Octacyanidorhenate(V) Ion as an Efficient Linker for Hysteretic Two‐Step Iron(II) Spin Crossover Switchable by Temperature,Light, and Pressure

A two‐step hysteretic Fe^II spin crossover (SCO) effect was achieved in programmed layered Cs{[Fe(3‐CNpy)₂][Re(CN)₈]}?H₂O ( 1 ) (3‐CNpy=3‐cyanopyridine) assembly consisting of cyanido‐bridged Fe^II‐Re^V square grid sheets bonded by Cs⁺ ions. The presence of two non‐equivalent Fe^II sites and the conjunction of 2D bimetallic coordination network with non‐covalent interlayer interactions involving Cs⁺, [Re^V(CN)₈]^3? ions, and 3‐CNpy ligands, leads to the occurrence of two steps of thermal SCO with strong cooperativity giving a double thermal hysteresis loop. The resulting spin‐transition phenomenon could be tuned by an external pressure giving the room‐temperature range of SCO, as well as by visible‐light irradiation, inducing an efficient recovery of the high‐spin Fe^II state at low temperatures. We prove that octacyanidorhenate(V) ion is an outstanding metalloligand for induction of a cooperative multistep, multiswitchable Fe^II SCO effect.     

Guest-Dependent Pressure-Induced Spin Crossover in FeII4[MIV(CN)8]2 (M=Mo,W) Cluster-Based Material Showing Persistent Solvent-Driven Structural Transformations

Discrete molecular species that can perform certain functions in response to multiple external stimuli constitute a special class of multifunctional molecular materials called smart molecules. Herein, cyanido-bridged coordination clusters {[Fe^II(2-pyrpy)₂]₄[M^IV(CN)₈]₂} ⋅ 4 MeOH ⋅ 6 H₂O (M=Mo ( 1 solv ), M=W ( 2 solv ) and 2-pyrpy=2-(1-pyrazolyl)pyridine are presented, which show persistent solvent driven single-crystal-to-single-crystal transformations upon sorption/desorption of water and methanol molecules. Three full desolvation–resolvation cycles with the concomitant change of the host molecules do not damage the single crystals. More importantly, the Fe₄M₂ molecules constitute a unique example where the presence of the guests directly affects the pressure-induced thermal spin crossover (SCO) phenomenon occurring at the Fe^II centres. The hydrated phases show a partial SCO with approximately two out-of-four Fe^II centres undergoing a gradual thermal SCO at 1 GPa, while in the anhydrous form the pressure-induced SCO effect is almost quenched with only 15 % of the Fe^II centres undergoing high-spin to low-spin transition at 1 GPa.     

Simultaneous Modulation of Magnetic and Dielectric Transition via Spin‐Crossover‐Tuned Spin Arrangement and Charge Distribution

Magnetic and dielectric properties have been tuned simultaneously by external stimuli with rapid and sensitive response, which is crucial to monitor the magnetic state via capacitive measurement. Herein, positive charged Fe^II ions were linked via negative charged [(Tp)Fe^III(CN)₃]^? (Tp=hydrotris(pyrazolyl)borate) units to form a neutral chain. The spin‐crossover (SCO) on Fe^II sites could be sensitively triggered via thermal treatment, light irradiation, and pressure. SCO switched the spin state of the Fe^II ions and antiferromagnetic interactions between Fe^III and Fe^II ions, resulting in significant change in magnetization. Moreover, SCO induced rotation of negative charged [(Tp)Fe^III(CN)₃]^? units, generating dielectric anomaly due to geometric change of charges distribution. This work provides a rational way to manipulate simultaneous variations in magnetic and dielectric properties utilizing SCO as an actuator to tune spin arrangement, magnetic coupling, and charge distribution.     

Responsive Four-Coordinate Iron(II) Nodes in FePd(CN)4

Metal node design is crucial for obtaining structurally diverse coordination polymers (CPs) and metal–organic frameworks with desirable properties; however, Fe^II ions are exclusively six-coordinated. Herein, we present a cyanide-bridged three-dimensional (3D) CP, FePd(CN)₄, bearing four-coordinate Fe^II ions, which is synthesized by thermal treatment of a two-dimensional (2D) six-coordinate Fe^II CP, Fe(H₂O)₂Pd(CN)₄⋅4 H₂O, to remove water molecules. Atomic-resolution transmission electron microscopy and powder X-ray and neutron diffraction measurements revealed that the FePd(CN)₄ structure is composed of a two-fold interpenetrated PtS topology network, where the Fe^II center demonstrates an intermediate geometry between tetrahedral and square-planar coordination. This four-coordinate Fe^II center with the distorted geometry can act as a thermo-responsive flexible node in the PtS network.     

