Anion coordination chemistry

Edited by Kristin Bowman-James, Antonio Bianchi, and Enrique Garc´ıa-Espa˜na Anion Coordination Chemistry Related Titles Sliwa, W., Kozlowski, C van Leeuwen, P W N M (ed.) Calixarenes and Resorcinarenes Supramolecular Catalysis Synthesis, Properties and Applications 2009 2008 ISBN: 978-3-527-32191-9 ISBN: 978-3-527-32263-3 Ribas Gispert, J Coordination Chemistry 2008 ISBN: 978-3-527-31802-5 Diederich, F., Stang, P J., Tykwinski, R R (eds.) Modern Supramolecular Chemistry Strategies for Macrocycle Synthesis 2008 Balzani, V., Credi, A., Venturi, M Molecular Devices and Machines Concepts and Perspectives for the Nanoworld 2008 ISBN: 978-3-527-31800-1 ISBN: 978-3-527-31826-1 Edited by Kristin Bowman-James, Antonio Bianchi, and Enrique Garc´ıa-Espa˜na Anion Coordination Chemistry The Editors Prof Dr Kristin Bowman-James Department of Chemistry University of Kansas 1251 Wescoe Hall Drive Lawrence, KS 66045 USA Prof Dr Antonio Bianchi University of Florence Department of Chemistry Via della Lastruccia 50019 Sesto Fiorentino Italy Prof Dr Enrique Garc´ıa-Espa˜na Instituto de Qu´ımica Molecular Departamento de Qu´ımica Inorg´anica C/ Catedr´atico Jos´e Beltr´an 46980 Paterna (Valencia) Spain The photograph of Professor Bowman-James on the back cover of the book was kindly supplied by David F McKinney/KU University Relations © 2011 The University of Kansas/Office of University Relations All books published by Wiley-VCH are carefully produced Nevertheless, authors, editors, and publisher not warrant the information contained in these books, including this book, to be free of errors Readers are advised to keep in mind that statements, data, illustrations, procedural details or other items may inadvertently be inaccurate Library of Congress Card No.: applied for British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library Bibliographic information published by the Deutsche Nationalbibliothek The Deutsche Nationalbibliothek lists this publication in the Deutsche Nationalbibliografie; detailed bibliographic data are available on the Internet at © 2012 Wiley-VCH Verlag & Co KGaA, Boschstr 12, 69469 Weinheim, Germany All rights reserved (including those of translation into other languages) No part of this book may be reproduced in any form – by photoprinting, microfilm, or any other means – nor transmitted or translated into a machine language without written permission from the publishers Registered names, trademarks, etc used in this book, even when not specifically marked as such, are not to be considered unprotected by law Typesetting Laserwords Private Limited, Chennai, India Printing and Binding Fabulous Printers Pte Ltd, Singapore Cover Design Formgeber, Eppelheim Printed in Singapore Printed on acid-free paper Print ISBN: 978-3-527-32370-8 ePDF ISBN: 978-3-527-63952-6 oBook ISBN: 978-3-527-63950-2 ePub ISBN: 978-3-527-63951-9 Mobi ISBN: 978-3-527-63953-3 V Contents Preface XI List of Contributors XIII 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 2.1 2.2 2.2.1 2.2.2 2.2.3 2.2.3.1 2.2.4 2.2.4.1 2.2.5 2.3 2.4 Aspects of Anion Coordination from Historical Perspectives Antonio Bianchi, Kristin Bowman-James, and Enrique Garc´ıa-Espa˜na Introduction Halide and Pseudohalide Anions Oxoanions 23 Phosphate and Polyphosphate Anions 29 Carboxylate Anions and Amino Acids 36 Anionic Complexes: Supercomplex Formation 42 Nucleotides 51 Final Notes 60 References 60 Thermodynamic Aspects of Anion Coordination 75 Antonio Bianchi and Enrique Garc´ıa-Espa˜na Introduction 75 Parameters Determining the Stability of Anion Complexes 76 Type of Binding Group: Noncovalent Forces in Anion Coordination 76 Charge of Anions and Receptors 84 Number of Binding Groups 85 Additivity of Noncovalent Forces 86 Preorganization 87 Macrocyclic Effect 91 Solvent Effects 93 Molecular Recognition and Selectivity 102 Enthalpic and Entropic Contributions in Anion Coordination 110 References 132 VI Contents 3.1 3.2 3.3 3.4 3.4.1 3.4.2 3.4.3 3.4.4 3.4.5 3.5 3.5.1 3.5.2 3.5.3 3.5.4 3.5.5 3.5.6 3.5.7 3.6 3.6.1 3.6.2 3.6.3 3.6.4 3.6.5 3.6.6 3.6.7 3.6.8 3.6.9 3.6.10 3.7 3.7.1 3.7.2 3.7.3 3.7.4 3.7.5 3.7.6 3.8 3.8.1 3.8.2 3.8.2.1 3.8.2.2 3.8.2.3 3.9 Structural Aspects of Anion Coordination Chemistry 141 Rowshan Ara Begum, Sung Ok Kang, Victor W Day, and Kristin Bowman-James Introduction 141 Basic Concepts of Anion Coordination Chemistry 142 Classes of Anion Hosts 143 Acycles 144 Bidentate 144 Tridentate 149 Tetradentate 155 Pentadentate 161 Hexadentate 162 Monocycles 164 Bidentate 164 Tridentate 165 Tetradentate 166 Pentadentate 174 Hexadentate 175 Octadentate 177 Dodecadentate 179 Cryptands 181 Bidentate 181 Tridentate 183 Tetradentate 184 Pentadentate 186 Hexadentate 188 Septadentate 192 Octadentate 193 Nonadentate 197 Decadentate 198 Dodecadentate 199 Transition-Metal-Assisted Ligands 201 Bidentate 201 Tridentate 203 Tetradentate 204 Hexadentate 204 Septadentate 206 Dodecadentate 208 Lewis Acid Ligands 210 Transition Metal Cascade Complexes 210 Other Lewis Acid Donor Ligands 213 Boron-Based Ligands 213 Tin-Based Ligands 214 Hg-Based Ligands 216 Conclusion 218 Contents Acknowledgments 218 References 218 4.1 4.2 4.2.1 4.2.2 4.2.3 4.2.4 4.2.5 4.2.6 4.2.7 4.3 4.3.1 4.3.1.1 4.3.1.2 4.3.2 4.3.3 5.1 5.2 5.3 5.4 5.5 5.6 5.7 6.1 6.2 6.3 6.4 6.4.1 6.4.2 6.4.3 Synthetic Strategies 227 Andrea Bencini and Jos´e M Llinares Introduction 227 Design and Synthesis of Polyamine-Based Receptors for Anions 227 Acyclic Polyamine Receptors 229 Tripodal Polyamine Receptors 234 Macrocyclic Polyamine Receptors with Aliphatic Skeletons 236 Macrocyclic Receptors Incorporating a Single Aromatic Unit 241 Macrocyclic Receptors Incorporating Two Aromatic Units 243 Anion Receptors Containing Separated Macrocyclic Binding