Search

Polycyclic aromatic hydrocarbons (PAHs) have found strong interest for their electronic properties and as model systems for graphene. While PAHs have been studied intensively as single units, here PAHs were constructed in ladder-type arrangements using cross-conjugated fulvalene and dithiafulvalene motifs as connecting units and moving forward a convenient synthetic approach for dimerizing (thio)ketones into olefins by the action of Lawesson's reagent. Some of the PAHs can also be regarded as "super-extended" tetrathiafulvalenes (TTFs) with some of the largest cores ever explored, being multi-redox systems that exhibit both reversible oxidations and reductions. Concomitant absorption redshifts were observed when expanding the ladder-type structures from one to two to three indenofluorene units, and optical and electrochemical HOMO-LUMO gaps were found to correlate linearly. Various conformations (and solid-state packing arrangements) were studied by X-ray crystallography and computations.

The first example of a two-state (neutral and reduced), stable electron-accepting material and its radical anion is presented. FV-PDI, generated from cyclocarbonylation and then a carbonyl coupling reaction, shows a largely degenerate LUMO of -4.38 eV based on the delocalization of π-electrons across the whole molecular skeleton through a fulvalene bridge. The stability and electron affinity allow spontaneous electron transfer to afford a stable radical anion. Spectroscopic characterization and structural elucidation showed that the radical anion [FV-PDI].- has remarkable stability and near-infrared absorptions extending to 1200 nm. Single-crystal X-ray diffraction analyses revealed significant changes in the molecular shape and packing arrangement of the formed radical anion. The central C-C bond linking the two PDI halves is lengthened from approximately 1.33 to 1.43 A, and the alternating arrangement of positively and negatively charged units favor the stable charge-transfer complex.

The bis(fulvalene)dimetal compounds [M2(fulv′)2] (fulv′ = 2,2′,4,4′-(Me3C)4C10H4)2, M = Fe, Mn) have been isolated from the reaction of [Mg2(fulv′)2] and M(OTf)2, and they have been fully character...

The mol­ecule of the title compound has a C-shape, with C s mol­ecular symmetry. The dihedral angle between the planes of the di­thiol and phenyl rings is 8.35 (9)°. In the crystal, mol­ecules form helical chains along [001], the shortest inter­actions being π⋯S contacts within the helices., The mol­ecule of the title compound, C18H10Br2S4, has a C-shape, with C s mol­ecular symmetry. The dihedral angle between the planes of the di­thiol and phenyl rings is 8.35 (9)°. In the crystal, mol­ecules form helical chains along [001], the shortest inter­actions being π⋯S contacts within the helices. The inter­molecular inter­actions were investigated by Hirshfeld surface analysis. Density functional theory (DFT) was used to calculate HOMO–LUMO energy levels of the title compound and its trans isomer.

The fulvalene diiridium platform was scrutinized for its potential to effect double vicinal C–H activation of C6H6 and C6H12, respectively. For this purpose, an improved preparation of Fv[Ir(CO)2]2 was developed, and the syntheses of the new complexes FvIr(CO)2Ir(CO)(η 2-C6F6), Fv[Ir(CO)(η 2-C6F6)]2, Fv[Ir(CH2=CH2)2]2 (X-ray), Fv[Ir(PMe3)(H)2]2 (X-ray), and (2,2′,3,3′-tetra-tert-butylFv)[Ir(CO)2]2 were accomplished. When irradiated in C6H6, these molecules succeeded to varying degrees, and best for (2,2′,3,3′-tetra-tert-butylFv)[Ir(CO)2]2, in the double metalation of the aromatic ring to engender ligating Ir2(ortho-μ-C6H4)(CO)2 (Ir–Ir) moieties, in addition to their precursor mono(phenyliridium hydride) constructs. A competing photochemical pathway is evident by the formation of diastereomers of Fv (or 2,2’,3,3’-tetra-tert-butylFv) [Ir(CO)(Ph)(H)]2 and the resulting dehydrogenated ligated [Ir(CO)(Ph)]2 (Ir–Ir). The structures of FvIr2(ortho-µ-C6H4)(CO)2 (Ir–Ir) and trans-Fv[Ir(CO)(Ph)]2 (Ir–Ir) were corroborated by X-ray analyses. Efforts to realize C–H bond activations with C6H12 generally failed or fared very poorly, with the exception of the tert-butylFv system, which enabled single, but not further, insertion to give (2,2′,3,3′-tetra-tert-butylFv)[Ir(CO)(Cy)(H)][Ir(CO)2] in 34% yield. To explore the relevant chemistry of phenyl- and alkyliridium species attached to Fv, several such derivatives were made by independent routes, adding knowledge to the fundamental behavior of this category of molecules. Where appropriate and for comparative purposes, similar reactions were performed on the corresponding Cp- and 1,2-di-tert-butylCpIr(CO)2 relatives.

