The ruthenium­(II) complexes [RuCl­(L1)­(L3)]Cl (1), [RuCl­(L1)­(L4)]­Cl (2), [RuCl­(L2)­(L4)]Cl (3), [RuCl­(L1)­(L5)]Cl (4), and [RuCl­(L2)­(L5)]Cl (5) of NNN-donor dipicolylamine (dpa) bases (L4, L5) having BODIPY (boron-dipyrromethene) moieties, NN-donor phenanthroline derivatives (L1, L2), and benzyldipicolylamine (bzdpa, L3) were prepared and characterized by spectroscopic techniques and their cellular localization/uptake and photocytotoxicity studied. Complex 1, as its PF6 salt (1a), has been structurally characterized with help of a single-crystal X-ray diffraction technique. It has a RuN5Cl core with the Cl bonded trans to the amine nitrogen atom of bzdpa. The complexes showed intense absorption spectral bands near 500 nm (ε ≈ 58000 M–1 cm–1) in 2 and 3 and 654 nm (ε ≈ 80000 M–1 cm–1) in 4 and 5 in 1/1 DMSO/DPBS (v/v). Complex 5 having biotin and PEGylated-disteryl BODIPY gave a singlet oxygen quantum yield (ΦΔ) of ∼0.65 in DMSO. Complex 5 exhibited remarkable PDT (photodynamic therapy) activity (IC50 ≈ 0.02 μM) with a photocytotoxicity index (PI) value of >5000 in red light of 600–720 nm in A549 cancer cells. The biotin-conjugated complexes showed better photocytotoxicity in comparison to nonbiotinylated analogues in A549 cells. The complexes displayed less toxicity in HPL1D normal cells in comparison to A549 cancer cells. The emissive BODIPY complexes 3 and 5 (ΦF ≈ 0.07 in DMSO) showed significant mitochondrial localization.

A series of multichromophoric ruthenium(II) complexes with the formulation [Ru(tpy-BODIPY)(tpy-R)]Cl 2 (1−4), having a heteroleptic Ru(II)-bis-tpy (tpy = 4′-phenyl-2,2′:6′,2″-terpyridine) moiety covalently linked to a boron-dipyrromethene (BODIPY) pendant, have been prepared and characterized and their application as a phototherapeutic and photodetection agent in cancer therapy has been explored. Ligand L 1 with a terpyridine-BODIPY moiety and complex 1 as its PF 6 salt (1a) have been structurally characterized by a single-crystal Xray diffraction study. Complex 1a has a distorted-octahedral RuN 6 core with a Ru(II)-bis-terpyridine unit that is covalently linked to one photoactive BODIPY unit. The complexes exhibit strong absorbance near 502 nm (ε ≈ (3.7−7.8) × 10 4 M −1 cm −1 ) and high singlet oxygen sensitization ability, giving singlet oxygen quantum yield (Φ Δ ) values ranging from 0.57 to 0.75 in DMSO. An emission-based study using complex 4 and Singlet Oxygen Sensor Green (SOSG) displays the formation of singlet oxygen inside the cells and also in the buffer medium upon light irradiation. DNA (pUC19) photocleavage experiments using ROS scavengers/stabilizers reveal photoinduced generation of singlet oxygen by a type-II process and of the superoxide anion radical by a type-I process. Complex 4 having a pendant biotin moiety as a cancer cell targeting group shows high photocytotoxicity with a remarkable phototherapeutic index (PI) value of >1400 in HeLa cancer cells with a low light dose activation (400−700 nm, 2.2 J cm −2 ). The complexes display reduced activity in noncancerous HPL1D cells. The emission property of the complexes is used for cellular imaging, thus making them suitable as next-generation theranostic PDT agents.

Catalytic activities of a series of functional bipyridine-based Ru complexes in β-alkylation of secondary alcohols using primary alcohols were investigated. Bifunctional Ru complex (3 a) bearing 6,6'-dihydroxy-2,2'-bipyridine (6DHBP) ligand exhibited the highest catalytic activity for this reaction. Using significantly lower catalyst loading (0.1 mol %) dehydrogenative carbon-carbon bond formation between numerous aromatic, aliphatic and heteroatom substituted alcohols were achieved with high selectivity. Notably, for the synthesis of β-alkylated secondary alcohols this protocol is a rare one-pot strategy using a metal-ligand cooperative Ru system. Remarkably, complex 3 a demonstrated the highest reactivity compared to all the reported transition metal complexes in this reaction.

