Recent Publications
1. Baig, N.; Shetty, S.; Al-Mousawi, S.; Al-Sagheer, F.; Alameddine, B.; “Synthesis, Characterization, Thermal, and Optical Properties of Conjugated Co-Polymers Derived from Phenanthrene-9,10-dione- and Dibenzo[f,h]quinoxaline” Mterials Today Chemistry 2018, Accepted.
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Abstract: Donor-Acceptor (D-A) conjugated polymers bearing phenanthrene-9,10-dione and dibenzo[f,h]quinoxaline as the acceptor units were synthesized via an optimized Suzuki cross-coupling reaction. Each of the abovementioned acceptors was reacted with three different donor co-monomers, namely, fluorene, carbazole and silafluorene derivatives bearing long alkyl chains. The resulting co-polymers display excellent solubility in common organic solvents with high chemical stability, allowing for the determination of their structural, thermal, and optical properties by various analytical techniques.
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Abstract: Triptycene-derived vinyl sulfide polymers 4a-d were synthesized from a versatile catalyst-free thiol-yne click reaction using 1,4-diethynyl triptycene 1 with various aryl dithiol building blocks 3a-d. The resulting triptycene-bearing poly(vinylene sulfide)s 4a-d display excellent solubility and chemical stability allowing for their structural, thermal, and photophysical characterization by various instrumental analysis techniques. The thioether groups in polymers 4a-d were selectively oxidized into their respective sulfone derivatives via mild reaction conditions affording the corresponding triptycene-based poly(vinylene sulfone)s 5a-d in quantitative yield.
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Abstract: New polyclathrochelate derivatives were obtained using the mild one-step polycondensation reaction of an iron(II) center chelated to three polar furil dioxime side groups and doubly capped with various aryl diborate central spacers. Nitrogen adsorption measurements of the polychlathrochelates (PCL1-4) reveal a strong correlation between the intrinsic microporosity and the nature of aryl diborate spacer whose small size (PCL1) or contorted structure (PCL2) afford polymers with Brunauer-Emmett-Teller (BET) surface areas of ~396 m2/g and ~275 m2/g, respectively. On the other hand, the BET surface area of the polymer diminishes either when the aryl diborate spacer has free rotation axes (PCL3) or a laterally extended aromatic structure (PCL4).
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Abstract: The synthesis of ethynylene triptycene-based copolymers with various aromatic spacers (3a-d) is reported using the palladium-catalyzed Sonogashira cross-coupling reaction. The alkyne groups of 3a-d were oxidized into their respective α-diketone copolymers 4a-d. Formation of 3,4a-d was confirmed by several characterization techniques, such as, gel permeation chromatography (GPC), 1H- and 13C-nuclear magnetic resonance (NMR), FT-infrared (FTIR), UV-vis absorption, and emission spectroscopies. It was found that the nature of the aromatic spacer influences the emission properties of the target α-diketone triptycene copolymers, causing either a red or blue-shift with respect to that of their ethynylene triptycene copolymer synthons. Copolymers 4a-c with fluorene spacers reveal emission in the range of 440-475 nm, thus, qualifying them to act as blue emitters.
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Abstract: New triptycene derivatives substituted at their 1,4- positions with tetraphenylbenzene and diphenyltriphenylene moieties were prepared by microwave-assisted [4+2] Diels-Alder cycloaddition reaction in very good yields. The target compounds were characterized by 1H- and 13C- nuclear magnetic resonance (NMR), high resolution mass spectrometry (HR-MS), UV-Visible and emission spectrophotometry. In addition, single crystal X-ray diffraction for two of these derivatives are presented. The tetra- and octa- brominated triptycene compounds underwent palladium-catalyzed Suzuki-Miyaura cross-coupling reactions affording the desired products in very good yields. This successful tetra- and octa- fold substitution paves the way for the employment of these new synthons to prepare polymer networks for various applications.
Abstract: A series of clathrochelate polymers are reported by reacting iron(II) chloride with 9,9-dialkyl fluorene-2,7-diboronic acid and various vicinal dioxime units. The novel polymers were fully characterized by 1H- and 13C nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), X-ray photoelectron spectroscopy (XPS), and UV-Vis absorption spectroscopy. The linearly-linked 2D organometallic polymers form oragnogel from 10 wt% concentrations in organic solvents of low and medium polarity.
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Abstract: Three polyaromatic-based polymers are reported to contain co-monomers of trapezoidal tribenzopentaphene (TBP) polycyclic aromatic hydrocarbons. The synthetic strategy consists of initially making highly soluble tetraphenylbenzene copolymers 4a–c, followed by a cyclodehydrogenation/aromatization reaction to obtain target polymers 5a–c. The polymers were characterized by gel permeation chromatography, FT-IR, UV-vis, emission, 1H-, and 13C-nuclear magnetic resonance spectroscopy. The target polymers 5a–c reveal emission spectra in the range of 430–480 nm; thus, qualifying them to act as blue emitters. Investigation of the polymers optical properties and their correlation with density functional theory calculations suggest a distorted TBP core from planarity caused by the introduction of a dodecyl group at its wide edge.
