The Schiff base ligands benzylidene­(4-tert-butylphenyl)­amine 4-methyl ester (L1), (4-nitrobenzylidene)­(4-tert-butylphenyl)­amine (L2), and (4-cyanobenzylidene)­(4-tert-butylphenyl)­amine (L3) and the new series of cyclometalated mononuclear piano-stool complexes [(η5-C5Me5)­RhCl­(L1)] (1), [(η5-C5Me5)­RhCl­(L2)] (2), [(η5-C5Me5)­RhCl­(L3)] (3), [(η5-C5Me5)­IrCl­(L1)] (4), [(η5-C5Me5)­IrCl­(L2)] (5), and [(η5-C5Me5)­IrCl­(L3)] (6) have been synthesized. The ligands L1–L3 and complexes 1–6 have been thoroughly characterized by satisfactory elemental analyses, spectral studies (ESI-MS, IR, 1H and 13C NMR, UV–vis), and structures of 1–3 authenticated by X-ray single-crystal analyses. Efficient binding of 1–6 with calf thymus DNA (CT DNA) have been established by UV–vis and emission spectroscopic studies. Protein binding (bovine serum albumin, BSA) has been investigated by UV–vis, fluorescence, synchronous, and 3D fluorescence spectroscopy. Binding of the complexes with DNA through minor groove and hydrophobic interaction with proteins via sub domain IIA cavity has been substantiated by molecular docking studies. The complexes exhibited significant cytotoxicity against the human lung cancer cell line (A549), and 1 and 2 showed better activity than cisplatin. The cytotoxicity, morphological changes, and apoptosis have been assessed by MTT assay, Hoechst 33342/PI staining, cell cycle analysis by fluorescence-activated cell sorting (FACS), and reactive oxygen species (ROS) generation by DCFH-DA dye. The complexes 1–6 induce apoptosis in the order 2 > 1 > 4 > 3 > 5 > 6.

A pyrazole-appended quinoline-based 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (L1, BODIPY) has been synthesized and used as a ligand for the preparation of iridium(III) complexes [Ir(phpy)(L1)]PF (1; phpy = 2-phenylpyridine) and [(η-CMe)Ir(L1)Cl]PF (2). The ligand L1 and complexes 1 and 2 have been meticulously characterized by elemental analyses and spectral studies (IR, electrospray ionization mass spectrometry, H andC NMR, UV/vis, fluorescence) and their structures explicitly authenticated by single-crystal X-ray analyses. UV/vis, fluorescence, and circular dichroism studies showed that complexes strongly bind with calf-thymus DNA and bovine serum albumin. Molecular docking studies clearly illustrated binding through DNA minor grooves via van der Waals forces and their electrostatic interaction and occurrence in the hydrophobic cavity of protein (subdomain IIA). Cytotoxicity, morphological changes, and apoptosis have been explored by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and Hoechst 33342 staining. IC values for complexes (1, 30 μM; 2, 50 μM) at 24 h toward the human cervical cancer cell line (HeLa) are as good as that of cisplatin (21.6 μM) under analogous conditions, and their ability to kill cancer cells lies in the order 1 > 2. Because of the inherent emissive nature of the BODIPY moiety, these are apt for intracellular visualization at low concentration and may find potential applications in cellular imaging and behave as a theranostic agent.

Progelator complex Zn-TRPA-2 undergoes Cl(-) triggered gelation to afford ZTP2G, while Zn-TRPA-2 capped Au-NPs under similar conditions gave another gel GNZTP2G which also represents a rare nano-composite metallogel. When Zn-TRPA-2 was triggered by Cl(-) and NO3(-) simultaneously, crystals of demetalated species NA-TRPA-2 grew inside the ZTP2G matrix. Interestingly, GNZTP2G exhibits superior viscoelastic properties over ZTP2G.