Based on first-principles calculations, we propose a new two-dimensional (2D) carbon allotrope (net-τ), which consists of quadrilateral, pentagonal, hexagonal, octagonal and decagonal rings. Our results demonstrate that the net-τ is a dynamically stable phase with intrinsic metallicity. Remarkably, it is found that the maximum theoretical capacity of the net-τ reaches 558 mAh g−1 on one side, which is 1.6 times that of commercial graphite and recently predicted ψ-graphene (372 mAh g−1). Meanwhile, the net-τ has a relatively low diffusion energy barrier (0.296 eV) and open-circuit potential (0.039 V), which shows its good potential as an anode material for lithium-ion batteries. Equally important, the net-τ may be synthesized by a bottom-up scheme through multiple intermediate reactions with benzocyclobutene and fulvalene. These interesting findings not only increase the family of two-dimensional metallic carbon allotropes, but also provide a novel strategy to realize high-performance anode materials by designing a 2D structure with high-order carbon rings.

A series of fulvalene-supported dimetallic dysprosium metallocene SMMs provides a roadmap to poly-cationic dysprosocenium single-molecule magnets., The dinucleating fulvalenyl ligand [1,1′,3,3′-(C5tBu2H2)2]2– (Fvtttt) was used to synthesize the dimetallic dysprosocenium cation [{Dy(η5-Cp*)}2(μ-BH4)(η5:η5-Fvtttt)]+ (3) as the salt of [B(C6F5)4]– (Cp* = C5Me5). Compound [3][B(C6F5)4] was obtained using a method in which the double half-sandwich complex [{Dy(BH4)2(THF)}2(Fvtttt)] (1) was reacted with KCp* to give the double metallocene [{Dy(Cp*)(μ-BH4)}2(Fvtttt)] (2), followed by removal of a bridging borohydride ligand upon addition of [(Et3Si)2(μ-H)][B(C6F5)4]. The dimetallic fulvalenyl complexes 1–3 give rise to single-molecule magnet (SMM) behaviour in zero applied field, with the effective energy barriers of 154(15) cm–1, 252(4) cm–1 and 384(18) cm–1, respectively, revealing a significant improvement in performance across the series. The magnetic properties are interpreted with the aid of ab initio calculations, which show substantial increases in the axiality of the crystal field from 1 to 2 to 3 as a consequence of the increasingly dominant role of the Fvtttt and Cp* ligands, with the barrier height and hysteresis properties being attenuated by the equatorial borohydride ligands. The experimental and theoretical results described in this study furnish a blueprint for the design and synthesis of poly-cationic dysprosocenium SMMs with properties that may surpass those of benchmark systems.

A new phase combining BEDT-TTF and [Cu(NCS)4]2– as the counter-anion, namely bis[bis(ethylenedithio)tetrathiafulvalenium] tetrathiocyanatocuprate(II) bis[bis(ethylenedithio)tetrathiafulvalene], (C10H8S8)2[Cu(NCS)4]·2C10H8S8 or (BEDT-TTF)4[Cu(NCS)4] was obtained during a galvanostatic electrocrystallization process. As previously observed with BEDT-TTF-based compounds with oxalatometallate anions, the BEDT-TTF molecules in (BEDT-TTF)4[Cu(NCS)4] exhibit the so-called pseudo-κ arrangement, with two BEDT-TTF molecules being positively charged and two electronically neutral. The bond lengths and angles in the two unique BEDT-TTF molecules differ slightly. The crystal structure consists of layers of BEDT-TTF molecules extending parallel to (001). The width of this layer corresponds to the length of the a axis [16.9036 (17) Å]. The BEDT-TTF layers are separated by layers of centrosymmetric square-planar [Cu(NCS)4]2– dianions.

