Chaotropic Monovalent Anion‐Induced Rectification Inversion at Nanopipettes Modified by Polyimidazolium Brushes

A nonintuitive observation of monovalent anion‐induced ion current rectification inversion at polyimidazolium brush (PimB)‐modified nanopipettes is presented. The rectification inversion degree is strongly dependent on the concentration and species of monovalent anions. For chaotropic anions (for example, ClO₄^?), the rectification inversion is easily observed at a low concentration (5 mm ), while there is no rectification inversion observed for kosmotropic anions (Cl^?) even at a high concentration (1 m ). Moreover, at the specific concentration (for example, 10 mm ), the variation of rectification ratio on the type of anions is ranged by Hofmeister series (Cl^?≥NO₃^?>BF₄^?>ClO₄^?>PF₆^?>Tf₂N^?). Estimation of the electrokinetic charge density (σ^ek) demonstrates that rectification inversion originates from the charge inversion owing to the over‐adsorption of chaotropic monovalent anion. To qualitatively understand this phenomenon, a concentration‐dependent adsorption mechanism is proposed.     

C3i‐Symmetric Octanuclear Cadmium Cages: Double‐Anion‐Templated Synthesis,Formation Mechanism,and Properties

A series of C_3i‐symmetric bicapped trigonal antiprismatic Cd₈ cages [2X@Cd₈L₆(H₂O)₆] ? n Y ? solvents (X=Cl^?, Y=NO₃^?, n=2: MOCC‐4 ; X=Br^?, Y=NO₃^?, n=2: MOCC‐5 ; X=NO₃^?, Y=NO₃^?, n=2: MOCC‐6 ; X=NO₃^?, Y=BF₄^?, n=2: MOCC‐7 ; X=NO₃^?, Y=ClO₄^?, n=2: MOCC‐8 ; X=CO₃^2?, n=0: MOCC‐9 ), doubly anion templated by different anions, were solvothermally synthesized by means of a flexible ligand. Interestingly, the CO₃^2? template for MOCC‐9 was generated in situ by two‐step decomposition of DMF solvent. For other MOCCs, spherical or trigonal monovalent anions could also play the role of template in their formation. The template abilities of these anions in the formation of the cages were experimentally studied and are discussed for the first time. Anion exchange of MOCC‐8 was carried out and showed anion‐size selectivity. All of the cage‐like compounds emit strong luminescence at room temperature.     

Photomagnetic Response in Highly Conductive Iron(II) Spin‐Crossover Complexes with TCNQ Radicals

Co‐crystallization of a cationic Fe^II complex with a partially charged TCNQ^.δ? (7,7′,8,8′‐tetracyanoquinodimethane) radical anion has afforded molecular materials that behave as narrow band‐gap semiconductors, [Fe(tpma)(xbim)](X)(TCNQ)_1.5?DMF (X=ClO₄^? or BF₄^?; tpma=tris(2‐pyridylmethyl)amine, xbim=1,1′‐(α,α′‐o‐xylyl)‐2,2′‐bisimidazole). Remarkably, these complexes also exhibit temperature‐and light‐driven spin crossover at the Fe^II center, and are thus the first structurally defined magnetically bistable semiconductors assembled with the TCNQ^.δ? radical anion. Transport measurements reveal the conductivity of 0.2 S cm^?1 at 300 K, with the low activation energy of 0.11 eV.     

Dual Role of the 1,2,3‐Triazolium Ring as a Hydrogen‐Bond Donor and Anion–π Receptor in Anion‐Recognition Processes

Several bis(triazolium)‐based receptors have been synthesized as chemosensors for anion recognition. The central naphthalene core features two aryltriazolium side‐arms. NMR experiments revealed differences between the binding modes of the two triazolium rings: one triazolium ring acts as a hydrogen‐bond donor, the other as an anion–π receptor. Receptors 9²⁺?2BF₄ ^? (C₆H₅), 11²⁺?2BF₄ ^? (4‐NO₂?C₆H₄), and 13²⁺?2BF^4? (ferrocenyl) bind HP₂O₇^3? anions in a mixed‐binding mode that features a combination of hydrogen‐bonding and anion–π interactions and results in strong binding. On the other hand, receptor 10²⁺?2 BF₄ ^? (4‐CH₃O?C₆H₄) only displays combined Csp₂?H/anion–π interactions between the two arms of the receptors and the bound anion rather than triazolium (CH)⁺???anion hydrogen bonding. All receptors undergo a downfield shift of the triazolium protons, as well as the inner naphthalene protons, in the presence of H₂PO₄^? anions. That suggests that only hydrogen‐bonding interactions exist between the binding site and the bound anion, and involve a combination of cationic (triazolium) and neutral (naphthalene) C?H donor interactions. Theoretical calculations relate the electronic structure of the substituent on the aromatic group with the interaction energies and provide a minimum‐energy conformation for all the complexes that explains their measured properties.     