Abstract: Four Iron(II) clathrochelate derived polymers (P1-4) were synthesized under mild reaction conditions using iron(II) chloride with benzene-1,4-diboronic acid in presence of various vicinal dioxime moieties. The polymers were characterized by different instrumental analyses techniques and their structures were further confirmed by comparison of their respective synthesized prototypical monomers (M). Evaluation of P1-4 intrinsic microporosity was carried out by nitrogen adsorption measurements where polymer P4 reveals a Brunauer-Emmett-Teller (BET) surface area of 412 m2/g and average pore volume of 0.36 cm3/g.
Abstract: 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.
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Abstract: 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.
Abstract: 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, MII8L4 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.
Abstract: 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.
Abstract: 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.
Abstract: Stacked dimers of four polycondensed aromatic hydrocarbons, with structures varying from high to reduced symmetries, have been calculated with dispersion-corrected density functional theory. The configurations of the stacked dimers are readily classified by two in-plane displacements and a relative rotation. The potential energy surface in these three coordinates was calculated with rigid monomers and appears to be slightly flat. Full geometry optimization was performed for selected low-energy structures, resulting in an energy ranking of a series of conformations whose geometries were characterized in considerable detail. The dissociation energy values reveal a clear preference for the symmetrical disk-shaped and triangular structures to dimerize into two in-plane-displaced arrangements, whereas the less symmetrical trapezoidal structures show a tendency to stack in displaced antiparallel over parallel arrangements. According to methodical checks, the key computational results, namely, the shape of the potential energy surface and the geometrical structures and energy ranking of dimer conformations, are essentially insensitive to computational assumptions such as the atomic orbital basis set and density functional chosen. This is shown in particular for the basis set superposition error, which, for the selected level of theory [B97-D3(BJ)/TZV(d,p)] was estimated by the counterpoise correction procedure to be in the narrow range between 7% and 8% of the uncorrected dissociation energies.
15. Alameddine, B; Schindler, M.; Jenny, T. A.; “Synthesis of Alkyl- Substituted Tribenzopentaphenes as Versatile Polycondensed Aromatic Hydrocarbon π-π Stacking Building Blocks” Synthesis, 2012, 44, 1928-1934. DOI: 10.1055/s-0031-1291010
16. Aebischer, O.; Alameddine, B.; Jenny, T. A.; “Hexabenzocoronenes - Controlling their Self-assembly by Engineering the Lateral Substituents” Chimia, 2008, 62, 967.DOI: 10.2533/chimia.2008.967
17. Aebischer, A.; Aebischer, O. F.; Alameddine, B.; B. Donnio; Dadras, M.; Güdel, H.-U.; Guillon, D.; Jenny, T. A. “Controlling the Lateral Aggregation of Perfluoroalkylated Hexabenzocoronenes” J. Mat. Chem. 2007, 17(13), 1262-1267. DOI: 10.1039/b616057c
18. Alameddine, B.; Aebischer, O.; Savary, C.; Jenny, T. A.; “Synthesis of Perfluoroalkylated Bulky Triaryl Amines” Synthesis, 2007, 2, 271-276.DOI: 10.1055/s-2006-958953
19. Sanaur, S.; Whalley, A.; Alameddine, B.; Carnes, M.; Nuckolls, C.;“ Jet-printed Electrodes and Semiconducting Oligomers for Elaboration of Organic Thin-film Transistors” Organic Electronics, 2006, 7, 423-427. DOI: 10.1016/j.orgel.2006.05.003
20. Aebischer, O.; Aebischer, N.; Tondo, P.; Alameddine, B.; Dadras, M.; Guedel, H.; Jenny T. A.“Self-aggregated Perfluoroalkylated Hexa-peri-hexabenzocoronenes Fibers Observed in Cryo-SEM and Fluorescence Spectroscopy” Chemical Communications, 2006, 40, 4221-4223.
DOI: 10.1039/b609056g
21. Aebischer, O.; Tondo, P.; Alameddine, B.; Jenny T. A.“Synthesis of Novel Perfluorinated Hexa-peri-hexabenzocoronenes” 2006, Synthesis, 17, 2891-2896.DOI: 10.1055/s-2006-942550
22. Alameddine, B.; Aebischer, O.; Amrein, W.; Deschenaux, R.; Donnio, B.; Guillon, D.; Savary, C.; Scanu, D.; Scheidegger, O.; Jenny T. A. “ Mesomorphic Hexabenzo- coronenes Bearing Perfluorinated Chains” Chem. Mater.; 2005, 17(19), 4798 – 4807.DOI: 10.1021/cm050612o
23. Tran, F.; Alameddine, B.; Jenny, T. A.; Wesolowski, T. “π-Stacking Behavior of Selected Nitrogen-Containing PAHs” J. of Phys. Chem. A 2004, 108(42), 9155-9160.DOI: 10.1021/jp048713h