Rare-Earth Metal Tetrathiafulvalene Carboxylate Frameworks as Redox-Switchable Single-Molecule Magnets.

Using the redox-active tetrathiafulvalene tetrabenzoate (TTFTB ) as the linker, a series of stable and porous rare-earth metal-organic frameworks (RE-MOFs), [RE (μ -OH) (μ -O)(H O) (TTFTB) ] (1-RE, where RE=Y, Sm, Gd, Tb, Dy, Ho, and Er) were constructed. The RE (μ -OH) (μ -O) (H O) ](CO ) clusters within 1-RE act as segregated single-molecule magnets (SMMs) displaying slow relaxation. Interestingly, upon oxidation by I , the S=0 TTFTB linkers of 1-RE were converted into S= TTFTB radical linkers which introduced exchange-coupling between SMMs and modulated the relaxation.

Enhanced dielectricity coupled to spin-crossover in a one-dimensional polymer iron(ii) incorporating tetrathiafulvalene.

In designing multifunctional materials for potential switches that can be used as memory devices, the high-spin (HS) to low-spin (LS) crossover (SCO) one-dimensional polymer, [Fe(L)(4,4'-bpy)] , was constructed from a designed redox-active tetrathiafulvalene (TTF) functionalized Schiff-base and the ditopic linker 4,4'-bipyridine (bpy). It exhibits an 8 K hysteretic SCO centred at = 325 K which is coupled to changes in its dielectric constant. The crystal structures above and below the transition temperature reveal similar parallel linear ···Fe-bpy-Fe-bpy··· chains displaying expansion of the Fe octahedron in the HS state.

Spin crossover modulation in a coordination polymer with the redox-active bis-pyridyltetrathiafulvalene (pyTTF) ligand.

A one-dimensional Fe coordination polymer (CP) has been formed which includes the redox-active ligand bis-pyridyltetrathiafulvalene (pyTTF) and a Schiff base-like NO ligand. This CP is both spin crossover (SCO) and redox-active in the solid-state, and chemical oxidation results in SCO modification.

Dinuclear acetylide-bridged ruthenium(ii) complexes with rigid non-aromatic spacers.

Rigid dinuclear ruthenium complexes containing non-aromatic caged and polycyclic spacer groups were synthesised and characterised. The complexes, [trans,trans-{Ru(dmpe)2(C[triple bond, length as m-dash]CtBu)}2(μ-C[triple bond, length as m-dash]C-X-C[triple bond, length as m-dash]C)], where X = 1,4-bicyclo[2.2.

Concomitant Use of Tetrathiafulvalene and 7,7,8,8-Tetracyanoquinodimethane within the Skeletons of Metal-Organic Frameworks: Structures, Magnetism, and Electrochemistry.

In search of multifunctional metal-organic frameworks (MOFs), redox-active donors and acceptors, namely, tetrathiafulvalene (TTF) and 7,7,8,8-tetracyanoquinodimethane (TCNQ), were concomitantly used as skeletal components with diamagnetic metal nodes (Cd and Zn) to construct unique framework materials. Six isostructural frameworks were synthesized by diffusion of metal salts, TTF(py), and either paramagnetic Li(TCNQ) or diamagnetic HTCNQ. They were characterized by single-crystal X-ray diffraction and FT-IR and UV-vis-NIR spectroscopy, and their physical properties were studied, including two postsynthetic modifications involving crystal-to-crystal transformations following a solid-solution reaction with I.

Toward a dodecanuclear molecular Re(i) box: structural and spectroscopic properties.

Two tetrapyridyl ligands of 1,2,4,5-tetraethynyl(4-pyridyl)benzene (tpeb) and tetra(4-pyridyl)-tetrathiafulvalene (TTF(py)) were used to react with trinuclear (Re(CO))(CNS) (CNS = cyanurate trianion) moieties to afford hexanuclear [(Re(CO))(tpeb)(CNS)]·4CHCN·toluene (1) and dodecanuclear [(Re(CO))(TTF(py))(CNS)]·8CHCN·12DMF (2) boxes, respectively, under solvothermal conditions. Surprisingly, similar tetrapyridyl ligands with different core units (i.e.

Porous Molecular Conductor: Electrochemical Fabrication of Through-Space Conduction Pathways among Linear Coordination Polymers.

