Base‐Assisted Imidization: A Synthetic Method for the Introduction of Bulky Imide Substituents to Control Packing and Optical Properties of Naphthalene and Perylene Imides

Abstract

We report the direct imidization of naphthalene and perylene dicarboxylic anhydrides/esters with bulky ortho,ortho‐diaryl‐ and ortho,ortho‐dialkynylaniline derivatives. This imidization method uses n‐butyllithium as a strong base to increase the reactivity of bulky amine derivatives, proceeds under mild reaction conditions, requires only stoichiometric amounts of reactants and gives straightforward access to new sterically crowded rylene dicarboximides. Mechanistic investigations suggest an isoimide as intermediary product, which was converted to the corresponding imide upon addition of an aqueous base. Single‐crystal X‐ray diffraction analyses reveal dimeric packing motifs for monoimides, while two‐side shielded bisimides crystallize in isolated molecules without close π–π‐interactions. Spectroscopic investigations disclose the influence of the bulky substituents on the optical properties in the solid state.

1-Mono- and 1,7-Disubstituted Perylene Bisimide Dyes with Voluminous Groups at Bay Positions: In Search for Highly Effective Solid-State Fluorescence Materials

“…Finally, if we compare the discussed findings on molecular packing in the crystal structures and their impact on the solidstate fluorescence quantum yield (Φ fl ) of bay-substituted PBIs 2 and 3 with data reported for imide-functionalized PBIs 4, we can draw interesting conclusions concerning the affectivity of these two shielding approaches (Figures 10 and S13). Crystal structures and partially solid-state fluorescence quantum yield of imide-substituted PBIs (Figure 10b) including BASF's Lumogen Orange 4a 61 as well as on more heavily shielded chromophores were reported by Wong and co-workers 28 (4d′−f′, R = nBu) and by our group 62 (4c−e, R = H), where the latter just differ in the kind of residue R in the paraposition of the imide substituents. Their respective solid-state fluorescence quantum yield is plotted against the chromophore concentration (M PBI /M W ) in Figure 10.…”

“…This is valid for all reported molecular structures obtained from single-crystal structures of the two series of PBIs 3 and 4 (Figure S13). Second, the decoration of the bay area of PBIs 3 predominantly induces longitudinal displacements in the solid state, which enable possible J-type coupling, while for imide-substituted PBIs 4, either laterally displaced (4d, 4f′) 62,28 or staggered arrangements (4e′) 28 with partially close π−π interactions are observed. These lead mostly to broad and unstructured solid-state fluorescence spectra with maxima ranging between 590 and 700 nm.…”

Bis-N-Heterocyclic Carbene Complexes of Coinage Metals Containing Four Naphthalimide Units: A Structure–Emission Properties Relationship Study

“…15−18 The photophysical properties of these compounds can be controlled by tuning (1) the substituents on the aromatic rings and (2) the aggregation and π-stacking of the aromatic rings in the solid state (either in the self-assembled materials or in the discrete molecular species). 19,20 For example, the presence of electron donor groups on the aromatic ring of N-substituted naphthalimides (NNIs) creates a charge transfer (CT) state that lies between the singlet and triplet ππ* excited states and causes an efficient phosphorescence from the 3 ππ* state. 21 It has been well established that the aggregation of aromatic rings usually causes a quenching (ACQ) in the luminescence signals of the perylene mono-or bis-imides.…”

“…The synthesis of new luminescent compounds has always been a fascinating topic of research. Many chemists and biochemists have made attempts to develop new fluorophores for use in various research fields. , Recently, aromatic π-systems such as perylene and naphthalene mono- or bis-imide derivatives have attracted more attention due to their interesting photophysical properties − and applications in biochemistry, − materials chemistry, − and sensing. − The photophysical properties of these compounds can be controlled by tuning (1) the substituents on the aromatic rings and (2) the aggregation and π-stacking of the aromatic rings in the solid state (either in the self-assembled materials or in the discrete molecular species). , For example, the presence of electron donor groups on the aromatic ring of N-substituted naphthalimides (NNIs) creates a charge transfer (CT) state that lies between the singlet and triplet ππ* excited states and causes an efficient phosphorescence from the 3 ππ* state . It has been well established that the aggregation of aromatic rings usually causes a quenching (ACQ) in the luminescence signals of the perylene mono- or bis-imides .…”