Units 249 Cryptands 252 Design and Synthesis of Amide Receptors 258 Acid Halides as Starting Materials 259 Acyclic Amide Receptors 259 Macrocyclic Amide Receptors 267 Esters as Starting Materials 270 Using Coupling Reagents 276 References 279 Template Synthesis 289 Jack K Clegg and Leonard F Lindoy Introductory Remarks 289 Macrocyclic Systems 290 Bowl-Shaped Systems 297 Capsule, Cage, and Tube-Shaped Systems 300 Circular Helicates and meso-Helicates 306 Mechanically Linked Systems 308 Concluding Remarks 314 References 315 Anion–π Interactions in Molecular Recognition 321 David Qui˜nonero, Antonio Frontera, and Pere M Dey´a Introduction 321 Physical Nature of the Interaction 322 Energetic and Geometric Features of the Interaction Depending on the Host (Aromatic Moieties) and the Guest (Anions) 323 Influence of Other Noncovalent Interactions on the Anion–π Interaction 330 Interplay between Cation–π and Anion–π Interactions 330 Interplay between π−π and Anion–π Interactions 332 Interplay between Anion–π and Hydrogen-Bonding Interactions 334 VII VIII Contents 6.4.4 6.5 6.6 7.1 7.2 7.2.1 7.2.2 7.2.3 7.2.4 7.2.5 7.3 7.3.1 7.3.2 7.3.3 7.3.4 7.3.5 7.3.6 7.3.7 7.4 8.1 8.2 8.2.1 8.3 8.3.1 8.3.2 8.3.3 8.3.4 8.4 8.4.1 8.4.2 8.4.3 8.4.4 8.4.5 8.4.6 8.4.7 Influence of Metal Coordination on the Anion–π Interaction 337 Experimental Examples of Anion–π Interactions in the Solid State and in Solution 338 Concluding Remarks 353 References 354 Receptors for Biologically Relevant Anions 363 Stefan Kubik Introduction 363 Phosphate Receptors 364 Introduction 364 Phosphate, Pyrophosphate, Triphosphate 366 Nucleotides 387 Phosphate Esters 395 Polynucleotides 407 Carboxylate Receptors 410 Introduction 410 Acetate 412 Di- and Tricarboxylates 425 Amino Acids 433 Peptide C-Terminal Carboxylates 444 Peptide Side-Chain Carboxylates 450 Sialic Acids 451 Conclusion 453 References 453 Synthetic Amphiphilic Peptides that Self-Assemble to Membrane-Active Anion Transporters 465 George W Gokel and Megan M Daschbach Introduction and Background 465 Biomedical Importance of Chloride Channels 466 A Natural Chloride Complexing Agent 468 The Development of Synthetic Chloride Channels 468 Cations, Anions, Complexation, and Transport 468 Anion Complexation Studies 470 Transport of Ions 470 Synthetic Chloride Transporters 470 Approaches to Synthetic Chloride Channels 471 Tomich’s Semisynthetic Peptides 472 Cyclodextrin as a Synthetic Channel Design Element 473 Azobenzene as a Photo-Switchable Gate 474 Calixarene-Derived Chloride Transporters 474 Oligophenylenes and π-Slides 477 Cholapods as Ion Transporters 479 Transport Mediated by Isophthalamides and Dipicolinamides 481 Contents 8.5 8.5.1 8.5.2 8.5.3 8.5.4 8.5.5 8.6 8.6.1 8.6.2 8.6.3 8.6.3.1 8.6.3.2 8.6.4 8.6.5 8.6.6 8.6.7 8.6.8 8.6.8.1 8.6.8.2 8.6.8.3 8.6.8.4 8.6.9 8.6.10 8.6.11 8.7 The Development of Amphiphilic Peptides as Anion Channels 481 The Bilayer Membrane 482 Initial Design Criteria for Synthetic Anion Transporters (SATs) 482 Synthesis of the N-Terminal Anchor Module 483 Preparation of the Heptapeptide 484 Initial Assessment of Ion Transport 485 Structural Variations in the SAT Modular Elements 488 Variations in the N-Terminal Anchor Chains 488 Anchoring Effect of the C-Terminal Residue 489 Studies of Variations in the Peptide Module 491 Structural Variations in the Heptapeptide 492 Variations in the Gly-Pro Peptide Length and Sequence 493 Variations in the Anchor Chain to Peptide Linker Module 494 Covalent Linkage of SATs: Pseudo-Dimers 496 Chloride Binding by the Amphiphilic Heptapeptides 498 The Effect on Transport of Charged Sidechains 499 Fluorescent Probes of SAT Structure and Function 500 Aggregation in Aqueous Suspension and in the Bilayer 501 Fluorescence Resonance Energy Transfer Studies 503 Insertion of SATs into the Bilayer 504 Position of SATs in the Bilayer 505 Self-Assembly Studies of the Amphiphiles 505 The Biological Activity of Amphiphilic Peptides 508 Nontransporter, Membrane-Active Compounds 509 Conclusions 509 Acknowledgments 509 References 510 Anion Sensing by Fluorescence Quenching or Revival 521 Valeria Amendola, Luigi Fabbrizzi, Maurizio Licchelli, and Angelo Taglietti Introduction 521 Anion Recognition by Dynamic and Static Quenching of Fluorescence 522 Fluorescent Sensors Based on Anthracene and on a Polyamine Framework 529 Turning on Fluorescence with the Indicator Displacement Approach 538 Epilog 550 References 551 9.1 9.2 9.3 9.4 9.4.1 Index 553 IX XI Preface While Park and Simmons provided the first seminal report of the supramolecular chemistry of anions in 1968, it was Jean-Marie Lehn who suggested in 1978 that it was truly a form of coordination chemistry At that time supramolecular chemistry, which refers to the interactions of molecular and ionic species beyond the covalent bond, was in its formative years The term supramolecular chemistry was built on the lock and key concept first proposed by Emil Fischer in 1894 The actual term, however, was coined by Jean-Marie Lehn at the early stages of the development of this field In many respects this concept can be merged with another key chemical concept, that of coordination chemistry, also introduced in the late nineteenth century by Alfred Werner All three men, Fischer, Lehn, and Werner, were recognized for their seminal contributions to science with Nobel Prizes As pointed out in Chapter 1, anions were of interest to chemists as early as the 1920s Yet in the early years of supramolecular chemistry, the focus on anions began only as a small seedling that has now grown into a giant tree with many branches Anion coordination chemistry now impinges on numerous fields of science, including medicine, environmental remediation, analytical sensing, as well as many aspects of