Syntheses of multi-functional Aggregation-Induced Emission (AIE) active molecules in a simple manner have been drawing great attention in current luminescence materials research. In this report a simple diamine molecule (N¹-tritylethane-1,2-diamine(1)) is reacted with salicylaldehyde using a Schiff-base technique which results in a new AIE active organic molecule [2-((2-(tritylamino)ethylideneamino)methyl)phenol (2)]. Computational calculations support that the nature of the transition is intra-molecular charge transfer/twisted intramolecular charge transfer (ICT/TICT). The mechanism of AIE has been attributed to restricted intramolecular rotation (RIR). Packing diagrams support that the nature of the aggregation is J-aggregation. The compound, 2, exhibits an irreversible mechanoluminescence (ML) property with a drastic colour change from blue to green (λ_max, 445 nm → 512 nm) upon grinding. However, it undergoes a reversible transition with the same colour change (blue → green) through applying pressure axially (using a hydraulic press). The reversible transition is observed by lowering the temperature of 2 to that of liquid nitrogen. The causes of such transitions showing variations in the emission colour upon different triggers have been investigated. In addition, 2 has been successfully tested for the sensing of Zn(II) and shows a rare turn-on luminescence change, the mechanism behind which has been explored. The detection limit for Zn(II) is determined to be 0.064 ppm.

The hidden potential of an AIE-ESIPT active, simple substituted benzothiazole compound has been explored.

Design and syntheses of ‘aggregation induced emission (AIE)’ active blue-emitting bis-cyclometalated iridium(III) complexes with appended diphosphine ligands [Ir(F₂ppy)₂(L₁/L₂)₂(Cl)] (F₂ppy = 2-(2′,4′-difluoro) phenylpyridine; L₁ = 1,2-bis(diphenylphosphino)ethane; L₂ = bis(diphenylphosphino)propane) have been realized on a suitable route. The free phosphorous donor atom present on the appended diphosphine is shown to provide selective binding to the mercuric ion (Hg²⁺). The selective binding ability of the probe molecule towards mercuric ions results in a detectable signal due to complete quenching of their AIE properties. The quenching effect of the probe molecule has been explored and found to be the result of the degradation of the probe iridium(III) complex triggered by the presence of mercuric ions due to an interplay of a soft–soft interaction between the free phosphorous atom of the probe molecule and mercuric ions. These complexes were modelled to obtain deeper understanding of excited state properties and the results were tentatively correlated with the experimental data.

A simple and efficient pyrene based luminescent multifunctional probe was utilized in selective and sensitive ratiometric detection of H ⁺ , Al ³⁺ and picric acid.

A simple synthetic protocol involving two steps was developed for the syntheses of a series of monocyclometalated iridium(III) complexes. Initially, an intermediate, [IrHCl[(o-C₆H₃X)P(Ar)_x−(PAr_xR_y)₂] [A (i, j, k, l)], six-coordinated iridium(III) complex involving a 4-membered chelate was isolated. Then, it was transformed into a monocyclometalated iridium(III) complex, [(C^N)Ir(PAr_x−1R_y)₂(Cl(H)] (1–12), by the replacement of the 4-membered chelates with 5-membered cyclometalates. The intermediates and the complexes were structurally characterized by FTIR, ¹H, ¹³C and ³¹P NMR spectroscopies. Octahedral coordination for Ir(III) in 2, 8 and 9 was established by single crystal X-ray diffraction. Photo-physical experiments and quantum chemical calculations revealed a mixed LC/MLCT/LLCT nature for the lowest excited states of all these complexes that emit bright light in the solid state. Fine tuning of the emission wavelength throughout the visible range was achieved by suitable combinations of chromophoric cyclometalates and non-chromophoric aryl phosphine ligands. More interestingly, all the studied complexes were found to be aggregation-induced emission (AIE) active. One of these AIE active materials (6) was encapsulated inside polymeric micelles that inhibit the macroscopic precipitation of the aggregated complex, <200 nm water-soluble particle exhibiting a strong emission. These colloidal luminescent particles were used as a potential non-toxic bio-imaging probe.