Macrocycle-Directed Construction of Tetrahedral Anion–π Receptors for Nesting Anions with Complementary Geometry

Manipulation of the emerging anion–π interactions in a highly cooperative manner through sophisticated host design represents a very challenging task. In this work, unprecedented tetrahedral anion–π receptors have been successfully constructed for complementary accommodation of tetrahedral and relevant anions. The synthesis was achieved by a macrocycle-directed approach by using large macrocycle precursors bearing four reactive sites, which enabled a kinetic-favored pathway and afforded the otherwise inaccessible tetrahedral cages in considerable yields. Crystal structure suggested that the tetrahedral cages have an enclosed three-dimensional cavity surrounded by four electron-deficient triazine faces in a tetrahedral array. The complementary accommodation of a series of tetrahedral and relevant anions including BF₄⁻, ClO₄⁻, H₂PO₄⁻, HSO₄⁻, SO₄²⁻ and PF₆⁻ was revealed by ESI-MS and DFT calculations. Crystal structures of ClO₄⁻ and PF₆⁻ complexes showed that the anion was nicely encapsulated within the tetrahedral cavity with up to quadruple cooperative anion–π interactions by an excellent shape and size match. The strong anion–π binding was further confirmed by negative ion photoelectron spectroscopy measurements.     

Size‐Regulable Vesicles Based on Anion–π Interactions

Taking tetraoxacalix[2]arene[2]triazine as a functionalization platform, a series of new amphiphilic molecules were synthesized in 18 to 53 % yields by using a fragment coupling protocol. These amphiphilic molecules self‐assembled into stable vesicles in a mixture of THF and water, with the surface of the vesicles engineered by electron‐deficient cavities. Various anions are able to selectively influence the size of self‐assembled vesicles, following the order of F^?<ClO₄^?<SCN^?<BF₄^?<Br^?<Cl^?<NO₃^?, as revealed by DLS measurements. Such a sequence was independent with the hydration cost and in agreement with the binding strength of anions with tetraoxacalix[2]arene[2]triazine host molecule, indicating that the anion–π interaction most probably competed over other possible weak interactions and accounted for this interesting selectivity. In addition, the chloride permeation process across the membrane of the vesicles was also preliminarily studied by means of fluorescent experiments. This study, in addition to providing the potentiality of heteracalixaromatics as new models to construct functional vesicles, opens a new avenue to study the anion–π interactions in aqueous and also potentially in living systems.     

Complexation of inorganic anions by β-cyclodextrin studied by polarography and 1H NMR

Abstract

Complexation of o-chloronitrobenzene with β-cyclodextrin has been studied in 0.1 M aqueous solutions containing PF₆ ^?, ClO₄ ^?, C₂O₄ ^2-, SCN^?, SO₄ ^2- and F^? anions by a polarographic method. Using an equation which takes account of the change in the cyclodextrin concentration due to the simultaneous complexation of the anion, both stability constants have been calculated. Interaction of the ClO₄ ^? anion with β-cyclodextrin has been confirmed by ¹H NMR techniques. It has been found that the ClO₄ ^? anion is trapped in the β-cyclodextrin cavity. The stability constant has been calculated. Results of polarographic and ¹H NMR studies have been compared.     

Anion-templated assembly of half-sandwich rhodium-based multinuclear metallamacrocycles