Pentafulvalene is a symmetrical unsaturated hydrocarbon built from two five-membered rings connected by an exocyclic double bond, where each ring is one electron short of being a 6π-electron aromatic system. Here, we show computationally that by selectively introducing electron withdrawing and donating substituents, we can design pentafulvalene derivatives that exhibit tunable aromaticity properties. Pentafulvalene can be shaped into a species with connected aromatic-antiaromatic rings, which can also achieve π-bond shifting by carbon tunneling. We propose an NMR technique that can experimentally prove such tunneling mechanism. In addition, we devised a doubly aromatic fulvalene involving both Hückel and Baird aromaticities. These results can open possibilities to create novel molecules in terms of spin state, aromaticity, and reactivity by quantum tunneling.

Reactions following the addition of dihydrogen under maximum atmospheric pressure to bis(trimethylsilyl)acetylene (BTMSA) complexes of titanocenes, [(η5-C5H5-nMen)2Ti(η2-BTMSA)] (n = 0, 1, 3, and 4) (1A-1D), and zirconocenes, [(η5-C5H5-nMen)2Zr(η2-BTMSA)] (n = 2-5) (4A-4D), proceeded in diverse ways and, depending on the metal, afforded different products. The former complexes lost, in all cases, their BTMSA ligand via its hydrogenation to bis-1,2-(trimethylsilyl)ethane when reacted at 80 °C for a prolonged reaction time. For n = 0, 1, and 3, the titanocene species formed in situ dimerised via the formation of fulvalene ligands and two bridging hydride ligands, giving known green dimeric titanocenes (2A-2C). For n = 4, a titanocene hydride [(η5-C5HMe4)2TiH] (2D) was formed, similarly to the known [(η5-C5Me5)2TiH] (2E) for n = 5; however, in contrast to this example, 2D in the absence of dihydrogen spontaneously dehydrogenated to the known Ti(iii)-Ti(iii) dehydro-dimer [{Ti(η5-C5HMe4)(μ-η1:η5-C5Me4)}2] (3B). This complex has now been fully characterised via spectroscopic methods, and was shown through EPR spectroscopy to attain an intramolecular electronic triplet state. The zirconocene-BTMSA complexes 4A-4D reacted uniformly with one hydrogen molecule to give Zr(iv) zirconocene hydride alkenyls, [(η5-C5H5-nMen)2ZrH{C(SiMe3)[double bond, length as m-dash]CH(SiMe3)}] (n = 2-5) (5A-5D). These were identified through their 1H and 13C NMR spectra, which show features typical of an agostically bonded proton, [double bond, length as m-dash]CH(SiMe3). Compounds 5A-5D formed equilibria with the BTMSA complexes 4A-4D depending on hydrogen pressure and temperature.

The spin transport in ferrocene molecules has been examined by using the nonequilibrium Green’s function formalism with density functional theory. The ferrocene molecules were sandwiched between the two nickel electrodes in a parallel magnetic configuration, which enhanced the current in comparison with that in an antiparallel spin state and resulting in tunnel magnetoresistance (TMR). The current, having an opposite spin state to that of the ferromagnetic electrode, was the main channel for electron transport. In addition, it became clear that ferrocenylene molecules, having a fulvalene structure with an extended π-conjugation, enhanced the TMR effect.

We have found that Cu(NO3)2 and 1,3-dione dioxime afford a variety of multicopper complexes under ambient conditions. Specifically, Cu(NO3)2 and cyclohexane-1,3-dione dioxime gave a trinuclear complex in which the central α-carbons of the three dioxime ligands are oxidized into carbonyl groups, two of which were further reacted with solvent MeOH to give a hemiacetal structure. On the other hand, Cu(NO3)2 and cyclopentane-1,3-dione dioxime gave a dinuclear complex in which Cu(II) was reduced to Cu(I) and two of the three ligands couple to give the fulvalene structure. Together with the previously reported reaction of Cu(NO3)2 and pentane-2,4-dione dioxime into a pentanuclear complex in which the four ligands were changed into trioximes, surprisingly rich chemistry has been discovered for combinations of Cu(NO3)2 and 1,3-dione dioximes.

