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The multinuclear NMR was utilized to investigate the kinetics of water exchange and substitution on [[(CO)3M(H2O)3].sup.+] (M = Mn, Tc, Re) complexes. The substitution of water in fac-[[(CO)3M(H2O)3].sup.+] by dimethyl sulfide (DMS) is slightly faster than that by C[H.sub.3]CN, 3 times faster of Mn, 1.5 times faster for Tc and 1.2 times faster for Re.

Gd(III) (S =7/2) polyaminocarboxylates, used as contrast agents for Magnetic Resonance Imaging were studied in frozen solutions by High-Frequency-High Field Electron Paramagnetic Resonance (HF-EPR). The EPR spectra recorded at 240 GHz and temperatures below 150 K allowed the direct and straightforward determination of parameters governing the strength of zero-field splitting (ZFS).

A demonstration that the diastereomer ratio for Ln(super III) DTPA derivatives remains constant throughout the lanthanide series, in contrast to Ln(super III) EPTPA derivatives, where it varies as a function of the cation size with a maximum for the middle lanthanides is presented. An HPLC analysis showed that the diastereomer ratio for Ln(super III) DTPA derivatives remains constant throughout the lanthanide series.

The water-soluble endohedral gadofullerene derivatives are characterized with regard to their magnetic resonance imaging (MRI) contrast agent properties. The pH dependency of the proton relaxivities makes these gadofullerene derivatives prime candidates for pH-responsive magnetic resonance imaging contrast agent applications.

The outer-sphere oxidation of mixed-valence Co (super II)/Fe (super II) complexes are studied. The results indicate that the outer sphere oxidation reactions involve a great amount of solvent-assisted hydrogen bonding.

The compositional parameters of the Eu(super 2+) and Sr(super 2+) ions in non aqueous solutions are ascertained by the X-ray absorption fine structure (XAFS) method and compared with those of the aqua ions. The ionic radii of both the ions are found to be similar but the slightly softer nature of the Eu(super 2+) ion results in shorter M-N and longer M-O bonds.

Research has been conducted on the cyanide exchange on [M(CN) (sub)4] (super)2- (M= Ni, Pd, and Pt) square planar complexes. The kinetic studies of this exchange have been carried out as a pH function via the use of (super)13 C NMR analysis and the details are reported.

Research has been conducted on the lanthanide complexes of the tripodal ligands. The structure and solution properties of these complexes and the relaxivity properties of the gadolinium tripodal ligand complexes have been investigated and the results are discussed.

The first variable-temperature and variable-pressure stopped-flow spectrophotometric study of the sequential threading of alpha-cyclodextrin (alpha-CD) onto the guest dye Mordant Orange 10, S, is described. The quantitative ground-state and activation enthalpy, entropy and volume change studies indicate that hydrational, van der Waals, and conformational changes in S and alpha-CD determine the equilibrium and kinetic character of the system.

MRI-related Gd(III) complexes were studied using EPR spectroscopy.

The platinum-bound iodide in the organoplatinum(II) complex is not directly involved in the binding of sulfur dioxide or the metal-bound halide in the complex has any influence on the binding process. The dissociative exchange of sulfur dioxide fastly occurs at ambient temperatures, making it ideal for sensor response applications.

Nuclear magnetic resonace and infrared spectroscopy analyses demonstrate that the square-planar complexes of rhodium and iridium that are involved in the catalytic carbonylation of olefins, exhibit different affinities to carbon monoxide and under pressures form the corresponding tricarbonyl halides. Data further reveal that only the iridium complex reacts with hydrogen.

Research is presented concerning the use of controlled potential coulometry to prepare a (EuII(diethylenetriamine pentaacetate)(H20))3- complex from (EuIII(diethylenetriamine pentaacetate))2-.

Research has been conducted on N,N-dimethylformamide (DMF). The rate of the DMF exchange in the nickel(II) cation and in the monochloro species has been investigated via (super)13 C NMR spectroscopy.

