Preparation of graphene/tetrathiafulvalene nanocomposite switchable surfaces

A one step process for simultaneous reduction and functionalization of graphene oxide using tetrathiafulvalene (TTF) is described. Chemical oxidation of TTF to TTF(2+) using an aqueous solution of Fe(ClO(4))(3) expels the charged molecule from the graphene nanosheets, while subsequent immersion in neutral TTF solution allows the capture of the TTF molecules.     

Switching of pseudorotaxanes and catenanes incorporating a tetrathiafulvalene unit by redox and chemical inputs

An acyclic polyether 1a, incorporating a central tetrathiafulvalene (TTF) electron donor unit and two 4-tert-butylphenoxy groups at its termini, has been synthesized. Two macrocyclic polyethers containing two different electron donors, namely a TTF unit with, in one case, a 1,4-dioxybenzene ring (2a), and, in the other case (2b), a 1,5-dioxynaphthalene ring system, have also been synthesized. These two macrocyclic polyethers have been mechanically interlocked in kinetically controlled template-directed syntheses with cyclobis(paraquat-p-phenylene) cyclophane (3(4+)) to afford the [2]catenanes 2a/3(4+) and 2b/3(4+), respectively. X-ray crystallography reveals that the [2]-catenane 2b/3(4+) has the TTF unit of 2b located inside the cavity of 3(4+). The spectroscopic (UV/vis and 1H NMR) and electrochemical properties of compounds 1a, 2a, 2b, 2a/3(4+), and 2b/3(4+) and of the [2]pseudorotaxane 1a.3(4+) were investigated. The absorption and emission properties of the mono- and dioxidized forms of the TTF unit in these various species have also been studied. The results obtained in acetonitrile solution can be summarized as follows. (a) While TTF2+ exhibits a strong fluorescence, no emission can be observed for the TTF2+ units contained in the polyethers and in their pseudorotaxanes and catenanes. (b) A donor-acceptor absorption band is observed upon two-electron oxidation of the TTF unit in the macrocyclic polyethers 2a and 2b. (c) The spontaneous self-assembly of 1a and 3(4+) to give the [2]pseudorotaxane 1a.3(4+) is strongly favored (Kass. = 5 x 10(5) L mol-1) but slow (at 296 K, k = 11.3 L mol-1 s-1 and delta G++ = 15.9 kcal mol-1) because of the steric hindrance associated with the bulky end groups of 1a. (d) In the pseudorotaxane 1a.3(4+), the reversible displacement of the cyclophane from the TTF unit in the threadlike substrate occurs on oxidation/reduction of its electroactive components. (e) Switching between the two translational isomers of the catenanes 2a/3(4+) and 2b/3(4+) occurs by cyclic oxidation and reduction of the TTF unit contained in 2a and in 2b, respectively. (f) Addition of o-chloroanil to the pseudorotaxane 1a.3(4+) and to the catenanes 2a/3(4+) and 2b/3(4+) causes the displacement of the TTF unit from the cavity of the cyclophane 3(4+) because of the formation of an adduct between the TTF unit and o-chloroanil.     

Synthesis and Supramolecular Structure of a Novel π-Extended TTF Derivative

A novel π-extended TTF derivative （C24H2ON658, Mr=649.02） has been synthesized and characterized by IR, ^1H NMR and MS. The crystal structure was prepared by crystallization from CH2Cl2-MeOH. The crystal belongs to the monoclinic system, space group P21/c with a = 5.465（5）, b = 26.835（5）, c = 10.180（5）A, β= 101.929（5）°, V = 1460.7（15） A^3, Z = 2, Dc = 1.476 g/cm^3, F（000） = 668,μ = 0.638 mm^-1, the final R = 0.0390 and wR = 0.0586 for 1694 observed reflections with I 〉 2σ（I）. The structure reveals planarity of the two dithiole rings, different from the boat-shaped structure usually found in neutral derivatives of TTF. The central ring of the benzene also adopts a planar conformation, while it is twisted from planarity of the two dithiole rings and forms a dihedral angle of 61.8°. The molecule exhibits a three-dimensional supramolecular architecture constructed through hydrogen bonds. In the molecular structure a noticeable feature can be found that there exist S…S interactions which further reinforce the 3D supramolecular framework.     

