NOx Related Chemistry is a volume of a series that presents timely and informative summaries of the current progress in a variety of subject areas within inorganic chemistry, ranging from bio-inorganic to solid state studies. This acclaimed serial features reviews written by experts in the field and serves as an indispensable reference to advanced researchers. Each volume contains an index, and each chapter is fully referenced. - Best-qualified scientists write on their own recent results dealing with basic fundamentals of NO-chemistry, with an eye into biological and environmental issues- Editors and authors are recognized scientists in the field- Features comprehensive reviews on the latest developments- An indispensable reference to advanced researchers
Front Cover 1
NOx Related Chemistry 4
Copyright 5
Contents 6
Contributors 10
Preface 12
Chapter One: NOx Linkage Isomerization in Metal Complexes 14
1. Introduction 15
1.1. Modes of binding of NOx moieties in monometallic complexes 16
1.1.1. Nitric oxide complexes 16
1.1.2. NO2 complexes 17
1.1.3. NO3 complexes 18
1.2. Methods that induce linkage isomerization 18
1.3. Techniques for detecting linkage isomers 18
1.4. Factors that affect linkage isomerization 19
2. Linkage Isomerism in Non-Porphyrin NOx Complexes 20
2.1. Group 6 (Cr and Mo) complexes 20
2.1.1. NO complexes 20
2.1.2. NO2 complexes 23
2.2. Group 7 (Mn and Re) complexes 24
2.2.1. NO complexes 24
2.3. Group 8 (Fe, Ru, and Os) complexes 26
2.3.1. NO complexes 26
2.3.2. NO2 complexes 31
2.3.3. NO3 complexes 33
2.4. Group 9 (Co, Rh, and Ir) complexes 34
2.4.1. NO complexes 34
2.4.2. NO2 complexes 35
2.5. Group 10 (Ni, Pd, and Pt) complexes 36
2.5.1. NO complexes 36
2.5.2. NO2 complexes 38
3. Linkage Isomerism in NOx-Coordinated Metalloporphyrins 41
3.1. Manganese NOx porphyrins 42
3.2. Ruthenium and iron NOx porphyrin complexes 50
3.3. Cobalt NOx porphyrins 58
3.4. Hyponitrite complexes of transition metal porphyrins 60
3.4.1. The nitric oxide dimer and its reduced forms 64
3.4.2. Metal hyponitrite binding modes 67
3.5. Heme proteins 83
4. Conclusion 91
Acknowledgment 91
References 91
Chapter Two: Three Redox States of Metallonitrosyls in Aqueous Solution 100
1. Introduction: General Scope 101
2. Complexes with n=6 102
2.1. Structure, spectroscopy, and electronic description. Total spin S=0. Dominant M–NO+ distribution 102
2.1.1. Significance and importance of the ``back-bonding model´´ 104
2.1.2. Role of the s*-FeNO interaction in the trans-effect exerted over NO 106
2.1.3. ``Negative´´ trans-influence of the nitrosyl moiety 107
2.1.4. Different reactivity of the L ligand trans to NO 108
2.1.5. Other metal centers: Validity of the formal charge descriptions 108
2.1.6. Frontier MOs 109
2.2. Formation and dissociation of NO-complexes: Nitrosylations and denitrosylations 109
2.2.1. Reactions with M(II) precursors (M=Fe, Ru): Proton-assisted dehydration of bound nitrite 109
2.2.2. Reactions with high-spin M(III) precursors 110
2.2.3. Reactions with low-spin, nonheme Fe(III) systems 110
2.2.4. Nitrosylation of nitrile-hydratase and models 112
2.2.5. Nitrosylation of low-spin Fe(III)-heme models, [FeIII(TMPS)(CN)(H2O)]4- and [FeIII(TMPS)(CN)2]5- 114
2.2.6. Nitrosylations of other [FeIII(CN)5(Y)]n- complexes 115
2.2.7. Nitrosylations with Ru(III) precursors 116
2.2.8. Why is the release of NO so fast for the {FeIINO+} heme-nitrosyls? 117
2.3. Electrophilic reactivity toward O-, N-, and S-binding nucleophiles 118
2.3.1. General approach to electrophilic reactivity 118
2.3.2. Correlation of nucleophilic rates with M(NO+)/M(NO) redox potentials 120
