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The Synthesis And Characterisation Of Polymetallic Transition Metal Complexes Towards Single Molecule Magnets
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Book Synopsis The Synthesis and Characterisation of Polymetallic Transition Metal Complexes Towards Single-molecule Magnets by : Kristoffer Graham
Download or read book The Synthesis and Characterisation of Polymetallic Transition Metal Complexes Towards Single-molecule Magnets written by Kristoffer Graham and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The synthesis and characterisation of sixteen new complexes are reported. The use of the ligand edte (((HOCH2CH2)2NCH2CH2N(CH2CH2OH)2)), H4L1) has resulted in five new iron complexes. Two Fe6 complexes and an Fe3 complex display non-zero ground states of S = 5 and S = 3 respectively. An Fe12 complex which displays a unique cluster topology and an Fe2 dimer are also reported, both with a ground state S = 0. A further six new iron clusters are reported using bicine (((HOCH2CH2)2N(CH2COOH)), H3L2). Two homeo-structural Fe6 complexes display spin ground states of S = 5 and S = 4, whereas a mixed-valence Fe6 cluster has a ground state of S = 3 and a large magnetic anisotropy. Further measurements are needed below 1.8 K to confirm any SMM behaviour. In addition an Fe12 cluster with a unique core topology possesses a spin ground state of S = 0. Two remaining Fe6 clusters are still to be magnetically characterised. The final three iron complexes are reported using the ligand tricine (((HOCH2)3CNHCH2COOH)H4L3). Fe9 posesses a ground state S = 11/2. Magnetic characterisation of Fe7 and Fe12 complexes are still needed to determine the spin ground state of these clusters. Two new Cr(III) clusters are reported using bis-tris (((HOCH2)3CN(CH2CH2OH)2), H4L4), the first a simple monomer and the second a Cr4 tetramer characterised with a spin ground state S = 0.
Book Synopsis Synthesis and Characterization of Low Coordinate Transition Metal Complexes by : Aimee M. Bryan
Download or read book Synthesis and Characterization of Low Coordinate Transition Metal Complexes written by Aimee M. Bryan and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation describes the synthesis, characterization, and reactivity studies of new low-coordinate complexes of readily available and inexpensive transition metals such as iron, cobalt and nickel. The compounds were magnetically characterized in detail and tested for single molecule magnet (SMM) behavior. SMMs are a topic of intense research because of their potential applications in magnetic memory, high-density information storage and quantum computing technologies. Low-coordinate compounds display magnetic moments that indicate high orbital angular momentum and are very promising candidates for SMM behavior because they also tend to have large negative zero-field splitting (D) values. The complexes reported here are stabilized by using a variety of amido, aryloxo and thiolato ligands with bulky terphenyl groups and also using aryl and alkyl substituted silylamides. A superconducting quantum interference device (SQUID) and Evans' methods were used to study the magnetic properties and single crystal X-ray crystallography and NMR (1H and 13C) were used to confirm the structures of these compounds in both the solid and solution states. Further characterization studies included UV-visible, near-IR, and IR spectroscopy, melting point, elemental analysis and DFT calculations, where applicable, in order to determine the electronic configurations and bonding schemes. At present there are ca. 100 stable open shell two-coordinate mononuclear transition metal complexes currently known but ca. 20% have a linear coordination at the metal atom with only a few being strictly 180° at their metal center. Very few of these compounds had been magnetically characterized. In Chapter 2, the synthesis and magnetic characterization of the late transition metal Co2+ (d7) and Ni2+ (d8) primary amido complexes Co{N(H)Ar(iPr6)}2, Co{N(H)Ar(Me6)}2, Ni{N(H)Ar(iPr6)}2 and Ni{N(H)Ar(Me6)}2 (Ar(Me6) = C6H3-2,6(C6H2-2,4,6-Me3)2, Ar(iPr6) = C6H3-2,6(C6H2-2,4,6-(i)Pr3)2) are described. The investigations showed that they exhibit interesting magnetic behavior. The bent versus linear geometries of the complexes enable direct observation of the effects of orbital angular momentum quenching upon bending the metal