A series of half‐sandwich rhodium‐based metallamacrocycles with tetra‐ and hexanuclearities have been synthesized. They are assembled by linking the deprotonated 2,4‐diacetyl‐5‐hydroxy‐5‐methyl‐3‐(3‐pyridinyl)cyclohexanone (HL) ligand in the presence of counteranions. When the counteranion was the tetrahedral BF₄^? ion, tetranuclear metallamacrocycle [(Cp*RhL)₄][BF₄]₄ ( 1 d ) was formed. However, the larger OTf^?, PF₆^?, and SbF₆^? counterions favored the formation of hexanuclear metallamacrocycles [(Cp*RhL)₆?2OTf][OTf]₄ ( 1 a ), [(Cp*RhL)₆?2PF₆][PF₆]₄ ( 1 b ), and [(Cp*RhL)₆?2SbF₆][SbF₆]₄ ? 6CH₃CN ( 1 c ) when the reactions were performed under the same conditions. Single‐crystal X‐ray analysis indicated that, in the solid state, two counteranions were encapsulated in each belt‐like host molecule of hexanuclear metallamacrocycles 1 a , b , and c . Based on the results of ¹H NMR analysis in methanol, the nuclearities of 1 a – c and the two encapsulated anions in each molecular cavity were maintained in solution. In addition, tetranuclear metallamacrocycle 1 d was converted into the hexanuclear metallamacrocycles 1 a′ , b , and c after addition of the appropriate anion as its [NBu₄]⁺ salt. The compound 1 a′ was characterized by single‐crystal X‐ray diffraction to have the formula [(Cp*RhL)₆?2OTf][BF₄]₄ ? 2M eOH ? 2H₂O. From the interconversion of the hexanuclear metallamacrocycles, we have concluded that the hexanuclear belt‐like host in 1 a – c has an clear selectivity for larger anions, in the sequence SbF₆^?≈PF₆^?>OTf^?>BF₄^?>Cl^?.     

Anion Complexation and The Hofmeister Effect

The ¹H NMR spectroscopic analysis of the binding of the ClO₄^? anion to the hydrophobic, concave binding site of a deep‐cavity cavitand is presented. The strength of association between the host and the ClO₄^? anion is controlled by both the nature and concentration of co‐salts in a manner that follows the Hofmeister series. A model that partitions this trend into the competitive binding of the co‐salt anion to the hydrophobic pocket of the host and counterion binding to its external carboxylate groups successfully accounts for the observed changes in ClO₄^? affinity.     

The Hofmeister Anion Effect on Ionophore‐based Ion‐selective Nanospheres Containing Solvatochromic Dyes

Recently reported ionophore‐based ion‐selective nanospheres contained pH‐independent and positively charged solvatochromic dyes. Here, we evaluate systematically the effect of anions to the fluorescence response of the nanospheres. The anion interference was found significant for anion concentrations above 10 mM. The sensor responses in the presence of various anion background was studied. While target ion (K⁺) causes the fluorescence of the nanospheres to decrease, increasing anion background also leads to lower fluorescence intensity. Lipophilic anions such as ClO₄^?, SCN^?, and I^? exhibited much more interference than hydrophilic anions (e. g., NO₃^?, Cl^?, F^?, SO₄^2?). The trend of the anion interference followed the Hofmeister series. A theoretical model was also demonstrated based on anion adsorption on the surface of the nanospheres.     

Silver(I) complexes with (1-pyrazolyl)pyridazine ligands: Synthesis,crystal structures and luminescent properties

Four Ag(I) coordination complexes formulated as {[Ag(L¹)(ClO₄)]}_n (1), {[Ag(L¹)(NO₃)]}_n (2), {[Ag(L¹)(PF₆)]}₂ (3) and {[Ag(L²)](ClO₄)·CH₃OH}_n (4), (L¹ = 3,6-bis(1-pyrazolyl)pyridazine, L² = 3,6-bis(3,5-dimethyl-1-pyrazolyl)pyridazine) have been synthesized in the presence of different anions [ClO₄^? (1) and (4), NO₃^? (2), PF₆^? (3)] and structurally characterized by FT-IR spectra, elemental analysis and X-ray diffraction. Studies of X-ray diffraction reveal that complexes 1, 2 and 4 show infinite helical chains, which are the alternate left- and right-handed helical chains. Furthermore, helical chains are arranged to 2D sheet via C–H?O (from anion O atoms) hydrogen bonds. As the anion changed to PF₆^?, a dinuclear molecule is formed in complex 3, further constructing a 2D sheets by C–H?F hydrogen bonds. The photoluminescence properties of all the complexes 1–4 have been investigated in the solid state at room temperature.     

