Photoinduced Color Change and Photomechanical Effect of Naphthalene Diimides Bearing Alkylamine Moieties in the Solid State

Abstract

Photoinduced color change of naphthalene diimides (NDIs) bearing alkylamine moieties has been observed in the solid state. The color change is attributed to the generation of a NDI radical-anion species, which may be formed through a photoinduced electron-transfer process from the alkylamine moiety to the NDI. The photosensitivity of NDIs is highly dependent on the structures of the alkylamine moieties. Crystallographic analysis, kinetic analysis, UV/Vis/NIR spectroscopic measurements, and analysis of the photoproduct suggested that a radical anion was formed through an irreversible process initiated by proton abstraction between an amine radical cation and the neutral amine moiety. The radical anions formed stacks including mixed-valence stacks and radical-anion stacks, as shown by the broad absorption bands in near-IR spectra. These photosensitive NDIs also showed crystal bending upon photoirradiation, which may be associated with a change in the intermolecular distance of the NDI stacks by the formation of monomeric radical anions, mixed-valence stacks, and radical-anion stacks.

o‐Amino Analogs of Green Fluorescence Protein Chromophore: Photoisomerization, Photodimerization and Aggregation‐induced Emission

“…A similar behavior was also reported for the crystals of m ‐HBDI that underwent photodimerization . It should be noted that other types of photoreactions such as isomerization and ionization occurred in the solid state could also induce crystal bending . Prolonged irradiation of the crystal of O0 would crack the crystal perpendicular to the long axis.…”

Redox‐Active Metal–Organic Frameworks: Highly Stable Charge‐Separated States through Strut/Guest‐to‐Strut Electron Transfer

“…Appearance of a strong EPR signal with a g value of 2.001 for the irradiated crystals of 1 corroborates the formation of radical anions of bpNDI, where the radical is on the carbon atom (Figure 3 d). 7e On the other hand, free bpNDI ligands also showed similar photochromic behaviour (radical anion formation) upon UV irradiation owing to the intramolecular photoinduced electron transfer (PET) from the pyridine nitrogen to the NDI aromatic core (Figure S8 in the Supporting Information) 7e. The PET mechanism operating in the free bpNDI linkers is supported by the fact that the diprotonated bpNDIH 2 2+ showed no colour change upon irradiation.…”

Switching Photomechanical Response by a Structural Phase Transition in a Naphthalene Diimide Derivative

“…Compound 2 was prepared according to the literature using naphthalene‐1,4,5,8‐tetracarboxylic dianhydride (802 mg, 3.0 mmol), N , N ‐dimethyl‐1,4‐butanediamine (736 mg, 6.0 mmol), and 1,4‐diazabicyclo[2.2.2]octane (3.38 g, 30 mmol) in dry DMF (30 mL). The obtained material was purified twice by silica gel (Wako 50NH 2 ) column chromatography (CH 2 Cl 2 ) to yield compound 2 (782 mg, 56 %).…”

“…We have previously reported photomechanical crystals composed of naphthalene diimide molecules having dialkylamino groups on the side chain . Parent molecule 1 is shown in Figure a.…”