Olivier Jeannin

ortho‐, meta‐, and para‐Dihydroindenofluorene Derivatives as Host Materials for Phosphorescent OLEDs

This work reports the first structure-properties relationship study of ortho [2,1-c]-, meta [1,2-a]-, and para [1,2-b]dihydroindenofluorenes, highlighting the influence of bridge rigidification on the electronic properties. This study has made it possible to devise an extended π-conjugated molecule with both a high triplet state energy level and excellent thermal and morphological stability. As a proof of concept, dihydroindenofluorenes were used as the host in sky-blue phosphorescent organic light-emitting diodes (PhOLEDs) with high performance.

A Single-Component Molecular Metal Based on a Thiazole Dithiolate Gold Complex

A single component molecular conductor has been isolated from electrocrystallization of the monoanionic gold bis(dithiolene) complex based on the N-ethyl-1,3-thiazoline-2-thione-4,5-dithiolate (Et-thiazdt) ligand. The crystal structure of the system exhibits layers built from parallel uniform one-dimensional stacks of the planar molecule. At room temperature and ambient pressure the system is semiconducting (0.33 S x cm(-1)) with a small activation energy. However, the single crystal conductivity is strongly pressure dependent reaching 1000 S x cm(-1) at 21 kbar. At 13 kbar there is a crossover between semiconducting and metallic regimes. Thus, the present system is the first well characterized single-component molecular metal without TTF dithiolate ligands. First-principles DFT calculations show that the ground state is antiferromagnetic with a very small band gap. A simulation of the effect of pressure on the electronic structure provides a rationale for the observed variations of the conductivity and gives insight on how to further stabilize the metallic state of the system.

Dependence of the Properties of Dihydroindenofluorene Derivatives on Positional Isomerism: Influence of the Ring Bridging

The future of organic electronics is driven by the synthesis and the study of novel molecular fragments for the construction of highly efficient polymers or oligomers. In this context, polyand oligophenylene derivatives constitute an important class of highly promising molecules, which have been widely studied for the last two decades. Of particular interest in the chemistry and physics of oligophenylenes is the bridged-para-terphenyl unit, namely, 6,12dihydroindeno[1,2-b]fluorene (Scheme 1). Although it has been known since the 1950s, investigations of the dihydroindeno[1,2-b]fluorenyl core only started a decade ago thanks to the pioneering work of M llen, which made this molecule a key building block for electronics. There are nowadays numerous examples of efficient dihydroindeno[1,2-b]fluorenylbased semiconductors that have found application in various fields, such as fluorescent 5–8] and phosphorescent organic light-emitting diodes (OLEDs), organic field-effect transistors, and organic solar cells. This wide range of applications clearly shows the high potential of this building block, but also its versatility. However, the dihydroindeno[1,2-b]fluorene is not the only member of the bridged-terphenyl family, since it possesses four other positional isomers with different phenyl linkages (para/meta/ortho) and different ring-bridging positions (anti vs. syn ; Scheme 1). There are hence five dihydroindenofluorene positional isomers, each possessing its own ring topology, which in turn has structural and electronic consequences. However, in contrast to the dihydroindeno[1,2-b]fluorene, other positional isomers remain very scarce in the literature owing to synthetic difficulties. For example, the dihydroindeno[2,1-a]fluorenyl (syn para-terphenyl) unit (Scheme 1) has only been investigated for organic electronics very recently, and thanks its particular syn geometry has emerged as a promising scaffold for a new generation of excimer-based OLEDs. Similarly, antiaromatic fully conjugated indenofluorene derivatives have recently attracted particular attention; Haley and co-workers have for example reported a new class of (2,1-c)indenofluorenes with high electron affinities. However, the anti and syn meta-terphenyl isomers, that is, dihydroindeno[1,2-a]fluorene and dihydroindeno[2,1-b]fluorene, although known for 60 years, are almost absent from the literature, and their intrinsic properties have never been studied. As the design of novel molecular fragments is of key importance for the future of organic electronics, we report herein the first examples of the use of dihydroindeno[1,2b]fluorene (1) and dihydroindeno[2,1-a]fluorene (2 ; Scheme 1. The five positional dihydroindenofluorene isomers.