The first porous molecular conductor (PMC), which exhibits porosity, a through-space conduction pathway and rich charge carriers (electrons), was prepared through electrocrystallization from Cd and N, N'-di(4-pyridyl)-1,4,5,8-naphthalenetetracarboxdiimide (NDI-py). [Cd(NDI-py)(OH)](NO)· nDMA (PMC-1) was assembled by π-π stacking among one-dimensional (1D) linear coordination polymers. The NDI cores were partially reduced into radical anions to form conductive π-stacked columns, yielding (1.

Probing charge transfer characteristics in a donor-acceptor metal-organic framework by Raman spectroelectrochemistry and pressure-dependence studies.

The stimuli responsive behaviour of charge transfer donor-acceptor metal-organic frameworks (MOFs) remains an understudied phenomenon which may have applications in tuneable electronic materials. We now report the modification of donor-acceptor charge transfer characteristics in a semiconducting tetrathiafulvalene-naphthalene diimide-based MOF under applied electrochemical bias and pressure. We employ a facile solid state in situ Raman spectroelectrochemical technique, applied for the first time in the characterisation of electroactive MOFs, to monitor the formation of a new complex TTFTC˙+-DPNI from a largely neutral system, upon electrochemical oxidation of the framework.

Mixed Valency as a Strategy for Achieving Charge Delocalization in Semiconducting and Conducting Framework Materials.

The fundamentally important phenomenon of mixed valency has been discussed in detail over the past 50 years, predominantly in the context of dinuclear complexes, which are used as model systems for understanding electron delocalization in more complex biological and physical systems. Very recently, mixed valency has been shown to be an important mechanism for charge transfer, leading to delocalization and conductivity in two- and three-dimensional framework materials such as metal-organic frameworks and related systems including covalent organic frameworks and semicrystalline semiconducting metal-organic graphenes. This Viewpoint provides a current perspective on the field of mixed-valence frameworks, where the property is either intrinsic or generated postsynthetically via an external stimulus.

Photo- and Electronically Switchable Spin-Crossover Iron(II) Metal-Organic Frameworks Based on a Tetrathiafulvalene Ligand.

A major challenge is the development of multifunctional metal-organic frameworks (MOFs), wherein magnetic and electronic functionality can be controlled simultaneously. Herein, we rationally construct two 3D MOFs by introducing the redox active ligand tetra(4-pyridyl)tetrathiafulvalene (TTF(py) ) and spin-crossover Fe centers. The materials exhibit redox activity, in addition to thermally and photo-induced spin crossover (SCO).

A heterometallic ferrimagnet based on a new TTF-bis(oxamato) ligand.

An oxamato unit has been introduced into a tetrathiafulvalene (TTF) system for the first time via direct condensation, generating a new π-extended TTF ligand, TTF-EtHopba (opba = ortho-phenylenebis-oxamato). On the basis of this ligand, the Cu(ii) complex [(n-Bu)N][Cu(TTF-opba)] (1) has been obtained. By employing this complex as a "metalloligand", we have successfully prepared an interesting heterometallic one-dimensional complex {[Cu(TTF-opba)][Mn(CHOH)]} (2), via coordination of the free carbonyl-oxygen atoms of the two oxamato groups with Mn(ii) ions.

Chiral heterobimetallic chains from a dicyanideferrite building block including a π-conjugated TTF annulated ligand.

The π-conjugated tetrathiafulvalene (TTF) annulated ligand was introduced into a dicyanometallate for the first time, leading to the synthesis of the versatile redox-active dicyanideferrite building block [(n-Bu)N][Fe(TTFbp)(CN)] (HTTFbp = N-(2-(4,5-bis(methylthio)-1,3-dithiol-2-ylidene)-5-(picolinamido) benzo[d][1,3]dithiol-6-yl) picol inamide). The incorporation of the new precursor with chiral Mn Schiff-base complexes resulted in two enantiopure one-dimensional complexes, [Mn((R,R)-salphen)Fe(TTFbp)(CN)] (2-(RR)) and [Mn((S,S)-salphen)Fe(TTFbp)(CN)] (2-(SS)) (Salphen = N,N'-1,2-diphenylethylene-bis(salicylideneiminato) dianion), which were synthesized and structurally characterized. Circular dichroism (CD) and vibrational circular dichroism (VCD) spectra confirmed the enantiomeric nature of the optically active complexes, and structural analyses revealed the formation of neutral cyanide-bridged double chains in 2-(RR) and 2-(SS).

Synthesis, properties and surface self-assembly of a pentanuclear cluster based on the new π-conjugated TTF-triazole ligand.