3. Complexes with n=7 121
3.1. Structure, spectroscopy, and electronic descriptions for 5- and 6-coordination. Total spin S=1/2 or 3/2. Alternative... 121
3.1.1. Heme and nonheme 5C nitrosyls with S=1/2 121
3.1.2. Nonheme and heme 6C nitrosyls with S=1/2 125
3.1.3. Nonheme nitrosyls with S=3/2 127
3.2. The trans-effect in heme- and nonheme complexes 127
3.3. Formation and dissociation of NO-complexes: Disproportionation reactions 128
3.3.1. Nitrosylations 128
3.3.2. Dinitrosyl complexes and disproportionation reactions 129
3.4. Nucleophilic reactivity: The reactions of [ML5(NO)]n with oxygen 133
4. Complexes with n=8 136
4.1. Structure, spectroscopy, and electronic description: Dominant 1NO-/1HNO (S=0) 136
4.1.1. NO--complexes 136
4.1.2. HNO-complexes 139
4.2. Characterization of the NO-/HNO interconversions in solution 142
4.3. A potential-pH diagram in aqueous solution for the different complexes based on the [Ru(Me3[9]aneN3)(bpy)]2+ fragment 145
4.4. Comparative reactivity of NO- and HNO complexes 146
4.4.1. Ligand exchange in solution 146
4.4.2. Redox reactivity 147
4.5. Nucleophilic reactivity: The reactions with dioxygen 149
5. Conclusions 149
References 150
Chapter Three: Recent Progress in Photoinduced NO Delivery With Designed Ruthenium Nitrosyl Complexes 158
1. Introduction 158
2. Photoactive Ru Nitrosyls: What We Knew Before Our Work 163
3. Photoactive {RuNO}6 Nitrosyls Derived from Pentadentate Polypyridine Ligands 165
4. Tuning the Photosensitivity of Ru Nitrosyls to Light of Longer Wavelengths 168
5. Incorporation of Ru Nitrosyls into Polymeric Matrices 172
6. Enhancement of Light Absorption of {Ru-NO}6 Nitrosyls Through Direct Attachment of Dyes 173
7. Conclusion 180
Acknowledgments 181
References 181
Chapter Four: Metal-Assisted Activation of Nitric Oxide—Mechanistic Aspects of Complex Nitrosylation Processes 184
1. Introduction 185
2. Nitric Oxide Activation by Iron(II)/(III) Centers 186
2.1. Nitric oxide activation by synthetic iron(III) porphyrins and hemoproteins 186
2.1.1. Nitric oxide binding to simple iron(III) porphyrin models 187
2.1.2. Interactions of nitric oxide with highly charged iron(III) porphyrins 194
2.1.3. Nitric oxide reactivity toward P450 functional models 199
2.1.4. Nitric oxide activation by selected hemoproteins 204
2.1.4.1. Nitric oxide binding to P450cam 204
2.1.4.2. Nitric oxide binding to metmyoglobin 206
2.1.4.3. Nitric oxide binding to cytochrome c 208
2.1.4.4. Nitric oxide binding to Alcaligenes xylosoxidans cytochrome c 208
2.2. NO binding to iron(III) porphyrazine complexes 210
2.3. Nitrosylation reactions of iron(II) aqua and chelate complexes 213
2.3.1. Nitric oxide binding to the iron(II) center in ILs 215
2.3.2. Influence of the fluoride anion on autoxidation of [FeII(edta)(H2O)]2- 216
2.4. Reactivity of nitric oxide toward [Fe–S] models 218
2.5. Interactions of nitric oxide with pentacyanoferrate(II)/(III) 221
2.5.1. Interaction of nitric oxide with pentacyanoferrate(III) 221
2.5.2. Interaction of nitric oxide with pentacyanoferrate(II) 223
3. Nitric Oxide Activation by Ruthenium(III) Centers 225
3.1. Nitric oxide binding to the RuIII(edta) complex 225
3.1.1. Interaction of RuIII(edta) with nitric oxide in buffered aqueous solution 226
3.1.2. Interaction of RuIII(edta) with nitric oxide in ILs 227
3.2. Interaction of nitric oxide with ruthenium(III) ammine and terpyridine complexes 228
3.2.1. Nitric oxide binding to ruthenium(III) ammine complexes 228
3.2.2. Nitric oxide binding to ruthenium(III) terpyridine complexes 230
3.3. Reactivity of NAMI-A complex toward nitric oxide 233
4. Reductive Nitrosylation Reactions 237