Synthesis,Characterization and SOD Activities of IP-copper（Ⅱ）-L-amino Acid Complexes

Four new ternary complexes： [Cu（IP）（L-Val）（H2O）]ClO4·1.5H2O（1）, [Cu（IP）（L-Leu）（H2O）]ClO4（2）, [Cu（IP）（L-Tyr）（H2O）]ClO4·H2O（3） and [Cu（IP）（L-Trp）（H2O）]ClO4·1.5H2O（4） have been synthesized and character/zed by elementa/analysis, molar conductivity, infrared absorption spectroscopy, electronic absorption spectroscopy and cyclic voltammetry, where IP=imidazo[4,5-f][1,10] phenanthroline, L-Val=L-valinate, L-Leu=L-leucinate, L-Tyr=L-tyrosinate and L-Trp=L-tryptophanate. Complex 3 was structurally characterized by X-ray diffraction method, which crystallizes in orthorhornbic space group P21212 in a unit cell of dimensions a=3.0567（4） nm, b=0.74079（9） nm, c= 1.06198（13） nm, V=2.4047（5） nm^3, Z=4,μ=0.1084 cm^-1. The SOD-like activities of catalytic disrnutation of superoxide anions （O2^-· ） by the complexes were determined by means of modified nitroblue tetrazolium （NBT） photoreduction. The IC50 values of complexes 1, 2, 3 and 4 are 0.072, 0.147, 0.429 and 0.264 μmol·L^-1, respectively     

Face‐Capped M4L4 Tetrahedral Metal–Organic Cage: Iodine Capture and Release,Ion Exchange,and Electrical Conductivity

An M⁴L₄ type metal–organic cage (MOC‐19) has been synthesized from the one‐pot reaction of tri(pyridinylmethylene)phenylbenzeneamine (TPBA) with hydrated Zn(ClO₄)₂ under mild conditions and characterized by single‐crystal X‐Ray diffraction. Iodine capture studies show that the porous crystals of MOC‐19 exhibit a versatile behavior to accumulate iodine species not only in vapor (for I₂) but also in solution (for I₂ and I₃^?), and anion‐exchange experiments indicate the capacity to extract IO₃^? anions from aqueous solution. Enrichment of iodine species from KI/I₂ aqueous solution proceeds facilely, revealing a pseudo‐second‐order kinetics of I₃^? adsorption. Furthermore, the electrical conductivity of MOC‐19 single crystals could be significantly altered by I₂ inclusion.     

Raman Spectroscopic Study on Alkyl Chain Conformation in 1‐Butyl‐3‐methylimidazolium Ionic Liquids and their Aqueous Mixtures

Ionic liquids of 1‐butyl‐3‐methylimidazolium ([BMIM]) cation with different anions (Cl^?, Br^?, I^?, and BF₄^?), and their aqueous mixtures were investigated by using Raman spectroscopy and dispersion‐included density functional theory (DFT). The characteristic Raman bands at 600 and 624 cm^?1 for two isomers of the butyl chain in the imidazolium cation showed significant changes in intensity for different anions as well as in aqueous solutions. The area ratio of these two bands followed the order I^?>Br^?>Cl^?>BF₄^? (in terms of the anion X in [BMIM]X), indicating that the butyl chain of [BMIM]I tends to adopt the trans conformation. The butyl chain was found to adopt the gauche conformation upon dilution, irrespective of the anion type. The Raman bands in the butyl C?H stretch region for [BMIM]X (X=Cl^?, Br^?, and I^?) blueshifted significantly with the increase in the water concentration, whereas that for [BMIM]BF₄ changed very little upon dilution. The blueshift in the C?H stretch region upon dilution also followed the order: [BMIM]I>[BMIM]Br>[BMIM]Cl>[BMIM]BF₄, the same order as the above trans conformation preference of the butyl chain in pure imidazolium ionic liquids, which suggested that the cation‐anion interaction plays a role in determining the conformation of the chain.     

Energy-level tailoring in a series of redox-rich quinonoid-bridged diruthenium complexes containing tris2-pyridylmethyl)amine as a co-ligand