(Eu(DOTAM)(H20)(super3+)) was studied to determine the mechanism of the water exchange from variable temperature and pressure (super1)H and (super17) 0 NMR data.

Research has been conducted on the CO exchange on cis-[M(CO) (sub)2 X (sub)2] (super)- in dichloromethane. The use of high gas pressure NMR sapphire tubes is discussed.

Research is presented describing the use of NMR to measure variable-pressure (9.4 T) and variable-temperature (at 4.7 and 9.4 T) 17O nuclear relaxation rates for the Eu(II) aqua ion. The implications for magnetic resonance imaging contrast agents and ligand exchange at Ca(II) are discussed.

Research has been conducted on the water substitution in the half-sandwich complexes by Cl (super)-, Br (super)-, I (super)-, nicotinamide, pyridine, thiourea and dimethylsulfide. The use of the stopped-flow spectroscopy is described.

The synthesis of a series of trinuclear lanthanoid complexes of 1,3,5-triamino-1,3,5-trideoxy-cis-inositol with a unique, sandwich-type cage structure was described. Magnetic susceptibility calculations and spectroscopic techniques were used to characterize the trinuclear complexes. Experimental results revealed extremely weak antiferromagnetic coupling interactions among the three Gd centers. It was also found that the stability of the lanthanoid complexes increases monotonically as the ionic radius of the metal center decreases.

The trinuclear {Gd3(H(sub -3)taci)2(H2O)6}3+ was characterized in aqueous solution via multiple field 17O nuclear magnetic resonance and electron paramagnetic resonance spectroscopy. The water exchange on {Gd3(H(sub -3)2taci)2(H2O)6}3+ had more associative properties and was approximately 70 times slower compared to the Gd(III) aqua ion. The observed low rotational correlation of the complex was attributed to the spherical structure, with the large hydrophobic surface inhibiting the formation of a substantial hydration sphere.

The preparation and characterization of a range of complexes with general formula (MO(X)(CN)4)n- of Re(V), Tc(V), W(IV), Mo(IV), and Os(VI) were conducted using 13C, 15N, 17O and 99Tc NMR utilizing 13C- and 15N-enriched cyano complexes. A correlation between M-O and M-CN bond strength from X-ray crystallographic data and (1J(183W-13C)) coupling is reported. The cyanide exchange kinetics were correlated with previously determined proton and oxygen exchange, spanning a kinetic domain of more than 12 orders of magnitude for the five metal centers studied.

The synthesis of isostructural compounds with a (Ru(Hsub2O-ax)(Hsub2O-eq)sub4L)super2+ general formula was undertaken, with the hexaaqua complex of ruthenium(II) as a starting material. The effect of L on the cyclic voltammetric response, on the rate of exchange reaction and on calculated structures were evaluated. The formal redox potential Eo'(+2/+2) was found to increase with the pi-accepting abilities of the ligands. Good correlation was found between the lability and calculated Ru-Hsub2Oax bond energies.

Integrated nuclear magnetic resonance study was utilized to investigate the structural and dynamic behavior of {Ln(EGTA)(H(sub 2)O)(sub x)}(super -) complexes in aqueous solution. It was revealed that a high water exchange rate for the ennea-coordinated complex was secondary to the severe steric constraints at the water binding site in the solution structure of the complex. The nature of the water exchange on lanthanide(III) complexes was directly related to the coordination of the complexes in the solution.

The structure of Ln(III) complexes of DTPA-bis(alkylamides) is not significantly affected when the complexes' alkyl functions are replaced with polyhydroxylated functions. The Ln(III) ion and hydroxyl groups do not interact and the coordination polyhedron is unchanged. Variable-temperature NMRD and variable-pressure and variable-temperature O NMR are used to examine the dynamics and solution structure of Ln(III)-DTPA-bis(glucamide) (DTPA-BGLUCA). The expected relaxivities of the polysaccharides attached to Gd(DTPA) chelates can be estimated.