coordination geometry. The electronic configuration of the linear cobalt(II) complexes does not predict first order orbital angular momentum and yet, the magnetic moment of Co{N(H)Ar(iPr6))2 is much higher than the spin only value which suggests a large spin-orbit coupling effects due to mixing of the ground and excited states. In Chapter 3, the synthesis and characterization of the mononuclear chromium, iron, cobalt and nickel terphenyl substituted thiolate complexes Cr(SAr(Me6))2, Cr(SAr(iPr4))2, Fe(SAr(iPr4))2, Co(SAr(iPr4))2 and Ni(SAr(iPr4))2 are described. Their structures show bent coordination geometries of varying degree with strong secondary M-[eta]6 and M-C(ipso) flanking aryl ring interactions of ca. 2.153 [Angstrom] for Fe(SAr(iPr4))2, ca. 1.625 [Angstrom] for Co(SAr(iPr4))2 and ca. 1.731 [Angstrom] for Ni(SAr(iPr4))2. This observation is in sharp contrast to the almost linear coordination observed for the derivatives of the related but more crowded terphenyl thiolate ligand, SAr(iPr6), in M(SAr(iPr6))2 complexes where M = Cr, Fe, Co and Ni and the strictly linear geometry observed for the terphenyloxo analogs M(OAr(iPr4))2 where M = Fe and Co. Magnetic moments for these species are, in general, lower than the spin-only values. Expect for chromium, this is an unexpected observation for late transition metal low-coordinate complexes. The suppression of magnetic moments is most like due to the strong M-arene interactions which effectively increases the coordination number at the metal atom. These results demonstrate the important role that substituents play on the flanking rings of the terphenyl ligands and begs further investigations involving the role of dispersion in the isolation of low coordination mononuclear transition metal complexes. The divalent silylamides M{N(SiMe3)2}2 (M = Mn, Fe, and Co) are key synthons for low-coordinate transition-metal derivatives. In Chapter 4, the previously reported, but incorrectly characterized cobalt(II) silylamide, [Co{N(SiMe3)2}2]2 has been spectroscopically and magnetically characterized for the first time. In addition, the new Lewis base complexes [Co{N(SiMe3)2}2(PMe3)], and [Co{N(SiMe3)2}2(THF)], as well as a previously reported complex [Co{N(SiMe3)2}2(py)] were isolated and characterized. Magnetic studies showed that they had considerably larger magnetic moments than the spin-only value of 3.87 [mu](B), which is indicative of a significant zero-field splitting and g-tensor anisotropy. In addition to their interesting magnetic behavior and unexpectedly large D values in the range of -20 to -80 cm−1. The electronic spectrum of [Co{N(SiMe3)2}2]2 in solution showed that earlier characterization spectra of "Co{N(SiMe3)2}2" match that of the bright green THF adduct and not the dark brown cobalt dimer [Co{N(SiMe3)2}2]2. In Chapter 5, it is shown that the reaction of the versatile cobalt(II) amide, [Co{N(SiMe3)2}2]2, with four equivalents of the sterically crowded terphenyl phenols, HOAr(Me6) and HOAr(iPr4) (Ar(iPr4) = C6H3-2,6(C6H3-2,6-(i)Pr2)2) produced the first well-characterized, monomeric two-coordinate cobalt(II) bisaryloxides, Co{OAr(Me6))2 and Co(OAr(iPr4))2. Not only are these very rare examples of two-coordinate transition metal(II) aryloxides, but the magnetic moments of both the linear and the bent species were well in excess of the spin only value for cobalt(II) ion. It was demonstrated that careful manipulation of the synthetic conditions for Co(OAr(iPr4))2 could produce varying occupancies of the cobalt(II) site and that after weighting the magnetic susceptibilities of the compounds accordingly, the moments were shown to be in close agreement with each other. Chapter 6 reports the synthesis of the unstable nickel(II) bis(silylamide) complex Ni{N(SiMe3)2}2 via the reaction of NiI2 and two equivalents of NaN(SiMe3)2 in tetrahydrofuran, as well as two of its Lewis base adducts, Ni{N(SiMe3)2}2(THF) and Ni{N(SiMe3)2}2(py)2. The reaction of two equivalents of LiN(SiMe3)2 with NiCl2(DME) in tetrahydrofuran afforded the reduced homoleptic tetrameric nickel(I) amide complex, [Ni{N(SiMe3)2}]4. This unique polymetallic structure having a Ni4N4 planar array has four S = 1/2 nickel (I) ions and an antiferromagnetic exchange coupling constant of J = -102(2) cm−1. This study provides strong evidence that the formation of nickel(II) and nickel(I) amido complexes is possible without the use of sterically demanding ligand sets.
