Johannes Gierschner 교수

Abstract In this Review, the extreme care that must be taken when predicting the optical properties of conjugated polymers via the oligomer approach, and when comparing theoretical and experimental data, is illustrated. In the first part, conceptual strategies for the correct determination of optical transitions from experimental spectra and relevant extrapolation procedures at the polymer limit are introduced. The impact of conformational, substitution, solvent, and solid‐state effects on the o

The last few years have seen a steady increase in small molecule based conjugated materials, which promise innovative (opto)electronic applications. This requires however a systematic understanding of structure–property relationships, which can only be achieved via libraries of structurally well-defined single crystalline materials based on systematically designed molecular structures. In this feature article, we are presenting structure–property relationships of functionalized distyrylbenzene (

Fluorescence emission and excitation spectra of para-phenylene vinylenes nPV with n=1–4 styryl units are investigated experimentally and theoretically as a function of the temperature and the polarizability of the solvent. At low temperatures, the vibronic structures of the S0↔S1 emission and excitation bands are mirror symmetrical with negligible 0–0 energy gaps. The frequencies of the prominent vibrational modes are assigned to the second longitudinal acoustic phonon modes of the entire molecu

The present Perspective critically re-examines the photophysics of para-distyrylbenzene (DSB) as a prototype of herringbone-arranged H-aggregates to resolve the apparent contradiction of the frequently reported “aggregation-induced emission quenching” in H-aggregates on one side and highly emissive DSB crystals on the other and discusses the signatures and fate of excitons in single- and polycrystalline samples, including size and polarization effects.

There has been much interest in dual-emission materials in the past few years for materials and life science applications; however, a systematic overview of the underlying processes is so-far missing. We resolve this issue herein by classifying dual-emission (DE) phenomena as relying on one emitter with two emitting states (DE1), two independent emitters (DE2), or two correlated emitters (DE3). Relevant DE mechanisms for materials science are then briefly described together with the electronic a

Abstract Luminescent small, all‐organic molecules are of tremendous interest in materials and life science applications. Nevertheless, targeted design requires a basic understanding of the excited state deactivation pathways of the molecules themselves, and the modulations of the processes that occur in the solid state. This particularly concerns crystalline molecular solids, as here not only solid‐state rigidification contributes to these modulations, but specific intermolecular interactions as

Materials design has become a vigorous aspect for organic solid‐state lasing, which often lacks a fundamental understanding of structure–property relationships. The development of such an understanding is undertaken in this progress report, which systematically explores the now‐available libraries of organic single crystals exhibiting light amplification under optical pumping. By doing so, intra‐ and intermolecular contributions are disentangled for the non‐/occurrence, type, threshold, waveleng

The intermolecular arrangement in the solid state and the consequences on the optical and photophysical properties are studied on different derivatives of oligophenylenevinylenes by UV/VIS absorption and angular-resolved polarized fluorescence spectroscopy. Unsubstituted distyrylbenzene (DSB) organizes in a herringbone manner, with the long axes of the molecules oriented in parallel, but the short axes almost perpendicular to each other. Fluorinated distyrylbenzene (F(12)DSB) as well as the DSB:

We demonstrate that for a range of phenylene- and thiophene-based conjugated polymers of practical relevance for optoelectronic applications, exciton couplings in one-dimensional stacks deviate significantly from the nearest neighbor approximation. Instead, long-range interactions with non-nearest neighbors have to be included, which become increasingly important with growing oligomer size. While the exciton coupling vanishes for infinitely long ideal polymer chains and provides a sensitive meas

Abstract A novel system of light‐harvesting supramolecular block copolymers (SBCPs) in water is demonstrated. To realize cucurbit[8]uril (CB[8])‐based SBCPs generating artificial light‐harvesting in water, finely color‐tuned supramolecular homopolymers (SHPs) comprising CB[8] host and different cyanostilbene guests (named as B , G , Y , and R ) emitting blue, green, yellow, and red fluorescence are first synthesized and characterized, respectively. Light‐harvesting SBCPs with mixed guest emitter

Absorption spectra of cyanine^⊕·Br^⊖ salts show a remarkable solvent dependence in non/polar solvents, exhibiting narrow, sharp band shapes in dichloromethane but broad features in toluene; this change was attributed to ion pair association, stabilizing an asymmetric dipolar structure, similar to the situation in the crystal (Bouit, P.-A., et al. <i>J. Am. Chem. Soc.</i> <b>2010</b>, <i>132</i>, 4328). Our density functional theory (DFT)-based quantum mechanics/molecular mech

Using electronic absorption and fluorescence spectroscopic techniques, as well as quantum chemical calculations, we have studied the electronic spectra of thia-bridged stilbenophane (TSP) with close cofacial contact of two trans-stilbene (t-SB) units. Compared to the t-SB monomer, the experimental consequences of the cofacial arrangement are (i) a splitting of the main absorption band with a weakly allowed emitting state, and (ii) a strongly red-shifted, unstructured emission spectrum with long

Abstract In the current overview, the concept of π‐conjugation in organic compounds is reexamined. Starting from valence bond and molecular orbital (MO) theory, the principal elements of conjugation are worked out starting from a simple Hückel picture; this includes the definition of the conjugated path, bond length alternation, as well as MO localization effects, and requires the distinction between formal and effective conjugation. The latter will be needed to understand the electronic and opt