Daryle H. Busch

SPECTRAL AND ELECTROCHEMICAL STUDIES OF THE COPPER(II) COMPLEXES OF TWO MACROCYCLIC LIGANDS

Abstract Copper(II) complexes of the types Cu(CR)(ClO4)2-.H2O, [Cu(CR)X](ClO4).nH2O (where X = Cl, Br, I and n = 1; X = NCS, n = 0), [Cu(CRH)](ClO4)2.H2O and [Cu(CRH)X](ClO4) (where X = Cl, Br, I) have been prepared. The ligands CR and CRH are the related four nitrogen-donor macrocycles 2,12-dimethyl-3,7,11,17-tetraazabicyclo [11.3.1]heptadeca-1(17), 2, 11, 13, 15-pentaene and meso-2, 12-dimethyl-3,7,11,17-tetraazabicyclo[11.3.1]heptadeca-1(17), 13,15-triene, respectively. All the compounds have the normal magnetic moments expected for Cu(II) complexes with S = ½. Conductance studies in methanol show that the halo-perchlorate complexes are formally five coordinate. The probable structures of the complexes in both the solid and solution are discussed in terms of their visible, infrared and e.s.r. spectra, as well as on the basis of data obtained from conventional polarography and cyclic voltammetry.

FIVE-COORDINATE COBALT(II) COMPLEXES OF MACROCYCLIC LIGANDS — A NEW REVERSIBLE OXYGEN CARRYING SYSTEM

We report the synthesis and characterization of cobalt(II) complexes with two macrocyclic Schiff base ligands, 5,7,7,12,14,14-hexamethyl-1,4,8,11,-tetraazacyclotetradeca-4,11-diene(Me6 [14]4,11-die...

COBALT(III) COMPLEXES OF THE TETRADENTATE MACROCYCLE 2, 12-DIMETHYL-3, 7, 11, 17-TETRAAZABICYCLO(11.3.1)HEPTADECA-1(17), 2, 11, 13, 15-PENTAENE

Abstract A series of cobalt(III) complexes of 2,12-dimethyl-3,7,11,17-tetraazabicyclo(11.3.1)heptadeca-1 (17),2,11,13,15-pentaene, CR, has been prepared. In addition to materials of common compositions and structures, the series includes a diiodo complex, a complex containing a bidentate nitrate ligand, an NO− derivative, and one in which ethylenediamine acts as a monodentate ligand with a dangling, unprotonated primary amine group.

Inclusion Chemistry for the Modeling of Heme Proteins

Early attention to the modeling of heme proteins is enhancing the understanding of biochemistry. Those studies are also contributing to the development of techniques for the modeling of still more intricate, multifunctional, variously selective natural systems. Selectivity in simple systems may involve the molecular capability to bind only one of a family of related species or it may mean the ability to select and control one of a number of possible functions of a given bound species. Complicated systems simultaneously combine the two kinds of simple selectivities for two or more different classes of guest, often with synergistic interrelationships. The subject is developed around examples of binary, tertiary, and quarternary complexes designed to model the behavior of monooxygenases.

Kinetics and intermediates in the autoxidation of (cyclidene) iron(II) dioxygen carriers in a variety of solvent systems

Abstract The autoxidation of [FeII(Me,Me,m-xyl)Cl]+ was studied in a variety of solvent systems, with the two extremes being aprotic acetonitrile containing the powerful axial ligand N-methylimidazole ( MeCN MIM ) and protic methanol with the weak axial ligand chloride ( MeOH LiCl ), and the results are compared with those from a previous investigation for the solvent system 3:1:1 acetone : pyridine : water (APW). The differences in the solvent systems are mainly manifested in the product distribution, whereas the rate law maintains its algebraic form and the previously proposed general mechanism of autoxidation (electron transfer operating in parallel with the dioxygen adduct equilibrium) requires only slight modification in order to account for the behavior of the full range of systems. Systems in which chloride serves as the axial ligand, yield only the product of the electron transfer step, [FeIII(Me,Me,m-xyl)Cl]2+, and its hydrolysis products, [FeIII(Me,Me,m-xyl)OH]2+, and [{FeIII(Me,Me,m-xyl)}2O]4+. In contrast, systems in which the nitrogenous bases pyridine or 1-methylimidazole replace chloride as the axial ligand also produce a (peroxo)iron(III) species, in addition to [FeIII(Me,Me,m-xyl)B]3+, where the axial ligand depends on the medium. The formation of FeIII(Me,Me,m-xyl)OH]2+ and [{FeIII(Me,Me,m-xyl)}2O]4+ depends, as expected, on the water content of the system. The effects of substituents, at constant bridging group and cavity size, on the autoxidation of [FeII(R3,R2,m-xyl)Cl]+ with R3 = Me, Ph and R2 = Me, Bz in MeOH LiCI are dramatic. Remarkably, the combined steric and/or electron-withdrawing effect of replacing methyl groups at both the R2 and R3 positions appears to be multiplicative rather than additive.