A Mixed-Valence {Fe13} Cluster Exhibiting Metal-to-Metal Charge-Transfer-Switched Spin Crossover

It is promising and challenging to manipulate the electronic structures and functions of materials utilizing both metal-to-metal charge transfer (MMCT) and spin-crossover (SCO) to tune the valence and spin states of metal ions. Herein, a metallocyanate building block is used to link with a Fe^II-triazole moiety and generates a mixed-valence complex {[(Tp^4-Me)Fe^III(CN)₃]₉[Fe^II₄(trz-ph)₆]}⋅[Ph₃PMe]₂⋅[(Tp^4-Me)Fe^III(CN)₃] ( 1 ; trz-ph=4-phenyl-4H-1,2,4-triazole). Moreover, MMCT occurs between Fe^III and one of the Fe^II sites after heat treatment, resulting in the generation of a new phase, {[(Tp^4-Me)Fe^II(CN)₃][(Tp^4-Me)Fe^III(CN)₃]₈ [Fe^IIIFe^II₃(trz-ph)₆]}⋅ [Ph₃PMe]₂⋅[(Tp^4-Me)Fe^III(CN)₃] ( 1 a ). Structural and magnetic studies reveal that MMCT can tune the two-step SCO behavior of 1 into one-step SCO behavior of 1 a . Our work demonstrates that the integration of MMCT and SCO can provide a new alternative for manipulating functional spin-transition materials with accessible multi-electronic states.     

A Mixed‐Valence {Fe13} Cluster Exhibiting Metal‐to‐Metal Charge‐Transfer‐Switched Spin Crossover

It is promising and challenging to manipulate the electronic structures and functions of materials utilizing both metal‐to‐metal charge transfer (MMCT) and spin‐crossover (SCO) to tune the valence and spin states of metal ions. Herein, a metallocyanate building block is used to link with a Fe^II‐triazole moiety and generates a mixed‐valence complex {[(Tp^4‐Me)Fe^III(CN)₃]₉[Fe^II₄(trz‐ph)₆]}?[Ph₃PMe]₂?[(Tp^4‐Me)Fe^III(CN)₃] ( 1 ; trz‐ph=4‐phenyl‐4H‐1,2,4‐triazole). Moreover, MMCT occurs between Fe^III and one of the Fe^II sites after heat treatment, resulting in the generation of a new phase, {[(Tp^4‐Me)Fe^II(CN)₃][(Tp^4‐Me)Fe^III(CN)₃]₈ [Fe^IIIFe^II₃(trz‐ph)₆]}? [Ph₃PMe]₂?[(Tp^4‐Me)Fe^III(CN)₃] ( 1 a ). Structural and magnetic studies reveal that MMCT can tune the two‐step SCO behavior of 1 into one‐step SCO behavior of 1 a . Our work demonstrates that the integration of MMCT and SCO can provide a new alternative for manipulating functional spin‐transition materials with accessible multi‐electronic states.     

[Fe(TPT)2/3{MI(CN)2}2]⋅nSolv (MI=Ag,Au): New Bimetallic Porous Coordination Polymers with Spin‐Crossover Properties

Two new heterobimetallic porous coordination polymers with the formula [Fe(TPT)_2/3{M^I(CN)₂}₂] ? nSolv (TPT=[(2,4,6‐tris(4‐pyridyl)‐1,3,5‐triazine]; M^I=Ag (nSolv=0, 1 MeOH, 2 CH₂Cl₂), Au (nSolv=0, 2 CH₂Cl₂)) have been synthesized and their crystal structures were determined at 120 K and 293 K by single‐crystal X‐ray analysis. These structures crystallized in the trigonal R‐3m space group. The Fe^II ion resides at an inversion centre that defines a [FeN₆] coordination core. Four dicyanometallate groups coordinate at the equatorial positions, whilst the axial positions are occupied by the TPT ligand. Each TPT ligand is centred in a ternary axis and bridges three crystallographically equivalent Fe^II ions, whilst each dicyanometallate group bridges two crystallographically equivalent Fe^II ions that define a 3D network with the topology of NbO. There are two such networks, which interpenetrate each other, thereby giving rise to large spaces in which very labile solvent molecules are included (CH₂Cl₂ or MeOH). Crystallographic analysis confirmed the reversible structural changes that were associated with the occurrence of spin‐crossover behaviour at the Fe^II ions, the most significant structural variation being the change in unit‐cell volume (about 59 ų per Fe^II ion). The spin‐crossover behaviour has been monitored by means of thermal dependence of the magnetic properties, Mössbauer spectroscopy, and calorimetry.     

