Bassam Alameddine

Influence of linear and branched perfluoroalkylated side chains on the π–π stacking behaviour of hexa-peri-hexabenzocoronene and thermotropic properties

The thermotropic properties and self-assembly of two different series of hexa-peri-hexabenzocoronenes (HBC) bearing either linear or branched perfluoroalkylated side chains, each with a wide range of alkyl spacer and perfluorinated tail lengths, have been studied. Correlations between thermogravimetric analysis, differential scanning calorimetry, polarised optical microscopy and small-angle X-ray scattering experiments revealed, as expected, that the transition temperatures and phase stability are influenced by the determining roles of the aliphatic spacer length and odd/even nature, as well as the size and structure (linear vs. bifurcation) of the perfluorinated sections. Most of the investigated HBC derivatives showed a single-column hexagonal columnar phase, where the columns are structured by a double segregation process between HBC aromatic cores and aliphatic spacers, on the one hand, and between aliphatic spacers and fluorinated tails, on the other hand. For the derivatives with long linear spacers, cores of untilted or quasi-untilted HBC stacks are surrounded by a cylindrical aliphatic envelope segregated from the fluorinated periphery, whereas for those with shorter linear spacers, the same structure is kept, except that the aliphatic envelope deviates from cylindricality and causes a symmetry break to rectangular envelope for the first term of the series. Of the four HBC with branched spacers, two are amorphous, whereas a columnar phase is maintained for the other two derivatives, but with tilted HBC stacks. Consequently, the evolution of the polymorphism in the series could be correlated with the variation of both interface areas.

Large heterometallic coordination cages with gyrobifastigium-like geometry

Large (Mw > 10 kDa) heterometallic coordination cages with gyrobifastigium-like geometry are obtained by using metalloligands with sterically demanding FeII clathrochelate cores and four divergent pyridyl groups. Upon reaction with cis-blocked PtII and PdII complexes, ML4 cages are formed. The gyrobifastigium geometry of these cages is in contrast to the barrel-like structures which are typically observed for metallasupramolecular assemblies with M8L4 stoichiometry.

Tribenzopentaphene derivatives with lateral aromatic groups: the effect of the nature and position of substituents on emission properties

Nine new derivatives of the trapezoidal tribenzopentaphene (TBP) polycyclic aromatic hydrocarbon (PAH) were synthesized via the Suzuki–Miyaura palladium catalyzed cross-coupling reaction. The novel TBP derivatives, which bear various rigid and flexible aromatic groups either at their more accessible (R1) or congested (R2) bases, were fully characterized using high resolution mass spectrometry (HR-MS), nuclear magnetic resonance (NMR), UV-Vis absorption and emission spectroscopy. Our investigation reveals that extended conjugation between TBP and the aromatic side groups is possible when the latter are carefully selected and attached at the TBP wide base (R1), which causes an emission red-shift of the resulting target compounds. On the other hand, emission properties and density functional calculations suggest that attaching side groups at the sterically demanding base position (R2) induces a pronounced distortion from the planarity of the TBP central core structure.

Synthesis of Arylamine Tribenzopentaphenes and Investigation of their Hole Mobility

We report the versatile synthesis of two tribenzo[fj,ij,rst]pentaphene (TBP) derivatives bearing two diarylamine substituents attached at the opposite ends of the aromatic core. Field effect transistor (FET) devices of the bis-diarylamine-TBP compounds were fabricated using spin coating under different concentrations, spin speed, and solvent conditions. Emission spectra and surface investigation by atomic force microscopy (AFM) reveal the formation of aggregates induced by the strong π–π stacking of the aromatic core leading to island features, and thus, unexpected low hole mobilities. The synthetic strategy we show herein, however, offers the possibility to decorate the TBP core structure with various charge-carrier peripheral groups and optimized alkyl chains, which should improve the crystalline property of their thin films upon deposition, leading consequently to a better hole transport mobility.

Laterally stretched polycyclic aromatic hydrocarbons: synthesis of dibenzophenanthroheptaphene and tetrabenzotriphenylenopyranthrene derivatives

Efficient methods for the synthesis of dibenzophenanthroheptaphene (DBPH) and tetrabenzotriphenylenopyranthrene (TBTP) were developed. As a result, a series of unprecedented derivatives of DBPH (1a–c) and TBTP (2a–b) were conventionally obtained from the Scholl cyclodehydrogenation reaction of their respective tribenzopentaphene synthons. An alternative convergent synthesis of DBPH is also shown herein. The novel compounds were fully characterized by high-resolution matrix-assisted laser desorption ionization time of flight mass spectrometry (HR-MALDI-TOF-MS), nuclear magnetic resonance (NMR), UV-Vis absorption and emission spectroscopy. In addition, density functional calculations were carried out to gain insight into the structure and electronic properties of these novel molecules, which corroborates the experimental observations.