Book Synopsis Directed Assembly of Single-Molecule and Single-Chain Magnets by : Thomas Harris
Download or read book Directed Assembly of Single-Molecule and Single-Chain Magnets written by Thomas Harris and published by . This book was released on 2010 with total page 390 pages. Available in PDF, EPUB and Kindle. Book excerpt: The work herein describes the design, synthesis, and characterization of magnetic molecules and chain compounds, with an emphasis on probing slow magnetic relaxation. Chapter 1 presents an extensive survey of the literature of cyano-bridged single-molecule and single-chain magnets, focusing on a building block approach wherein simple cyanometalate precursor complexes direct the assembly of larger architectures. Specific synthetic strategies to obtain multinuclear clusters and chain compounds of desired structure and magnetic properties are outlined in detail. Finally, perspectives on the future directions in the field are presented. Chapter 2 exemplifies the utility of the building block approach in generating high-nuclearity cyano-bridged clusters. It describes the design and synthesis of the facially-capped tricyanide building unit, [TpCr(CN)3]-, as its incorporation into the face-centered cubic cluster [Tp8(H2O)6Cu6Cr8(CN)24]4+. Ferromagnetic exchange between CrIII and CuII ions gives rise to an S = 15 spin ground state, one of the highest yet observed for a cyano-bridged cluster. In addition, the formation of this cluster is accompanied by a linkage isomerism of 12 of the 24 cyanide ligands, providing the first example of a molecule undergoing partial cyanide isomerism. Chapter 3 presents a survey of actinide-containing molecules that have demonstrated evidence of magnetic exchange coupling. The strong magnetic anisotropy characteristic of these elements marks them as promising candidates for single-molecule magnets, however the spin-orbit coupling that gives rise to this anisotropy also complicates analysis of exchange interactions. Current methods for extracting coupling information in these systems are outlined in detail. In addition, molecules that bear exchange-coupled centers but as of yet have not been thoroughly characterized are presented. Chapter 4 describes a detailed investigation of a series of iron(II) pyrrolide complexes of formulae [(tpaR)Fe]-, representing the first examples of transition metal-based mononuclear single-molecule magnets. Static magnetic measurements and high-field EPR spectroscopy reveal the presence of exceptionally strong uniaxial anisotropy in the complexes. Moreover, dynamic magnetic measurements carried out in a small dc field demonstrate that this anisotropy leads to slow relaxation in the complexes. In addition, this relaxation dynamics is probed through Mössbauer spectroscopy, which reveals that the phenomenon occurs in zero applied field in at least two complexes. Chapter 5 describes the synthesis and characterization of a series of cyano-bridged single-chain magnets. Reaction of the S = 3/2, high-anisotropy building unit [ReCl4(CN)2]2- with [M(DMF)6]2+ (M = Mn, Fe, Co, Ni) is shown to direct the formation of the chain compounds (DMF)4MReCl4(CN)2. Dc susceptibility measurements uncover the presence of intrachain antiferromagnetic (Mn) and ferromagnetic (Fe, Co, Ni) exchange. Most importantly, ac susceptibility measurements reveal that all of the chain compounds exhibit slow magnetic relaxation at low temperature. Notably, the Fe congener displays significant magnetic hysteresis at low temperatures, thus demonstrating classical magnet-like behavior in a one-dimensional system. Chapter 6 describes the synthesis the incorporation of [ReCl4(CN)2]2- into the zig-zag chain compound (Bu4N)[TpCuReCl4(CN)2], which is found to demonstrate the strongest ferromagnetic exchange yet observed through cyanide. The strong coupling arises from judicious selection of ReIV and CuII ions, whose molecular orbitals interact through the cyanide bridge such that orbital overlap is minimized. Moreover, the compound is shown to display metamagnetic behavior, and the complete magnetic phase diagram is elucidated through a combination of experimental and theoretical analysis. Finally, the anisotropy tensors of the ReIV centers are shown to cancel, leading to a small effective chain anisotropy and thus the absence of single-chain magnet behavior. Chapter 7 concludes this work by demonstrating that [ReCl4(CN)2]2- can also be employed in the assembly of molecular magnets, as it presents the synthesis and characterization of two linear trinuclear clusters of formulae [(PY5Me2)2M2ReCl4(CN)2]2+ (M = Mn, Ni; PY5Me2 = 2,6-bis(1,1-bis(2-pyridyl)ethyl)-pyridine). Dc susceptibility measurements reveal the presence of antiferromagnetic exchange in the Mn congener, while ferromagnetic exchange is observed in the Ni analogue. In addition, dc magnetization experiments show the presence of axial magnetic anisotropy in both clusters.