In the crystal of the title compound, the benzoic acid mol­ecules are linked by O—H⋯O hydrogen bonds, forming inversion dimers with (8) motifs. The dimers are linked further via weak C—H⋯O hydrogen bonds, and S⋯S and S⋯C contact inter­actions into a layer structure., In the title compound (systematic name: 4,4′-{[2-(5,6-di­hydro-[1,3]di­thiolo[4,5-b][1,4]dioxin-2-yl­idene)-1,3-di­thiole-4,5-di­yl]bis­(sulfanedi­yl)}di­benzoic acid 0.25-hydrate), C22H14O6S6·0.25H2O, the tetra­thia­fulvalene (TTF) core adopts a boat conformation, where the central S2C=CS2 plane makes dihedral angles of 31.34 (4) and 26.83 (6)°, respectively, with the peripheral S2C=CS2 and S2C2O2 planes. In the crystal, the benzoic acid mol­ecules are linked via O—H⋯O hydrogen bonds, forming inversion dimers with R 2 2(8) motifs. The dimers are linked through weak C—H⋯O hydrogen bonds into a chain structure along [-101]. The chains stack along the a axis through S⋯S and S⋯C short contacts, forming layers parallel to the ac plane.

Diindenosilole Si1, a silicon-bridged fulvalene derivative, was successfully reduced to its dianions using various alkali metals, and the structures were characterized by X-ray crystallographic analysis. Radical anions of Si1 as well as dianions of π-extended Si3 could also be synthesized, and the structural and physical properties were systematically compared. It was also found that the NMR spectra of dianions Si12– and Si32– show countercation and temperature dependency for their signal broadness, indicating the possible existence of thermal interconversion between closed-shell singlet states and open-shell triplet states.

The synthesis of a η5-coordinated LiCp complex by simple addition of a Li-salt in benzene is presented. A strongly zwitterionic fulvalene serves as the Cp-precursor. Evidence for the coordination of Li+ was obtained by the characterisitic 7Li NMR chemical shifts, variable temperature experiments in solution and by X-ray structure analysis in the solid state.

Tetrabenzo[5.7]fulvalene, one of the first recognized stable members of mixed fulvalenes, has attracted widespread interest for its remarkable structure. However, little has been known about its photoactivity, most likely owning to its very weak luminescence in solution state. Here we show for the first time that this compound exhibits aggregation-induced emission (AIE) properties. Its photoluminescence and X-ray crystal structure reveal an interesting mechanism of AIE phenomenon.

In this paper, the relationship between reversible reactions and second-order nonlinear optical (NLO) responses forFvRu2(CO)4-linkedpolyoxometalate (POM) derivatives have been systematically investigated by using density functional theory (DFT) method. The order of β values illustrates that the NLO responses can be enhanced by introducing POM and electron donating group(-NH2).According to the TDDFT results, the large βtot values of the studied systems arise mainlydue to the electronic transition from FvRu2(CO)4 group to the POM group.It is noticeable thatthe geometric interconversion resulting for systems 1/1′-4/4′allows the NLO responses to be switched “ON” or “OFF”.The aim of this work is to combine the attractive reversible reactions and NLO response of FvRu2(CO)4-linked POM derivatives to obtain the switchable NLO materials.

Sunlight photolysis of the triplet state (S = 1) dititanium compound 1 induced its rearrangement to diamagnetic 2, which was a molecule containing two hydrogens less. The cage structure of 2 was determined by single crystal X-ray diffraction and was corroborated fully by 1H and 13C NMR spectra that identified three simple bridging moieties — a hydrogen atom, a methine carbon and a methylene carbon. Its extremely short Ti−Ti distance 2.7537(7) A causes a strong distortion of the bridging fulvalene ligand, which becomes η5- bonded to one Ti(IV) and connected by two σ-bonds from nearest carbon atoms of its other ring to the other Ti(IV) of 2. Other photolytical byproducts in very minor amounts were also isolated, which differed from 2 by the absence of one bridging moiety: compound 4 lacked the methine group and compound 5 had no bridging hydrogen. In the latter cases, the Ti−Ti distance fell in the range 3.2077(8) – 3.5543(12) A and the fulvalene ligand was coordinated in the common µ-η5: η5-mode to both titanium atoms. The octamethylfulvalene ligands in 4 and 5 had their ring planes rotated mutually by about 40° in order to relieve the steric hindrance between their methyl groups. The thermally robust µ-oxo complex 3 obtained from reacting 2 with water showed a very similar structure.