The solvent exchange process for (eta5-C5Me5)M(S)3]2+ (M = Rh, S = MeCN) was found to proceed via a dissociative mechanism. Intermolecular exchange with free Me2SO on (eta5-C5Me5)M(S)3]2+ (S = Me2SO) takes place exclusively from a conformational isomer which is in equilibrium with a second, more compact conformer. The rate constants associated with the solvent exchange process on the half-sandwich species were shown to be governed primarily by electronic properties of the ligands.

The effects of temperature and pressure on the coordination equilibrium of La(DOTA)- (DOTA = 1,4,7,10-tetraaza-1,4,7,10-tetrakis(carboxymethyl) cyclododecane) was analyzed by nuclear magnetic resonance spectroscopy. Spectroscopic analysis of the La(DOTA)- complex indicated the presence of coordination equilibrium that was superimposed on the conformational equilibrium. The paramagnetic Ln(DOTA)- complexes also exhibited an isomer equilibrium that favored a reverse antiprismatic conformation.

The lability of mononuclear octahedral complex as compared to the dinuclear triple-helical complex of cobalt has been investigated. Electrospray mass spectroscopy (ESMS) was utilized to study the ligand exchange in the triple-helical complex and establishes the formation pathway of this complex. The slow racemization of the dinuclear triple complex is due to the slow dissociative mechanism of cobalt from the complex. Its inertness arises from the rigidity of the ligand which results in a tight pitch.

A self-consistent theoretical model in a simultaneous multiple parameter least-squares fitting procedure is used to treat experimental data from nuclear magnetic resonance, electron paramagnetic resonance and nuclear magnetic resonance dispersion of monomeric and dimeric Gd(super 3+) complexes. It is found that a simultaneous treatment of data from the three techniques results in an improved definition of the many parameters affecting the proton relaxivity of Gd(super 3+) complexes. Findings show that further relaxivity gain for these complexes will be hampered by the slow water exchange rate on the complexes.

The exchange of water molecule with iridium(III) on the homoleptic mononuclear metal center (Ir(H2O)6)3+ involves an associative interchange mechanism. A negative volume and near-zero entropy of activation confirm the occurrence of this mechanism. This is the slowest water exchange of similar nature giving a rate constant of 1.1x10(super -10) s(super -1). The deprotonated (Ir(H2O)5(OH))2+ is more reactive than (Ir(H2O)6)3+. Water exchange on this species takes place through an interchange mechanism.

The dimeric gadolinium(III) complex, (BO(Gd(DO3A)(H2O))2), (BO(DO3A)2 = 2,11-dihydroxy-4,9-dioxa-1,12-bis(1,4,7,10-tetraaza-4,7,10-tris(carboxymethy l)cyclododecyl)dodecane), which exhibits rapid water exchange and slow rotation is a magnetic resonance imaging contrast agent. Parameters of water exchange kinetics and rotational motion are analyzed based on the variable-temperature and -pressure (super 17)O NMR study. With decreasing rotation and increasing water exchange, the molecule has an increased 1H relaxivity.

The ruthenium complex Ru(DMF)6(CF3SO3)2 (II) is the starting reagent of the preparation of macrocyclic amine complexes.and phosphine oxide complexes. The structure of the compound II is triclinic. Another ruthenium complex Ru(DMF)6(CF3SO3)3 (I) has monoclinic structure. Compound I and II are soluble in different nonaqueous solvents and can be characterized by the well-defined oxidation state of the metal and the hydration of the compound. These compounds are characterized by NMR and cyclic voltammetry techniques.

The water exchange rate and the relaxivity of the complex (Ln{DTPA-BMA}{H2O}) where Ln = Nd, Eu, Tb, Dy and Ho and DTPA-BMA = 1,7-bis(N-methylcarbamoyl methyl)-1,4,7-triazaheptane-1,4,7-triacetate or diethylenetriaminepentaacetate-bis(methylamide), depend on the lanthanide size. The rate and mechanism of the water exchange is characterized by the steric crowding of the water binding site.

