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Macrocyclic Receptors for Environmentally Sensitive Metal Ions
Published in Satish Kumar, Priya Ranjan Sahoo, Violet Rajeshwari Macwan, Jaspreet Kaur, Mukesh, Rachana Sahney, Macrocyclic Receptors for Environmental and Biosensing Applications, 2022
Satish Kumar, Priya Ranjan Sahoo, Violet Rajeshwari Macwan, Jaspreet Kaur, Mukesh, Rachana Sahney
In this chapter, various macrocyclic receptor molecules were considered based on several classes of macrocyclic ligands like crown ethers, lariat crown ethers, cyclam, cyclen, cryptands, cyclophanes, podands, cyclodextrins, calix[n]arenes, cucurbit[n]urils and pillar[n]arenes. The macrocyclic host molecules and their functionalized derivatives were described and summarized with regard to their metal ion complexation ability, binding affinity, selectivity, sensitivity, spectroscopic properties, including others such as extraction ability, ion transport and redox nature. Many of these macrocycles presented highly selective recognition of targeted metal ion species. Some of them were even capable of detecting the analytes at sub-micro levels. The binding and recognition efficacy of a receptor for different metal ions depends on factors such as the ring size of the macrocycle, incorporation of substituent units/ functional groups, spacer length, presence of heteroatoms (N, O, S) and the solvent system. Preorganization of multiple chelating units within the ligand framework with limited conformational liberty enables the construction of more rigid systems with cavities of precisely tailored shapes and sizes.
Recent Advances in Non-Platinum-Based Cathode Electrocatalysts for Direct Methanol Fuel Cells
Published in Prasanth Raghavan, Fatima M. J. Jabeen, Ceramic and Specialty Electrolytes for Energy Storage Devices, 2021
Bhagyalakhi Baruah, Ashok Kumar
Macrocyclic compounds are polydentate ligands, in which the donor atoms are either incorporated or attached to a cyclic backbone [57]. Macrocycles are the large molecules that have a minimum of one large ring with nine or more atoms, among which three are donor atoms [58]. Macrocyclic materials have attained much attention due to some remarkable properties, including [57] their ability to differentiate among the same group of metal ions depending upon the ring size and the enhanced stability exhibited by optimally fitted macrocyclic ligands (macrocyclic effect). In 1934, iron phthalocyanine (FePc), the frst transition metal N4 (MN4) macrocycle was discovered by Linstead [59]. Among the various macrocyclics, phthalocyanines (Pc), combined with different transition metals, such as nickel, iron, manganese, zinc, cobalt, and copper, have been extensively studied as cathode electrocatalyst in fuel cells [29, 60] 61, 62]. The cobalt- and copper-based macrocyclic complexes are the most stable, whereas iron- and cobalt-based complexes exhibit good catalytic activity as well as stability [63]. As shown in Figure 11.7, oxygen molecules can interact with the MN4 macrocycle-based catalyst, “end-on” or “side-on” mode, depending on the available coordination sites and energy of d-orbitals of the metal’s center. Moreover, oxygen molecules can interact through the “bridge-cis” and “bridge-trans” configurations, where two metal sites are involved [57]. The binding of oxygen molecules to the catalysts depends on the binding of the d-orbitals in the central metal ion of the macrocycle [64].
Containers and Vessels for Supramolecular Catalysis
Published in Jubaraj Bikash Baruah, Principles and Advances in Supramolecular Catalysis, 2019
The stabilisations of reactive sites by concealing within hydrophobic pockets eventually lead to isolate reactive species. Importantly, the catalytic sites of metalloenzymes causing dioxygen activation involve various steps. The binding of O2 at a reduced metal centre, formation of metal-superoxo or peroxo species and oxygen—oxygen bond cleavage reactions are some such reactions. Studies on model compounds have shown that mononuclear complexes have the ability to form metal-dioxygen (M-O2) complexes which are used for various oxidation reactions. Dioxygen binds to metal ions in different ways, as shown in Figure 3.40. The macrocyclic N-tetramethylated cyclam ligands listed in Figure 3.40 stabilise different metal-oxygen complexes. The ability to stabilise depends on the size and type of metal ion used. Mononuclear complexes with different first-row transition metal ions possess end-on metal-superoxo and side-on metal-peroxo species. The complexes have different binding modes depending on the metal ions and the size of the macrocyclic ring. The macrocyclic ligands stabilise each such species through the control provided by the geometric and electronic requirements available due to the ligands to stabilise a particular species.