17H-Tetrabenzo[a,c,g,i]fluoren-17-one possessing a nonplanar, helicene-like structure was efficiently prepared by aerial oxidation of 17H-tetrabenzo[a,c,g,i]fluorene under mild basic conditions. A quinone methide and an unsymmetrical fulvalene containing a tetrabenzofluorene unit were synthesized from the ketone. Treatment of 17-bromotetrabenzo[a,c,g,i]fluorene with a base afforded a symmetric fulvalene as an air-sensitive blue solid. Electrochemical analyses revealed that these compounds have high electron affinities.

Two ethynyl-derivatized isomers of bis(fulvalene)diiron (BFD, 1,1′-biferrocenylene) were prepared and covalently attached to glassy carbon electrodes through their ethynyl group by three different electrode modification methods. Cyclic voltammetry and square wave (SW) voltammetry were used to characterize surface coverages of 1.4–5.5 × 10–10 mol cm–2, the higher of these corresponding to roughly a monolayer, based on computation of an idealized close-packing structure for ethynylbis(fulvalene)diiron (E-BFD) on a solid surface. In a dichloromethane solution containing a smaller electrolyte anion such as [PF6]− or [ClO4]−, the E-BFD-modified electrodes exhibited two quasi-Nernstian one-electron oxidations. In contrast, the current for the second oxidation process, [E-BFD]+/2+, was diminished in electrolytes containing one of the large fluoroaryl borate anions, [B(C6F5)4]− or [B(C6H3(CF3)2)4]−. The effect was enhanced for electrodes having higher surface coverages being probed at shorter voltammetric time sc...

The highly dipolar fulvalene 1 reacts with pentacarbonyl iron(0) and hexacarbonyl tungsten(0) complexes under irradiation with UV light. The cyclopentadienyl complexes 2 and 3 formed are analysed by means of NMR and IR spectroscopy as well as X-ray analysis. They are the first zwitterionic carbonyl complexes of fulvenes or fulvalenes. In the case of iron, the dinuclear complex 2 consisting of a dicarbonyliron(+I)-tetracarbonylferrat(–I) moiety is formed, whereas in the case of tungsten, the mononuclear tricarbonyl tungsten(0) complex 3 is obtained.

Two CuI complexes based on the π-conjugated tetrathiafulvalene-annulated phenanthroline ligands (TTF-Phen, L1 and L2), [CuI(Xantphos)(L1)]BF4 (1, Xantphos = 9,9-dimethyl-4,5-bis(diphenylphosphino)xanthene) and [CuI(Binap)(L2)]BF4 (2, Binap = 2,2’-bis(diphenylphosphino)-1,1’-binaphthyl), have been synthesized. They have been fully characterized, and their photophysical and electrochemical properties are reported together with those of L1 and L2 for comparison. Both CuI complexes show metal-to-ligand charge transfer (MLCT) absorption bands, whereas the 3MLCT luminescence is strongly quenched.

The use of opto-thermal molecular energy storage at the nanoscale creates new opportunities for powering future microdevices with flexible synthetic tailorability. Practical application of these molecular materials, however, requires a deeper microscopic understanding of how their behavior is altered by the presence of different types of substrates. Here we present single-molecule resolved scanning tunneling microscopy imaging of thermally- and optically-induced structural transitions in (fulvalene)tetracarbonyldiruthenium molecules adsorbed onto a Ag(100) surface as a prototype system. Both the parent complex and the photoisomer display distinct thermally-driven phase transformations when they are in contact with a Ag(100) surface. This behavior is consistent with the loss of carbonyl ligands due to strong molecule-surface coupling. Ultraviolet radiation induces marked structural changes only in the intact parent complex, thus indicating a photoisomerization reaction. These results demonstrate how stimuli-induced structural transitions in this class of molecule depend on the nature of the underlying substrate., Comment: 4 figures

A study of the scope and limitations of varying the ligand framework around the dinuclear core of FvRu(2) in its function as a molecular solar thermal energy storage framework is presented. It includes DFT calculations probing the effect of substituents, other metals, and CO exchange for other ligands on Delta H-storage. Experimentally, the system is shown to be robust in as much as it tolerates a number of variations, except for the identity of the metal and certain substitution patterns. Failures include 1,1',3,3'-tetra-tert-butyl (4), 1,2,2',3'-tetraphenyl (9), diiron (28), diosmium (24), mixed iron-ruthenium (27), dimolybdenum (29), and di-tungsten (30) derivatives. An extensive screen of potential catalysts for the thermal reversal identified AgNO3-SiO2 as a good candidate, although catalyst decomposition remains a challenge.

