The development of red emissive aggregation-induced emission (AIE) active probes for organelle-specific imaging is of great importance. Construction of metal complex-based AIE-active materials with metal-to-ligand charge transfer (MLCT), ligand-to-metal charge transfer (LMCT) emission together with the ligand-centered and intraligand (LC/ILCT) emission is a challenging task. We developed a red emissive ruthenium(II) complex, 1[PF], and its perchlorate analogues of the 4,7-dichloro phenanthroline ligand. 1[PF] has been characterized by spectroscopic and single-crystal X-ray diffraction. Complex 1 showed AIE enhancement in water, highly dense polyethylene glycol media, and also in the solid state. The possible reason behind the AIE property may be the weak supramolecular π···π, C-H···π, and C-Cl···H interactions between neighboring phen ligands as well as C-Cl···O halogen bonding (XB). The crystal structures of the two perchlorate analogues revealed C-Cl···O distances shorter than the sum of the van der Waals radii, which confirmed the XB interaction. The AIE property was supported by scanning electron microscopy, transmission electron microscopy, dynamic light scattering, and atomic force microscopy studies. Most importantly, the probe was found to be low cytotoxicity and to efficiently permeate the cell membrane. The cell-imaging experiments revealed rapid staining of the nucleolus in HeLa cells via the interaction with nucleolar ribosomal ribonucleic acid (rRNA). It is expected that the supramolecular interactions as well as C-Cl···O XB interaction with rRNA is the origin of aggregation and possible photoluminescence enhancement. To the best of our knowledge, this is the first report of red emissive ruthenium(II) complex-based probes with AIE characteristics for selective rRNA detection and nucleolar imaging.

A bis-heteroleptic Ru(II) complex, 1[PF 6 ] 2 , of substituted pyridyl-1,2,3-triazole ligand (L1) has been developed for the photoluminescence(PL) detection of phosphate (HP 2 O 7 3À /PPi) and Ag + ion in distilled CH 3 CN and mixed aqueous buffer (carbonate-bicarbonate buffer/CH 3 CN; v/v, 9.5 : 0.5; 0.1 M; pH 10.6) at two different wavelengths, respectively. The multianalyte probe, 1[PF 6 ] 2 showed significant PL enhancement in the presence of H 2 PO 4 À , PPi, and Ag + with low detection limits of 0.48 μM, 0.43 μM, and 0.46 μM, respectively. The PL enhancement with phosphate ions is due to the triazole CÀ H•••anion H-bonding interaction that has been supported by 1 H NMR titration (for PPi) and single-crystal X-ray structure (for H 2 PO 4 À ). A unique Ag(I)-triazolide complex formation is responsible for the PL enhancement in Ag + ion detection. Triplet state TDDFT calculations were carried out to explain the PL enhancement of 1 • PPi and 1-Ag adducts. In 1-Ag, the L1 ligand becomes a better σ-donor as well as π-donor. Consequently, the 3 MLCT-3 MC energy gap is increased and the 1-Ag emits efficiently from the 3 MLCT state. The probe also shows low cytotoxicity against Hela cells and is used for intracellular Ag + imaging.

A new cyclometalated Ir(III) complex of methylene bridged benzimidazole substituted 1,2,3-triazole methanol ligand has been synthesized for the photoluminescent detection of pyrophosphate (H2P2O72-) anion. The solution structure of 1[PF6] was...

Two bis-heteroleptic Ru(ii) complexes of a 4,7-dihydroxy-1,10-phenanthroline ligand were synthesized for the detection of the nerve agent gas mimic, DCP, and the organophosphate pesticide, dichlorvos, through the “off–on” luminescence response.