4.1. Reductive nitrosylation reactions of Fe(III) porphyrin complexes 237
4.2. Reductive nitrosylation of aquacobalamin and cobalt porphyrins 241
4.2.1. Reductive nitrosylation of water-soluble cobalt porphyrins 242
4.2.2. Reductive nitrosylation of aquacobalamin at low pH 245
5. Concluding Remarks 248
Acknowledgments 248
References 249
Chapter Five: New Insights on {FeNO}n (n=7, 8) Systems as Enzyme Models and HNO Donors 256
1. Background 257
2. {FeNO}7 Complexes as Models for Nonheme Oxygenase Enzymes 258
2.1. High-spin {FeNO}7 complexes 258
2.2. Low-spin {FeNO}7 complexes 263
3. {FeNO}7 Complexes as Precursors to {FeNO}8 Complexes 264
3.1. Low-spin {FeNO}8 complexes 264
3.2. High-spin {FeNO}8 complexes 268
4. Diiron Complexes Containing {FeNO}7 Unit(s) 270
5. Summary and Outlook 273
References 275
Chapter Six: Design, Reactivity, and Biological Activity of Ruthenium Nitrosyl Complexes 278
1. Introduction 279
2. Tetraaza Ruthenium Complexes 281
3. Polypyridine Ruthenium Complexes as NO Delivery Systems 282
4. UV-Vis Electronic Spectrum 285
5. Electrochemistry 288
6. FTIR 290
6.1. Hydroxide electrophylic attack on bipyridine nitrosyl ruthenium complexes 290
7. Photochemical Reactivity 292
8. Vasorelaxation 295
9. Cytotoxicity 300
10. Neglected Tropical Diseases 302
11. Trinuclear Oxo-Centered Ruthenium Carboxylates 303
References 305
Chapter Seven: Complete and Partial Electron Transfer Involving Coordinated NOx 308
1. Introduction and Presentation of NOx Oxidation States 308
1.1. x=1+ 309
1.2. x=0 309
1.3. x=1- 310
1.4. x=2- 311
2. Nitrosylmetal Complexes Without Additional Redox-Active Ligands 312
3. Nitrosylmetal Complexes with Additional Redox-Active Ligands 313
3.1. 1,4-Diaza-1,3-butadiene complexes 313
3.2. Porphyrin complexes 313
3.3. 1,2-Dioxolene complexes 316
4. Noninnocent Ligand Potential of the NO2-/NO2 Redox System 321
5. Conclusions 322
Acknowledgments 323
References 324
Chapter Eight: Oxidation Mechanism of Hydroxamic Acids Forming HNO and NO: Implications for Biological Activity 328
1. Introduction 329
2. HXs Oxidation In Vitro and In Vivo 330
2.1. Radiation studies 331
2.1.1. Pulse radiolysis 331
2.1.2. Steady-state radiolysis 334
2.1.3. Oxidation mechanism 335
2.2. Metmyoglobin and H2O2 reactions system 337
2.3. Effects of HXs on cells subjected to oxidative stress 340
2.4. SAHA as a radiosensitizer of hypoxic tumor cells 342
3. Conclusions 343
Acknowledgment 344
References 344
Chapter Nine: Reaction Steps in Nitrogen Monoxide Autoxidation 348
1. History 348
2. Gas-Phase Reaction and Atmospheric Chemistry 350
3. Liquid-Phase Reaction and Biology 351
4. Thermochemistry and Kinetics 352
5. Mechanisms 354
5.1. Termolecular Reaction 354
5.2. Steady-state Approach 354
6. Conclusions 365
Acknowledgments 365
References 366
Index 368
Contents of Previous Volumes 378
NOx Linkage Isomerization in Metal Complexes
Dennis Awasabisah; George B. Richter-Addo Department of Chemistry and Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, Norman, Oklahoma, USA
Abstract
The binding of small molecules to metals often imparts varied chemistry to the small molecules. Such chemistry is dependent on the coordination mode of the small molecule ligands, as the coordination mode affects the electronic distributions along the ligand atoms. In this review, we outline the current knowledge of the linkage isomerization of NOx ligands in their metal complexes for both non-porphyrin and porphyrin systems. We present their modes of preparation and detection and speculate on the consequences of such linkage isomerization on the resultant chemistry.