Molecular photoswitches, i.e. molecules capable of isomerizing between two states when submitted to light stimuli, has found applications in several areas such as molecular logic, molecular electronics, and, if the two isomers differ substantially in energy, molecular solar thermal (MOST) systems. In a MOST system the photoswitchable molecule absorbs a photon where after a photoinduced isomerisation to a high energy metastable photoisomer occurs. The photon energy is thus stored within the molecule. Fulvalenediruthenium compounds, has been suggested as a candidate in MOST systems thanks to the large difference in energy between the two isomers, its relative stability, and its ability to absorb sunlight. We here present a fluorinated fulvalene ruthenium derivative and show that its processing properties is remarkably different, while having retained photoisomerization efficiency, compared to its hydrocarbon analog. © 2014 The Authors.

Upon reaction of the dipyrido-anellated guanidinium salt 1 with one equivalent of CpNa we were able to synthesize the dipyrido-anellated diaminofulvalene 4 in one step in 33% isolated yield. This shortens the initial route that applies a literature-known fulvalene synthesis via uronium salt 3 by two steps and avoids the need for a sacrificial equivalent of CpNa. Although the X-ray structure analysis reveals a shorter exocyclic double bond than observed in the diaminofulvalene V, a theoretical analysis based upon DFT calculations shows a stronger zwitterionic character for the dipyridofulvalene 4.

We present electronic structure calculations of the ultraviolet/visible (UV–Vis) spectra as well as hyperpolarizabilities (HP) of push–pull chromophores based on a donor-cyclic bridge-acceptor framework. The bridges are comprised of anti-aromatic polycycles or fulvalene analogues. Both UV/Vis and HP are sensitive functions of the conjugated framework and do not follow conventional wisdom, in particular for fulvalene analogues. Effects can be rationalized by determining mesomers of the bridge that can be stabilized or destabilized by the donor or acceptor. In particular, fulvalene analogues display high susceptibility to this effect and the strongest HP-chromophores exhibit a computed static hyperpolarizability of 372 × 10−30 cm5 esu−1 and 311 × 10−30 cm5 esu−1.

UV–vis–near-IR electronic absorption spectra of unsymmetrically substituted derivatives of 1,1′-biferrocenylene (bis(fulvalene)diiron = BFD) have been systematically evaluated upon oxidation using spectroelectrochemical techniques. Upon reversible electrochemical oxidation to the BFD+ monocation and BFD2+ dication state, the characteristic intervalence charge-resonance (IVCR) transitions of a class III mixed-valence system in solution state was confirmed. The class III mixed-valence character of the parent BFD+ system was not altered upon unsymmetric substitution. Peak-fit analysis and TD-DFT calculations were utilized to assign the observed IVCR transitions.

[{Ru(MeCN)(PPh3)}2(µ-η5:η5-C10H8)(µ-MeSSMe)](BF4)2 (2A) and its analogues were isolated as the intermediates of an intramolecular bis(thiolato)-bridging reaction, and characterized by 1H NMR spectr...

The H-assisted isomerization of fulvene to benzene is characterized in detail using quantum chemistry, transition state theory, classical trajectory, and master equation calculations. This multistep isomerization involves 10 transition states, nine of which are found to contribute non-negligibly to the overall kinetics. Calculated temperature- and pressure-dependent rate coefficients are presented for H + fulvene → products, with care taken to quantify uncertainties in the theoretical predictions arising from various aspects of the calculation. The rate coefficients agree with past theoretical work within these estimated uncertainties. This fast isomerization proceeds via a cyclopropylcarbinyl intermediate––a substituted cyclopropyl group adjacent to a radical carbon––that provides a facile route for the carbon bonding rearrangement. Analogous H-assisted isomerization pathways involving cyclopropylcarbinyl intermediates are characterized using quantum chemistry calculations for four second-ring isomers of naphthalene: fulvalene, azulene, 1-methyleneindene, and 2-methyleneindene. These processes, and those for larger polycyclic aromatic hydrocarbons (PAHs), may be characterized in a general way as occurring in five steps: H additions, H shifts, cyclopropylcarbinyl intermediate formation, cyclopropylcarbinyl intermediate ring opening, and H-atom regeneration. Trends in the energetics of each of these steps with respect to PAH size and composition are discussed.