Synthesis and Supramolecular Structure of a Novel :r-Extended TTF Derivative

A novel x-extended TTF derivative (C24H20N6S8, Mr=649.02) has been synthesized and characterized by IR,1H NMR and MS. The crystal structure was prepared by crystallization from CH2Cl2-MeOH. The crystal belongs to the monoclinic system, space group P21/c with a=5.465(5), b=26.835(5), c=10.180(5) A, β=101.929(5)°, V=1460.7(15) A3, Z=2, Dc=1.476 g/cm3,F(000)=668,μ=0.638 mm-1, the final R=0.0390 and wR=0.0586 for 1694 observed reflections with I > 2σ(I). The structure reveals planarity of the two dithiole tings, different from the boat-shaped structure usually found in neutral derivatives of TTF. The central ring of the benzene also adopts a planar conformation, while it is twisted from planarity of the two dithiole rings and forms a dihedral angle of 61.8°. The molecule exhibits a three-dimensional supramolecular architecture constructed through hydrogen bonds. In the molecular structure a noticeable feature can be found that there exist S…S interactions which further reinforce the 3D supramolecular framework.     

Trialkyltetrathiafulvalene-sigma-tetracyanoanthraquinodimethane [R(3)TTF-sigma-TCNAQ] diads: synthesis, intramolecular charge-transfer properties, and X-ray crystal structure.

We report the use of the electron-donating 4,5-dipentyl-4'-methyl-TTF (TTF = tetrathiafulvalene) moiety in combination with the electron acceptor 11,11,12,12-tetracyanoanthraquinodimethane (TCNAQ) unit in the novel D-sigma-A diad molecules 11, 17, and 18. These compounds display a weak, broad, low-energy intramolecular charge-transfer (ICT) band in the UV-vis spectra (lambda(max) 430-450 nm). Cyclic voltammetric studies show two reversible one-electron oxidation processes for the R(3)TTF moiety, and a reversible two-electron reduction process for the TCNAQ moiety. The electron affinity of TCNAQ is significantly enhanced by the electron-withdrawing sulfonamide and sulfonic ester groups (compounds 17 and 18, respectively). Simultaneous electrochemistry and EPR (SEEPR) experiments show no significant intramolecular interaction between the R(3)TTF and TCNAQ moieties in compounds 11 and 18. X-ray crystallographic data are presented for 5, 11, and 20. The structure of 5 reveals hydrogen-bonded dimers. In molecule 11 the bond lengths and conformations of both donor and acceptor moieties are typical for neutral species. Compound 20 is an unusual calcium complex of TCNAQ derivative obtained by dicyanomethylation of anthraquinone-2-carboxylic acid.     

Tetrathiafulvalene-Inserted Diphenoquinone: Synthesis,Structure, and Dynamic Redox Property

A new tetrathiafulvalene (TTF) derivative is synthesized, which is substituted with two phenoxy radicals on one 1,3-dithiole ring, and may have either open-shell diradical or closed-shell extended-quinoidal ground states. X-ray single crystal analysis and NMR measurements prove that this molecule has a closed-shell extended quinoidal structure both in the solid state and in solution. DFT calculations show the donor–acceptor electronic properties of this molecule with a well-separated HOMO–LUMO distribution and a small HOMO–LUMO energy gap. Because of this donor–acceptor character, this molecule gives both the dication and the dianion species by electrochemical oxidation and reduction. Furthermore, during the redox process between the neutral and dication states, this molecule exhibits unique changes in the cyclic voltammogram upon repeating the cycles or varying the scan rate. The observed electrochemical behavior is explained by the conformational changes in the electrochemically generated species, thus indicating that this molecule is classified as a dynamic redox system.     

