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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 PF6salt (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–1cm–1) in 2and 3and 654 nm (ε ≈ 80000 M–1cm–1) in 4and 5in 1/1 DMSO/DPBS (v/v). Complex 5having biotin and PEGylated-disteryl BODIPY gave a singlet oxygen quantum yield (ΦΔ) of ∼0.65 in DMSO. Complex 5exhibited 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 3and 5(ΦF≈ 0.07 in DMSO) showed significant mitochondrial localization.

Ternary oxidovanadium(IV) complexes of curcumin (Hcur), dipicolylamine (dpa) base, and its derivatives having pendant noniodinated and di-iodinated boron-dipyrromethene (BODIPY) moiety (L1and L2, respectively), namely, [VO(dpa)(cur)]ClO4(1), [VO(L1)(cur)]ClO4(2), and [VO(L2)(cur)]ClO4(3) and their chloride salts (1a–3a) were prepared, characterized, and studied for anticancer activity. The chloride salts were used for biological studies due to their aqueous solubility. Complex 1was structurally characterized by single-crystal X-ray crystallography. The complex has a VO2+moiety bound to dpa ligand showing N,N,N-coordination in a facial mode, and curcumin is bound in its mono-anionic enolic form. The V–O(cur) distances are 1.950(18) and 1.977(16) Å, while the V–N bond lengths are 2.090(2), 2.130(2), and 2.290(2) Å. The bond transto VO is long due to trans effect. The complexes are stable in a solution phase over a long period of time of 48 h without showing any apparent degradation of the curcumin ligand. The diiodo-BODIPY ligand (L2) or Hcur alone showed limited solution stability in dark. The emissive BODIPY (L1) containing complex 2ashowed preferential mitochondrial localization in MCF-7 cells in cellular imaging experiments. The cytotoxicity of the complexes was studied by MTT assay. The BODIPY complex 3ashowed excellent photodynamic therapy effect in visible light (400–700 nm) giving IC50values of 2–6 μM in HeLa and MCF-7 cancer cells, while being less toxic in dark (∼100 μM). The cell death was apoptotic in nature involving reactive oxygen species (ROS). Mechanistic data from pUC19 DNA photocleavage studies revealed photogenerated ROS as primarily 1O2from the BODIPY moiety and ·OH radicals from the curcumin ligand.

Platinum(II) complexes [Pt(L1)(R-BODIPY)]Cl (1) and [Pt(L2)(R-BODIPY)]Cl (2), where R-BODIPY is 8-(4-ethynylphenyl)-distyryl-4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene-3, L1is 4′-phenyl-2,2′:6′,2″-terpyridine, and L2is (2,2′:6′,2″-terpyridin-4′-oxy)ethyl-β-d-glucopyranoside, were synthesized and characterized, and their photocytotoxicity was studied. The phenylacetylide complex [Pt(L1)(CCPh)]Cl (3) was prepared and used as a control. Complexes 1and 2showed near-IR absorption bands at 713 nm (ε = 3.47 × 104M–1cm–1) and 715 nm (3.2 × 104M–1cm–1) in 10% dimethyl sulfoxide (DMSO)–Dulbecco’s Modified Eagle’s Medium (DMEM) (pH 7.2). The BODIPY complexes are emissive in 10% DMSO–DMEM at pH 7.2 with λem(λex, Φf) = 822 nm (710 nm, 0.022) for complex 1and λem(λex, Φf) = 825 nm (710 nm, 0.026) for complex 2. They generated singlet oxygen (1O2) in red light as evidenced from 1,3-diphenylisobenzofuran (DPBF) titration experiments. The singlet oxygen quantum yield (ΦΔ) values for 1and 2were ∼0.6 signifying their photosensitizing ability. They were remarkably photodynamic therapy (PDT) active in red light showing significant red light-induced cytotoxicity in cervical HeLa, lung cancer A549, and breast cancer MCF-7 cells (IC50: 2.3–24.7 μM in light) with negligible dark toxicity (IC50> 100 μM). A significant enhancement in cellular uptake was observed for 2having glucose-appended terpyridine ligand compared to 1. The confocal microscopy showed significant mitochondrial localization of the complexes as evidenced from the JC-1 assay. The complexes released the photoactive R-BODIPY ligand upon red light-irradiation as evidenced from the mass and 1H NMR spectral studies. Complex 2is remarkable in satisfying the essential requirements of targeted PDT in red light.

The in situsolvothermal conversion of metal–organic gels (MOGs) to crystalline metal–organic frameworks (MOFs) represents a versatile and ingenious strategy that has been employed for the synthesis of MOF materials with specific morphologies, high yield, and improved functional properties. Herein, we have adopted an in situsolvothermal conversion of bimetallic MOGs to crystalline bimetallic MOFs with the aim of introducing a redox-active metal heterogeneity into the monometallic counterpart. The formation of bimetallic NiZn-MOFand CoZn-MOFviain situsolvothermal sol–gel–crystal and sol–crystal transformation is found to depend on the solvent systems used. The sol-to-gel-to-crystal transformation of NiZn-MOFviathe formation of NiZn-MOGis found to occur through the gradual disruption of gel fibers leading to subsequent formation of microcrystals and single crystals of NiZn-MOF. These bimetallic MOFs and MOGs serve as promising electrocatalysts for oxygen reduction reaction (ORR) with an excellent methanol tolerance property, which can be attributed to the enhanced mass and charge transfer, higher oxygen vacancies, and bimetallic synergistic interactions among the heterometals. This work demonstrates a convenient strategy for producing bimetallic MOGs to MOFs through the introduction of a redox-active metal heterogeneity in the inorganic hybrid functional materials for fundamental and applied research. Our results connect MOGs and MOFs which have been regarded as having opposite physical states, that is, soft vs hard, and provide promising structural correlation between MOGs and MOFs at the molecular level.