Iron(II)-8-mercaptoquinoline,iron(II)-5-chloro-8-mercaptoquino-line and iron(II)-5-bromo-8-mercaptoquinoline complexing in the iron(III) hexacyanoferrate(II) gelatin-immobilized matrix systems

Novel complexing processes in the Fe^II-8-mercaptoquinoline, Fe^II-5-chloro-8-mercaptoquinoline and Fe^II-5-bromo-8-mercaptoquinoline systems, not used previously in coordination chemistry, namely complexing as an iron(III)hexacyanoferrate(II) gelatin-immobilized matrix (GIM) in contact with an aqueous solution of the corresponding ligand, have been observed and analysed. Incorporation of these ligands into the inner coordination sphere is preceded by the decomposition of the immobilized compound KFe[Fe(CN)₆] to form hydroxides or oxohydroxides of Fe^II and Fe^III under the action of OH^- ions. It has been shown that Fe^IIFeIII redox process and the formation of FeB₃ chelates (B^- is a singly deprotonated form of the corresponding ligand) take place during complexing under such conditions.     

Cyanide-bridged [Fe8M6] clusters displaying single-molecule magnetism (M=Ni) and electron-transfer-coupled spin transitions (M=Co)

Cyanide‐bridged metal complexes of [Fe₈M₆(μ‐CN)₁₄(CN)₁₀ (tp)₈(HL)₁₀(CH₃CN)₂][PF₆]₄?n CH₃CN?m H₂O (HL=3‐(2‐pyridyl)‐5‐[4‐(diphenylamino)phenyl]‐1H‐pyrazole), tp^?=hydrotris(pyrazolylborate), 1 : M=Ni with n=11 and m=7, and 2 : M=Co with n=14 and m=5) were prepared. Complexes 1 and 2 are isomorphous, and crystallized in the monoclinic space group P2₁/n. They have tetradecanuclear cores composed of eight low‐spin (LS) Fe^III and six high‐spin (HS) M^II ions (M=Ni and Co), all of which are bridged by cyanide ions, to form a crown‐like core structure. Magnetic susceptibility measurements revealed that intramolecular ferro‐ and antiferromagnetic interactions are operative in 1 and in a fresh sample of 2 , respectively. Ac magnetic susceptibility measurements of 1 showed frequency‐dependent in‐ and out‐of‐phase signals, characteristic of single‐molecule magnetism (SMM), while desolvated samples of 2 showed thermal‐ and photoinduced intramolecular electron‐transfer‐coupled spin transition (ETCST) between the [(LS‐Fe^II)₃(LS‐Fe^III)₅(HS‐Co^II)₃(LS‐Co^III)₃] and the [(LS‐Fe^III)₈(HS‐Co^II)₆] states.     

Weak Antiferromagnetic Exchange and Ferromagnetic Alignment of FeII (S=2) Spins in Differently Charged {HAT ⋅ (FeIICl2)3}n (n=2- and 3-) Assemblies of Hexaazatriphenylenes (HAT)