Tetrathiafulvalene (TTF)‐Bridged Resorcin[4]arene Cavitands: Towards New Electrochemical Molecular Switches

We report the synthesis of novel resorcin[4]arene‐based cavitands featuring two extended bridges consisting of quinoxaline‐fused TTF (tetrathiafulvalene) moieties. In the neutral form, these cavitands were expected to adopt the vase form, whereas, upon oxidation, the open kite geometry should be preferred due to Coulombic repulsion between the two TTF radical cations (Scheme 2). The key step in the preparation of these novel molecular switches was the P(OEt)₃‐mediated coupling between a macrocyclic bis(1,3‐dithiol‐2‐thione) and 2 equiv. of a suitable 1,3‐dithiol‐2‐one. Following the successful application of this strategy to the preparation of mono‐TTF‐cavitand 3 (Scheme 3), the synthesis of the bis‐TTF derivatives 2 (Scheme 4) and 19 (Scheme 5) was pursued; however, the target compounds could not be isolated due to their insolubility. Upon decorating both the octol bowl and the TTF cavity rims with long alkyl chains, the soluble bis‐TTF cavitand 23 was finally obtained, besides a minor amount of the novel cage compound 25a featuring a highly distorted TTF bridge (Scheme 6). In contrast to 25a , the deep cavitand 23 undergoes reversible vase → kite switching upon lowering the temperature from 293 to 193 K (Fig. 1). Electrochemical studies by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) provided preliminary evidence for successful vase → kite switching of 23 induced by the oxidation of the TTF cavity walls.     

Star-shaped pyrrole-fused tetrathiafulvalene oligomers: synthesis and redox, self-assembling, and conductive properties

A series of star-shaped pyrrole-fused tetrathiafulvalene (TTF) oligomers 1-3 was synthesized via an S(N)Ar reaction of fluorinated benzenes with the pyrrolyl sodium salts. Electrochemical and chemical oxidations of 1-3 revealed that a radical cation moiety on each TTF unit was successfully accumulated in all oligomers. Self-assembled structures of neutral and oxidized species were characterized by SEM and XRD, and their conductive properties of the iodine-doped 1-3 as well as an intermolecular mixed-valence ion radical salt were investigated.     

New Concepts in Tetrathiafulvalene Chemistry

Tetrathiafulvalene (TTF) and its derivatives were originally prepared as strong electron-donor molecules for the development of electrically conducting materials. This Review emphasizes how TTF and its derivatives offer new and in some cases little-exploited possibilities at the molecular to the supramolecular levels, as well as in macromolecular aspects. TTF is a well-established molecule whose interest goes beyond the field of materials chemistry to be considered an important building block in supramolecular chemistry, crystal engineering, and in systems able to operate as machines. At the molecular level, TTF is a readily available molecule which displays a strong electron-donor ability. However, its use as a catalyst for radical-polar crossover reactions, thus mimicking samarium iodide chemistry, has only recently been addressed. Important goals have been achieved in the use of TTF at the macromolecular level where TTF-containing oligomers, polymers, and dendrimers have allowed the preparation of new materials that integrate the unique properties of TTF with the processability and stability that macromolecules display. The TTF molecule has also been successfully used in the construction of redox-active supramolecular systems. Thus, chemical sensors and redox-switchable ligands have been prepared from TTF while molecular shuttles and molecular switches have been prepared from TTF-containing rotaxanes and catenanes. A large synthetic effort has been devoted to the preparation of the so-called organic ferromagnets, many of which are derived from TTF. The main task in these systems is the introduction of ferromagnetic coupling between the conduction electrons and localized electrons. TTF has also played a prominent role in molecular electronics where TTF-containing D-sigma-A molecules have allowed the preparation of the first confirmed unimolecular rectifier. Recently, it has been confirmed that TTF can display efficient nonlinear optic (NLO) responses in the second and third harmonic generation as well as a good thermal stability. These findings can be combined with the redox ability of TTF as an external stimuli to provide a promising strategy for the molecular engineering of switchable NLO materials. Fullerenes endowed with TTF exhibit outstanding photophysical properties leading to charge-separated (CS) states that show remarkable lifetimes.     