In a Molecular Solar-Thermal Energy Storage (MOST) system, solar energy is converted to chemical energy using a compound that undergoes reversible endothermic photoisomerization. The high-energy photoisomer can later be converted back to the parent compound and the excess energy is released as heat. One of the most studied MOST systems is based on fulvalene-tetracarbonyl-diruthenium, and this paper demonstrates, for the first time, the possibility to tune the photochemical properties of this system by positive steric hindrance working on the fulvalene unit.

Redox-active alkyl and acyl SAMs (self-assembled monolayers) on gold prepared from BFD-terminated thiols (BFD = bis(fulvalene)diiron, 1,1′-biferrocenylene) have been investigated in aqueous buffered solutions at various pH values by electroanalytical methods, and their redox potentials were determined at pH 7. Excellent redox stability over the whole range from pH 0 to 12, far superior to that of the corresponding ferrocene-terminated SAMs, is established by oxidizing alkanethiol BFD-SAMs to alkanethiol BFD+-SAMs for more than 1 h without any significant decomposition (

Effect of interaction of tetracyanoethylene (TCNE) and tetrathia fulvalene (TTF) with boron- and nitrogen-doped graphene has been investigated by Raman spectroscopy. The G- and 2D bands of boron- and nitrogen-doped graphenes in the Raman spectra show significantly different changes on interaction with electron-donor and -acceptor molecules. Thus, tetracyanoethylene (TCNE) and tetrathiafulvalene (TTF) have different effects on the Raman spectra of boron- and nitrogen-doped graphenes. The changes in the Raman spectra brought about by electron-donor and -acceptor molecules can be understood in general terms on the basis of molecular charge transfer. (c) 2012 Elsevier B.V. All rights reserved.

Caught in the light: The fulvalene diruthenium complex shown on the left side of the picture captures sun light, causing initial Ru-Ru bond rupture to furnish a long-lived triplet biradical of syn configuration. This species requires thermal activation to reach a crossing point (middle) into the singlet manifold on route to its thermal storage isomer on the right through the anti biradical.

Cp-functionalized monotroticenes [(η7-C7H7)Ti(η5-C5H4E)] (2, E = Ph2SiCl; 3, E = tBu2SnCl; 12, E = I) and bitroticenes [(η7-C7H7)Ti(η5-C5H4)]2E′ (5, E′ = PPh; 6, E′ = BN(SiMe3)2; 7, E′ = Cp2Ti) were prepared by salt elimination metathesis between the monolithiated troticene [(η7-C7H7)Ti(η5-C5H4Li)]·pmdta (1b) (pmdta = N,N′,N′,N″,N″-pentamethyldiethylene-triamine) and the appropriate electrophile. The troticenyl-substituted zirconocene monochloride [(η7-C7H7)Ti(η5-C5H4ZrClCp*2)] (Cp* = η5-C5Me5) (8) and hafnocene ethoxide [(η7-C7H7)Ti{η5-C5H4Hf(OEt)Cp2}] (Cp = η5-C5H5) (11), and the heterobimetallic μ-oxo complexes [(η7-C7H7)Ti(η5-C5H4MCp2)]2O (9, M = Zr; 10, M = Hf) were obtained instead of the expected zircona- and hafna[1]troticenophanes by reaction of the dilithiated troticene [(η7-C7H6Li)Ti(η5-C5H4Li)]·pmdta (1a) with [Cp2MCl2] (M = Zr, Hf) or [Cp*2ZrCl2] in stoichiometric amounts. These compounds were characterized by single crystal X-ray diffraction analyses and, in the case of 2, 3, 5–7, 9, 10 and 12, also by elemental analyses and 1H, 13C and 119Sn NMR spectroscopy. Exposure of the troticenyl organotin chloride 3 to moisture resulted in its partial hydrolysis and formation of the organostannoxane-bridged bitroticene 4, while palladium-catalyzed Negishi C–C cross-coupling reaction between the troticenylzinc chloride [(η7-C7H7)Ti(η5-C5H4ZnCl)] (13) and the iodotroticene 12 or iodobenzene (PhI) led to the fulvalene complexes [(η7-C7H7)Ti(η5-C5H4)]2 (14) and [(η7-C7H7)Ti(η5-C5H4Ph)] (15). Compound 4 displays an unsymmetrical structure with the troticenyl fragments cis with respect to the Sn–O–Sn core, whereas compound 14 is centrosymmetrically trans oriented.