the global field of nanotechnology Scientists from all areas of chemistry and beyond have joined forces to explore this exciting new field By the early 1990s, there were a number of texts devoted to various aspects of supramolecular chemistry, but none that focused entirely on anions At that time the three of us realized the need for such a text, and we gathered the expertise of anion researchers far and wide to contribute to the book that was published in 1997, Supramolecular Chemistry of Anions Since that time a small number of excellent texts and many reviews have been published, focusing on anions and reporting advances in this rapidly evolving field In this sequel to our earlier text, using the same strategy of enlisting the aid of noted scientists in the field, we have tried to incorporate some of the imagination and excitement that has gone into the science of anions in the last 15 years The chapters are laid out in a manner similar to that in our first volume, covering basic topics in anion coordination Chapter approaches the historical development of anion chemistry from a slightly different viewpoint than usual, by covering both biological and supramolecular developments It is followed by two chapters outlining what we consider to be the core foundations 9.4 Turning on Fluorescence with the Indicator Displacement Approach Figure 9.21 The crystal and molecular structure of the [CuII (21)(Im)]3+ ternary complex [26] Hydrogen atoms have been omitted for clarity The system is further stabilized by π -stacking interactions between the imidazolate ion (donor) and the phenyl groups of the 1,4-xylyl spacers (acceptors) Structure redrawn from data deposited at the Cambridge Crystallographic Data Center (QUHLAG) strong affinity toward ambidentate ligands, in particular the imidazolate ion In fact, [CuII2 (21)]4+ in water, at pH = 7, induces deprotonation of ImH and incorporates the imidazolate anion Im− , to give the stable ternary complex 22, [CuII2 (21)(Im)]3+ Such a species has been isolated in the crystalline form and its molecular structure elucidated through X-ray diffraction studies (see Figure 9.21) [26] It is shown that the imidazolate anion bridges the two copper(II) ions, completing a slightly distorted square coordinative arrangement of each metal center The square is the coordination polygon preferred by CuII , which may account for the high stability of the [CuII2 (21)(Im)]3+ complex Moreover, two further favorable energy terms seem to contribute to the stability of the ternary complex: (i) the π-stacking interaction between the imidazolate ion and the phenyl ring of the two 1,4-xylyl spacers and (ii) the interaction between the unpaired electrons of the two CuII centers, mediated by the imidazolate bridge and responsible for a weak antiferromagnetic coupling Thus, system [CuII2 (21)]4+ seemed an ideal receptor for the fluorimetric sensing of the ImH-containing amino acid histidine through the indicator displacement paradigm An additional advantage was that [CuII2 (21)]4+ , because of the favorable energy terms outlined before, binds the imidazolate ion at pH = and not in a distinctly alkaline solution such as dinuclear complexes of ZnII The fluorescent dye coumarine 343 (19) was tested as a possible partner of CuII2 (21)]4+ in the chemosensing ensemble The constant associated with the formation of the [CuII2 (21)(In)]3+ complex was preliminarily determined: log KIn = 4.3 At this point, the solution of the chemosensing ensemble was prepared: coumarine 343: 10−6 M, [CuII2 (19)]4+ : 2.5 × 10−4 M, pH = (HEPES 0.05 M) Then, such a solution was titrated with histidine (HIS), and, in subsequent experiments, with some selected amino acids: glycine (GLY), alanine (ALA), phenylalanine Figure 9.22a shows the profiles obtained for the varying titration experiments, indicating how the emission band of the coumarine indicator develops on addition of the amino acid Results seem rather poor from the point of view of the selectivity In fact, the titration profiles obtained for HIS and GLY are coincident, showing no 545 300 Fluorescence intensity (540 nm) (a.u.) Fluorescence intensity (490 nm) (a.u.) Anion Sensing by Fluorescence Quenching or Revival 200 100 0.0 (a) 0.1 0.2 0.3 [amino acid] (mM) 200 GLY HIS ALA PHE 150 100 50 0.0 0.4 (b) 1.0 2.0 3.0 [amino acid] (μM) 4.0 Figure 9.22 Profile of the spectrofluorimetric titrations with selected amino acids of (a) an aqueous solution containing coumarine 343 × 10−6 M, [CuII (21)]4+ 2.5 × 10−4 M, buffered to pH = (HEPES 0.05 M) and (b) eosine Y 10−6 M, [CuII (21)]4+ = 2.4 × 10−6 M [25] Eosine Y log K 546 Coumarine 343 HIS GLY ALA PHE Figure 9.23 Log Kass values associated with the equilibrium [CuII (21)(AA)]4+ in aqueous solution [CuII (21)]4+ + AA at pH = (bars, AA = aminoacid) Dashed lines indicate log KIn values for the equilibrium: [CuII (21)]4+ + In− [CuII (21)(In)]3+ (In− = indicator) [24] discrimination However, these titration experiments were not useless, because, from the profiles in Figure 9.22a, the value of Kin for [CuII2 (21)]4+ being known, it was possible to calculate, using a nonlinear least-squares procedure, the constant of the association equilibrium involving the dimetallic receptor and each amino acid Pertinent log Kass values are showed in the bar diagram in Figure 9.23 It is observed that histidine displays the expected higher affinity for the dimetallic receptor [CuII2 (21)]4+ , forming, in particular, a complex whose association constant is more than order of magnitude than that for glycine However, the indicator 9.4 Turning on Fluorescence with the Indicator Displacement Approach coumarine 343 (19) forms with [CuII2 (21)]4+ a complex whose stability is distinctly lower than that observed for the complexes