The new π-extended redox-active ligand with both TTF and triazole units, 6-(4,5-bis(propylthio)-1,3-dithiol-2-ylidene)-1H-[1,3]dithiolo[4',5':4,5]benzo [1,2-d] [1-3]triazole, has been successfully prepared. Based on the versatile ligand and Cu(tta)2 precursors (tta(-) = 4,4,4-trifluoro-1-(thiophen-2-yl)butane-1,3-dione), a TTF-based pentanuclear Cu(II) cluster (Cu5(tta)4(TTFN3)6) is synthesized and structurally characterized. Their absorption and electrochemical properties are investigated.

Dinuclear Ruthenium Complex Based on a π-Extended Bridging Ligand with Redox-Active Tetrathiafulvalene and 1,10-Phenanthroline Units.

The synthesis of a π-extended bridging ligand with both redox-active tetrathiafulvalene (TTF) and 1,10-phenanthroline (phen) units, namely, bis(1,10-phenanthro[5,6-b])tetrathiafulvalene (BPTTF), was realized via a self-coupling reaction. Using this ligand and Ru(tbbpy)2Cl2 (tbbpy = 4,4'-di-tert-butyl-2,2'-bipyridine), the dinuclear ruthenium(II) compound [{Ru(tbbpy)2}2(BPTTF)](PF6)4 (1) has been obtained by microwave-assisted synthesis. Structural characterization of 1 revealed a crossed arrangement of the TTF moieties on adjacent dimers within the crystal structure.

Crystal Structures, Magnetic Properties, and Electrochemical Properties of Coordination Polymers Based on the Tetra(4-pyridyl)-tetrathiafulvalene Ligand.

Seven new coordination polymers based on the redox-active tetra(4-pyridyl)-tetrathiafulvalene ligand (TTF(py)4) and different transition-metal ions, namely, {[Cu(hfac)2][TTF(py)4]·2(CH2Cl2)}n (1), {[Co(acac)2][TTF(py)4]0.5·(CHCl3)}n (2), {[Mn(hfac)2][TTF(py)4]0.5}n (3), {[Cu2(OAc)4][TTF(py)4]0.

The electronic, optical and magnetic consequences of delocalization in multifunctional donor-acceptor organic polymers.

Two organic polymers containing alternating electron donating triarylamine and electron accepting thiazolo[5,4-d]thiazole (TzTz) moieties have been synthesized and their redox states investigated. When donor and acceptor units are proximal (polymer )1, electron density is delocalized, leading to a small electrical and optical band gap; these are larger with the inclusion of an adjoining alkynyl-phenyl bridge (polymer 2), where electron density is more localized due to the rotation of the monomer units. As a result, 1 and 2 display different optical and fluorescence properties in their neutral states.

Electronic, optical, and computational studies of a redox-active napthalenediimide-based coordination polymer.

The new one-dimensional coordination framework (Zn(DMF)NO3)2(NDC)(DPMNI), where NDC = 2,6-naphthalenedicarboxylate and DPMNI = N,N'-bis(4-pyridylmethyl)-1,4,5,8-naphthalenetetracarboxydiimide, which has been crystallographically characterized, exhibits two redox-accessible states due to the successive reduction of the naphthalenediimide (NDI) ligand core. Solid-state electrochemical and vis-near-IR spectroelectrochemical measurements coupled with density functional theory (DFT) calculations enabled the origins of the optical transitions in the spectra of the monoradical anion and dianion states of the material to be assigned. Electron paramagnetic resonance (EPR) spectroscopy revealed that the paramagnetic radical anion state of the DPMNI core could be accessed upon broad-spectrum white light irradiation of the material, revealing a long-lived excited state, possibly stabilized by charge delocalization which arises from extensive π-π* stacking interactions between alternating NDC and NDI aromatic cores which are separated by a distance of 3.

Enhancing selective CO2 adsorption via chemical reduction of a redox-active metal-organic framework.

A new microporous framework, Zn(NDC)(DPMBI) (where NDC = 2,7-naphthalene dicarboxylate and DPMBI = N,N'-di-(4-pyridylmethyl)-1,2,4,5-benzenetetracarboxydiimide), containing the redox-active benzenetetracarboxydiimide (also known as pyromellitic diimide) ligand core has been crystallographically characterised and exhibits a BET surface area of 608.2 ± 0.7 m(2) g(-1).