Book Synopsis Synthesis and Characterization of Transition Metal Complexes with Bulky Tin Ligands for Application in Small Molecule Activation by : Veeranna Yempally
Download or read book Synthesis and Characterization of Transition Metal Complexes with Bulky Tin Ligands for Application in Small Molecule Activation written by Veeranna Yempally and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The role of bulky tin ligands in the stabilization of transition metal complexes with electronic unsaturation has been studied to understand the mode of binding of small molecules at an unsaturated metal center. We were able to isolate electronically unsaturated Pt-Sn bimetallic complexes effective in the reversible activation of small molecules including CO, H2, C2H4, and NH3 at room temperature. We have examined the effect of the modification of ligands in Pt-Sn bimetallic complexes for the activation of small molecules and have observed that the Pt(SnBut3)2(CNBut)2 bimetallic complex reversibly activates hydrogen at room temperature both in the solid state and in solution. Similarly, we have also prepared bimetallic Pt-Sn complexes with an NHC carbine ligand which were also shown to activate hydrogen and alkenes reversibly. A bimetallic Fe-Sn cluster complex, Fe2 ([mu]-SnBut2)2(CO)8, was synthesized from the reaction of But3SnH with the Fe2(CO)9 and shown to be selective at activating the benzylic C-H bond of alkylaromatic solvent molecules. The new complexes containing tin have been characterized spectroscopically to gain an insight into the reaction mechanism involved in small molecule activation.
Book Synopsis Synthesis and Characterisation of Some Transition Metal Complexes with Poly-yne Ligands by : Peiyi Li
Download or read book Synthesis and Characterisation of Some Transition Metal Complexes with Poly-yne Ligands written by Peiyi Li and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Synthesis, Characterization and Magnetic Properties of Transition Metal Clusters by : Marisol Ledezma Gairaud
Download or read book Synthesis, Characterization and Magnetic Properties of Transition Metal Clusters written by Marisol Ledezma Gairaud and published by . This book was released on 2001 with total page 286 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Synthesis, Characterization and Reactivity Studies of Low-coordinate Late Transition Metal Complexes and the Preparation and Characterization of a Low-coordinate Samarium Complex by : Pei Zhao
Download or read book Synthesis, Characterization and Reactivity Studies of Low-coordinate Late Transition Metal Complexes and the Preparation and Characterization of a Low-coordinate Samarium Complex written by Pei Zhao and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation focuses on the synthesis, characterization and reactivity study of terphenyl ligand stabilized bis([mu]-oxo) dimeric iron and cobalt complexes. The synthesis and characterization of low-coordinate cobalt alkyl and iron alkyl complexes are also described. In addition, it describes the preparation of the first monomeric homoleptic solvent-free bis(aryloxide) lanthanide complex. The solid state structures of new compounds were determined by single crystal X-ray crystallography. Magnetic properties of paramagnetic compounds were measured by superconducting quantum interference device (SQUID) or Evans' methods for solid state or solution phase, respectively. The new compounds were also characterized by UV-Visible spectroscopy. Furthermore, infrared spectroscopy, Mössbauer spectroscopy, electron paramagnetic resonance spectroscopy, mass spectrometry, cyclic voltammetry and elemental analysis were employed to characterize some of the compounds when applicable. In some cases, DFT calculations were applied to elucidate the bonding and energy levels of molecular orbitals in the complexes. In Chapter 2, The bis([mu]-oxo) dimeric complexes {Ar[superscript iPr8]OM([mu]-O)}2 (Ar [superscript iPr8] = -C6H-2,6-(C6H2-2,4,6-[superscript i]Pr3)2-3,5-[superscript i]Pr2; M = Fe or Co) were prepared by oxidation of the metal (I) half-sandwich complexes {Ar[superscript iPr8]M([eta]6-arene)} (arene = benzene or toluene; M = Fe or Co). The iron species {Ar[superscript iPr8]OFe([mu]-O)}2 was prepared by reacting {Ar[superscript iPr8]Fe([eta]6-benzene)} with N2O or O2 and the cobalt species {Ar[superscript iPr8]OCo([mu]-O)}2 was prepared by reacting {Ar[superscript iPr8]Co([eta]6-toluene)} with O2. Both {Ar[superscript iPr8]OFe([mu]-O)}2 and {Ar[superscript iPr8]OCo([mu]-O)}2 were characterized by X-ray crystallography, UV-vis spectroscopy, magnetic measurements and, in the case of the iron species, by Mössbauer spectroscopy. The solid-state structures of both compounds reveal unique M2([mu]-O)2 (M = Fe or Co) cores with formally three-coordinate metal ions. The Fe···Fe separation in {Ar[superscript iPr8]OFe([mu]-O)}2 bears a resemblance to that in the Fe2([mu]-O)2 diamond core proposed for the methane monooxygenase intermediate Q. The structural differences between {Ar[superscript iPr8]OFe([mu]-O)}2 and {Ar[superscript iPr8]OCo([mu]-O)}2 are reflected in rather differing magnetic behavior. Compound {Ar[superscript iPr8]OCo([mu]-O)}2 is thermally unstable and its decomposition at room temperature resulted in the oxidation of the Ar[superscript iPr8] ligand via oxygen insertion and addition to the central aryl ring of the terphenyl ligand to produce the 5,5'-peroxy-bis[4,6-[superscript i]Pr2-3,7-bis(2,4,6-iPr3-phenyl)oxepin-2(5H)-one]. The structure of the oxidized terphenyl species is closely related to that of a key intermediate proposed for the oxidation of benzene. In Chapter 3, the homoleptic, cobalt(I) alkyl [Co{C(SiMe2Ph)3}]2 was prepared by reacting CoCl2 with [Li{C(SiMe2Ph)3}(THF)] in a 1:2 ratio though the initial intent was to synthesize a dialkyl cobalt (II) complex. Attempts to synthesize the corresponding iron(I) species led to the iron(II) salt [Li(THF)4][Fe2([mu]-Cl)3{C(SiMe2Ph)3}2]. Both complexes were characterized by X-ray crystallography, UV-vis spectroscopy, and magnetic measurements. The structure of [Co{C(SiMe2Ph)3}]2 consists of dimeric units in which each cobalt(I) ion is [sigma]-bonded to the central carbon of the alkyl group -C(SiMe2Ph)3 and [pi]-bonded to one of the phenyl rings of the -C(SiMe2Ph)3 ligand attached to the other cobalt(I) ion in the dimer. The structure of [Li(THF)4][Fe2([mu]-Cl)3{C(SiMe2Ph)3}2] features three chlorides bridging two iron(II) ions. Each iron (II) ion is also [sigma]-bonded to the central carbon of a terminal -C(SiMe2Ph)3 anionic ligand. The magnetic properties of [Co{C(SiMe2Ph)3}]2 reveal the presence of two independent cobalt (I) ions with S = 1 and a significant zero-field splitting of D = 38.0(2) cm−1. The magnetic properties of [Li(THF)4][Fe2([mu]-Cl)3{C(SiMe2Ph)3}2] reveal extensive antiferromagnetic exchange coupling with J = -149(4) cm−1 and a large second-order Zeeman contribution to its molar magnetic susceptibility. Formation of the alkyl [Co{C(SiMe2Ph)3}]2 and the halide complex [Li(THF)4][Fe2([mu]-Cl)3{C(SiMe2Ph)3}2] under similar conditions is probably due to the fact that Co(II) is more readily reduced than Fe(II). Some other synthetic routes were also attempted to synthesize a dialkyl cobalt (II) complex and they are described in this chapter. Neither [Co(NPh2)2]2 nor cobaltocene reacts with [Li{C(SiMe2Ph)3}(THF)] to afford a dialkyl cobalt (II) complex. Metathesis reactions of cobalt halides with lithium salts of alkyl ligand HCPh2R (R = -Ph or -SiMe3) resulted in the reduction of cobalt (II) to cobalt metal and the coupling of ligands, which indicate that homolytic cleavage of the cobalt-carbon bond was probably involved in the metathesis reactions. Furthermore, in chapter 4, reaction of Sm[N(SiMe3)2]2(THF)2 with two equivalents of bulky aryloxide ligand HOAr[superscript iPr6] (Ar[superscript iPr6] = -C6H3-2,6-(C6H2-2,4,6-[superscript i]Pr3)2) afforded the first monomeric homoleptic solvent-free bis(aryloxide) lanthanide complex Sm(OAr[superscript iPr6])2. The complex was characterized by crystallography, UV-Visible spectrum, IR and magnetically by the Evans' method. The O-Sm-O angle is bent at 111.08(9)̊. The samarium ion in Sm(OAr[superscript iPr6])2 also shows weak interactions with the flanking aryl rings of the terphenyloxide ligands. The complex is paramagnetic at room temperature with magnetic moment of 3.51 [mu]B.