Cobalt­(III) complexes [Co­(TPA)­(L1)]­(ClO4)2 (1), [Co­(4-COOH-TPA)­(L1)]­(ClO4)2 (2), [Co­(TPA)­(L2)]­Cl2 (3), and [Co­(4-COOH-TPA)­(L2)]­Cl2 (4) having acetylacetonate-linked boron-dipyrromethene ligands (L 1 , acac-BODIPY; L 2 , acac-diiodo-BODIPY) were prepared and characterized, and their utility as bioimaging and phototherapeutic agents was evaluated (TPA, tris-(2-pyridylmethyl)­amine; 4-COOH-TPA, 2-((bis-(2-pyridylmethyl)­amino)­methyl)­isonicotinic acid). HL 1 , HL 2 , and complex 1 were structurally characterized by X-ray crystallography. Complexes 1 and 2 on photoactivation or in a reducing environment (excess GSH, ascorbic acid, and 3-mercaptopropionic acid) released the acac-BODIPY ligand. They exhibited strong absorbance near 501 nm (ε ∼ (5.2–5.8) × 104 M–1 cm–1) and emission bands near 513 nm (ΦF ∼ 0.13, λex = 490 nm) in dimethyl sulfoxide (DMSO). Complexes 3 and 4 with absorption maxima at ∼536 and ∼538 nm (ε ∼ (1.2–1.8) × 104 M–1 cm–1), respectively, afforded high singlet oxygen quantum yield (ΦΔ ∼ 0.79) in DMSO. Complexes 1–4 showed Co­(III)–Co­(II) redox responses near −0.2 V versus saturated calomel electrode (SCE) in dimethylformamide (DMF)–0.1 M tetrabutylammonium perchlorate (TBAP). The photocleavage of pUC19 DNA by complex 4 revealed the formation of both singlet oxygen and superoxide anion radicals as the reactive oxygen species (ROS). Confocal fluorescence microscopy showed the selective accumulation of complex 1 in the endoplasmic reticulum (ER) in A-549 cells. Complex 4 exhibited a high phototherapeutic index value (PI > 7000) in HeLa cancer cells (IC50 ∼ 0.007 μM in visible light of 400–700 nm, total dose ∼5 J cm–2). The ancillary ligands in the complexes demonstrated a structure–activity relationship and modulated the Co­(III)–Co­(II) redox potential, the complex solubility, acac-BODIPY ligand release kinetics, and phototherapeutic efficacy.

Two multichromophoric homoleptic ruthenium(II) complexes [Ru(tpy-BODIPY)2]Cl2 (complexes 1 and 2, tpy = 4-phenyl-2,2:6,2-terpyridine, BODIPY = boron-dipyrromethene) were prepared, characterized and their phototherapeutic activity and bioimaging properties studied. The complexes having...

A perceived drawback of ruthenium(II) polypyridyl photosensitizers for phototherapeutic applications is their inadequate absorption in the visible region. Ru(II) dyads attached to lightharvesting organic chromophores are studied to address this issue. Biotin-appended compounds having one chromophore, namely BODIPY (boron-dipyrromethene) (1) and Ru(II)-(tpy) 2 (2), or a dyad system containing BODIPY linked to Ru(II)-(tpy) 2 via a diphenylacetylene linker (3) were prepared and studied as photodetection agent and photosensitizes for Photodynamic Therapy (PDT) applications. The bichromophoric 3 with a strong absorption profile (ɛ � 71000 M À 1 cm À 1 at λ max = 503 nm) and high singlet oxygen quantum yield (Φ Δ = 0.63 in DMSO) was studied for PDT activity. This complex produced a superoxide anion radical via type-I and singlet oxygen via type-II photosensitization processes on light exposure, as evidenced from DNA photo-cleavage experiments and in vitro DCFDA assay using reactive oxygen species scavengers/quenchers. Dyad 3 displayed an apoptotic photo-cytotoxic effect against HeLa and H1299 cancer cells with a photocytotoxicity index (PI) value of > 625 in HeLa cells with a PDT efficacy much superior to those of its monochromophoric analogs 1 and 2. The intrinsic emission of complex 3, utilized for cellular imaging, showed selectivity towards lysosomes. Finally, the remarkable potential of complex 3 was evidenced using a clinically relevant 3D multicellular tumor spheroid model.