Versatile Room‐Temperature‐Phosphorescent Materials Prepared from N‐Substituted Naphthalimides: Emission Enhancement and Chemical Conjugation

Abstract

Purely organic materials with room-temperature phosphorescence (RTP) are currently under intense investigation because of their potential applications in sensing, imaging, and displaying. Inspired by certain organometallic systems, where ligand-localized phosphorescence ((3) π-π*) is mediated by ligand-to-metal or metal-to-ligand charge transfer (CT) states, we now show that donor-to-acceptor CT states from the same organic molecule can also mediate π-localized RTP. In the model system of N-substituted naphthalimides (NNIs), the relatively large energy gap between the NNI-localized (1) π-π* and (3) π-π* states of the aromatic ring can be bridged by intramolecular CT states when the NNI is chemically modified with an electron donor. These NNI-based RTP materials can be easily conjugated to both synthetic and natural macromolecules, which can be used for RTP microscopy.

Stimuli‐Responsive Reversible Switching of Intersystem Crossing in Pure Organic Material for Smart Photodynamic Therapy

“…[12] Theoretical Verification of CBT-Induced ISC To elucidate the mechanism of ultra-efficient ISC in PE3 and PE4, we carried out time-dependent density functional theory (TD-DFT) calculations of the singlet and the triplet excited states.A ccording to perturbation theory,asmaller singlet-triplet energy gap (DE ST )a nd greater spin-orbit coupling (SOC) constants facilitate higher F ISC . [12] Theoretical Verification of CBT-Induced ISC To elucidate the mechanism of ultra-efficient ISC in PE3 and PE4, we carried out time-dependent density functional theory (TD-DFT) calculations of the singlet and the triplet excited states.A ccording to perturbation theory,asmaller singlet-triplet energy gap (DE ST )a nd greater spin-orbit coupling (SOC) constants facilitate higher F ISC .…”

Intersystem Crossing Mechanisms in the Room Temperature Phosphorescence of Crystalline Organic Compounds

“…RTP of a polymethylmethacrylate film incorporating 0.5% N-aryl naphthalimide derivative (31) was attributed to an intramolecular CT transition by G. Zhang, et al 36 The small energy gap between 1 CT and 3 CT was suggested to be a cause of the enhanced ISC. This hypothesis was supported by the fact that an N-alkyl derivative (32), a non-CT compound, did not show RTP.…”

Dual-Emissive Waterborne Polyurethanes Prepared from Naphthalimide Derivative

“…Moreover, RTP materials have a potential application in encryption ink [15]. Generally speaking, organometallic molecules may more easily exhibit RTP properties, because heavy metal ions enhance spin-orbit coupling or decrease the small energy gap between singlet and triple states caused by charge transfer of metal to ligand (MLCT) or ligand to metal (LMCT) [16]. However, organometallic materials face some difficulties in application, due to their toxicity and instability in aqueous conditions.…”