Reactions of [{Ru(tmpa)}₂(μ‐Cl)₂][ClO₄]₂, ( 2 [ClO₄]₂, tmpa=tris(2‐pyridylmethyl)amine) with 2,5‐dihydroxy‐1,4‐benzoquinone ( L¹ ), 2,5‐di‐[2,6‐(dimethyl)‐anilino]‐1,4‐benzoquinone ( L² ), or 2,5‐di‐[2,4,6‐(trimethyl)‐anilino)]‐1,4‐benzoquinone ( L³ ) in the presence of a base led to the formation of the dinuclear complexes [{Ru(tmpa)}₂(μ‐ L¹ _{?2 H})][ClO₄]₂ ( 3 [ClO₄]₂), [{Ru(tmpa)}₂(μ‐ L² _{?2 H})][ClO₄]₂ ( 4 [ClO₄]₂), and [{Ru(tmpa)}₂(μ‐ L³ _{?2 H})][ClO₄]₂ ( 5 [ClO₄]₂). Structural characterization of 5 [ClO₄]₂ showed the localization of the double bonds within the quinonoid ring and a twisting of the mesityl substituents with respect to the quinonoid plane. Cyclic voltammetry of the complexes show two reversible oxidation and quinonoid‐based reduction processes. Results obtained from UV/Vis/NIR and EPR spectroelectrochemistry are invoked to discuss ruthenium‐ versus quinonoid‐ligand‐centered redox activity. The complex 3 [ClO₄]₂ is compared to the reported complex [{Ru(bpy)}₂(μ‐ L¹ _{?2 H})]²⁺ ( 1²⁺ , bpy=2,2′‐bipyridine). The effects of substituting the bidentate and better π‐accepting bpy co‐ligands with tetradentate tmpa ligands [pure σ‐donating (amine) as well as σ‐donating and π‐accepting (pyridines)] on the redox and electronic properties of the complexes are discussed. Comparisons are also made between complexes containing the dianionic forms of the all‐oxygen‐donating L¹ ligand with the L² and L³ ligands containing an [O,N,O,N] donor set. The one‐electron oxidized forms of the complexes show absorption in the NIR region. The position as well as the intensity of this band can be tuned by the substituents on the quinonoid bridge. In addition, this band can be switched on and off by using tunable redox potentials, making such systems attractive candidates for NIR electrochromism.     

Tuning the Electronic Properties in Ruthenium–Quinone Complexes through Metal Coordination and Substitution at the Bridge

A rare example of a mononuclear complex [(bpy)₂Ru(L¹_?H)](ClO₄), 1 (ClO₄) and dinuclear complexes [(bpy)₂Ru(μ‐L¹_?2H)Ru(bpy)₂](ClO₄)₂, 2 (ClO₄)₂, [(bpy)₂Ru(μ‐L²_?2H)Ru(bpy)₂](ClO₄)₂, 3 (ClO₄)₂, and [(bpy)₂Ru(μ‐L³_?2H)Ru(bpy)₂](ClO₄)₂, 4 (ClO₄)₂ (bpy=2,2′‐bipyridine, L¹=2,5‐di‐(isopropyl‐amino)‐1,4‐benzoquinone, L²=2,5‐di‐(benzyl‐amino)‐1,4‐benzoquinone, and L³=2,5‐di‐[2,4,6‐(trimethyl)‐anilino]‐1,4‐benzoquinone) with the symmetrically substituted p‐quinone ligands, L, are reported. Bond‐length analysis within the potentially bridging ligands in both the mono‐ and dinuclear complexes shows a localization of bonds, and binding to the metal centers through a phenolate‐type “O^?” and an immine/imminium‐type neutral “N” donor. For the mononuclear complex 1 (ClO₄), this facilitates strong intermolecular hydrogen bonding and leads to the imminium‐type character of the noncoordinated nitrogen atom. The dinuclear complexes display two oxidation and several reduction steps in acetonitrile solutions. In contrast, the mononuclear complex 1 ⁺ exhibits just one oxidation and several reduction steps. The redox processes of 1 ¹⁺ are strongly dependent on the solvent. The one‐electron oxidized forms 2 ³⁺, 3 ³⁺, and 4 ³⁺ of the dinuclear complexes exhibit strong absorptions in the NIR region. Weak NIR absorption bands are observed for the one‐electron reduced forms of all complexes. A combination of structural data, electrochemistry, UV/Vis/NIR/EPR spectroelectrochemistry, and DFT calculations is used to elucidate the electronic structures of the complexes. Our DFT results indicate that the electronic natures of the various redox states of the complexes in vacuum differ greatly from those in a solvent continuum. We show here the tuning possibilities that arise upon substituting [O] for the isoelectronic [NR] groups in such quinone ligands.     

Syntheses and structures of one CuI‐containing coordination polymer and two macrocyclic supramolecular complexes based on flexible 1,3,4‐oxadiazole‐containing ligands