Oxygen-17 NMR helps study the oxygen exchange kinetics in complexes of Re(V), Tc(V), W(IV) and Mo(IV) with trans-dioxotetracyanometalate ligands. The exchange involves an inversion of the metal complex and subsequent oxygen exchange. The rate of exchange is pH dependent and the rate law involves two terms. A comparison of the (MO(OH)(CN)4)(n+1)- ions and aqua complexes shows the latter to be more reactive, involving dissociative activation.

X-ray studies enable the determination of the structures of a series of pi-arene aqua complexes of Co, Ir, Ru and Rh. Examination of the anation kinetics of these species by stopped-flow spectrophotometry and water exchange reactions reveals that the kinetics follow a second-order rate law. Kinetic data suggest a dissociative interchange mechanism for the anation, and nature of the entering ligand exerts no influence on the rate-law. Pi-arene ligands increases the rate of water exchange.

170 NMR and T-jump techniques help examine the influence of pressure on water exchange and complex formation reactions of Cu(tren)H2O(2+). Water exchange rate constant for the pentacoordinate system is smaller than that for hexacoordinate systems. Measured volumes of activation reveal the presence of an associative interchange mechanism and help arrive reaction volume profiles. Examination of volume profiles demonstrates that chelate ligands induce mechanistic changeover in the substitution of aquated Cu(II) ions.

Kinetic studies using UV-vis spectrophotometry help analyze the mechanism of aquation and anation reactions of bicycloalkyl-substituted (ethylenediamine)dichloroplatinum(II) complexes. Kinetic studies as a function of pH, temperature, pressure and concentration help determine various thermodynamic parameters of the reactions. Measured activation volume of the aquation reaction indicates the absence of a dissociative mechanism. Aquation involves a pentacoordinate intermediate.

The rate constants and the volumes of activation for a series of water exchange reactions of aquapentakis(methylamine)metal(III) complexes, where M is Cr, Co or Ru, as a function of temperature and pressure. A dissociative shift in the reaction mechanism initiated by the steric congestion of the metal complex skeleton is observed. The shift is independent of the nature of the operating reaction mechanism.

C-13 NMR spectroscopic studies on the (MO2(CN)4)(n+2)(-) complexes of the Mo(IV), W(IV), Te(V) and Re(V) systems yield pKa values that agree well with previously determined dissociation constants for the systems. 0-17 line broadening NMR methods yield the reaction kinetics for proton transfer of the systems. The study results indicate that the complexes have enriched oxo sites due to water/hydroxide exchange and subsequent proton transfer.

The oxygen atom exhibits an exchange rate known as the water-exchange rate. Water protons reveal the same exchange rate at lower levels. The water-exchange rate is in close proximity with the proton-exchange rate, which facilitates the comprehension of the functioning of the relaxation aspects, depending on the gadolinium compounds. The exchange interaction mode can be determined by using variable-temperature and variable-pressure 17O NMR. The 17O relaxation on lanthanide compounds is influenced by the second-coordination sphere.

The monocomplex formation reactions of (Ru(H2O)6)2+ with a series of monodentate ligands is determined through UV-visible and 1H-NMR techniques. The different rate constants and the enthalpies and entropies of activation for the reactions were calculated. The results show the similarities in the interchange rate constants which reveal a dissociative interchange mechanism. In addition, spectroscopic studies indicate that the binding sites of the neutral ligands are unique with dimethyl sulfoxide binding through its sulfur atom.

The compound (TiO(DMSO)5)(CF3SO3)2 was synthesized from the stepwise addition of DMSO to anhydrous titanium(III) trifluoromethanesulfonate in triethyl orthoformate. The mechanism of DMSO exchange on the complex (TiO(M/DMSO)5)2+ indeurated nitromethane diluent was also investigated. The complex was found to exhibit two distinct DMSO-exchange processes. A D mechanism for the observed axial intermolecular solvent exchange was proposed. Also observed was an equatorial exchange process, for which was proposed a mechanism involving axial-equatorial migration with an expanded transition state.