Thesis (Ph. D.)--Florida State University, 2004. / Advisor: Dr. Naresh Dalal, Florida State University, College of Arts and Sciences, Dept. of Chemistry and Biochemistry. Title and description from dissertation home page (Jan. 18, 2005). Includes bibliographical references.

Anhydrous monophenylphosphinates of manganese(II), Mn[H(C₆H₅)PO₂]₂ (Form I, Form II and Form 1(B)) and cadmium(II), Cd[H(C₆H₅)PO₂]₂ (Form I and Form II) were synthesized and characterized by solubility tests, Differential Scanning Calorimetry (DSC), Infrared Spectroscopy, X-ray Powder Diffractometry, Electron Spin Resonance (ESR) spectroscopy, magnetic susceptibility measurements and Electron Spectroscopy for Chemical Analysis (ESCA). These materials are considered to be polymeric with metal ions connected in chains by double bridging phosphinate groups with cross-linkage forming sheets and octahedral metal centers. Magnetic susceptibility studies showed that Mn[H(C₆H₅)PO₂]₂ (Form I) exhibits relatively strong antiferromagnetic exchange interactions (J is about -4.50 cm⁻¹) and the effects on this magnetic exchange of doping diamagnetic cadmium ions into the material have been investigated. A series of mixed metal phosphinates of the form Mn₁₋x Cdx [H(C₆H₅)PO₂]₂ (Form I) where x=0 to 1.00 were prepared and investigated. The effect of doping with cadmium is to break the infinite manganese(II) monophenylphosphinate chain into finite segments and to generate monomer impurities in odd numbered segments. As the extent of doping is increased the average chain length decreases and the fraction of monomer increases. In addition, the exchange coupling constant, J, was found to decrease (from -4.50 to -2.70 cm⁻¹) as the average chain length decreases. Mn[H(C₆H₅)PO₂]₂ (Form 1(B)), which is precipitated from concentrated solutions, contains much shorter chain fragments than the pure Form I material. Mn[H(C₆H₅)PO₂]₂ (Form II) has a distinct infrared spectrum and X-ray powder diffraction pattern and shows much weaker antiferromagnetic behavior (J is about -2.40 cm⁻¹) than the Form I compound. Magnetic studies suggest that in this compound the average chain length is significantly smaller than in Mn[H(C₆H₅)PO₂]₂ (Form I). The hydrated monophenylphosphinates of manganese(II), Mn[H(C₆H₅)PO₂]₂•H₂0 and Mn[H(C₆H₅)PO₂]₂•2H₂0, were synthesized and characterized in this work. The structures of these compounds are considered to be similar to those of the anhydrous materials except in the hydrated compounds one or two of the metal coordination sites are occupied by water molecules. The dihydrate shows only very weak antiferromagnetic properties (J is about -0.50 cm⁻¹). The diphenylphosphinates of manganese(II) and cadmium(II) were also prepared and characterized. The infrared spectra and X-ray powder diffraction patterns for these materials are distinct from each other,which indicates the compounds are not isomorphous. Only rather weak magnetic exchange was observed in the manganese compound. Zn[H(C₆H₅)PO₂]₂ has also been synthesized and partially characterized in this work. The infrared spectrum and X-ray powder diffraction pattern obtained for this compound are unique among all the metal phosphinates studied in this work. / Science, Faculty of / Chemistry, Department of / Graduate

No description available.

In this work magnetic properties of copper(II) complexes on N-(hydroxyalkyl) pyrrole-2-aldimines were investigated by various techniques, one of which was magnetic susceptibility. Magnetic moments are not directly determined experimentally, but magnetic susceptibilities are.

Part I. The syntheses of a series of stable ferrocenylsilane compounds and their corresponding polyradical cations are reported. Electron spin properties of these molecules were investigated by cyclic voltammetry, ESR, and magnetic susceptibility measurements. All the compounds presented, showed significant electronic communication (>100 mV) between the redox centers by CV. Part II. Baeyer-Villiger oxidation of (1,9-dimethyl-PCU-8,11-dione) was performed using m-chloroperoxybenzoic acid in 1:2 molar ratios. The product obtained was the corresponding dilactone 113. The structure of the reaction products was established unequivocally via single crystal X-ray diffraction methods. The reaction of the 1,9-dimethyl-PCU-8,11-dione with 1:1 molar ratio of m-chloroperoxybenzoic acid produced again the dilactone 113, and not the expected monolactone 114. Ceric ammonium nitrate (CAN) promoted oxidation reaction of 1,9-dimethyl-PCU-8,11-dione afforded a mixture of dimethylated lactones, which indicated unique reaction mechanism pathways. These individual isomers, 115 and 116, have been isolated from these mixtures via column chromatography by using silica gel as adsorbent followed by fractional recrystallization of individual chromatography fractions. Structures of these pure products have been established unequivocally by application of single crystal X-ray crystallographic methods.