Effects of protonation and metal coordination on intramolecular charge transfer of tetrathiafulvalene compound

A protonated bifunctional pyridine-based tetrathiafulvalene (TTF) derivative (DMT-TTF-pyH)NO3 and a copper(II) complex Cu(acac)2(DMT-TTF-py)2 have been obtained and studied. Electronic spectra of the protonated compound show a large ICT (intramolecular charge transfer) band shift (Deltalambda=136 nm) compared with that of the neutral compound. Cyclic voltammetry also shows a large shift of the redox potentials (DeltaE1/2(1)=77 mV). Theoretical calculation suggests that the pyridium substituent is a strong pi-electron acceptor. Crystal structures of the protonated compound and the metal complex have been obtained. The dihedral angle between least-squares planes of the pyridyl group and the dithiole ring might reflect the intensity of the ICT effect between the TTF moiety and the pyridyl group. It is also noteworthy that the TTF moiety could be oxidized to TTF2+ dication by Fe(ClO4)(3).6H2O when forming a metal complex, while the protonated TTF derivative can only be oxidized to the TTF*+ radical cation by Fe(ClO4)(3).6H2O even with an excess amount of the Fe(III) salt, which can be used to control the oxidation process to obtain neutral TTF, TTF*+ radical cation, or TTF2+ dication.     

A redox-switchable alpha-cyclodextrin-based [2]rotaxane

A bistable [2]rotaxane comprising an alpha-cyclodextrin (alpha-CD) ring and a dumbbell component containing a redox-active tetrathiafulvalene (TTF) ring system within its rod section has been synthesized using the Cu(I)-catalyzed azide-alkyne cycloaddition, and the redox-driven movements of the alpha-CD ring between the TTF and newly formed triazole ring systems have been elucidated. Microcalorimetric titrations on model complexes suggested that the alpha-CD ring prefers to reside on the TTF rather than on the triazole ring system by at least an order of magnitude. The fact that this situation does pertain in the bistable [2]rotaxane has not only been established quantitatively by electrochemical experiments and backed up by spectroscopic and chiroptical measurements but also been confirmed semiquantitatively by the recording of numerous cyclic voltammograms which point, along with the use of redox-active chemical reagents, to a mechanism of switching that involves the oxidation of the neutral TTF ring system to either its radical cationic (TTF*+) or dicationic (TTF2+) counterparts, whereupon the alpha-CD ring, moves along the dumbbell to encircle the triazole ring system. Since redox control by both chemical and electrochemical means is reversible, the switching by the bistable [2]rotaxane can be reversed on reduction of the TTF*+ or TTF2+ back to being a neutral TTF.     

Molecular wires comprising pi-extended ethynyl- and butadiynyl-2,5-diphenyl-1,3,4-oxadiazole derivatives: synthesis, redox, structural, and optoelectronic properties