Expanded Halogen-Bonded Anion Organic Networks with Star-Shaped Iodoethynyl-Substituted Molecules: From Corrugated 2D Hexagonal Lattices to Pyrite-Type 2-Fold Interpenetrated Cubic Lattices

Halogen bonding interactions between halide anions and neutral polyiodinated linkers are used for the elaboration of anion organic frameworks, by analogy with well-known MOF derivatives. The extended, 3-fold symmetry, 1,3,5-tris(iodoethynyl)-2,4,6-trifluorobenzene (1) cocrystallizes with a variety of halide salts, namely, Et3S(+)I(-), Et3MeN(+)I(-), Et4N(+)Br(-), Et3BuN(+)Br(-), Me-DABCO(+)I(-), Bu3S(+)I(-), Bu4N(+)Br(-), Ph3S(+)Br(-), Ph4P(+)Br(-), and PPN(+)Br(-). Salts with 1:1 stoichiometry formulated as (1)·(C(+),X(-)) show recurrent formation of corrugated (6,3) networks, with the large cavities thus generated, filled either by the cations and solvent (CHCl3) molecules and/or by interpenetration (up to 4-fold interpenetration). The 2:1 salt formulated as (1)2·(Et3BuN(+)Br(-)) crystallizes in the cubic Ia3 space group (a = 22.573(5) Å, V = 11502(4) Å(3)), with the Br(-) ion located on 3 site and molecule 1 on a 3-fold axis. The 6-fold, unprecedented octahedral coordination of the bromide anion generates an hexagonal three-dimensional network of Pa3 symmetry, as observed in the pyrite model structure, at variance with the usual, but lower-symmetry, rutile-type topology. In this complex system, the I centering gives rise to a 2-fold interpenetration of class Ia, while the cations and solvent molecules are found disordered within interconnected cavities. Another related cubic structure of comparable unit cell volume (space group Pa3̅, a = 22.4310(15) Å, V = 11286.2(13) Å(3)) is found with (1)2·(Et3S(+)I(-)).

Supramolecular Luminescent Lanthanide Dimers for Fluoride Sequestering and Sensing

Lanthanide complexes (Ln=Eu, Tb, and Yb) that are based on a C2 -symmetric cyclen scaffold were prepared and characterized. The addition of fluoride anions to aqueous solutions of the complexes resulted in the formation of dinuclear supramolecular compounds in which the anion is confined into the cavity that is formed by the two complexes. The supramolecular assembly process was monitored by UV/Vis absorption, luminescence, and NMR spectroscopy and high-resolution mass spectrometry. The X-ray crystal structure of the europium dimer revealed that the architecture of the scaffold is stabilized by synergistic effects of the EuFEu bridging motive, π stacking interactions, and a four-component hydrogen-bonding network, which control the assembly of the two [EuL] entities around the fluoride ion. The strong association in water allowed for the luminescence sensing of fluoride down to a detection limit of 24 nM.

Tuning the optical properties of aryl-substituted dispirofluorene-indenofluorene isomers through intramolecular excimer formation.

Two families of positional isomers of dispirofluorene-indenofluorene substituted by phenyl groups at the 2,7-positions of the fluorene moieties present drastically different optical properties. The emission wavelengths may be gradually and conveniently modulated for one of the two isomers by the phenyl groups substituent whose bulkiness controls the extent of the excimeric interaction evidenced in this paper.