of HIS and GLY and is therefore quantitatively displaced by both amino acids Thus, in order to obtain discrimination, one should choose an indicator with a KIn definitely greater than Kass of GLY but lower than Kass of HIS Eosine Y (23) was a good choice O O Br O O Br Br O Br 23 In fact, log KIn , determined by titrating with [CuII2 (21)]4+ a solution of eosine Y buffered to pH = 7, was 7.2 Such a value is only slightly lower than that of log Kass of HIS, but, in any case, the indicator displacement should be favored by a mass effect, due to the fact that, over the course of the titration, the concentration of the amino acid becomes higher and higher than that of the indicator (up to 1000-fold) In fact, titration experiments, illustrated by pertinent profiles in Figure 9.21b, disclosed a well-defined selective behavior in favor of HIS Ultimately, receptor [CuII2 (21)]4+ prefers imidazolate with respect to the carboxylate group because it can establish stronger metal–ligand interactions However, the same receptor, in the presence of bridging anions of the same coordinating tendencies, can exert geometrical selectivity This occurs, for instance, in a classical issue of anion chemistry: the discrimination of orthophosphate (Pi) and pyrophosphate (PPi) [27] Figure 9.24a shows the profiles obtained by titrating with Pi and PPi a neutral solution containing the chemosensing ensemble {[CuII2 (21)]4+ + coumarine 343} [28] However, such a system does not work well: PPi displaces effectively the indicator, producing a full revival of fluorescence, while Pi induces a less pronounced recovery of the emission, but still displays a competitive behavior This state of affairs can be accounted for on the basis of the bar diagram shown in Figure 9.25 The log KIn value for coumarine 343 (dashed line) is distinctly lower than log Kass for PPi, which accounts for complete indicator displacement by pyrophosphate However, log KIn is only slightly lower than log Kass for Pi, and a significant displacement of the indicator takes place on excess addition of the anion Thus, in order to achieve discrimination between PPi and Pi, a fluorescent indicator displaying a higher affinity for the receptor is required Such an indicator can again be eosine Y In fact, titration profiles shown in Figure 9.24b indicate the occurrence of an effective discrimination of PPi with respect to Pi, a behavior that can be satisfactorily interpreted on the basis of the bar diagram in Figure 9.25 Eosine Y forms with receptor [CuII2 (21)]4+ a complex of stability comparable to that of PPi and much higher than that of Pi 547 Fluorescence intensity (540 nm) (a.u.) Fluorescence intensity (490 nm) (a.u.) Anion Sensing by Fluorescence Quenching or Revival 400 300 200 150 Pi 100 PPi Cl − 50 100 0.0 (a) 0.1 0.2 0.3 0.4 (b) [anion], (mM) 10 [anion], (μM) (b) In = eosine Y : 10−6 M, [CuII (21)]4+ = 2.4 × 10−6 M Nitrate and sulfate display the same behavior (no indicator displacement and no fluorescence revival) as chloride with both indicators [28] Figure 9.24 Titration of the chemosensing ensemble {[CuII (21)]4+ + indicator(In)} in an aqueous solution buffered to pH = 7, with pyrophosphate ( ), orthophosphate ( ), and chloride (♦); (a) In = coumarine 343 : 10−6 M, [CuII (21)]4+ = 2.5 × 10−4 M and Eosine Y log K 548 Coumarine 343 PPi Pi Chloride Nitrate Sulfate Figure 9.25 Log Kass values associated with the equilib[CuII (21)(X)](4−n)+ in aqueous rium: [CuII (21)]4+ + Xn− solution at pH = (bars, Xn− = anion) Dashed lines indicate log KIn values for the equilibrium: [CuII (21)]4+ + [CuII (21)(In)]3+ (In− = indicator) [28] In− Selectivity may derive from the capability of PPi to place its terminal oxygen atoms in the vacant coordinative sites of the two CuII centers, without inducing any serious structural modification of the hexamine macrocycle, relaxed to its minimum energy conformation Such a conformation does not necessarily correspond to that observed in the [CuII (21)(Im)]3+ complex in Figure 9.21 but can be similar to that 9.4 Turning on Fluorescence with the Indicator Displacement Approach Figure 9.26 The crystal and molecular structure of the [CuII (21)(CH3 COO)2 ]2+ complex [29] Hydrogen atoms have been omitted for clarity Structure redrawn from data deposited at the Cambridge Crystallographic Data Center (KEBZAS) assumed by the envisaged receptor in its complex with two acetate ions, as shown by the crystal and molecular structure displayed in Figure 9.26 [29] On the other hand, bridging by the orthophosphate anion of the two CuII ions when the receptor is conformationally arranged as shown in Figure 9.26 should induce a preliminary pronounced structural reorganization, whose endothermicity is reflected in the much lower value of log Kass Chloride, nitrate, and sulfate ions experience an even higher difficulty in spanning the two metal ions of the [CuII2 (21)]4+ receptor (Kass < 103 ) and not displace eosine Y and coumarine 343, even if added in a large excess The use of the indicator displacement paradigm seems quite convenient in designing analytical procedures for anion determination in solution, compared to the approach that involves the covalent linking of the fluorogenic subunit to the receptor’s framework The first evident advantage is that no synthetic efforts are required to link covalently the fluorophore to the envisaged receptor Moreover, synthetic modifications on the receptor may change its binding tendencies and alter its genuine binding selectivity Finally, when planning the synthesis of a fluorescent sensor using the covalent approach, one cannot predetermine the signal transduction mechanism (whether emission will be quenched or enhanced on anion interaction), an event that has to be experimentally verified