No abstract

Semiempirical quantum-chemical calculations are used to simulate the optical properties of a series of green light-emitting nematic liquid crystals containing fluorene, thiophene, or thienothiophene groups with solid-state photoluminescence quantum efficiencies up to 0.36. We use a simple model of two parallel and closely spaced molecules in an anticofacial configuration to study intermolecular interactions in the solid state and slide one past the other to mimic the high orientational and low positional order of the nematic phase. We find that switching between H and J aggregates can be triggered by longitudinal displacements of the molecules with respect to one another by an extent that closely follows the chemical structure of the interacting chromophores. We discuss the implications of aggregate formation for efficient light emission in conjugated oligomers and polymers that show nematic or smectic order.

The synthesis and characterization of two new anthradithiophene (ADT) derivatives substituted by thiophenyl or 2‐octylthiophenyl units at the 5,11‐positions and donor (triphenylamine) or acceptor (aldehyde functions) moieties at the 2,8‐positions of their backbone are described. Optical measurements were performed to evaluate the effect of electron‐rich/‐poor substituents on their stability towards photo‐oxidation and were supported by quantum chemical calculations and cyclic voltammetry experiments.

The cover picture shows the comparison of the color of two anthradithiophene (ADT) derivatives bearing triphenylamine and formyl units with that of their parent ADT system in the solid state and in solution. This research was performed by a Belgian collaboration between the Université Libre de Bruxelles and the Université de Mons. This cooperation is highlighted by the well‐known monuments of both cities: the atomium of Brussels and the belfry of Mons. Details are discussed in the article by Y. H. Geerts et al. on p. 3131 ff.