9,9′-Spirobifluorene and 4-phenyl-9,9′-spirobifluorene: pure hydrocarbon small molecules as hosts for efficient green and blue PhOLEDs

We report herein a new pure hydrocarbon material, 4-phenyl-9,9′-spirobifluorene (4-Ph-SBF), with a high triplet energy level (ET: 2.77 eV) as a host for blue phosphorescent organic light-emitting diodes (PhOLEDs). Structural, thermal, electrochemical and photophysical properties have been investigated in detail and compared to its constituting building block 9,9′-spirobifluorene (SBF) in order to precisely study the influence of the incorporation of a phenyl unit in C4. A surprising out of plane deformation of the fluorene ring and a highly twisted structure have been notably found for 4-Ph-SBF due to the substitution in C4. As both 4-Ph-SBF and SBF possess a high triplet energy level (2.77/2.87 eV resp.), they have been successfully used as host materials for green and blue PhOLEDs. The performance of blue PhOLEDs, ca. 20 cd A−1, appears to be among the highest reported for pure hydrocarbon derivatives.

Combining halogen bonding and chirality in a two-dimensional organic metal (EDT-TTF-I2)2(D-camphorsulfonate)·H2O

A chiral organic conductor with metallic conductivity has been obtained by electrocrystallisation of a diiodotetrathiafulvalene derivative and enantiopure D-camphorsulfonate anion, associated in the solid state by halogen bonding interactions.

Charge‐Assisted Halogen Bonding: Donor–Acceptor Complexes with Variable Ionicity

Charge-assisted halogen bonding is unambiguously revealed from structural and electronic investigations of a series of isostructural charge-transfer complexes derived from iodinated tetrathiafulvalene and tetracyanoquinodimethane derivatives, (EDT-TTFI2)2(TCNQF(n)), n=0-2, which exhibit variable degrees of ionicity. The iodinated tetrathiafulvalene derivative, EDT-TTFI2, associates with tetracyanoquinodimethane (TCNQ) and its derivatives of increasing reduction potential (TCNQF, TCNQF2) through highly directional C-I⋅⋅⋅N≡C halogen-bond interactions. With the less oxidizing TCNQ acceptor, a neutral and insulating charge-transfer complex is isolated whereas with the more oxidizing TCNQF2 acceptor, an ionic, highly conducting charge-transfer salt is found, both of 2:1 stoichiometry and isostructural with the intermediate TCNQF complex, in which a neutral-ionic conversion takes place upon cooling. A correlation between the degree of charge transfer and the C-I⋅⋅⋅N≡C halogen-bond strength is established from the comparison of the structures of the three isostructural complexes at temperatures from 300 to 20 K, thus demonstrating the importance of electrostatics in the halogen-bonding interaction. The neutral-ionic conversion in (EDT-TTFI2)2(TCNQF) is further investigated through the temperature dependence of its magnetic susceptibility and the stretching modes of the C≡N groups.

Trinuclear Mo3S7 clusters coordinated to dithiolate or diselenolate ligands and their use in the preparation of magnetic single component molecular conductors.

A general route for the preparation of a series of dianionic Mo3S7 cluster complexes bearing dithiolate or diselenolate ligands, namely, [Mo3S7L3](2-) (where L = tfd (bis(trifluoromethyl)-1,2-dithiolate) (4(2-)), bdt (1,2-benzenedithiolate) (5(2-)), dmid (1,3-dithia-2-one-4,5-dithiolate) (6(2-)), and dsit (1,3-dithia-2-thione-4,5-diselenolate) (7(2-))) is reported by direct reaction of [Mo3S7Br6](2-) and (n-Bu)2Sn(dithiolate). The redox properties, molecular structure, and electronic structure (BP86/VTZP) of the 4(2-) to 7(2-) clusters have also been investigated. The HOMO orbital in all complexes is delocalized over the ligand and the Mo3S7 cluster core. Ligand contributions to the HOMO range from 61.67% for 4(2-) to 82.07% for 7(2-), which would allow fine-tuning of the electronic and magnetic properties. These dianionic clusters present small energy gaps between the HOMO and HOMO-1 orbitals (0.277-0.104 eV). Complexes 6(2-) and 7(2-) are oxidized to the neutral state to afford microcrystalline or amorphous fine powders that exhibit semiconducting behavior and present antiferromagnetic exchange interactions. These compounds are new examples of the still rare single-component conductors based on cluster magnetic units.