Synthesis, spectral, biological, and computational studies of template engineered macrocyclic metal complexes
Published in Journal of Coordination Chemistry, 2022
Jai Kumar, Devender Singh, Arti Jangra, Harish Kumar, Parvin Kumar, Suresh Kumar, Radhika Khanna, Ramesh Kumar
During the last few decades, the synthesis of macrocyclic complexes has drawn the attention of researchers due to their applications in various fields of science, including medical, analytical, and environmental chemistry. In the literature, macrocyclic complexes of Cu2+, Ni2+, and Co2+ have been reported as a potential agent to inhibit the growth of microbes, including bacteria and fungi [1–7]. Moreover, the macrocyclic complexes of the above-said metal ions have been reported to possess antioxidant [8], anticancer [9], nematicidal [10], and pesticidal [11] properties. In addition to that, macrocyclic complexes may be utilized as magnetic resonance imaging (MRI) contrast agents [12, 13]. Prompted by these remarkable properties of macrocyclic complexes of cobalt, nickel, and copper, some novel azamacrocyclic Cu2+, Ni2+, and Co2+ complexes were synthesized, characterized, and screened for their antibacterial and antioxidant activities. Furthermore, the reported complexes were also explored for their molecular docking and ADMET studies. Density functional theory (DFT) studies of all the complexes were also performed to find various quantum parameters.
One-pot synthesis and characterization of Schiff base macrocyclic complexes as a potential bioactive core – a review
Published in Journal of Coordination Chemistry, 2021
J. P. Remiya, T. S. Sikha, B. Shyni
Metal complexes of Schiff base macrocyclic ligands are synthetic models for biologically occurring macrocycles such as metal-containing sites in metalloproteins or enzymes [7]. These discoveries provided the inspiration to design and synthesize macrocyclic compounds to explore the abnormal properties such as spectral, structural, mechanistic, electrochemical, kinetic and thermodynamic aspects of cyclic metal complexes [8]. The ability of macrocyclic ligands to coordinate different metal ions is utilized as therapeutic agents at the intersection of bioinorganic chemistry, anticorrosives in industries and in synthetic organic chemistry. The metal-oxygen, metal-nitrogen and metal-sulfur bonded macrocyclic compounds are effective as stereospecific catalysts for hydrolysis, oxidation, epoxidation, reduction and biocidal activity [9–11]. In monoclonal antibody technology, macrocyclic complexes of radioisotopes are conjugated to proteins, yielding drugs for radioimmunotherapy and other medicinal applications [12–15]. Particular interest has centered upon the use of macrocyclic compounds as luminescent sensors for photodynamic therapy and biomedical diagnostics [16], as dyes and pigments [17] and as magnetic resonance imaging (MRI) contrast agents [18].
Facile one pot synthesis of tetraamide macrocyclic complexes using malonyldihydrazide and p-nitrobenzaldehyde at room temperature
Published in Inorganic and Nano-Metal Chemistry, 2019
N. Tazin, V. D. Ragole, D. S. Wankhede
Macrocyclic chemistry deals with synthesis of macrocyclic ligands, complexes and their applications in various fields of life. Synthesis and characterization of macrocyclic complexes including nitrogen donor macrocyclic ligands is a vastly explored area which includes variety of complexes such as those with polyaza, cyclidenes, porphyrins and bis-macrocyclic ligands.[1] The area of research including synthesis and characterization of tetraamide macrocyclic complexes is special owing to the presence of two possible donor atoms nitrogen and oxygen in amide group.[2] It has been established that macrocyclic complexes including amide groups possess the structural features of both macrocyclic tetraamines and oligopeptides and can stabilize higher oxidation states of the metal ions.[3–4] These observations have prompted us to undertake present study. Hence in present paper, we report facile one pot synthesis of a series of seven tetraamide macrocyclic complexes of first row transition metal ions such as Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) using malonyldihydrazide and p-nitrobenzaldehyde using template method. The complexes are obtained by room temperature stirring of the complex forming components for 10–12 hours. Thus we have successfully avoided the routine and traditional reflux method for synthesis of complexes.