Conversely, the critical requirement to be fulfilled when setting up a fluorescent ‘‘chemosensing ensemble’’ is that the receptor must effectively quench the noncovalently bound fluorophore Such an essential feature is provided by receptors containing as binding sites paramagnetic transition metal ions, which are photophysically active through electron transfer or energy transfer (Dexter type) mechanisms, but can be hardly achieved by receptors that not contain metals In this sense, dicopper(II) bistren cryptates such as [CuII (17)]4+ are ideal candidates for the fluorescent sensing of a variety of anionic substrates Further recent examples are shown in Scheme 9.3 The dimetallic receptor [CuII2 (25)]4+ includes dicarboxylates in water at pH = and displays linear recognition selectivity [30] Among phthalates, it shows a pronounced affinity for the 1,4-derivative (terephthalate), with respect to the 1,3-(isophthalate) and 1,2-(phthalate) positional isomers The indicator used was rhodamine, which contains a 1,4-benzenedicarboxylate subunit Among linear aliphatic dicarboxylates − OOC–(CH2 )n −COO− , [CuII2 (24)]4+ shows a definite preference for derivatives with n = (glutarate) and n = (adipate) Most interestingly, 549 550 Anion Sensing by Fluorescence Quenching or Revival NH HN N NH NH HN HN − O O N + O − O H3N L-Glutamate 24 − O O NH N NH NH C O HN O O C O O N HN N − HO P O O N N N N NH2 O O C OH OH 25 GMP Scheme 9.3 Bistren cryptands, whose dicopper(II) complexes show selective affinity for L-glutamate (24) [30] and GMP (25) [31] in an aqueous neutral solution it recognizes l-glutamate in the presence of any other neurotransmitter containing –NH2 and/or –COO− functionalities (including l-aspartate and GABA) [30] Receptor [CuII2 (25)]4+ , showing the larger ellipsoidal cavity among investigated dimetallic bistren cryptates, is able to include, in an MeOH/water solution (50 : 50, v/v), buffered at pH, nucleoside monophosphates and displays selective affinity toward guanosine monophosphate (GMP) [31] It has been hypothesized that GMP bridges the two CuII centers by two oxygen atoms: one from the phosphonate group, the other from the nucleobase in its enolate mesomeric form, as sketched in Scheme 9.3 Among the several tested indicators, 6-carboxyfluorescein gave the most satisfactory behavior 9.4.1 Epilog In this chapter, we have tried to describe an approach to the design of fluorescent sensors for anions Such an approach reflects essentially the activity of this group in the field and how it developed over the past 15 years A few selected examples have been presented and discussed to make the reader acquainted with the basic principles and experimental aspects of the fluorimetric investigations If steady-state spectrofluorimetry is the main technique, the study of the receptor–anion interaction cannot be based solely on the determination of fluorescence spectra, whether the envisaged anion induces an enhancement of a decrease in the emission intensity of a given fluorophore Selectivity is a thermodynamic property, and the affinity of the receptor for a given anion is expressed by the value of the equilibrium References constant for the formation of the receptor–anion complex Thus, detailed equilibrium studies should be carried out in order to fully characterize the system under investigation and to define the stoichiometry of the species present at equilibrium Therefore, titration data (families of spectra, titration curves) should be carefully analyzed, for instance, by using the excellent packages available for data treatment, based on nonlinear least-squares fitting (the authors have used HyperQuad) [32] In the presence of more complex equilibria, it may be useful to also carry out spectrophotometric titration experiments, as absorbance spectra typically show more rich and complex patterns, usually spread along a larger wavelength interval Chemists have a native tendency to explain reactivity (of any kind) on a structural basis, and in this particular field, a selective or specific interaction is interpreted on the basis of an especially favorable matching of the geometrical features of the receptor and the anion Thus, availability of X-ray structures of the receptor and its anion complex favor understanding of the solution behavior Most importantly, the knowledge of structural details can provide valuable suggestions for the design and synthesis of an anion receptor of improved selectivity, which, ultimately, remains the most fascinating and challenging aspect of chemical science References Oxford Dictionaries Online-English Dictionary, http://oxforddictionaries.com/definition/ sensor accessed on 24 June, 2011 Hulanicki, A., Głab, S., and Ingman, F (1991) Pure Appl Chem., 63, 1247–1250 Gale, P.A and Gunnlaugsson, T (Guest Editors) (2010) Chem Soc Rev., 39, 3581–4008 (themed issue on: Supramolecular chemistry of 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tetradentate 155–161 – tridentate 149–155 Acyclic polyamine receptors 229–234 Adenosine-5 -triphosphate (ATP) 51, 52, 55, 56–59, 363, 387–390, 395 ADP 51, 52, 56, 58, 387, 388–390, 392 Alkaline phosphatases, active site of Amide receptors design and synthesis 258–259 – acid halides as starting materials 259–270 – esters as starting materials 270–276 – using coupling reagents 276–279 Amidinium moieties 372 Amino acids 433–444 AMP 51, 55, 387, 388–390, 392–393, 395 Amphiphilic peptides, synthetic 465 – biomedical importance of chloride channels 466–468 – – natural chloride completing agent 468 – development, as anion channels 481–482 – – bilayer membrane 482 – – heptapeptide preparation 484 – – initial design criteria for synthetic anion transporters (SATs) 482–483 – – ion transport initial assessment 485–487 – – N-terminal anchor module synthesis 483–484 – SAT modular element structural variation 488 – – aggregation in aqueous suspension bilayer 501–503 – – anchor chain variations to peptide linker module 494–496 – – biological activity of amphiphilic peptides 508–509 – – charged sidechain transport 499–500 – – chloride binding by amphiphilic heptapeptides 498–499 – – covalent linkage 496–498 – – C-terminal residue anchoring effect 489–491 – – fluorescence resonance energy transfer (FRET) studies 503–504 – – gly-pro peptide length and sequence variations 493–494 – – heptapeptide structural variations 492 – – insertion into bilayer 504–505 – – nontransporters and membrane-active compounds 509 – – N-terminal anchor chain variations 488–489 – – position in bilayer 505 – – self-assembly studies of amphiphiles 505–508 – synthetic chloride channel approaches 471–472 – – azobenzene as photo-switchable gate 474 Anion Coordination Chemistry, First Edition Edited by Kristin Bowman-James, ˜ Antonio Bianchi, and Enrique Garc´ıa-Espana © 2012 Wiley-VCH Verlag GmbH & Co KGaA Published 2012 by Wiley-VCH Verlag GmbH & Co KGaA 554 Index Amphiphilic peptides, synthetic (contd.) – – calixarene-derived chloride transporters 474–477 – – cholapods as ion transporters 479–481 – – cyclodextrin as synthetic channel design element 473–474 – – oligophenylenes and π -slides 477–479 – – semisynthetic peptides 472 – – transport mediated by isophthalamides and dipicolinamides 481 – synthetic chloride channel development 468–469 – – anion complexation studies 470 – – ion transport 470 – – synthetic chloride transporters 470–471 Amphotericin B (AmB) 477 Anchor chain variations to peptide linker module 494–496 Anionic complexes and supercomplex formation 42–51 Anionic substrates 1, 5, 6, 7, 8, 29 Anion receptors 289, 293 – containing separated macrocyclic binding units 249–252 Anion recognition 76, 99, 102–109 Anion sensing and fluorescence quenching 521 – by dynamic and static quenching of fluorescence 522–529 – fluorescent sensors, based on anthracene and on polyamine framework 529–538 – indicator displacement approach 538–550 Anion–π interactions 142, 321 – energetic and geometric features and 323–329 – experimental examples, in solid state and in solution 338–353 – interplay between cation–π and 330–332 – interplay between hydrogen-bonding and 334–336 – metal coordination influence on 337–338 – physical nature 322–323 – π –π interactions and 332–334 AN number 96 Azacryptands 25, 26 Azamacrocycles 32 Azamacropolycycles 10 Azide anion 15 Azobenzene as photo-switchable gate 474 β-Cyclodextrin (β-CD) 473–474 b Biologically relevant anions, receptors for 363 – – – – – carboxylate receptors 410–412 – acetate 412–425 – amino acids 433–444 – di-and tricarboxylates 425–433 – peptide C-terminal carboxylates 444–450 – – peptide side-chain carboxylates 450–451 – – sialic acids 451–453 – phosphate receptors 364–366 – – nucleotides 387–395 – – phosphate esters 395–407 – – phosphate, pyrophosphate, and triphosphate 366–387 – – polynucleotides 407–410 Biomedical importance of chloride channels 466–468 – natural chloride completing agent 468 Bis-aminals 249–250 Biscyclopeptides 129 Bisintercalation 408–409 BLM experiment 485, 487 Bolaamphiphiles See Bolytes Bolytes 466 Boron-based ligands 213–214 Borromean ring 209, 210 Bouquet 465 Bowl-shaped systems and template synthesis 297–300 Brewster angle microscope (BAM) 506 Bromides 16 Butylamine 442 c C2-BISTREN 13 C3-BISPRN 28 C5-BISTREN 13, 14, 22 Calixarenes 350, 351, 410, 419, 421, 422, 474–477 Calixpyrroles 173, 380 Calometric method 110–113 Cambridge Structural Database (CSD) 338, 482 Capsule, cage, and tube-shaped systems 300–306 Carbonic anhydrases Carboxyfluorescein 431, 485 Carboxylate anions and amino acids 36–42 Carboxylates 363, 354, 373, 403, 407, 410–412 Cascade complexes 6, 16, 21, 23, 41, 42, 190–192, 195–196, 196, 371 – transition metal 210–213 Index Catenane formation 308, 309, 311, 313 Cation-π and anion–π interactions 330–332 Chaotropes Charge–charge interaction 43, 75, 84 Charged sidechain transport 499–500 Chemical sensor 521 Chemical Society Reviews Chloride binding, by amphiphilic heptapeptides 498–499 Chloride channels See amphiphilic peptides, synthetic Cholapods 417, 418 – as ion transporters 479–481 Chundle 465 Circular dichroism spectroscopy 402, 450 Circular helicates and meso-helicates, and template synthesis 306–308 35 Cl NMR study 10 Cl− views 12 13 C NMR study 10 Coulomb’s law 84 Coupling reagents 276–279 Covalent approach 538, 539 Critical points (CPs) 327–328 Cryptands 27, 252–258 – bidentate 181–183 – decadentate 198–199 – dodecadentate 199–201 – hexadentate 188–192 – nonadentate 197–198 – octadentate 193–197 – pentadentate 186–188 – septadentate 192–193 – tetradentate 184–186 – tridentate 183–184 Cryptate complex crystal structures 109 Crystallography 17 C-terminal residue anchoring effect 489–491 Cyanometallate anions 42 Cyclic polypyrrole anion receptors 19 Cyclodextrin as synthetic channel design element 473–474 Cystic fibrosis transport regulator (CFTR) 466 d DeGrado peptide 466 Dehalogenase 5, Dialkylamines 483 Dicarboxylates 38, 41 – and tricarboxylates 425–433 Didodecanoylphosphatidylethanolamine 483 Dihydrogenphosphate 370, 382 Ditin katapinand complex 216 DMSO 97, 98, 99, 122, 126, 378, 406, 414, 417 Double valence 142 Dynamic light scattering (DLS) 507 e Enthalpic and entropic contributions, in anion coordination 110–132 Esters, as starting materials 270–276 Ethylenediaminetetraacetic acid (EDTA) 496 f Fluorescence dequenching 485 Fluorescence quenching 522–529 Fluorescence resonance energy transfer (FRET) studies 501, 503–504 Fluorescent indicators 523, 539, 542, 544, 547 Fluorescent probes, of structure and variation 500–501 – aqueous suspension aggregation and bilayer, aggregation in 501–503 – fluorescence resonance energy transfer (FRET) studies 503–504 – SAT – – insertion into bilayer 504–505 – – position in bilayer 505 Fluorescent sensors, based on anthracene and on polyamine framework 529–538 Fluorophore-spacer-receptor (FSR) 538 19 F-NMR study 19 Formic acid 411 F− views 12, 14 g Gly-pro peptide length and sequence variations 493–494 Guanidiniocarbonyl pyrrole moiety 375, 407, 438 Guanidinium groups 29, 30, 32, 36, 37 Guanidinium moieties 372–373, 406 Guanosine monophosphate (GMP) 390, 395 Gutmann’s donor number (DN) 95 h H2 P2 O7 – 33–34 Halides 153 – pseudohalide anions 9–23 555 556 Index Haloalkane dehydrogenase 5, H-bonding donor group sampling 143–144 HCA II active site Heptapeptide – preparation 484 – structural variations 492 Heteroatom-bridged heteroaromatic calixarenes 350 Hexacyanocobaltate anions 46–47 Hexafluorobenzene 323, 325, 333, 353–354 Histidine 535, 538, 544, 545, 546 Historical perspectives, of anion coordination – anionic complexes and supercomplex formation 42–51 – carboxylate anions and amino acids 36–42 – halide and pseudohalide anions 9–23 – nucleotides 51–60 – oxoanions 23–36 H NMR studies 42, 54, 79, 263–264, 267, 272, 332, 344, 348, 349, 388, 393, 415, 436, 443, 521, 526, 527, 528 Hofmeister series 3, Host–guest relations and anion–π interactions 323–329 Hydraphiles 466 Hydrogen bonds 24, 81–83, 113–114, 330 – and anion–π interactions 334–336 2-hydroxypropyl 4-nitrophenyl phosphate (HPNP) 406, 407 8-hydroxy-1,3,6-pyrene trisulfonate (HPTS) 390 8-hydroxypyrene-1,3,6-trisulfonic acid (HTPS) 473 – – – – – – – – boron-based 213–214 Hg-based 216–218 tin-based 214–216 transition metal cascade complexes 210–213 Lewis acid ligands 210 Lewis base 6, 21 Ligand solvation 96–97 Lucigenin 486–487 m Imidazolium 187 Indicator displacement approach 538–550 Indole 501 In–in equilibrium Ion transport initial assessment 485–487 Macrocyclic effect, in anion coordination 88, 91–93 Macrocyclic polyamine receptors – with aliphatic skeletons 236–240 – incorporating single aromatic unit 241–243 – incorporating two aromatic units 243–249 Macrocyclic systems and template synthesis 290–297 Mechanically linked systems and template synthesis 308–314 Mecuracarborands 22 Mercury-based ligands 216–218 Metal coordination influence, on anion–π interactions 337–338 Metallocyanides 44, 84 Metallophosphatases Minimalist peptides 465, 466 Molecular recognition – and selectivity 102–109 Monocycles – bidentate 164–165 – dodecadentate 179–180 – hexadentate 175–177 – octadentate 177–179 – pentadentate 174–175 – tetradentate 166–174 – tridentate 165–166 Multi-ion hopping 352 Multiple condensation method 256 N-acetylneuraminic acid (NeuAc) 451 k n Katapinands 2, 90, 141, 181 – conformational changes in 91 Kosmotropes 3, NAD 391–392 NADP 391 23 Na exchange method 473 N 10 -Formyl-tetrahydrofolate 411 N-heptyl ester 491 NMR titration 37, 41, 42, 521, 522, 526, 527, 528 NO3– 25 i l Langmuir trough 506 Lewis acid 6, 8, 21 – ligands Index Noncovalent interactions 330 – interplay between cation–π and anion–π interactions 330–332 – interplay between hydrogen-bonding and anion–π interactions 334–336 – metal coordination influence on anion–π interactions 337–338 – π –π interactions and anion–π interactions 332–334 Nontransporters and membrane-active compounds 509 N-terminal anchor chain variations 488–489 N-terminal anchor module synthesis 483–484 Nucleotides 51–60, 387–395 o O-BISDIEN 25, 53, 58 O-BISTREN 11, 14, 22, 28 Oligonaphthalenediimides (O-NDIs) 352 Oligophenylenes and π -slides 477–479 Organoboron compound crystal structure 22 Organotin compound crystal structure 22 ORTEP diagram, of boron–silicon receptor fluoride complex Orthophosphate receptors 364 Out–out equilibrium Oxoanions 23–36 – acyclic polyamine receptors 229–234 – anion receptors containing separated macrocyclic binding units 249–252 – cryptands 252–258 – macrocyclic receptors – – with aliphatic skeletons 236–240 – – incorporating single aromatic unit 241–243 – – incorporating two aromatic units 243–249 – tripodal polyamine receptors 234–236 Polyamine complex 408, 532, 533, 535 Polyammonium receptor 42, 43, 45, 51–52, 84, 227, 229, 236 Polyazacryptands 17 Polyazacycloalkanes 43 Polyazamacrobicycle 254 Polyazamacrocycles 37, 54, 90, 367, 368, 371, 373, 387–388, 408, 412 Polynucleotides 407–410 Potentiometry 369 Preferential solvation 99, 100–101 Pressman cell See U-tube Primary valence 142 Prodigiosin 468 Proline 483 Pseudo-dimers 496–498 Pseudorotaxane 311, 312, 313 195 Pt NMR studies 47, 48, 49 Pyrene 501, 503 Pyridinophane 27 p Peptide C-terminal carboxylates 444–450 Peptide module variation studies 491 – gly-pro peptide length and sequence variations 493–494 – heptapeptide structural variations 492 Peptide side-chain carboxylates 450–451 Perchlorates 25, 26 Phosphatases Phosphate and polyphosphate anions 29 Phosphate-binding protein (PBP) 4, 85 Phosphate chelation 410 Phosphate receptors 364–366 – phosphate esters 395–407 – phosphate, pyrophosphate, and triphosphate 366–387 π –π interactions and anion–π interactions 332–334 Phosphodiesters receptors 404 31 P NMR studies 56, 58, 390 Polyamide receptors 227 Polyamine-based receptors, for anions design and synthesis 227–228 q Quaternization, of nitrogen atoms Quaterpyridyl ligand 305 368 r ReO− 26–27, 26 ResearchCollaboratory for Structural Bioinformatics (RCSB) protein database 366 Rotaxanes 310, 313, 314 Rubisco 8, s Salt bridges 77–79, 81 Sapphyrin 18–19, 379–380, 410, 438 Secondary valence 142 Selective solvation 99 Selectivity, in anion coordination 102–108, 131 Self-assembly 334, 341, 342, 344, 345, 350, 352 – studies, of amphiphiles 505–508 557 558 Index Semisynthetic peptides 472 Serratia