Hexaazatrianthracene (HATA) and hexaazatriphenylenehexacarbonitrile {HAT(CN)₆} are reduced by metallic iron in the presence of crystal violet (CV⁺)(Cl⁻). Anionic ligands are produced, which simultaneously coordinate three Fe^IICl₂ to form (CV⁺)₂{HATA ⋅ (Fe^IICl₂)₃}²⁻ ⋅ 3 C₆H₄Cl₂ ( 1 ) and (CV⁺)₃{HAT(CN)_6. (Fe^IICl₂)₃}³⁻ ⋅ 0.5CVCl ⋅ 2.5 C₆H₄Cl₂ ( 2 ). High-spin (S=2) Fe^II atoms in both structures are arranged in equilateral triangles at a distance of 7 Å. An antiferromagnetic exchange is observed between Fe^II in {HATA ⋅ (Fe^IICl₂)₃}²⁻ ( 1 ) with a Weiss temperature (Θ) of −80 K, the PHI estimated exchange interaction (J) is −4.7 cm⁻¹. The {HAT(CN)₆ ⋅ (Fe^IICl₂)₃}³⁻ assembly is obtained in 2 . The formation of HAT(CN)₆^.3− is supported by the appearance of an intense EPR signal with g=2.0037. The magnetic behavior of 2 is described by a strong antiferromagnetic coupling between the Fe^II and HAT(CN)₆^.3− spins with J₁=−164 cm⁻¹ (−2 J formalism) and by a weaker antiferromagnetic coupling between the Fe^II spins with J₂=−15.4 cm⁻¹. The stronger coupling results in the spins of the three Fe^IICl₂ units to be aligned parallel to each other in the assembly. As a result, an increase of the χ_MT values is observed with the decrease of temperature from 9.82 at 300 K up to 15.06 emu ⋅ K/mol at 6 K, and the Weiss temperature is also positive being at +23 K. Thus, a change in the charge and spin state of the HAT-type ligand to ⋅3⁻ results in ferromagnetic alignment of the Fe^II spins, yielding a high-spin (S=11/2) system. DFT calculations showed that, due to the high symmetry and nearly degenerated LUMO of both HATA and HAT(CN)₆, their complexes with Fe^IICl₂ have a variety of closely lying excited high-spin states with multiplicity up to S=15/2.     

Potassium bis(ethylenediamine)­copper(II) ferricyanide

The title compound, potassium bis(ethylenediamine‐N,N′)copper(II) hexacyanoferrate(III), K[Cu(C₂H₈N₂)₂]‐[Fe(CN)₆], contains [Cu(en)₂]²⁺ and [Fe(CN)₆]^3? complex ions, where en is ethylenediamine. The Fe^III and K⁺ ions lie on twofold axes and the Cu^II atom lies on an inversion center. The [Cu(en)₂]²⁺ ion has square‐planar coordination with a mean Cu—N distance of 1.992 (2) Å and the [Fe(CN)₆]^3? ion has distorted octahedral coordination with a mean Fe—C distance of 1.947 (2) Å.     

FeII Spin‐Crossover Phenomenon in the Pentadecanuclear {Fe9[Re(CN)8]6} Spherical Cluster

The self‐assembly of iron(II) ions with rare octacyanidorhenate(V) metalloligands in a methanolic solution results in the formation of a nanometric pentadecanuclear {Fe^II₉[Re^V(CN)₈]₆(MeOH)₂₄}?10 MeOH ( 1 ) molecule with a six‐capped body‐centered cubic topology. The cluster demonstrates a thermally‐induced spin‐crossover phase transition at T_1/2=195 K which occurs selectively for a single Fe^II ion embedded in the center of a cluster core.     

Colossal Anisotropic Thermal Expansion through Coupling Spin Crossover and Rhombus Deformation in a Hexanuclear {FeIII4FeII2} Compound

Colossal and anisotropic thermal expansion is a key function for microscale or nanoscale actuators in material science. Herein, we present a hexanuclear compound of [(Tp*)Fe^III(CN)₃]₄[Fe^II(Ppmp)]₂⋅2 CH₃OH ( 1 , Tp*=hydrotris(3,5-dimethyl-pyrazol-1-yl)borate and Ppmp=2-[3-(2′-pyridyl)pyrazol-1-ylmethyl]pyridine), which has a rhombic core structure abbreviated as {Fe^III₂Fe^II₂}. Magnetic susceptibility measurements and single-crystal X-ray diffraction analyses revealed that 1 underwent thermally-induced spin transition with the thermal hysteresis. The Fe^II site in 1 behaved as a spin crossover (SCO) unit, and significant deformation of its octahedron was observed during the spin transition process. Moreover, the distortion of the Fe^II centers actuated anisotropic deformation of the rhombic {Fe^III₂Fe^II₂} core, which was spread over the whole crystal through the subsequent molecular rearrangements, leading to the colossal anisotropic thermal expansion. Our results provide a rational strategy for realizing the colossal anisotropic thermal expansion and shape memory effects by tuning the magnetic bistability.     

