Strong Enhancement of π‐Electron Donor/Acceptor Ability by Complementary DD/AA Hydrogen Bonding

Abstract

π‐Conjugated organic materials possess a wide range of tunable optoelectronic properties which are dictated by their molecular structure and supramolecular arrangement. While many efforts have been put into tuning the molecular structure to achieve the desired properties, rational supramolecular control remains a challenge. Here, we report a novel series of supramolecular materials formed by the co‐assembly of weak π‐electron donor (indolo[2,3‐a]carbazole) and acceptor (aromatic o‐quinones) molecules via complementary hydrogen bonding. The resulting polarization creates a drastic perturbation of the molecular energy levels, causing strong charge transfer in the weak donor–acceptor pairs. This leads to a significant lowering (up to 1.5 eV) of the band gaps, intense absorption in the near‐IR region, very short π‐stacking distances (≥3.15 Å), and strong ESR signals in the co‐crystals. By varying the strength of the acceptor, the characteristics of the complexes can be tuned between intrinsic, gate‐, or light‐induced semiconductivity with a p‐type or ambipolar transport mechanism.

Band gap engineering of donor–acceptor co-crystals by complementary two-point hydrogen bonding

“…For the H-bonding electron acceptors, we selected a series of o-quinones (a-e) and diazafluorenone (f) (Scheme 2). The acceptors Scheme 1 (a) Previously reported H-bonded multicomponent semiconductors 22,39,40 had reversible reductions ranging from À1.48 V (f) to À0.81 V (d) vs. Fc (Fig. 1), corresponding to LUMO energies of À3.32 and À3.99 eV, respectively.…”

“…We hypothesized that such polarization would be greatly enhanced if all H-bond donors were placed on an electron-donor and all H-bond acceptors were located on the p-acceptor. 39 In this work we present a new series of DDÁ Á ÁAA H-bonded bicomponent semiconductors composed of strong p-electron donors derived from diindolopyrrole (DIP) and a series of p-electron acceptors a-f (Scheme 2) and demonstrate how H-bonding can be employed to control their co-crystallization and their electronic properties. The high HOMO of DIP comparing to other donors used in this context 39 leads to stronger donor-acceptors interactions and allows us to control the bandgap in the 0.8-1.7 eV range by varying the acceptor counterparts.…”

“…39 In this work we present a new series of DDÁ Á ÁAA H-bonded bicomponent semiconductors composed of strong p-electron donors derived from diindolopyrrole (DIP) and a series of p-electron acceptors a-f (Scheme 2) and demonstrate how H-bonding can be employed to control their co-crystallization and their electronic properties. The high HOMO of DIP comparing to other donors used in this context 39 leads to stronger donor-acceptors interactions and allows us to control the bandgap in the 0.8-1.7 eV range by varying the acceptor counterparts. The effect of H-bonding on the HOMO of the complexes is now directly probed by photoelectron spectroscopy providing experimental evidence for orbital polarization via H-bonding.…”

Low-Power Laser Micro-Shaping of Dye-Volatile Cocrystals: The Gentle Cutting Edge of Photoresponsive Materials

“…Using the confocal Raman Witec 300 R 532 nm solid-state laser with a range of power settings (0.1-20 mW), and multiple objectives (10,20,50, and 100× Zeiss objectives with NA = 0.25, 0.5, 0.8, and 0.9, respectively), a series of detailed drawings were engraved into the crystals using a pre-made input files with listed coordinates.…”

“…improving solid-state physicochemical properties of molecular solids, [1][2][3] such as pharmaceuticals, 4 photo-or thermo-responsive materials, [5][6][7] as well as for tuning the optical, 8,9 and conducting properties of organic materials. 10 Halogen bonding 11,12 has been used as a design element to generate dynamic cocrystals 13 with potential applications in stabilization or separation 14 of volatile molecules, as a tool for constructing amphidynamic 15,16 and liquid crystals, 17 for templating solidstate reactions, 18 and other uses in materials chemistry. 19,20 Stimuli-responsive behaviour of molecular crystals has recently attracted great interest, 21 and in particular a wide range of light-matter interactions have been achieved, including chemical reactions (e.g.…”