Entrepreneurship in Polymer Chemistry.

Launching a startup company is like synthesizing a new molecule. There is a starting point and a general concept for how to achieve the desired end. Known steps may be taken, but a successful synthesis is rarely the result of the original plan and relies on perseverance and creativity.

Complete mapping of the thermoelectric properties of a single molecule.

Theoretical studies suggest that mastering the thermocurrent through single molecules can lead to thermoelectric energy harvesters with unprecedentedly high efficiencies. This can be achieved by engineering molecule length, optimizing the tunnel coupling strength of molecules via chemical anchor groups or by creating localized states in the backbone with resulting quantum interference features. Empirical verification of these predictions, however, faces considerable experimental challenges and is still awaited.

Tailored homo- and hetero- lanthanide porphyrin dimers: a synthetic strategy for integrating multiple spintronic functionalities into a single molecule.

We present the design, synthesis and magnetic properties of molecular magnetic systems that contain all elements necessary for spin-valve control in molecular spintronic devices in a single molecule. We investigate the static and dynamic magnetic properties and quantum spin properties of butadiyne-linked homo- and hetero-nuclear lanthanide-porphyrin dimers. A heterometallated porphyrin dimer containing both Tb and Dy centres is created rationally by the stepwise oxidative homocoupling of distinct lanthanide-porphyrin monomers.

Strong Coupling of Microwave Photons to Antiferromagnetic Fluctuations in an Organic Magnet.

Coupling between a crystal of di(phenyl)-(2,4,6-trinitrophenyl)iminoazanium radicals and a superconducting microwave resonator is investigated in a circuit quantum electrodynamics (circuit QED) architecture. The crystal exhibits paramagnetic behavior above 4 K, with antiferromagnetic correlations appearing below this temperature, and we demonstrate strong coupling at base temperature. The magnetic resonance acquires a field angle dependence as the crystal is cooled down, indicating anisotropy of the exchange interactions.

Cycloheptatrienyl trianion: an elusive bridge in the search of exchange coupled dinuclear organolanthanide single-molecule magnets.

The preparation of η-cyclopentadienyl (η-CR), η-arene (η-CR), and η-cyclooctatetraenyl (η-CR) bridging motifs are common in organometallic chemistry; however, the synthetic preparation of η-cycloheptatrienyl (η-CR) bridging motifs has remained a synthetic challenge in 4f chemistry. To this end, we have developed a synthetic route towards a series of rare dinuclear organolanthanide inverse sandwich complexes containing the elusive η-CH bridge. Herein, we present the structures and magnetic properties of the lanthanide inverse sandwich complexes [KLn(CH)(N(SiMe))] (Ln = Gd (), Dy (), Er ()) and [K(THF)Er(CH)(N(SiMe))] ().

Mononuclear, Dinuclear, and Trinuclear Iron Complexes Featuring a New Monoanionic SNS Thiolate Ligand.

The new tridentate ligand, S(Me)N(H)S = 2-(2-methylthiophenyl)benzothiazolidine, prepared in a single step from commercial precursors in excellent yield, undergoes ring-opening on treatment with Fe(OTf)2 in the presence of base affording a trinuclear iron complex, [Fe3(μ2-S(Me)NS(-))4](OTf)2 (1) which is fully characterized by structural and spectroscopic methods. X-ray structural data reveal that 1 contains four S(Me)NS(-) ligands meridionally bound to two pseudooctahedral iron centers each bridged by two thiolates to a distorted tetrahedral central iron. The combined spectroscopic (UV-vis, Mössbauer, NMR), magnetic (solution and solid state), and computational (DFT) studies indicate that 1 includes a central, high-spin Fe(II) (S = 2) with two low-spin (S = 0) peripheral Fe(II) centers.

Tetraanionic biphenyl lanthanide complexes as single-molecule magnets.