Three coordination complexes with Cu^I centres have been prepared using the symmetrical flexible organic ligands 1,3‐bis{[5‐(quinolin‐2‐yl)‐1,3,4‐oxadiazol‐2‐yl]sulfanyl}propane (L1) and 1,4‐bis{[5‐(quinolin‐2‐yl)‐1,3,4‐oxadiazol‐2‐yl]sulfanyl}butane (L2). Crystallization of L1 with Cu(SO₃CF₃)₂ and of L2 with Cu(BF₄)₂ and Cu(ClO₄)₂ in a CH₂Cl₂/CH₃OH mixed‐solvent system at room temperature afforded the coordination complexes catena‐poly[[copper(I)‐μ‐1,3‐bis{[5‐(quinolin‐2‐yl)‐1,3,4‐oxadiazol‐2‐yl]sulfanyl}propane] methanesulfonate dichloromethane 0.6‐solvate], {[Cu(C₂₅H₁₈N₆O₂S₂)](CF₃SO₃)·0.6CH₂Cl₂}_n, (I), bis(μ‐1,4‐bis{[5‐(quinolin‐2‐yl)‐1,3,4‐oxadiazol‐2‐yl]sulfanyl}butane)dicopper(I) bis(tetrafluoridoborate)–dichloromethane–methanol (1/1.5/1), [Cu₂(C₂₆H₂₀N₆O₂S₂)₂](BF₄)₂·1.5CH₂Cl₂·CH₃OH, (II), and bis(μ‐1,4‐bis{[5‐(quinolin‐2‐yl)‐1,3,4‐oxadiazol‐2‐yl]sulfanyl}butane)dicopper(I) bis(perchlorate)–dichloromethane–methanol (1/2/1), [Cu₂(C₂₆H₂₀N₆O₂S₂)₂](ClO₄)₂·2CH₂Cl₂·CH₃OH, (III). Under the control of the dumbbell‐shaped CF₃SO₃⁻ anion, complex (I) forms a one‐dimensional chain and neighbouring chains form a spiral double chain. Under the control of the regular tetrahedron‐shaped BF₄⁻ and ClO₄⁻ anions, complexes (II) and (III) have been obtained as bimetallic rings, which further interact viaπ–π interactions to form two‐dimensional networks. The anions play a decisive role in determining the arrangement of these discrete molecular complexes in the solid state.     

A Schiff base lateral macrobicycle derived from 4,13‐diaza‐18‐crown‐6 in its protonated form

In the structure of the title compound, 28,31,36,39‐tetraoxa‐9,17,42‐triaza‐1,25‐diazoniapentacyclo[23.8.5.1^11,15.0^3,8.0^18,23]nonatriaconta‐3,5,7,9,11,13,15,16,18,20,22‐undecene bis(perchlorate), C₃₃H₄₃N₅O₄²⁺·2ClO₄⁻ or (H₂L)(ClO₄)₂, the cation and one of the two independent anions lie on crystallographic twofold axes, while the second perchlorate anion is disordered about a centre of inversion. The conformation of the macrobicycle L is conditioned by two strong intramolecular hydrogen‐bonding interactions involving the pivot and imine N atoms, and is quite different from that observed when a metal ion is placed inside its cavity. The two imine groups are not coplanar with the pyridine moiety, and the deviation from planarity is considerably larger than that found in the corresponding Ba complex. Moreover, the fold of the macrobicycle in H₂L²⁺ causes a significant approach of the two pivot N atoms compared with their disposition in the Ba complex. This is the first X‐ray crystal structure analysis of an uncoordinated Schiff base lateral macrobicycle.     

Wrapping an Organic Reducing Reagent in a Cationic Boron Complex and Its Use in the Synthesis of Polyhalide Monoanionic Networks

The reaction between BF₃ ? OEt₂ and one of two guanidines, 1,8‐bis(tetramethylguanidinyl)naphthalene (btmgn) and 1,2,4,5‐tetrakis(tetramethylguanidinyl)naphthalene (ttmgn), yields the salts [(btmgn)(BF₂)]BF₄ and [(ttmgn)(BF₂)₂](BF₄)₂. NMR spectroscopic data show that the boron atoms in the cation and anion exchange in the case of [(ttmgn)(BF₂)₂](BF₄)₂, but not in the case of [(btmgn)(BF₂)]BF₄. The rate constant for this exchange was estimated to be 4 s^?1 at 80 °C for solutions in CH₃CN. These salts were subsequently used for the reduction of dihalides Br₂ or I₂ to give polyhalide salts. We report the synthesis and first complete characterization (including structural analysis) of salts that contain pentabromide monoanions. In these salts, the Br₅^? anions interact to give dimeric units or polymeric chains. Our results are compared to previous quantum chemical calculations on the gas‐phase structure of the Br₅^? anion. The possible pathways that lead to the polyhalides are evaluated. In the case of [(ttmgn)(BF₂)₂](BF₄)₂, reduction is accompanied by ttmgn oxidation, whereas in the case of [(btmgn)(BF₂)]BF₄ reduction is initiated by aromatic substitution.