Book Synopsis Synthesis and Characterization of Transition Metal Clusters by : Allan George Hee
Download or read book Synthesis and Characterization of Transition Metal Clusters written by Allan George Hee and published by . This book was released on 2004 with total page 562 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Polynuclear Transition Metal Complexes and Single-molecule Magnets by : Ziming Sun
Download or read book Polynuclear Transition Metal Complexes and Single-molecule Magnets written by Ziming Sun and published by . This book was released on 1998 with total page 1058 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Synthesis, Characterization, and Reactivity of Transition Metal Complexes Containing Multi-donor Ligands by : John C. Linehan
Download or read book Synthesis, Characterization, and Reactivity of Transition Metal Complexes Containing Multi-donor Ligands written by John C. Linehan and published by . This book was released on 1986 with total page 514 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Synthesis, Characterization, and Reactivity of Transition Metal Complexes Supported by Heteropolydentate Ligation by : Adam Ruddy
Download or read book Synthesis, Characterization, and Reactivity of Transition Metal Complexes Supported by Heteropolydentate Ligation written by Adam Ruddy and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Design, Synthesis and Characterization of Metal Complexes of D⁶ and D⁰ Electronic Configuration and Their Inorganic-Organic Hybrids by : Chi-Ming Frankie Leung
Download or read book Design, Synthesis and Characterization of Metal Complexes of D⁶ and D⁰ Electronic Configuration and Their Inorganic-Organic Hybrids written by Chi-Ming Frankie Leung and published by . This book was released on 2017-01-26 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Design, Synthesis and Characterization of Metal Complexes of D⁶ and D⁰ Electronic Configuration and Their Inorganic-organic Hybrids: From Covalent Conjugation to Supramolecular Assembly and Luninescence Chemosensing" by Chi-ming, Frankie, Leung, 梁志明, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled DESIGN, SYNTHESIS AND CHARACTERIZATION OF METAL COMPLEXES 6 10 OF d AND d ELECTRONIC CONFIGURATION AND THEIR INORGANIC-ORGANIC HYBRIDS - FROM COVALENT CONJUGATION TO SUPRAMOLECULAR ASSEMBLY AND LUMINESCENCE CHEMOSENSING Submitted by LEUNG CHI MING, FRANKIE for the Degree of Doctor of Philosophy at The University of Hong Kong in January 2015 6 10 Various classes of transition metal complexes with d and d electronic configuration and their inorganic-organic hybrids have been prepared and employed for molecular recognition studies. A series of crown ether-based bis-alkynyl-bridged gold(I) complexes have been designed, synthesized and characterized. The alkali metal cation-binding properties of the complexes have been studied by UV-vis, emission, H NMR and ESI-mass spectroscopy. The binding of K has switched "on" or "off" the emission associated with intramolecular aurophilic interaction of the complexes upon formation of the ion-bound adducts in a sandwich fashion. Various spacers between the two crown ether units were found to affect the binding affinities. In addition, a tetranuclear alkynylgold(I) complex with four amide groups has been successfully synthesized and characterized. The photoluminescence of the complex has been switched on upon the binding of cadmium ion due to the suppression of photo-induced electron transfer (PET) and rigidification of the molecule. The binding mode has been studied by 2D NOESY H NMR experiments. By combining the advantages of supramolecular chemistry and nanotechnology, the conjugation of transition metal complexes to gold nanoparticles (GNPs) has been studied. A number of lipoic acid-containing ruthenium(II) and rhenium(I) bipyridine complexes have been synthesized and characterized. Covalent functionalization of GNPs with these complexes has resulted in interesting supramolecular assemblies with Forster resonance energy transfer (FRET) properties that could be modulated via esterase hydrolysis. The enzymatic activity has been determined by Michaelis-Menten kinetics. The quenching mechanism has also been studied by transient absorption and time-resolved emission decay measurements. Besides, a number of adamantane-containing Ru(II) and Re(I) complexes have been synthesized and characterized. These complexes were non-covalently functionalized with the β-cyclodextrin capped gold nanoparticles (β-CD-GNPs) through the host-guest interaction between cyclodextrin and adamantine, which were characterized by using 2D ROESY H NMR experiments. The FRET properties of the conjugates could be modulated via both esterase hydrolysis and competitive displacement of steroid. The FRET efficiencies were found to vary with the nature of the chromophores and the length of the spacer between the transition metal complexes and the GNPs. In addition, the conjugation of transition metal complexes to various anisotropic nano-materials has also been studied. A bis-adamantane-containing Re(I) complex has been synthesized and characterized. The complex was found to induce the "end-to-end" assembly of cyclodextrin-end-modified gold nanorods (β-CD-GNRs) of different aspect ratios, which have been characterized by transmiss
