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Studies were conducted to explore the electronic properties of the cyclometalated (C^N) complexes of iridium and platinum metals with catechol ligand. The complexes were observed to exhibit a reversible reduction of the semiquinone form to the catechol form of the ligand and an irreversible oxidation to the unstable quinone form of the ligand.

The syntheses and systematic X-ray investigations of complexes [Cp.sub.2]Nb(SiY[Me.sub.2])(H)(SiX[Me.sub.2]) and the neutron diffraction (ND) studies of complexes [Cp.sub.2]Nb-(SiH[Me.sub.2](H)(SiCl[Me.sub.2]) and [Cp.sub.2]Nb(SiH[Me.sub.2])(H)(SiBr[Me.sub.2]) is reported. The complexes show the largest structural distortions for the silyl groups substituted by heavy halogen atoms.

The crystal structure of NF4BF4 was verified at different temperatures. The low-temperature X-ray structure and solid-state [.sup.19.F] MAS NMR spectra are in line with the conclusions reached from the vibrational spectra, that solid [NF4.sup.} salts contain only tetrahedral [NF4.sup.} cations.

A series of cationic bis-cyclometalated iridium(III) complexes are synthesized and their electrochemical, photophysical, electroluminescent properties are studied. The complexes are found to be luminescent both in a fluid solution and as neat solids at 298 K, while single-layer electroluminescent devices that give blue, green, and red electroluminescence are also fabricated.

The approaches are reported to achieve efficient blue to near-UV emission from triscyclometalated iridium(III) materials. The approach to tuning the photophysical properties of cyclometalated Ir complexes investigated in the study involved the control of the relative energies of emissive and non-emissive excited states.

The synthesis and photophysical characterization of a series of (N,C(super 2')-(2-para-tolylpyridyl)2Ir(LL') [tpy)2Ir(LL')] (LL' = 2,4-pentanedionato (acac), bis(pyrazolyl)borate ligands and their analogues, diphosphine chelates and tert-butylisocyanide (CN-t-Bu) are reported. The electrochemical and photophysical properties of the (typ)2Ir(LL') complexes are discussed in detail.

Research has been conducted on the square planar platinum complexes. The synthesis, photolysis and electrochemistry of these cyclometalated complexes have been investigated and the details are presented.

The slow interconversion of [FeIII(TF4TMAP)(H2O)2]5+ and [FeIII(TF4TMAP)OH]4+ takes place mainly through bimolecular reaction between the aqua and hydroxo forms with k = 1.6 x 10(supra6) M-1 s-1 (298 K) and Ea = 6.7 plus or minus 0.4 kcal mol-1. Exchange of a proton, motion of the iron into or out of the porphyrin plane and addition or loss of a coordinated water are all involved in the interconversion between [FeIII(TF4TMAP)OH]4+ and [FeIII(TF4TMAP)(H2O)2]5+.

The phase change in phases II and II of N(CH3)4IO4 is a result of the commencement of free ion rotation rather than the rotational oscillation axes' positional disorder, according to research of its Raman spectra and crystal structures. The finding is in agreement with L. Pauling's initial proposal. In high temperature phase I, both ions are believed to be rotationally disordered; in room-temperature phase II, the lesser counterion is rotationally disordered while the greater ion is ordered; in low-temperature phase III, the cation and anion are both ordered.

The N (1') site and the phosphate group of Zn2+, Cd2+ and Hg2+ complexes with 2-(alpha-hydroxybenzyl)thiamine monophosphate chloride or (LH)+Cl- serve as metal binding sites. The N (1') group in the pyrimidine ring of HgL2Cl2 exhibited metal phosphate binding reactions based on P solid-state nuclear magnetic resonance spectroscopy. The crystal structures of (LH)+Cl- and HgL2Cl2 are composed of four molecules per unit cell. Electrostatic and stacking interactions together with hydrogen bonds stabilize the water molecules of the complexes.

Nickel tetrakis(N-methyl-4-pyridiniumyl)porphyrin(NiT4-N-MePyP4+) was shown to bind axial bonds more strongly than nickel tetrakis(2,3,5,6-tetrafluoro-N,N,N-trimethyl-4-aniliniumyl)-porphyrin (NiTF4TMAP+). Solution chemistry and crystal structure of the complexes revealed that the four coordinate (NiT4-N-MePyP4+) is in equilibrium with the six coordinate Ni(H2O)2TF4-TMAP4+ in aqueous solution and creates a hydrophobic effect, which strengthens porphyrin interactions in the solution.