Inverse sandwich biphenyl complexes [(NN(TBS))Ln]2(μ-biphenyl)[K(solvent)]2 [NN(TBS) = 1,1'-fc(NSi(t)BuMe2)2; Ln = Gd, Dy, Er; solvent = Et2O, toluene; 18-crown-6], containing a quadruply reduced biphenyl ligand, were synthesized and their magnetic properties measured. One of the dysprosium biphenyl complexes was found to exhibit antiferromagnetic coupling and single-molecule-magnet behavior with Ueff of 34 K under zero applied field. The solvent coordinated to potassium affected drastically the nature of the magnetic interaction, with the other dysprosium complex showing ferromagnetic coupling.

Isolation of a hexanuclear chromium cluster with a tetrahedral hydridic core and its catalytic behavior for ethylene oligomerization.

A chromium complex [2-(NHCH2PPh2)C5H4N]CrCl3·THF2 (1) of the ligand PyNHCH2PPh2 has been synthesized, characterized, and examined for its catalytic behavior toward ethylene oligomerization. When complex 1 was treated with (i-Bu)3Al, an unprecedented divalent polyhydride chromium cluster μ,κ(1),κ(2),κ(3)-N,N,P-{[2-(NCH2PPh2)C5H4N]Cr(μ-H)}4[(μ-Cl)Cr(μ-Cl)Al(i-Bu)2Cl]2 (2) was obtained. The complex contains a Cr4H4 core, which is expected to be diamagnetic, and which remains coordinated to two additional divalent high-spin Cr atoms via bridging interactions.

Coupling strategies to enhance single-molecule magnet properties of erbium-cyclooctatetraenyl complexes.

Two different coupling strategies were employed to create Er(III) single-molecule magnets (SMMs) using high blocking temperature mononuclear precursors. The magnetic properties of three lanthanide-COT complexes, [Er(III)2(COT'')3] (1) (COT'' = 1,4-bis(trimethylsilyl)cyclooctatetraenyl dianion) and K2(THF)4[Ln(III)2(COT)4] (Ln = Gd (2), Er (3); THF = tetrahydrofuran, COT = cyclooctatetraenyl dianion), are reported. Both Er(III) complexes behave as SMMs and exhibit magnetic hysteresis at 12 K in solid state.

Fine-tuning the local symmetry to attain record blocking temperature and magnetic remanence in a single-ion magnet.

Remanence and coercivity are the basic characteristics of permanent magnets. They are also tightly correlated with the existence of long relaxation times of magnetization in a number of molecular complexes, called accordingly single-molecule magnets (SMMs). Up to now, hysteresis loops with large coercive fields have only been observed in polynuclear metal complexes and metal-radical SMMs.

A sandwich complex with axial symmetry for harnessing the anisotropy in a prolate erbium(III) ion.

A mononuclear Er(III) sandwich type complex, [Li(DME)3][Er(III)(COT")2], was isolated using 1,4-bis(trimethylsilyl)cyclooctatetraenyl dianion (COT"). Remarkably, this low-symmetry complex exhibits magnet-like behavior of magnetic remanence and coercivity in the hysteresis loops up to 8 K with an energy barrier (Ueff) of 187(1) K, thus making this molecule a unique single-ion magnet.

Structural and magnetic conformation of a cerocene [Ce(COT'')2]- exhibiting a uniconfigurational f1 ground state and slow-magnetic relaxation.

Magnet-like behaviour, in the form of slow relaxation of the magnetization, was observed for a monometallic cerium(III) sandwich complex. The use of trimethylsilyl substituted COT ligands (COT'') led to the formation of a staggered COT'' arrangement in the cerocene-type sandwich complex with a well-defined oxidation state of +3 for the Ce ion.

A dinuclear cobalt complex featuring unprecedented anodic and cathodic redox switches for single-molecule magnet activity.

One-electron oxidation or reduction of the paramagnetic dinuclear Co(II) complex dmp2Nin{Co[N(SiMe3)2]}2 (1; dmp2Nin(2-) = bis(2,6-dimethylphenyl)nindigo), by fully reversible chemical or electrochemical methods, generates the radical salts [1(OEt2)](+) and [1](-), respectively. Full structural and magnetic analyses reveal the locus of the redox changes to be nindigo-based, thus giving rise to ligand-centered radicals sandwiched between two paramagnetic and low-coordinate Co(II) centers. The presence of these sandwiched radicals mediates magnetic coupling between the high-spin (S = 3/2) cobalt ions, which gives rise to single-molecule magnet (SMM) activity in both the oxidized ([1(OEt2)](+)) and reduced ([1](-)) states.