marcescens 468 Sialic acids 451–453 SiF2− 26 Soccer ball ligand Solvation 93–97, 99–100 Spectrofluorimetric titration 523,524, 525, 526, 527, 529, 534, 539, 542, 546, 550 Spectrofluorimetry See Spectrofluorimetric titration Spectrophotometric titration 526, 527, 534, 535, 539, 540, 542, 551 Squaramide moieties 423 Stern–Volmer equation 523 Streptomyces lividans 469 Structural aspects, of anion coordination chemistry 141 – acyclic ligands 144 – – bidentate 144–148 – – hexadentate 162–163 – – pentadentate 161–162 – – tetradentate 155–161 – – tridentate 149–155 – anion host classes 143–144 – cryptands – – bidentate 181–183 – – decadentate 198–199 – – dodecadentate 199–201 – – hexadentate 188–192 – – nonadentate 197–198 – – octadentate 193–197 – – pentadentate 186–188 – – septadentate 192–193 – – tetradentate 184–186 – – tridentate 183–184 – lewis acid ligands 210 – – boron-based ligands 213–214 – – Hg-based ligands 216–218 – – tin-based ligands 214–216 – – transition metal cascade complexes 210–213 – monocycles – – bidentate 164–165 – – dodecadentate 179–180 – – hexadentate 175–177 – – octadentate 177–179 – – pentadentate 174–175 – – tetradentate 166–174 – – tridentate 165–166 – transition-metal-assisted ligands 201 – – bidentate 201–203 – – dodecadentate 208–210 – – hexadentate 204–206 – – septadentate 206–207 – – tetradentate 204 – – tridentate 203–204 Sulfate anion 27, 28 – in macrocycle 29 Sulfate-binding protein (SBP) Sulfate complex structure 87–88, 87 Supramolecular cage 303 Supramolecular chemistry Synporins 465, 466 Synthetic anion transporters (SATs) – initial design criteria for 482–483 – modular element structural variation 488 – – aggregation in aqueous suspension bilayer 501–503 – – anchor chain variations to peptide linker module 494–496 – – biological activity of amphiphilic peptides 508–509 – – charged sidechain transport 499–500 – – chloride binding by amphiphilic heptapeptides 498–499 – – covalent linkage 496–498 – – C-terminal residue anchoring effect 489–491 – – fluorescence resonance energy transfer (FRET) studies 503–504 – – gly-pro peptide length and sequence variations 493–494 – – heptapeptide structural variations 492 – – insertion into bilayer 504–505 – – nontransporters and membrane-active compounds 509 – – N-terminal anchor chain variations 488–489 – – position in bilayer 505 – – self-assembly studies of amphiphiles 505–508 Synthetic channels 465, 466 Synthetic chloride channel approaches 471–472 – azobenzene as photo-switchable gate 474 – calixarene-derived chloride transporters 474–477 – cholapods as ion transporters 479–481 – cyclodextrin as synthetic channel design element 473–474 – oligophenylenes and π -slides 477–479 – semisynthetic peptides 472 – transport mediated by isophthalamides and dipicolinamides 481 Synthetic chloride channel development 468–469 – anion complexation studies 470 Index – ion transport 470 – synthetic chloride transporters 470–471 Synthetic receptors 77, 85 Synthetic strategies 227 – amide receptors design and synthesis 258–259 – – acid halides as starting materials 259–270 – – esters as starting materials 270–276 – – using coupling reagents 276–279 – polyamine-based receptors for anions design and synthesis 227–228 – – acyclic polyamine receptors 229–234 – – anion receptors containing separated macrocyclic binding units 249–252 – – cryptands 252–258 – – macrocyclic polyamine receptors with aliphatic skeletons 236–240 – – macrocyclic receptors incorporating single aromatic unit 241–243 – – macrocyclic receptors incorporating two aromatic units 243–249 – – tripodal polyamine receptors 234–236 t Telluronium complex 214 Template synthesis 289 – bowl-shaped systems 297–300 – capsule, cage, and tube-shaped systems 300–306 – circular helicates and meso-helicates 306–308 – macrocyclic systems 290–297 – mechanically linked systems 308–314 Templating anion 290, 300, 306 Terephthalate dianion 40 Tetraazacycloalkanes 52 Tetraazamcrocycle 44 Tetraperfluorophenyl-substituted N-confused porphyrin 340–341 Tetraprotonated macrocycles 25 Thermodynamic aspects, of anion coordination – enthalpic and entropic contributions 110–132 – molecular recognition and selectivity 102–109 – parameters determining anion complex stability 76 – – anion and receptor charge 84–85 – – noncovalent forces 76–84, 86–87 – – preorganization 87–93 – – solvent effects 93–102 Thioamides 377 Thymidine -triphosphate (TTP) 76–77 Tin-based ligands 214–216 Torpedo californica acetylcholine receptor 465 Transfer free energies 95, 100 Transition-metal-assisted ligands 201 – bidentate 201–203 – dodecadentate 208–210 – hexadentate 204–206 – septadentate 206–207 – tetradentate 204 – tridentate 203–204 Transition metal cascade complexes 210–213 Transport mediated by isophthalamides and dipicolinamides 481 Triazoles 151 Tricarboxylates and dicarboxylates 425–433 Triglycine 483 Tripodal polyamine receptors 234–236 Tripodal triamides 266 Triton X-100 471–472 Tryptophan 501, 534, 535 u Uridine diphosphate (UDP) 391 Uridine triphosphate (UTP) 391 U-tube 470 v Van’t Hoff isochore method Vancomycin 411, 449 110 w Wilhelmy plate 506 x X-ray diffraction z Zwitterionic hydrogen bonds 30 559 ... of Anion Coordination Chemistry 141 Rowshan Ara Begum, Sung Ok Kang, Victor W Day, and Kristin Bowman-James Introduction 141 Basic Concepts of Anion Coordination Chemistry 142 Classes of Anion. .. binding properties with anions Examples of this chemistry are included in Figures 1.5 and 1.6 and Refs [78–94] Anion coordination chemistry and classical metal coordination chemistry have an interface... the supramolecular chemistry of anions in 1968, it was Jean-Marie Lehn who suggested in 1978 that it was truly a form of coordination chemistry At that time supramolecular chemistry, which refers