The NMR study of the rotational isomers of tetrakis(N-methyl-2-pyridiniumyl)porphyrin shows the presence of N-methyl groups determines the rotational disposition of the next N-methylpyridiniumyl groups. The porphyrins have a regular, sandwich array structure. Two different types of protonated ferrocyanide anions are connected respectively with the water-rich region and water-poor region of the structure. The two type of ferrocyanide ions are linked through the hydrogen-bonded water.

Two neutral complexes, LRhCl3 and ((Me4dtne)Rh2Cl6)2H2O, are formed when the macrocyclic ligands 1,4,7-trimethyl-1,4,7-triazacyclononane (L) and 1,2-bis(4, 7-dimethyl-1,4,7-triaza-1-cyclononyl)ethane (Me4dtne) interact with RhCl.3H2O in ethanol. Red-brown crystals of air- and moisture-constant anti-(L2Rh2(H)2(micro-H)2)(PF6)2, among others, are formed when KpF6 is introduced to the interactions of the aqueous suspensions of the complexes with NaBH4. Single-crystal X-ray and neuron diffraction are employed to examine the conformation of the product.

The short Co-Co bond in the complex (eta5-Cp*)Co]2H3 can be explained if more detailed information regarding the complex's bridging hydride ligands is available. Towards this end, single crystals of the compound are studied using neutron diffraction methods. Results allow the comparison of the central bonding region in triply hydrogen-bridged metal-metal bonds.

The complex Zr(9-BBN)(sub 4)[9-BBN=(mu-H)(sub 2)BC8H14}(sub 4) are synthesized via the reaction of K(9-BBN) with ZrCl(sub 4) in diethyl ether. The structure of the little compound is determined by X-ray and neutron single-crystal diffraction techniques.

The most efficient organic light-emitting diodes (OLEDs) are built from multiple organic layers. Arylamines are used in a high percentage of small-molecule-based devices. The properties of the OLEDs and the mechanism of device failure are discussed.

The essential role of neutron diffraction in the full and precise geometrical characterization of large hydrido metal clusters is demonstrated. This study of [H4Co4(C5Me4Et)4], is the first compound H4Co4 compound that has been fully characterized by the neutron diffraction technique.

Research has been conducted on water-soluble anionic silver 2-mercaptonicotinate complex which possesses antifungal and antibacterial properties. The authors describe the synthesis of this complex.

Research has been conducted on (SO (sub)2) (sub)2 N (sub)3 (super)- anion. The authors report that this anion has been characterized via the use of single-crystal X-ray diffraction.

A report is presented on the preparation, photophysics and solid-state structures of octahedral organometallic iridium complexes. These complexes are used in photocatalysis and photelectrochemistry.

Two distinct novel polymeric silver(I) complexes containing tetracoordinated Ag+ centers are prepared by reacting 1,4-thioxane with silver triflate at ambient temperature. The molecular and crystal structures of the complexes are then examined by infrared spectroscopy and nuclear magnetic resonance measurements. Results show that the two polymeric complexes have excellent coordination to two sulfur and two oxygen ligands.

The x-ray structure of a Bronsted acid salt of H9O4+ hydronium ion with a weakly coordinating counterion is described. Crystalline (H9O4)+(CB11H6Br6)- consists of discrete H9O4+ and CB11H6Br6- ions, with a minimum distance of 4.58 angstroms for O-O between cations, which is too far for hydrogen bonding. A new Eigen-type structure for the H9O4+ ion has been proposed to replace and render stability to the original hydrogen bonding formulation.

A single-crystal neutron diffraction analysis of the cluster complex [H4Co4(C5Me4Et)4] was carried out on the new quasi-Laue diffractometer VIVALDI at the Institut Laue-Langevin. The structure consists of four face-bridging hydrides attached to a tetrahedral cobalt metal core. Average distances and angles in the core of the molecule are as follows: Co-Co = 2.571(8), Co-C = 2.158(6), Co-H = 1.749(7), H…H = 2.366(9) Å; Co-H-Co = 94.6(3), H-Co-H -- 85.1 (3)°. The hydride ligands are located off the Co-Co-Co planes by an average distance of 0.923(8) Å. It is suggested that the dimensions of the HCo3 fragments found in this molecule provide reasonable estimates for analogous distances and angles associated with chemisorbed H atoms situated on the 3-fold hollows of a cobalt surface. Crystallographic details: space group P21/a (monoclinic); a = 21.979(2), b = 10.924(1), c = 34.406(2) Å; β = 90.81(1)°; Z= 8. Final agreement factor: R(F) = 0.099 for 3779 reflections [I > 2σ(I)] collected at 20 K. [ABSTRACT FROM AUTHOR]