Cyano‐bridged Molecular Square: [Ni(iprtacn)Fe(phen)2(CN)2]2(PF6)4·6CH3CN – Preparation,Structure, Magnetic Properties and Binding with DNA

The cyano‐bridged molecular square Ni(iprtacn)]₂[Fe(phen)₂(CN)₂]₂(PF₆)₄ · 6CH₃CN ( 1 ) (iprtacn = 1,4,7‐triisopropyl‐1,4,7‐triazacyclononane, phen = 1, 10‐phenanthroline) was prepared and its crystal structure, magnetic properties, and binding with DNA were characterized. The four metal ions Ni^IIFe^IINi^IIFe^II of the complex 1 are almost coplanar. Magnetic susceptibilities measured over the range of 2–300 K show weak antiferromagnetic interactions between the two nickel(II) ions; best fitting for the experimental data leads to J = –1.27 cm^–1. UV/Vis and fluorescence spectra show that the complex is able to displace DNA‐bound EB and bind to DNA with strong interactions.     

Diamond‐ and Graphite‐Like Octacyanometalate‐Based Polymers Induced by Metal Ions

By using cyclohexane‐1,2‐diamine (chxn), Ni(ClO₄)₂ ? 6H₂O and Na₃[Mo(CN)₈] ? 4H₂O, a 3D diamond‐like polymer {[Ni^II(chxn)₂]₂[Mo^IV(CN)₈] ? 8H₂O}_n ( 1 ) was synthesised, whereas the reaction of chxn and Cu(ClO₄)₂ ? 6H₂O with Na₃[M^V(CN)₈] ? 4H₂O (M=Mo, W) afforded two isomorphous graphite‐like complexes {[Cu^II(chxn)₂]₃[Mo^V(CN)₈]₂ ? 2H₂O}_n ( 2 ) and {[Cu^II(chxn)₂]₃[W^V(CN)₈]₂ ? 2H₂O}_n ( 3 ). When the same synthetic procedure was employed, but replacing Na₃[Mo(CN)₈] ? 4H₂O by (Bu₃NH)₃[Mo(CN)₈] ? 4H₂O (Bu₃N=tributylamine), {[Cu^II(chxn)₂Mo^IV(CN)₈][Cu^II(chxn)₂] ? 2H₂O}_n ( 4 ) was obtained. Single‐crystal X‐ray diffraction analyses showed that the framework of 4 is similar to 2 and 3 , except that a discrete [Cu(chxn)₂]²⁺ moiety in 4 possesses large channels of parallel adjacent layers. The experimental results showed that in this system, the diamond‐ or graphite‐like framework was strongly influenced by the inducement of metal ions. The magnetic properties illustrate that the diamagnetic [Mo^IV(CN)₈] bridges mediate very weak antiferromagnetic coupling between the Ni^II ions in 1 , but lead to the paramagnetic behaviour in 4 because [Mo^IV(CN)₈] weakly coordinates to the Cu^II ions. The magnetic investigations of 2 and 3 indicate the presence of ferromagnetic coupling between the Cu^II and W^V/Mo^V ions, and the more diffuse 5d orbitals lead to a stronger magnetic coupling interaction between the W^V and Cu^II ions than between the Mo^V and Cu^II ions.     

An easy electrochemical procedure for tailoring thin films containing the [Fe(bpy)2(CH3CN)2] and/or [Fe(bpy)3]-like cores (bpy=2,2-bipyridine). Application to the design of a modified electrode with a supramolecular structure

A simple electrochemical procedure to tailor thin polymeric films containing the [Fe^II(bpy)₂(CH₃CN)₂]²⁺ and/or [Fe^II(bpy)₃]²⁺-like cores have been described (bpy=2,2^′-bipyridine). The procedure is based on the electroreductive precipitation of soluble polymers prepared in situ in CH₃CN by mixing Fe³⁺ ions and a bis bipyridyl ligand, (chiragen: chir). In the resulting [Fe^II(chir)(CH₃CN)₂]_n²⁺ films, the two labile S ligands can be easily replaced by a bidentate ligand. This method has been applied with success to design a modified electrode with a supramolecular structure.     

