Epindolidiones—Versatile and Stable Hydrogen‐Bonded Pigments for Organic Field‐Effect Transistors and Light‐Emitting Diodes

Abstract

1wileyonlinelibrary.com IntroductionHydrogen-bonded organic pigments are a class of materials familiar from applications in the colorant industry, where they fi nd widespread use as materials for robust outdoor paints, cosmetics, and printing inks. [ 1,2 ] Indigo, a natural product, is the oldest and still most widely produced organic dye and pigment ( Figure 1 ). [ 3 ] The intermolecular -NH … O = hydrogen bonding that characterizes indigo is exploited in most of the synthetic hydrogen-bonded pigments as well. This class of materials has proven to be nontoxic and safe for humans, and is considered safer than even several classes of food dyes. [ 4 ] Hydrogen-bonding as a supramolecular engineering tool is useful to control self-assembly and highly relevant to aqueous and biochemical systems. [ 5,6 ] Recently, we have found that indigo, [ 7 ] and some of its derivatives [ 8,9 ] demonstrate ambipolar transport in organic fi eldeffect transistors (OFETs), with mobility ranging from 0.01-0.4 cm 2 V -1 s -1 . We Epindolidiones-Versatile and Stable Hydrogen-Bonded Pigments for Organic Field-Effect Transistors and Light-Emitting DiodesEric Daniel Głowacki , * Giuseppe Romanazzi , Cigdem Yumusak , Halime Coskun , Uwe Monkowius , Gundula Voss , Max Burian , Rainer T. Lechner , Nicola Demitri , Günther J. Redhammer , Nevsal Sünger , Gian Paolo Suranna and Serdar Sariciftci Hydrogen-bonded pigments are remarkably stable high-crystal lattice energy organic solids. Here a lesser-known family of compounds, the epindolidiones, which demonstrates electronic transport with extraordinary stability, even in highly demanding aqueous environments, is reported. Hole mobilities in the range 0.05-1 cm 2 V -1 s -1 can be achieved, with lower electron mobilities of up to 0.1 cm 2 V -1 s -1 . To help understand charge transport in epindolidiones, X-ray diffraction is used to solve the crystal structure of 2,8-difl uoroepindolidione and 2,8-dichloroepindolidione. Both derivatives crystallize with a linear-chain H-bonding lattice featuring two-dimensional π-π stacking. Powder diffraction indicates that the unsubstituted epindolidione has very similar crystallinity. All types of epindolidiones measured here display strong low-energy optical emission originating from excimeric states, which coexists with higher-energy fl uorescence. This can be exploited in light-emitting diodes, which show the same hybrid singlet and low-energy excimer electroluminescence. Low-voltage FETs are fabricated with epindolidione, which operate reliably under repeated cyclic tests in different ionic solutions within the pH range 3-10 without degradation. Finally, in order to overcome the insolubility of epindolidiones in organic solvents, a chemical procedure is devised to allow solution-processing via the introduction of suitable thermolabile solubilizing groups. This work shows the versatile potential of epindolidione pigments for electronics applications.

Solution of an elusive pigment crystal structure from a thin film: a combined X-ray diffraction and computational study

“…11 Such difficulties in the growth of high quality single crystals were also observed for the closely related quinacridone family of hydrogen-bonded pigments. 12 The structural study of EPI thin films, therefore, presents an opportunity to attempt to solve the crystal structure directly from a thin film, for a material where, to date, no crystal structure has been forthcoming by any other means (such as single crystal X-ray diffraction or powder X-ray diffraction).…”

Growing low-dimensional supramolecular crystals directly from 3D particles

“…Besides, it was found that the generated adsorbate structures are temporally and thermally stable. Further, it can be said that the QAC arrays are chemically and mechanically resistant, [26][27][28][29][30][31][32] and can be built up within minutes or even seconds. [20][21] Additionally, previous investigations have shown, that alkyd resin can be used to seal a QAC adsorbate layer, providing a resistant protection layer without damaging the supramolecular structures.…”

“…We exemplify our approach using the organic semiconductor quinacridone (QAC), a cheap and commercially available pigment with promising electrical properties, low toxicity, excellent physical and chemical stability and biocompatibility for applications within the living organism. [26][27][28][29][30][31][32] The chemical structure of a single QAC molecule is shown in Fig. 1.…”

Functionalization of epindolidion: a new colorimetric and ratiometric fluorescent probe for Hg 2+

“…For a long time chemists have focused considerable and consistent attentions on their synthesis and pigment performance, and only a few researches were reported on functionalization of epindolidions, making them to be wonderful potential materials for organic semiconductors, Field-Effect Transistors and Light-Emitting Diodes [12][13][14] . Based on exploration about synthesis optimizing of epindolidions in our group 15 , it is meaningful to do more researches on the fluorescence features of epindolidions in solution to widen their applications.…”