Considerable attention has been paid by the scientific community to detect toxic carbon monoxide (CO) in sub-cellular organelles like mitochondria, lysosomes, nuclei, etc. due to their generation and accumulation through numerous biological processes and their role as signal transducer, therapeutics, etc. Various methods are also available for detection of CO, but fluorescence light-up detection is considered the best due to its easy and accurate sensing capability. As of now, no review is available in the literature dedicated to fluorescent detection of only CO both in vitro and in vivo, but considering the huge amount of work reporting every year, it is necessary to have an account of all the recent significant works devoted to it. This review will give special attention to the most noteworthy development of fluorescent light-up probes for the detection of cellular and sub-cellular targetable CO starting from 2012 and emphasizing also the mechanism of action and the applications.

1,7-Phenanthroline based bis−boron dipyrromethenes (bis−BODIPYs) B1 and B2 obtained via small substitutional changes (−Cl/–SCH3) have been described. The effect of restriction of intramolecular rotation (RIR) in emission enhancement in a viscous solvent (glycerol) has been studied besides the vital role of intermolecular interactions scrutinized by X-ray single-crystal studies. The efficiency of intersystem crossing (ISC) in the generation of singlet oxygen (ΦΔ ∼ 19.2% and 56.7%) by photoirradiation using visible light along with distinct photostability has been investigated by 1,3-diphenylisobenzofuran (DPBF) titration studies. The 1O2 generation quantum yield and photosensitizing durability of the bis−BODIPYs have been investigated by photooxidation of 1,5-dihydroxynaphthalene (DHN) in the presence of B1 and B2 as photosensitizers. The pseudo-first-order rate constants for photooxidation reactions and consumption rates of DHN reflected appreciable 1O2 generation quantum yields (ΦΔ: B1, 29.0; B2, 57.8%). Density functional theory (DFT) studies showed the distribution of electron density over the dipyrrin moiety. Overall results indicated that these new photosensitizers (PSs) may be very promising in photodynamic therapy of tumors, photobiology, and organic photochemistry.

Four organometallic complexes [(η(6)-C6H6)RuCl(pmpzdpm)], 1; [(η(6)-C6H6)RuCl(pypzdpm)], 2; [(η(6)-C10H14)RuCl(pmpzdpm)], 3 and [(η(6)-C10H14)RuCl(pypzdpm)], 4 containing 5-(2-pyrimidyl-piperazine)phenyldipyrromethene (pmpzdpm) and 5-(2-pyridylpiperazine)phenyldipyrromethene (pypzdpm) have been designed and synthesized. The complexes 1-4 have been fully characterized by elemental analyses and spectroscopic studies (ESI-MS, IR, (1)H, (13)C NMR, UV-vis). Their electrostatic/intercalative interaction with CT DNA has been investigated by UV-vis and competitive ethidium bromide displacement studies while their protein binding affinity toward bovine serum albumin (BSA) was realized by UV-vis, fluorescence, synchronous and three dimensional (3D) fluorescence studies. The interaction with DNA and protein has further been validated by in silico studies. Cellular uptake, in vitro cytotoxicity and flow cytometric analyses have been performed to determine the mode of cell death against the kidney cancer cell line ACHN. Cell cycle analysis suggested that the complexes cause cell cycle arrest in the subG1 phase and overall results indicated that the in vitro antitumor activity of 1-4 lies in the order of 3 >4 >1 >2 (IC50, 7.0 1; 8.0 2; 2.0 3; 4.0 μM,4 ).

Manipulating gelation properties of the isomeric zinc–terpyridine complexes C-1 (nongelator) and C-2 (gelator) using three different luminescent dyes, viz., acridine yellow (AY), ethidium bromide (EB), and azido-boron dipyrromethene, have been described. Hybrid gels created by the combination of C-1, C-2, and above-mentioned dyes have been termed complex-luminogen mixed gels (CLMGs). Ensuing CLMGs have been thoroughly characterized by spectral, morphological, and rheological studies. Cytotoxicity measurements and imaging against breast cancer cell line MDA-MB-231 unveiled that three out of the five CLMGs can be effectively used for cell imaging. Interestingly, direct use of the metal-containing hybrid gels for live cell imaging which is a distinctive approach, has been successfully achieved with significantly encouraging results.

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