Significant advances in the design, synthesis, and chemistry of verdazyl radicals have been made, including (i) the systematic study of the electrochemistry of verdazyl radicals, (ii) the development of formazans as ancillary ligands en route to inorganic verdazyl radicals, and (iii) magnetostructural studies of verdazyl diradicals and copper (II) verdazyl complexes. The electrochemical properties of a family of verdazyl radicals were explored. Type I and type II verdazyl radicals were reversibly oxidized and reduced, and the potentials of such processes observed to be sensitive to substituent effects. The incorporation of electron-withdrawing substituents made verdazyl radicals harder to oxidize and easier to reduce, while the presence of electron-donating groups had the opposite effect. Type II verdazyls were harder to oxidize and less delocalized (based on relative cell potentials) than type I analogues. The difficulty in oxidation of type II verdazyls relates to the electron-withdrawing nature of the carbonyl functionality, while the decreased delocalization relates to twisting of the N-substituents. Twisting of the N-substituents was confirmed through the use of X-ray crystal structures, and DFT calculations were used to illustrate the decrease in delocalization of the unpaired electron associated with the twisting. The similarities of formazans to -diketiminate ligands prompted the study of their coordination chemistry. Boratatetrazines, the first main group complexes of formazans illustrated their ability to mimick beta-diketiminate ligands. Reduction of boratatetrazines with cobaltocene afforded highly reactive borataverdazyl radical anions isolobal to parent organic systems. The radicals were readily oxidized back to the boratatetrazine precursors limiting their characterization to the solid-state. Synthetic pathways to 3-substituted formazans allowed for the incorporation of bulky N-substituents, a feature of -diketiminates that has influenced their utility as catalysts. 3-Cyanoformazans were shown to exist as either the open or closed structure in solution and the solid-state, while 3-nitroformazans exist exclusively as the closed strcutre due to the presence of the relatively large nitro-substituent. A number of transition metal complexes of 3-substituted formazans were synthesized, and their X-ray crystal structures used to establish a correlation between steric bulk at the ligand and complex structure. When ortho-substituents are incorporated the N-aryl substituents twist relative to the formazan backbone, while relatively smaller N-aryl substituents remain relatively planar. Palladium hexafluoroacetylacetonate complexes of formazans were anticipated to have utility as precursors to palladaverdazyls due to their electron poor nature. However, although the complexes did allow for the structure property relationship of metal-formazan complexes to be further developed, palladaverdazyls were not realized. Comparison with boratatetrazines suggests the nature of the Pd-N bond may play a role in the instability of palladaverdazyls. The synthesis and characterization of verdazyl-based spin dimers was reported. The incorporation of iso-propyl N-substituents allowed for the first truly stable verdazyl diradicals to be isolated. Electrochemical, electronic, and magnetic properties of diradicals bridged by para- and meta-benzene were explored. Diradicals bridged by para-benzene were antiferromagnetically coupled while meta-benzene bridged diradicals were ferromagnetically coupled. Magnetostructural studies of copper (II) complexes of verdazyls were complicated by the coordinative flexibility of copper (II) ions and the presence of Jahn-Tellar distorted ligand fields. However, a correlation between structure and properties was established: axially bound verdazyl radicals were weakly ferromagnetically coupled to copper (II) ions, and equatorially bound verdazyl radicals were strongly antiferromagnetically coupled to copper (II).

Thesis (Ph.D.)--McMaster University (Canada), 1993. / Source: Dissertation Abstracts International, Volume: 55-06, Section: B, page: 2189. Adviser: R. Bader.