Keywords
Heme
Hyponitrite
Isomerization
Isonitrosyl
Linkage
Nitrate
Nitric oxide
Nitrite
Nitrosyl
Porphyrin
1 Introduction
The interactions of ambidentate ligands with transitions metals have often resulted in complexes with very interesting chemistry. For example, the complex [(NH3)5Co(NO2)]Cl2, first prepared by Jörgensen (1) in 1894, contains the ambidentate ligand NO2 and the complex exists in two forms. Crystalline solids obtained for this compound showed a mixture of two different colored species: yellow and red, which were readily isolated with a pair of tweezers (1). Later, Werner identified these two species as isomers arising from the different modes of binding of the NO2 ligand to Co, either via the O or via the N atoms. This resulted in the birth of the concept of linkage isomerization in 1907 (2). About five decades later, Penland provided infrared spectroscopic data to show that the yellow [(NH3)5Co(NO2)]Cl2 complex had NO2 bound to Co via its N atom, and the red isomer had NO2 bonded to Co via the O atom (3). By way of definition, linkage isomerization may be defined as the existence of two or more species that have the same molecular formula, and the same bonding ligands, but differ in the mode of attachment of at least one of the ligands (usually ambidentate) to the central metal atom.
Linkage isomerization in complexes containing several other ambidentate ligands including those of SCN−, SeCN−, CN−(4–6), and NO (5,7) have been reported. We wish to limit this review to linkage isomerization in NOx complexes and to provide current knowledge in the area of linkage isomerization partly because of the myriad of applications and relevance of NOx complexes. There are only a handful of recent reviews in the literature on linkage isomerization in NOx complexes, including a review by Coppens and Novozhilova on photoinduced isomerization (7), and a more recent forum paper on NOx linkage isomerization in porphyrin complexes (8). This review covers linkage isomerization deriving from isolable metal complex precursors. Thus, we will not cover the systems involving laser ablated atomic systems (9).
The importance of linkage isomerization has been highlighted in a number of reviews (8,10,11). A good understanding of the various modes of binding of an ambidentate ligand, and factors that influence these modes of binding will provide more insight in the kind of chemistry they present. For instance, nitric oxide (NO) is known to bind to the iron center of a heme enzyme to carry out its function as a hypotensive agent (12–14). An increased knowledge of Fe–NO coordination has helped in designing better NO-releasing drugs, and understanding their use in the treatment of hypertension as in the case of sodium nitroprusside (SNP) (15,16). Recently, a book chapter was dedicated to a review on medical applications of solid NO complexes (17). Also, the chemistry of NOx complexes is relevant in understanding the mechanism of the denitrification process that forms part of the global nitrogen cycle (18–21), and in understanding the action of the metal-dependent reduction of nitrite (22).