2,5-Diphenyl-1,3,4-oxadiazole (OXD) derivatives with terminal ethynyl- (4a,b) and butadiynyl- (8a,b) substituents have been synthesized in high yields. 2-Methyl-3,5-hexadiyn-2-ol has not been exploited previously in the synthesis of terminal butadiynes. Crystals of 8a and 8b are remarkably stable to long-term storage under ambient conditions. The X-ray crystal structure of 8a reveals that the butadiyne moieties are spatially isolated by the aromatic moieties, which explains the high stability. Two series of derived pi-conjugated molecules, Donor-(C[triple bond]C)(n)-OXD (n = 1, 2) and OXD-(C[triple bond]C)(n)-Donor-(C[triple bond]C)(n)-OXD (n = 1) [Donor = tetrathiafulvalene (TTF), bithiophene, 9-(4,5-dimethyl-1,3-dithiol-2-ylidene)fluorene, and triphenylamine], have been synthesized using Sonogashira reactions and characterized by X-ray crystallography, cyclic voltammetry, and optical absorption/emission spectroscopy. The electron-withdrawing effect of the OXD units is manifested by a positive shift of the donor oxidation waves in these systems: the butadiynylene spacer (n = 2) further shifts the first oxidation waves by 40-80 mV compared to analogues n = 1. The absorption spectra of TTF-OXD hybrids 10d and 11 are blue-shifted by 80 nm compared to the bithienyl-bridged derivative 10f and are similar to the butadiynyl-OXD building-block 8a, demonstrating that conjugation is disrupted by a neutral TTF unit. Solutions of the TTF-OXD and 9-(4,5-dimethyl-1,3-dithiol-2-ylidene)fluorene-OXD hybrids, 10d, 10g, 11, and 13, are only very weakly fluorescent due to quenching from the electron-donor moieties. In contrast, the triphenylamine-OXD hybrids 12a, 12b, 14a, and 14b are fluorescent; the PLQYs of the butadiynylene derivatives 14a and 14b are lower than those of the ethynylene-bridged analogues 12a and 12b.     

卤素、 氰基及N原子修饰对四硫富瓦烯衍生物载流子传输性质影响的理论研究

基于密度泛函理论结合跳跃模型和能带理论研究了氟、 氯、 氰基和N原子的引入对四硫富瓦烯(TTF)衍生物载流子传输性质的影响. 计算结果表明, 嵌N修饰会降低分子重组能, 特别是当N原子靠近TTF主体环时作用更明显. 与引入卤素修饰相比, 引入氰基修饰的分子具有更小的电子和空穴重组能及更低的前线分子轨道(FMO)能级. 同时迁移率的计算结果显示, 分子6具有1.15 cm²·V^-1·s^-1的高电子迁移率, 考虑其较低的LUMO能级, 推测其有望成为潜在的优异电子传输材料, 而相似的电子和空穴迁移率使分子2有望成为潜在的双极性传输材料. 同时还考察了S和N原子之间的弱相互作用, 当S或N原子对分子HOMO(或LUMO)有贡献时, 其相应的空穴(或电子)传输能力会有所提高.     

New crown annelated tetrathiafulvalenes: synthesis, electrochemistry, self-assembly of thiol derivatives, and metal cation recognition

The synthesis of new S(2)O(4)-crown annelated tetrathiafulvalene (TTF) derivatives substituted with one terminal thiol group is described. Self-assembled monolayers (SAMs) of these compounds have been assembled on gold and platinum surfaces, the latter substrate giving improved quality films. SAMs of TTF derivative 16b are the most stable of those we have studied. Electrochemical data for SAMs of 5a, 5b, 8, 16a, and 16b in acetonitrile reveal two reversible one-electron waves, typical of the TTF system; the current increased linearly with scan rate, indicating a surface wave response. SAMs of 8, 16a, and 16b exhibited an electrochemical response in aqueous electrolytes, which was observed between 50 and 100 cycles. Moreover, if the potential scanned was limited to the first TTF oxidation, the cyclic voltammetry response was observed for at least 1000 cycles. Metal complexation by the crown ionophore of the SAMs in acetonitrile has been monitored by a positive shift in the first oxidation potential of the TTF unit (maximum DeltaE(1)(1/2) = 80 mV for Ag(+)). We also report the X-ray crystal structure of TTF-crown derivative 21 bearing two hydroxymethyl substituents, synthesized during the course of this work. The structure is characterized by infinite chains of molecules linked by strong intrachain hydrogen bonds between the terminal hydroxy groups.     