Book Synopsis Polynuclear Transition Metal Complexes Containing Azido and Pyrazolinato Bridging Ligands by : Stephanos Organtzis
Download or read book Polynuclear Transition Metal Complexes Containing Azido and Pyrazolinato Bridging Ligands written by Stephanos Organtzis and published by . This book was released on 2008 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Metal-Pyrrolide Complexes in Three-fold Symmetry by : William Hill Harman
Download or read book Metal-Pyrrolide Complexes in Three-fold Symmetry written by William Hill Harman and published by . This book was released on 2010 with total page 414 pages. Available in PDF, EPUB and Kindle. Book excerpt: Given the prominence of six-coordinate pseudo-octahedral complexes in transition metal chemistry, lower coordinate complexes in tetrahedral, trigonal pyramidal and trigonal bipyramidal configurations have garnered increased interest due to the changes in electronic structure and reactivity resultant from three-fold symmetry relative to the four-fold symmetry commonly observed in their pseudo-octahedral counterparts. Herein, we report a range of such effects in a collection of transition metal complexes supported by chelating, trianionic trispyrrolide ligands [tpaR]3-. In chapter one, two trigonal pyramidal iron(II) complexes, [(tpaPh)Fe]- and [(tpaMes)Fe]-, are discussed which are capable of undergoing oxygen atom transfer reactions and subsequent activation of strong C-H bonds. Additionally, the mesityl derivative is capable of oxygen atom transfer from nitrous oxide, an attractive but notoriously unreactive molecule. In chapter two, this family of iron(II) complexes is expanded to include tert-butyl, 2,4,6-triisopropylphenyl and 2,6-difluorophenyl substituted variants, and the magnetic properties of this homologous series of trigonal pyramidal iron(II) complexes are explored. Notably, a number of these complexes exhibit frequency dependent signals at low temperature in the imaginary component of ac magnetic susceptibility measurements performed in the presence of a small applied field. Further exploration of this behavior via magnetometry, high-field EPR and Mössbauer spectroscopy reveal a large barrier to magnetic relaxation in these complexes, in some cases comparable to the best known single molecule magnets. This phenomenon is accounted for by the unquenched orbital angular momentum present in a three-fold symmetric high spin d6 system, leading to significant uniaxial anisotropy and a barrier to spin inversion. Progress towards a magneto-structural analysis of this behavior is made for this series. Chapter three contains a through treatment of the coordination, redox and group transfer chemistry of the iron(II) platform [(tpaMes)Fe]-. In particular, it is shown that this complex is capable of supporting both high and low spin five coordinate adducts, including a rare example of a paramagnetic carbonyl complex of iron(II), [(tpaMes)Fe(CO)]-. Furthermore, the redox chemistry of this system is illustrated in the synthesis of the neutral iron(III) complex (tpaMes)Fe(i-PrNH2). As an extensiont to the oxygen atom chemistry presented in chapter one, nitrene group transfer to [(tpaMes)Fe]- is described, resulting in the synthesis of an iron(III) amido complex. The identity of this species is confirmed by high resolution electrospray mass spectrometry as well as Mössbauer, x-ray absorption and EPR spectroscopies. In chapter four, the vanadium chemistry of [tpaR]3- is introduced. In particular, the vanadium(III) complex (tpaMes)V(THF) is show to react with an aryl azide to yield an isolable vanadium(V) diazenylimido species, a member of a very rare structural type. This complex is shown to decompose unimolecularly by dinitrogen loss to generate the cooresponding vanadium(V) imido. In addition to the vanadium-nitrogen multiple bond chemistry described, the synthesis two pseudo-three-fold symmetric vanadium(IV) oxo species is discussed. Single crystal x-ray structures of both complexes reveal a distorted coordination geometry and a short vanadium-oxo distance, consistent with a triple bond. The oxidation of both of these complexes to the corresponding vanadium(V) oxo is performed and shown by x-ray crystallography to result in the relief of the distortion observed in the vanadium(IV) oxo complexes. Taken together, these results shed light on the nature of metal ligand multiple bonding in three-fold symmetric geometries. Chapter five discusses the chromium complexes of [tpaMes]3-, in particular the group transfer and redox chemistry of the system. Both chromium(II) and chromium(III) complexes are available by direct metallation, and the chromium(II) complex [(tpaMes)Cr(DME)]- is shown to undergo both oxygen atom and nitrene group transfer reactions to yield chromium(IV) oxo and imido complexes respectively. The chromium(IV) imido complex exhibits rich redox chemistry, and its oxidation to the isostructural chromium(V) and chromium(VI) complexes are demonstrated.