Kinetics of oxidation of cysteine and captopril via Cs3[Mo(CN)8] and Cs3[W(CN)8]

The kinetics of the oxidation of cysteine and captopril via octacyanomolybdate(V) and octacyanotungstate(V) in a buffered acidic media (pH range 2.20–4.80) have been studied spectrophotometrically. The rate law for the oxidation is: Rate = k [RSH] [Ox] [H⁺]⁻¹, where RSH is cysteine or captopril and Ox is Cs₃[Mo(CN)₈] or Cs₃[W(CN)₈]. The activation parameters (E_a, ΔH^#, ΔG^#, ΔS^#) for the oxidation of cysteine and captopril via Cs₃[Mo(CN)₈] or Cs₃[W(CN)₈] have been determined. The results indicate that Cs₃[Mo(CN)₈] is more reactive than Cs₃[W(CN)₈] as an oxidizing agent. Effects of pH, ionic strength, temperature, dielectric constant of the reaction medium and copper(II) ions on the oxidation rate have been studied. Mechanisms for the oxidation of cysteine to cystine and captopril to the corresponding disulfide have been proposed.     

Syntheses,crystal structures and magnetic properties of two cyano-bridged two-dimensional assemblies [Fe(salpn)]2 [Fe(CN)5NO] and [Fe(salpn)]2[Ni(CN)4]

Two cyano-bridged assemblies, [Fe^III(salpn)]₂[Fe^II(CN)₅NO] (1) and [Fe^III (salpn)]₂[Ni^II(CN)₄] (2) [salpn = N, N-1,2-propylenebis(salicylideneiminato)dianion], have been prepared and structurally and magnetically characterized. In each complex, [Fe(CN)₅NO]^2– or [Ni(CN)₄]^2– coordinates with four [Fe(salpn)]⁺ cations using four co-planar CN^– ligands, whereas each [Fe(salpn)]⁺ links two [Fe(CN)₅NO]^2– or [Ni(CN)₄]^2– ions in the trans form, which results in a two-dimensional (2D) network consisting of pillow-like octanuclear [—M^II—CN—Fe^III—NC—]₄ units (M = Fe or Ni). In complex (1), the NO group of [Fe(CN)₅NO]^2– remains monodentate and the bond angle of Fe^II—N—O is 180.0°. The variable temperature magnetic susceptibilities, measured in the 5–300 K range, show weak intralayer antiferromagnetic interactions in both complexes with the intramolecular iron(III)iron(III) exchange integrals of –0.017 cm^–1 for (1) and –0.020 cm^–1 for (2), respectively.     

Spectral Signatures of Ultrafast Spin Crossover in Single Crystal [FeII(bpy)3](PF6)2

Solvated iron(II)‐tris(bipyridine) ([Fe^II(bpy)₃]²⁺) has been extensively studied with regard to the spin crossover (SCO) phenomenon. Herein, the ultrafast spin transition dynamics of single crystal [Fe^II(bpy)₃](PF₆)₂ was characterized for the first time using femtosecond transient absorption (TA) spectroscopy. The single crystal environment is of interest for experiments that probe the nuclear motions involved in the SCO transition, such as femtosecond X‐ray and electron diffraction. We found that the TA at early times is very similar to what has been reported in solvated [Fe^II(bpy)₃]²⁺, whereas the later dynamics are perturbed in the crystal environment. The lifetime of the high‐spin state is found to be much shorter (100 ps) than in solution due to chemical pressure exerted by the lattice. Oscillatory behavior was observed on both time scales. Our results show that single crystal [Fe^II(bpy)₃](PF₆)₂ serves as an excellent model system for localized molecular spin transitions.     

Electrostatic bending and outer-sphere intervalence transfer in a flexible ligand-bridged ruthenium(III)-iron(II) complex

Abstract

In the mixed-valence complex [Ru^III(NH₃)₅(μ-dpypn)Fe^II(CN)₅] with the flexible bridging ligand 1,3-di(4-pyridyl)propane (dpypn), electrostatic interactions between the {Ru(NH₃)₅}³⁺ and {Fe(CN)₅}^3? moieties drive a strong bending of dpypn and approximation of the Ru^III and Fe^II centers, from which the enhanced electronic coupling between metal ions produces an intense intervalence-transfer absorption in the near-infrared region. Density functional theory calculations corroborate both the electrostatic bending in this heterobinuclear complex and a linear geometry in the homobinuclear counterparts [Ru(NH₃)₅(μ-dpypn)Ru(NH₃)₅]⁵⁺ and [Fe(CN)₅(μ-dpypn)Fe(CN)₅]^5?, for which no evidence of electronic coupling was found because of the separation between metal centers. Furthermore, the heterobinuclear species formed an inclusion complex with β-cyclodextrin where the imposed linear geometry prevents significant electronic coupling and intervalence charge transfer between the Ru^III and Fe^II centers.