Emergence of Aggregation Induced Emission (AIE), Room-Temperature Phosphorescence (RTP), and Multistimuli Response from a Single Organic Luminogen by Directed Structural Modification

Abstract

Multifunctional organic luminogens exhibiting simultaneous aggregation induced emission (AIE), room-temperature phosphorescence (RTP), and mechanochromism have recently attracted considerable attention owing to their potential applications in optoelectronics and bioimaging. However, a comprehensive correlation among these three distinguished properties is yet to be unveiled, which will help to decipher defined methodologies to design future generation multifunctional organic materials. Herein, we have demonstrated a route to obtain a multifunctional organic luminogen, starting from an ACQphore (TPANDI) by simple structural engineering. We have shown that a slight reduction in length of the planar acceptor moieties can effectively inhibit the undesirable π–π stacking interaction between molecules in the condensed state and thereby cause an ACQ to AIE type transformation from TPANDI to TPANMI and TPAPMI. Both TPANMI and TPAPMI exhibit RTP properties (even in ambient condition) because of the presence of a reasonably low singlet–triplet energy gap (ΔE ST). In our study, these two luminogens were found to be mechano-inactive. Interestingly, an insertion of cyano-ethylene group and benzene linker in between the triphenylamine and phthalimide moieties introduced another luminogen TPACNPMI, which can simultaneously exhibit AIE, RTP, and mechanochromic properties.

Spectroscopic and Biological Properties of the 3-Imino-1,8-naphthalimide Derivatives as Fluorophores for Cellular Imaging

“…The capacity of the compounds for aggregationinduced emission (AIE-gens) affects their potential use [42]; therefore, this type of research provides some information about the nature of the compounds. Most importantly, a slight change in the structure of a compound might favourably affect the properties that are displayed in the aggregated state [43]. Our previous research, in which naphtalhimides with imine bonds were compared with β-ketoenamines, also showed this [27].…”

Engineering TADF, mechanochromism, and second harmonic up-conversion properties in regioisomeric substitution space

“…42–45 Such “two-photon absorption” active materials are particularly useful for cell imaging since they inflict the target cell with the least amount of photo damage. Large π-conjugated organic chromophores with enforced co-planarity and donor–acceptor groups at the center or at the end of the molecular scaffolds tend to exhibit strong two–photon absorption behavior 46 due to higher transition dipole moment values between the ground, intermediate, and final states. Our molecules' strong charge transfer behavior prompted us to investigate their two-photon absorption behavior and here, it is discovered that all three luminogens are two-photon active in both the liquid and solid crystalline states (Fig.…”

Activation of TADF in Photon Upconverting Crystals of Dinuclear Cu(I)-Iodide Complexes by Ligand Engineering

“…The histogram containing the percentage contributions of several interactions is shown in Figure b,d. We observe that in both complexes, strong interactions such as N···H (enthalpy ∼2.97 kJ/mol), C···H (enthalpy ∼10.3 kJ/mol), and I···H (enthalpy ∼16–25 kJ/mol) are present in the bulk phase. These strong noncovalent interactions not only influence the photophysical processes but also dictate the direction of the polarizability in the bulk condensed phase, which has a large impact on the NLO properties of the complexes. , …”