Monofunctional platinum(II) complexes of formulation cis-[Pt(NH3)2(L)Cl](NO3), where L is an imidazole base conjugated to 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) with emissive (L1in 1) and nonemissive (L2in 2) moieties were prepared and characterized, and their singlet oxygen-mediated photoinduced cytotoxicity was studied. The 1-methylimidazole (1-MeIm) complex 3was prepared as a control and for structural characterization by X-ray crystallography. Complexes 1and 2showed strong visible absorption bands at 500 nm (ε = 2.7 × 104M–1cm–1) and 540 nm (1.4 × 104M–1cm–1). Complex 1is emissive with a band at 510 nm (ΦF= 0.09) in 1% dimethyl sulfoxide/Dulbecco’s Modified Eagle’s Medium (pH 7.2). Singlet oxygen generation upon photoirradiation with visible light (400–700 nm) was evidenced from 1,3-diphenylisobenzofuran titration experiments showing significant photosensitizing ability of the BODIPY complexes. Both 1and 2were remarkably photocytotoxic in visible light (400–700 nm, 10 J cm–2) in skin keratinocyte HaCaT and breast cancer MCF-7 cells giving IC50values in nanomolar concentration. The complexes were, however, essentially nontoxic to the cells in the dark (IC50> 80 μM). Complex 2having a diiodo-BODIPY unit is nonemissive but an efficient photosensitizer with high singlet oxygen generation ability in visible light (400–700 nm). Confocal microscopy using the emissive complex 1showed significant mitochondrial localization of the complex. Cell death via apoptotic pathway was observed from the Annexin-V-FITC/PI assay. The formation of Pt-DNA adducts was evidenced from the binding experiments of the complexes 1and 2with 9-ethylguanine as a model nucleobase from 1H NMR and mass spectral studies.

The partially fluorinated metal–organic frameworks (F-MOFs) have been constructed from 3-fluoro-4-pyridinecarboxylic acid and trans-3-fluoro-4-pyridineacrylic acid linkers using Mn2+, Co2+, and Cd2+metals via the solvothermal method, which show isostructural isomerism with their nonfluorinated counterparts synthesized using 4-pyridinecarboxylic acid and trans-4-pyridineacrylic acid, respectively. The simultaneous effect of partial fluorination and isoreticulation on structure and H2adsorption has been studied systematically in isostructural nonfluorinated and partially fluorinated MOFs, which shows that the increment in the hydrogen uptake properties in F-MOFs is not a universal phenomenon but is rather system-specific and changes from one system to another.

Ternary cobalt(III) complexes of curcumin (Hcur) and mitocurcumin [Hmitocur, a dicationic bis(triphenylphosphonium) derivative of curcumin] having a tetradentate phenolate-based ligand (H2L), namely, [Co(cur)(L)] (1) and [Co(mitocur)(L)]Cl2(2), were prepared and structurally characterized, and their photoinduced cytotoxicity was studied. The diamagnetic cobalt(III) complexes show an irreversible Co(III)–Co(II) redox response and a quasireversible curcuminoid-based reduction near −1.45 and −1.74 V SCE, respectively, in DMF/0.1 M [nBu4N](ClO4). The complexes exhibit a curcumin/mitocurcumin-based absorption band near 420 nm. Complex 1was structurally characterized by X-ray crystallography. The structure contains the metal in a CoN2O4distorted octahedral coordination arrangement with curcumin binding to the metal in its enolic form. Binding to cobalt(III) increases the hydrolytic stability of curcumin. Complex 2, having a dicationic curcuminoid, shows significant cellular uptake and photoinduced cytotoxicity compared to its curcumin analogue 1. The dicationic cobalt(III) complex 2has significantly better cellular uptake and bioactivity than the neutral species 1. Complex 2with mitochondrial localization releases the mitocurcumin dye upon exposure to visible light (400–700 nm) in human breast cancer MCF-7 cells through photoreduction of cobalt(III) to cobalt(II). Complex 2displays a remarkable photodynamic therapy (PDT) effect, giving an IC50value of ∼3.9 μM in visible light (400–700 nm) in MCF-7 cells while being much less toxic in the dark (>50 μM). The released mitocurcumin acts as a phototoxin, generating intracellular reactive oxygen species (ROSs). The overall process leads to light-controlled delivery of a curcuminoid (mitocur) into the tumor cells while the dye alone suffers from hydrolytic instability and poor bioavailability.