Synthesis of organic-metal hybrid nanowires by cooperative self-organization of tetrathiafulvalene and metallic gold via charge-transfer

Organic-metal hybrid nanowires were synthesized by cooperative self-organization of the one-dimensional stacking of tetrathiafulvalene (TTF) via charge-transfer interaction with metallic gold originating from the redox reaction between TTF and gold ions. The nanowires can be easily obtained as purple precipitates just by mixing TTF and HAuCl4 in a CH3CN solution at room temperature. The feed molar ratio of TTF to HAuCl4 was 4.4. The average diameter and length of the observed nanowires were 90 +/- 36 nm and 15 +/- 3 microm, respectively. The formation was facilitated by the arrangement of the neutral and oxidized TTF along the one direction in a mix-valence state, which was confirmed by a broad absorption that appeared in the region of 2000 nm and the composition of the nanowires of [(TTFCl(0.78))Au(0.12)].     

Quantum Mechanical and Experimental Validation that Cyclobis(paraquat‐p‐phenylene) Forms a 1:1 Inclusion Complex with Tetrathiafulvalene

The promiscuous encapsulation of π‐electron‐rich guests by the π‐electron‐deficient host, cyclobis(paraquat‐p‐phenylene) (CBPQT⁴⁺), involves the formation of 1:1 inclusion complexes. One of the most intensely investigated charge‐transfer (CT) bands, assumed to result from inclusion of a guest molecule inside the cavity of CBPQT⁴⁺, is an emerald‐green band associated with the complexation of tetrathiafulvalene (TTF) and its derivatives. This interpretation was called into question recently in this journal based on theoretical gas‐phase calculations that reinterpreted this CT band in terms of an intermolecular side‐on interaction of TTF with one of the bipyridinium (BIPY²⁺) units of CBPQT⁴⁺, rather than the encapsulation of TTF inside the cavity of CBPQT⁴⁺. We carried out DFT calculations, including solvation, that reveal conclusively that the CT band emerging upon mixing TTF with CBPQT⁴⁺ arises from the formation of a 1:1 inclusion complex. In support of this conclusion, we have performed additional experiments on a [2]rotaxane in which a TTF unit, located in the middle of its short dumbbell, is prevented sterically from interacting with either one of the two BIPY²⁺ units of a CBPQT⁴⁺ ring residing on a separate [2]rotaxane in a side‐on fashion. This [2]rotaxane has similar UV/Vis and ¹H NMR spectroscopic properties with those of 1:1 inclusion complexes of TTF and its derivatives with CBPQT⁴⁺. The [2]rotaxane exists as an equimolar mixture of cis‐ and trans‐isomers associated with the disubstituted TTF unit in its dumbbell component. Solid‐state structures were obtained for both isomers, validating the conclusion that the TTF unit, which gives rise to the CT band, resides inside CBPQT⁴⁺.     

Four-electron oxygen reduction by tetrathiafulvalene

The four-electron reduction of oxygen by tetrathiafulvalene (TTF) in acidified 1,2-dichloroethane and at the acidified water/1,2-dichloroethane interface has been observed. Spectroscopy and ion transfer voltammetry results suggest that the reaction proceeds by the fast protonation of TTF followed by the 4-electron reduction of oxygen to form water. Electronic structure computations give evidence of the formation of a helical tetramer assembly ([TTF(4)H(2)](2+)) of two protonated TTF and two neutral TTF molecules. The protonated tetramer is potentially able to deliver the four electrons needed for the oxygen reduction. The production of water was corroborated by (1)H NMR analysis.     

Stabilization of isolated mixed-valence trimers in a novel nickel dithiolene complex with CF2 substituents