Book Synopsis Synthesis and Characterization of Transition Metal Complexes by : Milan M. Milutinović
Download or read book Synthesis and Characterization of Transition Metal Complexes written by Milan M. Milutinović and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Transition metals and their complexes have an important impact on chemistry and are found in many application in life in general. Ruthenium and rhodium are two members of noble metals and proved to be suitable for anticancer activity. With the aim of changing the coordination environment in ruthenium and rhodium complexes, this thesis presents a series of Ru(II) polypyridyl and Rh(III) pincer-type complexes. All new Ru(II) and Rh(III) complexes were characterized by NMR spectroscopy, ESI-MS spectrometry and UV-Vis spectrophotometry . For some of the complexes a single crystal X-ray crystallography was performed. The substitution reactions of Ru(II) and Rh(III) complexes with mononucleotides, oligonucleotides and amino acids were studied quantitatively by UV-Vis spectroscopy. Measurements of the activation enthalpies and entropies for all synthesized complexes are supporting an associative mechanism for the substitution process. NMR spectroscopy studies were performed on some Ru(II) complexes where after the hydrolyses of the metal-Cl bond the complexes are capable to interact with guanine derivatives forming monofunctional adducts via N7 atom. The interactions of Ru(II) and Rh(III) complexes with fully complementary 15-mer and 22-mer duplexes of DNA and fully complementary 13-mer duplexes of RNA were studied by UV-Vis spectroscopy. The interactions of ruthenium(II) and rhodium(III) complexes with calf thymus and herring testes DNA were examined by absorption using UV-Vis spectroscopy, fluorescence emission spectral studies by ethidium bromide displacement studies and viscosity measurements. ; eng
Book Synopsis Linear Two-coordinate Transition Metal Complexes − Synthesis, Characterization, Spectroscopy, Magnetism and Reactivity by : Chun-Yi Lin
Download or read book Linear Two-coordinate Transition Metal Complexes − Synthesis, Characterization, Spectroscopy, Magnetism and Reactivity written by Chun-Yi Lin and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation primarily focuses on the synthesis, characterization and reactivity studies of a series of linear two-coordinate, late transition metal complexes. Except Chapter 1, all the chapters were published as peer-reviewed articles in academic journals. Chapter 1 consists of two parts: the first part provides a brief introduction and review on the current state of the field for two-coordinate, open-shell transition metal complexes. Chapter 2 details the synthesis, spectroscopic characterization of three strictly linearly coordinated Fe, Co and Ni complexes of formula M{N(SiMee3)Dipp}2. It was found from dispersion-corrected DFT calculations that attractive dispersion forces played an important role in stabilizing these species with unusual geometries. SQUID magnetic measurement showed that both Fe{N(SiMe3)Dipp}2 and Co{N(SiMe3)Dipp}2 have high magnetic moments compared to their spin-only value, which is due to the unquenched orbital angular momentum (OAM) contribution. Several collaborating efforts that resulted in a number of different publications are also included. Slow magnetic relaxation studies on Fe{N(SiMe3)Dipp}2 revealed a spin reversal barrier (U[subscript eff]) of 181 cm−1, a second highest value to date (June 2017) for a mononuclear transition metal complex. 57Fe Mößbauer spectroscopy showed a record high internal field of 162 T created by the unquenched OAM, which is the highest internal field reported so far for any Fe containing compound. Chapter 3 gives details of the reduction of M{N(SiMe3)Dipp}2 (M = Fe, Co, Ni). It was found that these species can be reduced to their +1 oxidation state and at the same time, remain two-coordinate at the metal center. These complexes, with formula of [K(18-crown-6)][M{N(SiMe3)Dipp}2], formed a rare series of the two-coordinate M(I) complexes. SQUID magnetic measurement showed that Fe and Co species had a high magnetic moment compared to their spin-only value, which is again due to the unquenched orbital angular momentum. In a similar fashion, chapter 4 reports the reduction of the first two-coordinate transition metal complexes, Mn{C(SiMe3)3}2, which was originally reported by Eaborn and coworkers in 1985. Mn{C(SiMe3)3}2 was reduced with KC8 in the presence of two different alkali metal ion complexing agents, 18-crown-6 and 15-crown-5. It was found that although the anion remained two-coordinate, the geometries differ due to the shallow potential well for the C−Mn−C coordination. In addition, although they have near-linear manganese coordination but the orbital magnetism is almost completely quenched as a result of 4s−3d[subscript z]2 orbital mixing which affords a non-degenerate ground state. Chapter 5 presents a serendipitous finding during our course of investigating the magnetic properties of three-coordinate transition metal complexes, M{N(SiMe3)Dipp}2(L) (M = Fe, Co, Ni; L = Lewis base), we found that the complexation of the Lewis bases are reversible. Using electronic and NMR spectroscopy, we were able to determine the binding constants of THF, THT (tetrahydrothiophene), pyridine, DMAP (4-dimethylaminopyridine), PMe3, PCy3 and IMes (1,3-bis(1,3,5-trimethylphenyl)imidazol-2-ylidene) to M{N(SiMe3)Dipp}2 and the binding strengths was found to be in the order of DMAP > pyridine > PMe3 > PCy3 ≈ IMes > THF > THT and those of the respective metals was in the order of Fe > Co > Ni. Finally, Chapter 6 is a Review that stems from our interest in two-coordinate transition metal complexes of +1 oxidation state. In particular, although Ni(I) complexes are far less numerous than complexes of its neighboring oxidation states (Ni(0) and Ni(II)), they have many applications that include small molecule activation, catalysis and magnetism.
Book Synopsis Synthesis and Characterisation of Transition Metal Complexes of Functional Dithiolene Ligands by : Tarnjeet Singh Bhachu
Download or read book Synthesis and Characterisation of Transition Metal Complexes of Functional Dithiolene Ligands written by Tarnjeet Singh Bhachu and published by . This book was released on 2006 with total page 552 pages. Available in PDF, EPUB and Kindle. Book excerpt:
