to postgraduates, academic researchers and those working in industry.

N-Heterocyclic Carbenes

N-Heterocyclic Carbenes
Author: Silvia Diez-Gonzalez
Publisher: Royal Society of Chemistry
Total Pages: 637
Release: 2016-11-04
Genre: Science
ISBN: 1782626816
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In less than 20 years N-heterocyclic carbenes (NHCs) have become well-established ancillary ligands for the preparation of transition metal-based catalysts. This is mainly due to the fact that NHCs tend to bind strongly to metal centres, avoiding the need of excess ligand in catalytic reactions. Also, NHC‒metal complexes are often insensitive to air and moisture, and have proven remarkably resistant to oxidation. This book showcases the wide variety of applications of NHCs in different chemistry fields beyond being simple phosphine mimics. This second edition has been updated throughout, and now includes a new chapter on NHC‒main group element complexes. It covers the synthesis of NHC ligands and their corresponding metal complexes, as well as their bonding and stereoelectronic properties and applications in catalysis. This is complemented by related topics such as organocatalysis and biologically active complexes. Written for organic and inorganic chemists, this book is ideal for postgraduates, researchers and industrialists.

Metal, Metal Oxides and Metal Sulphides for Biomedical Applications

Metal, Metal Oxides and Metal Sulphides for Biomedical Applications
Author: Saravanan Rajendran
Publisher: Springer Nature
Total Pages: 360
Release: 2021-01-25
Genre: Science
ISBN: 3030564134
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This book presents recent advances in inorganic nanomaterials for healthcare, with focus on the synthesis, medical applications and toxicity of metals, metal oxides and metal sulfides. Major applications include diagnosis, bioimaging, biosensing, healing and therapy in cancer, diabetes, cardiovascular diseases, obesity, metabolic syndrome, dentistry and antimicrobials.

N-Heterocyclic Carbenes

N-Heterocyclic Carbenes
Author: Steven P. Nolan
Publisher: Wiley-VCH
Total Pages: 0
Release: 2014-11-03
Genre: Science
ISBN: 9783527334902
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This comprehensive reference and handbook covers in depth all major aspects of the use of N-heterocyclic carbene-complexes in organic synthesis: from the theoretical background to characterization, and from cross-coupling reactions to olefin metathesis. Edited by a leader and experienced scientist in the field of homogeneous catalysis and use of NHCs, this is an essential tool for every academic and industrial synthetic chemist.

Silver Catalysis in Organic Synthesis

Silver Catalysis in Organic Synthesis
Author: Chao-Jun Li
Publisher: John Wiley & Sons
Total Pages: 400
Release: 2018-12-07
Genre: Science
ISBN: 3527807691
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Covers all the aspects of the recent achievements in silver catalyzed reactions Silver catalysis has emerged as a powerful tool in the field of organic synthesis. This comprehensive book systematically explores the unique performance of silver catalysis, introducing all the recent progress of silver catalysis in organic synthesis. It clearly emphasizes the unique features of silver catalysis and provides the reaction mechanism involved. This two-volume book also provides vivid schematics and tables throughout to enhance the accessibility to the relevant theory and mechanisms. Silver Catalysis in Organic Synthesis begins with an introduction to Silver Chemistry before moving on to chapters covering: Silver-Catalyzed Cycloaddition Reactions; Silver-Catalyzed Cyclizations; Silver-Mediated Radical Reactions; Silver-Mediated Fluorination, Perfluoroalkylation and Trifluoromethylthiolation Reactions; Coupling Reactions and C-H Functionalization; Silver-Catalyzed CO2 Incorporation; Silver-Catalyzed Carbene, Nitrene, and Silylene Transfer Reactions; Asymmetric Silver-Catalyzed Reactions; Silver-Catalyzed Reduction and Oxidation of Aldehydes and Their Derivatives; Silver Complexes in Organic Transformations; and Silver Nanoparticles in Organic Transformations. -Covers recently developed organic reactions catalyzed by silver, along with their reaction mechanism -Introduces many new reactions and mechanisms related to silver catalysis -Offers professionals and newcomers in the related fields a survey of new advances in silver catalysis in organic synthesis Silver Catalysis in Organic Synthesis will appeal to a wide readership including chemists, biochemists, pharmaceutical scientists, biomedical researchers, agriculture scientists, and graduate students in the related fields.

Inorganic and Organometallic Transition Metal Complexes with Biological Molecules and Living Cells

Inorganic and Organometallic Transition Metal Complexes with Biological Molecules and Living Cells
Author: Kenneth Kam-Wing Lo
Publisher: Academic Press
Total Pages: 408
Release: 2016-12-30
Genre: Science
ISBN: 012803887X
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Inorganic and Organometallic Transition Metal Complexes with Biological Molecules and Living Cells provides a complete overview of this important research area that is perfect for both newcomers and expert researchers in the field. Through concise chapters written and edited by esteemed experts, this book brings together a comprehensive treatment of the area previously only available through scattered, lengthy review articles in the literature. Advanced topics of research are covered, with particular focus on recent advances in the biological applications of transition metal complexes, including inorganic medicine, enzyme inhibitors, antiparasital agents, and biological imaging reagents. Geared toward researchers and students who seek an introductory overview of the field, as well as researchers working in advanced areas Focuses on the interactions of inorganic and organometallic transition metal complexes with biological molecules and live cells Foscuses on the fundamentals and their potential therapeutic and diagnostic applications Covers recent biological applications of transition metal complexes, such as anticancer drugs, enzyme inhibitors, bioconjugation agents, chemical biology tools, and bioimaging reagents