Structure, Dynamics and Reactivity in the Organic Solid State: Anthracene Derivatives and Charge Transfer Crystals

The work presented in this thesis tackles some important points concerning the collective properties of two typical categories of molecular crystals, i.e., anthracene derivatives and charge transfer crystals. Anthracene derivatives have constituted the class of materials from which systematical investigations of crystal-to-crystal photodimerization reactions started, developed and have been the subject of a new awakening in the recent years. In this work some of these compounds, namely, 9-cyanoanthacene, 9-anthacenecarboxylic acid and 9-methylanthracene, have been selected as model systems for a phenomenological approach to some key properties of the solid state, investigated by spectroscopic methods. The present results show that, on the basis of the solid state organization and the chemical nature of each compound, photo-reaction dynamics and kinetics display distinctive behaviors, which allows for a classification of the various processes in topochemical, non topochemical, reversible or topophysical. The second part of the thesis was focused on charge transfer crystals, binary systems formed by stoichiometric combinations of the charge donating perylene (D) and the charge accepting tetracyano-quinodimethane (A), this latter also in its fluorinated derivatives. The work was focused on the growth of single crystals, some of which not yet reported in the literature, by PVT technique. Structural and spectroscopic characterizations have been performed, with the aim of determining the degree of charge transfer between donor and acceptor in the co-crystals. An interesting outcome of the systematic search performed in this work is the definition of the experimental conditions which drive the crystal growth of the binary systems either towards the low (1:1) or the high ratio (3:1 or 3:2) stoichiometries.

Morphology Change of C60 Islands on Organic Crystals Observed by Atomic Force Microscopy

Organic-organic heterojunctions are nowadays highly regarded materials for light-emitting diodes, field-effect transistors, and photovoltaic cells with the prospect of designing low-cost, flexible, and efficient electronic devices.1-3 However, the key parameter of optimized heterojunctions relies on the choice of the molecular compounds as well as on the morphology of the organic-organic interface,4 which thus requires fundamental studies. In this work, we investigated the deposition of C60 molecules at room temperature on an organic layer compound, the salt bis(benzylammonium)bis(oxalato)cupurate(II), by means of noncontact atomic force microscopy. Three-dimensional molecular islands of C60 having either triangular or hexagonal shapes are formed on the substrate following a "Volmer-Weber" type of growth. We demonstrate the dynamical reshaping of those C60 nanostructures under the local action of the AFM tip at room temperature. The dissipated energy is about 75 meV and can be interpreted as the activation energy required for this migration process.

Dynamical properties of a strongly correlated model for quarter-filled layered organic molecular crystals

The dynamical properties of an extended Hubbard model, which is relevant to quarter-filled layered organic molecular crystals, are analyzed. We have computed the dynamical charge correlation function, spectral density, and optical conductivity using Lanczos diagonalization and large-N techniques. As the ratio of the nearest-neighbor Coulomb repulsion, V, to the hopping integral, t, increases there is a transition from a metallic phase to a charge-ordered phase. Dynamical properties close to the ordering transition are found to differ from the ones expected in a conventional metal. Large-N calculations display an enhancement of spectral weight at low frequencies as the system is driven closer to the charge-ordering transition in agreement with Lanczos calculations. As V is increased the charge correlation function displays a collective mode which, for wave vectors close to (pi,pi), increases in amplitude and softens as the charge-ordering transition is approached. We propose that inelastic x-ray scattering be used to detect this mode. Large-N calculations predict superconductivity with d(xy) symmetry close to the ordering transition. We find that this is consistent with Lanczos diagonalization calculations, on lattices of 20 sites, which find that the binding energy of two holes becomes negative close to the charge-ordering transition.

Organic reactions in ionic liquids: ionic liquid-accelerated facile synthesis of 3-alkyl-2,4-thiazolidinediones

The room temperature ionic liquid [bmim]PF6 is a new green solvent for the N-alkylation of 2,4-thiazolidinones. Significant rate enhancement and improved yields have been observed.

Organic reactions in ionic liquids: ionic liquid-promoted efficient synthesis of N-alkyl and N-arylphthalimides

Phthalic anhydride reacts rapidly with Aromatic and aliphatic amines in ionic liquid [Bmim][PF6] or [Bmim][BF4] at 130 °C to give N-aryl and N-alkylphthalimides in excellent yields.

Organic reactions in ionic liquids:ionic liquids ethylammonium nitrate promoted Knoevenagel condensation of aromatic aldehydes with active methylene compounds

The Knoevenagel condensation of aromatic aldehydes with active methylene compounds proceeded efficiently in a reusable ionic liquid, ethylammonium nitrate, at room temperature in the absence of any catalyst with high yields.

Organic reactions in ionic liquids: Ionic liquid-promoted three-component condensation of benzotriazole with aldehyde and alcohol

1-(alpha-Alkoxyalkyl)benzotriazoles are readily synthesized from three-component condensation of benzotriazole with aldehyde and alcohol in ionic liquid [Bmim]PF6.

Organic reactions in ionic liquids: ionic liquid-promoted efficient synthesis of disubstituted and trisubstituted thioureas derivatives

In ionic liquid [Bmim][BF4], a series of disubstituted and trisubstituted thiourea derivatives were synthesized from phenyl and butyl isothiocyanate with a variety of amine in excellent yield.

Organic reactions in ionic liquids:Ionic liquid promoted Knoevenagel condensation of aromatic aldehydes with (2-thio)barbituric acid

The Knoevenagel condensation of aromatic aldehydes with (2-thio)barbituric acid proceeded efficiently in reusable ionic liquids, EAN, BmimBF4, and BmimPF6 at room temperature in the absence of any catalyst with high yields.

Organic reactions in ionic liquids:Gewald synthesis of 2-aminothiophenes catalyzed by ethylenediammonium diacetate

Ionic liquids based on 1-butyl-3-methylimidazolium tetrafluoroborate (BmimBF4) and 1-butyl-3-methylimidazolium hexafluorophosphate (BmimPF6) were used as reusable alternatives to volatile organic solvents (VOCs) for ethylenediammonium diacetate (EDDA) catalyzed Gewald synthesis of 2-aminothiophenes. Significant rate enhancement and improvement of the yield were observed. The ionic liquids containing catalyst EDDA were recycled several times with no decreases in yields and reaction rates.

Organic reactions in ionic liquids:A new method for the synthesis of alkyl aryl sulfones by alkylation of sodium arenesulfinates with unactivated alkyl chlorides

A new method is reported for the synthesis of alkyl aryl sulfones by alkylation of sodium arenesulfinates with unactivated alkyl chlorides using ionic liquid based on 1-butyl-3-methylimidazolium tetrafluoroborate (BmimBF 4) mixed with water (2:1) as reaction media. The ionic liquid can be reused and the procedure gives the sulfones in moderate yields.

Organic reactions in ionic liquids:A simple and highly regioselective N-substitution of pyrrole

In ionic liquids [Bmim][PF6] or [Bmim][BF4], pyrrole replaced the halogen atom of an alkyl halide to give the corresponding N-substituted pyrrole in excellent yield. Benzenesulfonyl chloride, p-methylbenzenesulfonyl chloride and benzoyl chloride reacted similarly with pyrroles to afford the N-substituted pyrroles in quantitative yield. Michael addition reaction of pyrrole with electrophilic olefins was completed in a highly regioselective manner to afford the N-alkylpyrroles.