Synthetic Dioxygen Carriers for Dioxygen Transport

Synthetic Dioxygen Carriers, a Key Area for the 1990s The promising application areas for synthetic dioxygen carriers range from internal medicine and small devices to the commodity gas market and basic fuel production and there seems little doubt this area will impact the lives of most people in the developed nations during the coming decades. Government and societal leaders, both Nationally and internationally,1,2,3continue to look to synthetics as possible eventual sources of dioxygen transport materials for temporary whole blood substitutes, envisioning such scenarios as those associated with major disasters and military engagements. Existing research has been focused on portable devices4 to provide dioxygen enriched atmospheres for those suffering such maladies as emphysema and for the very different area of underwater dioxygen supply.5,6 Dioxygen electrode systems for batteries are attractive targets on the full range of scales from tiny hearing aid cells through electric automobiles to fuel cells for the storage of off-peak energy by electric utility companies. For many large scale uses, for example foundry operation, a moderate enrichment of the dioxygen level is adequate and this is an especially attractive target area for separation techniques based on the use of transition metal dioxygen carriers.7,8 The cleansing of contaminated atmospheres is a less than obvious but related area for application. Using the same basic science and technology, control of very low levels of O2is possible with such materials since the variability of O2affinities of carriers spans many orders of magnitude (at least 6 andpossibly 10 or 12). Commodity level applications are most dramaticallyshown by the potential demands of the synfuel industry as revealed by industrial response to the synfuel goals set by the Cartera administration.9,10,11 It was concluded by American dioxygen-supplyingindustry that the existing cryogenic technology couldnotbe expanded fast enough to meet the needs of the then projected synfuel industry and that at least one new major technology would have to be exploited. The first attempts to exploit transition metal dioxygen carriers were military.12,13

AXIAL COORDINATION IN COBALT(II) COMPLEXES OF TWO SYNTHETIC MACROCYCLIC LIGANDS CONTAINING THE BIDENTATE α-DIIMINE GROUP

Abstract In order to elucidate the nature of axial coordination in synthetic macrocyclic complexes of cobalt(II), we have synthesized two new series of such complexes, containing the macrocycles Me4 [14] 1,3,8,10-tetraeneN4 and Me2 [14] 1,3-dieneN4, by direct isolation of the Co(II) complexes from the condensation reaction mixtures. The complexes are formally five-coordinate in the solid state, but exhibit a tendency toward six-coordination in the presence of potential axial ligands, as demonstrated by electronic spectral and electron paramagnetic resonance studies. The Co(tetraeneN4)+2 and Co(dieneN4)+2 species are compared with the previously studied Co(Me6 [14] 4, 11-dieneN4)+2 moiety with respect to axial coordination. It is concluded that the presence of methyl substituents on the six-membered chelate rings of the latter complex have a marked effect on its tendency to coordinate axial ligands.

Oxygen Activation by Transition Metal Complexes of Macrobicyclic Cyclidene Ligands

The cyclidene ligand produces effective dioxygen binding in the metal ions cobalt(II) and iron(II). This and the facility with which the structure may be varied or expanded has led to the design of species with large cavities (vaulted cyclidenes) that bind both dioxygen and organic molecules. This provides look-alike models for the ternary complex that precedes the reaction cycle of cyctochromes P450. The synthesis and characterization of the iron, manganese and chromium derivatives of the vaulted cyclidenes has opened the way for their evaluation as functional models. The O2 complex of the vaulted iron(II) cyclidene has been prepared in solution; the reactions of the bound O2 have led to formation of peroxo complexes, analogous to those proposed for P450, and the promoted oxidations of organic substrates with O2 have been explored. With surrogate oxidants, the vaulted cyclidenes display reactivities reminescent of the iron porphyrins, and like the early versions of those oxidation catalysts, the cyclidenes are destroyed during the promoted reactions. Success in promoting reaction between activated metal centers and substrate that is clearly within the hydrophobic receptor has been limited. At this early stage it can be concluded that the cyclidene complexes display the same capabilities as oxidation catalysts that have previously been demonstrated for porphyrin complexes.

The thermal behavior of dithiooxamide ligands and their nickel complexes

Abstract The thermal behavior of substituted dithiooxamide ligands and their nickel complexes has been studied with differential scanning calorimetry and thermogravimetry. The thermal products were analyzed by mass spectral and IR techniques. The mechanism of the thermal decomposition of both the free ligands and metal complexes precludes the clean thermal formation of the polymeric nickel complexes from the neutral ligand derivatives, Ni(LH 2 ) 2 Br 2 .

Transmission of electronic effects in cobalt(III) complexes of macrocyclic ligands: 1H nuclear magnetic resonance study

A correlation has been found between the chemical shifts of the methyl groups and the ligand field strength of X in the complexes [Co(MAC)X2]ClO4, where X = Br–, Cl–, N3–, NCO–, SCN–, AcO–, NO2–, and CN–, and MAC is one of four methyl substituted tetradentate macrocycles.