Probing the aggregation behavior of 4-aminophthalimide and 4-(N,N-dimethyl) amino-N-methylphthalimide: a combined photophysical, crystallographic, microscopic and theoretical (DFT) study

Abstract

Two fluorescent molecules, 4-aminophthalimide (AP) and 4-(N,N-dimethyl)amino-N-methylphthalimide (DMP) have been used as the building blocks to fabricate fluorescent organic nano particles. DMP, the analogue of AP, has been synthesized by substituting all the amine hydrogens of AP with methyl groups to get an idea about the effect of intermolecular hydrogen bonding interactions (N-H···) on the aggregation behavior of these molecules. All the systems have been characterized by field emission scanning electron microscopy (FESEM). Photophysical behavior of these well characterized systems has been investigated in molecular as well as aggregated forms. Interestingly, while the AP-aggregates exhibit a blue-shifted absorption band (as compared to AP in its molecular form), DMP-aggregates exhibit a red-shifted absorption band (as compared to DMP in its molecular form). These absorption data indicate the formation of H and J aggregates for AP and DMP, respectively. The intermolecular interactions that are responsible for the molecular self assembly of AP and DMP are studied by using X-ray crystallography. X-ray analysis demonstrates the presence of strong intermolecular hydrogen bonding interactions in AP, but only weak interactions (C-H···O, C-H···π) in the case of DMP. X-ray analysis also demonstrates that varying the nature of intermolecular interactions leads to different modes of aggregation. Theoretical studies (DFT and TD-DFT) have been carried out to investigate how different modes of aggregation lead to changes in the optical (UV-VIS spectra) properties of these systems.

Aggregation induced emission enhancement of 4,4′-bis(diethylamino)benzophenone with an exceptionally large blue shift and its potential use as glucose sensor

“…24 Due to the facile manipulation of frontier orbital energy level, energy band gaps, carrier injection and transport balance of D-A molecules, the photoluminescence spectra can be easily shifted to the longer wavelengths. [25][26][27] In such intramolecular processes of a conjugated system with donor and acceptor subunits, the reaction product is usually called an intramolecular charge transfer (ICT) state. This fact greatly hinders the progress of D-A molecules to the short wavelength, i.e.…”

Fluoride ion sensing in aqueous medium by employing nitrobenzoxadiazole-postgrafted mesoporous silica nanoparticles (MCM-41)

“…34 The effects of aggregation of fluorophores on their photophysical properties has been extensively studied in the solution phase. [35][36][37] Here, aggregation may be a result of p-p stacking interactions among several NBD moieties that are bound to the silica surface. 34 Nevertheless, the overall absorption feature of both bound and unbound NBD indicates that the basic chromophoric properties of NBD are not significantly altered upon covalent attachment to the mesoporous silica surface.…”

Indirect solvent assisted tautomerism in 4-substituted phthalimide 2-hydroxy-Schiff bases

“…They show strong sensitivity upon different solvent environments and are used as fluorescence probes in cell biology, protein labeling as well as fluorescent polymers for flexible OLED's devices. For example, 4aminophthalimide, having an electron-donating amino group, exhibited a large quantum yield in THF (Φ fl = 0.70), dichloromethane (DCM) (Φ fl = 0.76) and acetone (Φ fl = 0.68), which forms a base to find applicability in materials science [39][40][41].…”