Synthesis, electronic structure, and magnetism of [Ni(6-Mes)2]+: a two-coordinate nickel(I) complex stabilized by bulky N-heterocyclic carbenes.

The two-coordinate cationic Ni(I) bis-N-heterocyclic carbene complex [Ni(6-Mes)2]Br (1) [6-Mes =1,3-bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene] has been structurally characterized and displays a highly linear geometry with a C-Ni-C angle of 179.27(13)°. Density functional theory calculations revealed that the five occupied metal-based orbitals are split in an approximate 2:1:2 pattern.

Synthesis and catalytic activity of iron complexes with bidentate NHC ligands.

A family of well-defined Fe(II) complexes of the type {BnN(N-CH2(CH2)n-N'-tert-butyl-imidazole-2-ylidene)2}FeCl2 (Bn = benzyl; n = 1 (1) or 2 (2)), {BnN(N-CH2(CH2)n-N'-methylbenzimidazole-2-ylidene)2}FeCl2 (n = 1 (3) or 2 (4)) and {BnN(N-CH2CH2CH2-N'-methylbenzimidazole-2-ylidene)2}FeBr2 (5) has been synthesized. These complexes are rare examples of Fe species supported by bidentate NHC ligands. Complexes 2, 3, 4 and 5 were characterized by X-ray crystallography and in all cases a distorted tetrahedral geometry is observed around the Fe center.

An organometallic building block approach to produce a multidecker 4f single-molecule magnet.

An organometallic building block strategy was employed to investigate the magnetic properties of a Ln(III) organometallic single-ion magnet (SIM) and subsequent single-molecule magnet (SMM) after coupling two of the monomeric units. New homoleptic Dy(III)COT″2 and Ln(III)2COT″3 (Ln = Gd, Dy) complexes have been synthesized. DFT calculations of the bimetallic Dy(III) complex indicate strong metal-ligand covalency and uneven donation to the Dy(III) ions by the terminal and internal COT″(2-) (cyclooctatetraenide) rings that correlate with the respective bond distances.

Probing the redox non-innocence of dinuclear, three-coordinate Co(II) nindigo complexes: not simply β-diketiminate variants.

Reduction of the dinuclear Co(II) nindigo complex dmp(2)Nin[Co(N{SiMe(3)}(2))](2), with 1 or 2 equiv. of K(0) (or KC(8)), affords the reduced complexes [dmp(2)Nin{Co(N{SiMe(3)}(2))}(2)](-) and [dmp(2)Nin{Co(N{SiMe(3)}(2))}(2)](2-), respectively. Inspection of these reduced species reveals ligand-centered reduction, with each cobalt ion retaining a formal 2+ oxidation state.

First structural evidence for multiple alkali metals between sandwich decks in a metallocene.

A tetralithio salt (1) derived by treating 1,4-bis(trimethylsilyl)-cyclooctatriene with (n)BuLi serves as the first structural evidence for a multi-alkali metallocene. Single-crystal XRD confirms two Li(+) each asymmetrically bind to η(3) and η(4) between two COT'' rings and two Li(+) terminally bind to η(3). Solid-state NMR studies confirm the presence of two distinct lithium ion sites while the solution NMR studies suggest the formation of an (COT'' dianion) ion-pair in solution.

An organometallic sandwich lanthanide single-ion magnet with an unusual multiple relaxation mechanism.

A dysprosium(III) sandwich complex, [Dy(III)(COT″)(2)Li(THF)(DME)], was synthesized using 1,4-bis(trimethylsilyl)cyclooctatetraenyl dianion (COT″). The complex behaves as a single-ion magnet and demonstrates unusual multiple relaxation modes. The observed relaxation pathways strongly depend on the applied static dc fields.