The preparation of the novel paramagnetic nickel dithiolene complex Ni(F2pdt)2-* (F2pdt2-: 2,2-difluoro-1,3-propanediyldithioethylene-1,2-dithiolate) and its X-ray crystal structure as n-Bu4N+ salt are described. (n-Bu4N)[Ni(F2pdt)2] (2) crystallizes in the orthorhombic system, space group Pna2(1) with a = 21.379(4) A, b = 8.9702(18) A, and c = 18.527(4) A. The radical anions are isolated from each other by the bulky n-Bu4N+ cations and exhibit a Curie-type magnetic behavior. Two reversible redox waves corresponding to the redox couples Ni(F2pdt)2(2-/-*) and Ni(F2pdt)2(-*/0) are observed at -0.55 and 0.30 V vs SCE, illustrating the electron withdrawing effect of the CF2 substituents. As a consequence, (TTF)3(BF4)2 oxidation of the radical anion does not afford the neutral Ni(F2pdt)2(0) but a TTF salt formulated as [TTF](3)[Ni(F2pdt)2]3[CH2Cl2]. It crystallizes in the triclinic system, space group P1 with a = 12.330(3) A, b = 12.726(3) A, c =15.706(3) A, alpha = 91.10(3), beta = 110.78(3), and gamma = 116.01(3). Donor and acceptor moieties are organized into (TTF)3(2+) and [Ni(F2pdt)2]3(2-) trimers whose dicationic and dianionic charges have been inferred from the intramolecular bond lengths evolution and the singlet-triplet magnetic behavior. These trimers arrange orthogonally to each other into chess-board-like slabs, characterized by a segregation of the CF2 fragments and further stabilized by weak C-H.F interactions. Extended Hückel calculations show that only the nickel dithiolene complex trimer actually contributes to the magnetic susceptibility.     

Building up 1‐D, 2‐D,and 3‐D Polyiodide Frameworks by Finely Tuning the Size of Aryls on Ar‐S‐TTF in the Charge‐Transfer (CT) Complexes of Ar‐S‐TTFs and Iodine

The arylthio‐substituted tetrathiafulvalenes (Ar‐S‐TTFs) are electron donors having three reversible states, neutral, cation radical, and dication. The charge‐transfer (CT) between Ar‐S‐TTFs ( TTF1 — TTF3 ) and iodine (I₂) is reported herein. TTF1 — TTF3 show the CT with I₂ in the CH₂Cl₂ solution, but they are not completely converted into cation radical state. In CT complexes of TTF1 — TTF3 with I₂, the charged states of Ar‐S‐TTFs are distinct from those in solution. TTF1 is at cation radical state, and TTF2 — TTF3 are oxidized to dication. The iodine components in complexes show various structures including 1‐D chain of V‐shaped (I₅)^–, and 2‐D and 3‐D iodine networks composed of I₂ and (I₃)^–.     

A multistate switchable [3]rotacatenane

Rotacatenanes are exotic molecular compounds that can be visualized as a unique combination of a [2]catenane and a [2]rotaxane, thereby combining both the circumrotation of the ring component (rotary motion) and the shuttling of the dumbbell component (translational motion) in one structure. Herein, we describe a strategy for the synthesis of a new switchable [3]rotacatenane and the investigation of its switching properties, which rely on the formation of tetrathiafulvalene (TTF) radical π-dimer interactions-namely, the mixed-valence state (TTF(2) )(+.) and the radical-cation dimer state (TTF(+.) )(2) -under ambient conditions. A template-directed approach, based on donor-acceptor interactions, has been developed, resulting in an improved yield of the key precursor [2]catenane, prior to rotacatenation. The nature of the binding between the [2]catenane and selected π-electron-rich templates has been elucidated by using X-ray crystallography and UV/Vis spectroscopy as well as isothermal titration microcalorimetry. The multistate switching mechanism of the [3]rotacatenane has been demonstrated by cyclic voltammetry and EPR spectroscopy. Most notably, the radical-cation dimer state (TTF(+.) )(2) has been shown to enter into an equilibrium by forming the co-conformation in which the two 1,5-dioxynaphthalene (DNP) units co-occupy the cavity of tetracationic cyclophane, thus enforcing the separation of TTF radical-cation dimer (TTF(+.) )(2) . The population ratio of this equilibrium state was found to be 1:1. We believe that this research demonstrates the power of constructing complex molecular machines using template-directed protocols, enabling us to make the transition from simple molecular switches to their multistate variants for enhancing information storage in molecular electronic devices.