NOx species are generated by combustion processes in industries and automobiles, and may be produced naturally by lightning strikes. This has led to a rising interest in finding improved catalysts for removal of these toxic gases from the atmosphere (23–25). In addition, and more recently, metastable linkage isomers of NOx complexes have been generated to produce photoswitchable complexes which may be applied in ultrafast optical switching and storage devices (26–31). Recent work by Schuy (32), Cervellino (33), and Tahri (34) have shown how the nitroprusside anion [(CN)5Fe(NO)]2 − could be incorporated into silica gel pores to generate its corresponding linkage isomer for potential use in optical devices. Photoinduced linkage isomerism, Schaniel et al. have noted, is known to modify the polarizability of [(CN)5Fe(NO)]2 − so as to cause a macroscopic change of single-crystal refractive index according to the Lorentz–Lorenz equation (27).
1.1 Modes of binding of NOx moieties in monometallic complexes
1.1.1 Nitric oxide complexes
NO is a colorless monomeric gas which is biosynthesized by the enzyme nitric oxide synthase (NOS) (35). NO is known to bind to transition metals in three main ways. The first is via the N end of the molecule to form the linear (Figure 1 Ia) and bent (Figure 1 Ib) nitrosyl (η1-NO) modes, or via the O end to produce the isonitrosyl (η1-ON) linkage isomer (Figure 1 Ic) (36). Isonitrosyl complexes of SNP (37), and some ruthenium nitrosyl complexes were detected in the solid state as metastable species just less than two decades ago by Coppens and coworkers (38). The third mode of binding is the side-on NO (or the η2-NO) binding mode to a metal as shown in Figure 1 Id. Complexes containing this mode of binding were first demonstrated by Coppens and coworkers for their metastable SNP species (37). Side-on NO species were obtained as short-lived species from photolysis of (OEP)Ru(NO)(O-i-C5H11) and (OEP)Ru(NO)(SCH2CF3) porphyrin complexes (39). Theoretical evidence for the existence of the metastable modes of binding have been demonstrated for SNP (40–42) and for some (por)Fe(NO) models (43).
1.1.2 NO2 complexes
The binding modes of NO2 have been reviewed by Hitchman and Rowbottom (44). Relevant to us in this review are the three nitrite binding modes shown in Figure 1 IIa–c. These are the N-nitro, O-nitrito, and the O,O-bidentate modes. The N-nitro mode has the nitrite ligand bound to the metal via the N atom (Figure 1 IIa). This appears to be the most common binding mode of NO2 in its complexes, thus this binding mode is usually referred to as the ground state binding mode for nitrite, although clearly this is an oversimplification. In the nitrito binding mode, NO2 is bound to the metal via the O atom as shown in Figure 1 IIb. Finally, in the O,O-binding mode, both oxygen atoms of nitrite are bound to the same metal to give an η2-NO2 configuration as shown in Figure 1 IIc.
1.1.3 NO3 complexes
There are two common binding modes of the nitrate 3− ligand. The first is binding via one oxygen atom to give the O-nitrato form (Figure 1 IIIa) and the second is binding through two NO3 oxygens to give the O,O-bidentate configuration (Figure 1 IIIb). The monodentate mode of binding has been observed in some metalloporphyrin complexes including (OEP)Fe(NO3) (45), (F8TPP)Fe(NO3) (46), (TpivPP)Fe(NO3)−(47), and (TPP)Mn(NO3) (48). Some examples of the O,O-bidentate binding mode in NO3-coordinated metalloporphyrins include (TPP)Fe(NO3) (49,50) and (TpivPP)Fe(NO3) (51). A review article on the coordination chemistry of the nitrate ligand was published in 1971 by Addison and Garner (52).
1.2 Methods that induce linkage...
| Erscheint lt. Verlag | 8.1.2015 |
|---|---|
| Sprache | englisch |
| Themenwelt | Naturwissenschaften ► Chemie ► Anorganische Chemie |
| Naturwissenschaften ► Chemie ► Physikalische Chemie | |
| Technik | |
| ISBN-10 | 0-12-801837-2 / 0128018372 |
| ISBN-13 | 978-0-12-801837-8 / 9780128018378 |
| Haben Sie eine Frage zum Produkt? |
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