The introductory Chapter to this thesis outlines fundamental aspects of 4f lanthanide(III) coordination chemistry, in particular compounds that possess the intriguing properties of slow relaxation of magnetisation, (or the ability to behave as single-molecule magnets, SMMs). The recent renaissance into the study of the magnetic behaviour of 4f-coordination complexes has led to the consideration of utilising organometallic precursors for the development of novel lanthanide containing compounds, which may possess interesting magnetic properties, subsequently forming the basis of Chapter Two. In Chapter Two, the syntheses and structures of the novel lithiated thiolate ligand, lithium triphenylsilylthiolate, (Ph3SiS-Li) (2.1), and the sulfur-bridged, dimetallic dysprosium(III) and gadolinium(III) complexes [(MeCp)2Dy(µ-SSiPh3)]2 (2.2) and [(MeCp)2Gd(µ-SSiPh3)]2 (2.3), are described in detail. The structural and physical properties of these compounds are analysed through NMR, elemental analysis and SQUID magnetometry, alongside supporting theoretical calculations to reveal that compound 2.2 is the first dimetallic, sulfur-bridged SMM reported, giving an energy barrier to the reversal of magnetisation of Ueff = 192 ± 5 K.56bChapter Three reports on the structural development of a series of lanthanide monomers, exhibiting the general motif [Ln(OSiPh3)3(THF)3] (where Ln = Dy(3.4), Er(3.5), Ho(3.6), Gd(3.7), Tb(3.8)), exploiting the siloxide ligand Ph3SiOH through two novel synthetic routes. This Chapter also provides new analytical insight to these complexes by exploring their magnetic properties through a series of SQUID measurements and through the analysis of their electronic properties using air sensitive, variable temperature optical absorption spectroscopy. Compounds 3.4 and 3.5 were revealed to be SMMs, with 3.5 having a much higher thermal barrier to the reversal of magnetisation, Ueff = ~ 28 K, than 3.4, which are supported by theoretical analysis. Chapter Four describes the utility of ligand 2.1 and Ph3SiOH in the context of 3d transition metal cyclopentadienyl chemistry, outlining the syntheses and structures of three distinct compounds; the trimetallic, [Cp2Mn3(µ-OSiPh3)4](4.7), the hetero-cubane tetramer [CpMn(µ-SSiPh3)]4 (4.8) and the dimetallic thiolate-bridged [CpCr(µ-SSiPh3)]2 (4.9) compound. These compounds were formed in reactions exploiting organometallic manganocene and chromocene precursors. Magnetic susceptibility measurements were conducted on these compounds to gain further insight into their structural properties. The magnetic exchange coupling constants for Mn(II) compounds 4.7 and 4.8 were J = - 4.4 cm-1 and J = - 3.0 cm-1 respectively. Furthermore, having demonstrated the use of metal-cyclopentadienyl building blocks in the synthesis of novel SMMs, Chapter Five discusses the possibility of further advancement on the development of this class of magnetic molecules.

Grafen v kombinaci s komplexy kovů by mohl poskytnout nové přísutpy v hybridních materiálech založených na grafenové bázi a v oblasti molekulárního magnetismu. Obě témata jsou velmi diskutovaná jako taková, nicméně, výzkumu vedoucího k možnosti jejich míchání není mnoho. Vzorky byly připraveny sonikací grafitu v kapalné fázi, což vedlo k exfoliaci grafenu. Následně byly nadeponovány pomocí modiikované Lagmuirovy– Schaeferovy depoziční metody různé komplexy kovů na substrát pokrytý grafenem. Klíčovým krokem bylo určení vlastností takto připraveného materiálu. Proto byly následně vlastnosti takového hybridního materiálu charakterizovány pomocí vysokofrekvenční elektronové paramagnetické rezonance (angl. HFEPR), rastrovacího elektronového mikroskopu, (angl. SEM), Ramanovou spektroskopií a čtyř bodovou metodou měření odporu. V této práci jsme potvrdili naši presumpci, že je možné vytvořit hybridní materiál smícháním exfoliovaného grafenu s molekulárními magnety pro získání nových magnetických a elektronických vlastností, které by mohly být využity v další generaci detektorů a elektroniky.

Elektronová spinová rezonance (ESR) je neinvazivní spektroskopická technika založená na magnetické rezonanci. Používá se v mnoha vědních oborech jako biologie, chemie a fyzika pro zkoumání systémů s nepárovými elektrony. Tato dizertační práce se věnuje spektroskopii vysokofrekvenční rezonance spinů elektronů (HF-ESR) a jejímu použití na paramagnetické koordinační sloučeniny. V první části je představen teoretický základ s rešerší literatury v této oblasti a jsou představeny aplikace HF-ESR. Dále jsou představeny metody použité ke studování těchto systémů. Zde jsou popsány doplňující metody (XPS, RS, UV-VIS, AFM, SEM) pro zkoumání vzorků a je představen návrh nové sublimační komory vysokého vakua, která byla sestavena pro tvorbu tenkých vrstech koordinačních sloučenin na površích. Následují výsledky dosažené pomocí HF-ESR na molekulárních kvantových bitech [Cu(dbm)2], jednomolekulárních magnetech [CoX2(dppf)], [Co(4MeO-L)2Cl2] a je nastíněna vize bolometrů na bázi grafenu pro detekci této třídy sloučenin. Výsledky jsou diskutovány a jejich implikace jsou shrnuty v závěru. Reference a autorské výstupy pak uzavírají celou tuto práci.