Project description:A series of ruthenium complexes with chloro-substituted bidentate ligands, proximal-[Ru(tpy)(Cl-pyqu)L] n+ [n = 1 for L = Cl, and n = 2 for L = OH2, tpy = 2,2';6',2''-terpyridine, pyqu = 2-(2'-pyridyl)quinoline] were synthesized and their reversible photoisomerizations and thermal isomerizations were investigated experimentally. The crystal structures of the complexes indicated that introduction of a chloro substituent at the 4- or 4'-position of the pyqu ligand did not change the structure around the metal center from that of the non-substituted complex, proximal-[Ru(tpy)(pyqu)L] n+. In contrast, the 6'-substituted complexes had sterically hindered environments around the metal center. The ruthenium aqua complexes showed reversible photoisomerization between the proximal and distal isomers. The quantum yield for photoisomerization of the 6'-substituted ruthenium aqua complex was almost twice as large as those of the other derivatives. This is explained by weakening of the ligand field on the ruthenium center by introduction of a chloro substituent at the 6'-position. Thermal back isomerization from the distal isomer to the proximal one was observed for the 6'-substituted complex, but such reactions were not observed for the other derivatives. The steric hindrance in the 6'-substituted aqua complex enhanced both thermal isomerization and photoisomerization.
Project description:Difluoroboron β-diketonate (BF2bdk) compounds show environment-sensitive optical properties in solution, aggregation-induced emission (AIE) and multi-stimuli responsive fluorescence switching in the solid state. Here, a series of 4-azepane-substituted β-diketone (bdk) ligands (L-H, L-OMe, L-Br) and their corresponding difluoroboron dyes (D-H, D-OMe, D-Br) were synthesized, and various responsive fluorescence properties of the compounds were studied, including solvatochromism, viscochromism, AIE, mechanochromic luminescence (ML) and halochromism. Compared to the β-diketones, the boron complexes exhibited higher extinction coefficients but lower quantum yields, and red-shifted absorption and emission in CH2Cl2. Computational studies showed that intramolecular charge transfer (ICT) dominated rather than π-π* transitions in all the compounds regardless of boron coordination. In solution, all the bdk ligands and boron dyes showed red-shifted emission in more polar solvents and increased fluorescence intensity in more viscous media. Upon aggregation, the emission of the β-diketones was quenched, however, the boronated dyes showed increased emission, indicative of AIE. Solid-state emission properties, ML and halochromism, were investigated on spin cast films. For ML, smearing caused a bathochromic emission shift for L-Br, and powder X-ray diffraction (XRD) patterns showed that the "as spun" and thermally annealed states were more crystalline and the smeared state was amorphous. No obvious ML emission shift was observed for L-H or L-OMe, and the boronated dyes were not mechano-active. Trifluoroacetic acid (TFA) and triethylamine (TEA) vapors were used to study halochromism. Large hypsochromic emission shifts were observed for all the compounds after TFA vapor was applied, and reversible fluorescence switching was achieved using the acid/base pair.
Project description:Platinum-based chemotherapy is the first-line treatment for different cancer types, and in particular, for malignant pleural mesothelioma patients (a tumor histotype with urgent medical needs). Herein, a strategy is presented to stabilize, transport, and intracellularly release a platinumIV (PtIV ) prodrug using a breakable nanocarrier. Its reduction, and therefore activation as an anticancer drug, is promoted by the presence of glutathione in neoplastic cells that also causes the destruction of the carrier. The nanocage presents a single internal cavity in which the hydrophobic complex (Pt(dach)Cl2 (OH)2 ), (dach = R,R-diaminocyclohexane) is encapsulated. The in vitro uptake and the internalization kinetics in cancer model cells are evaluated and, using flow cytometry analysis, the successful release and activation of the Pt-based drug inside cancer cells are demonstrated. The in vitro findings are confirmed by the in vivo experiments on a mice model obtained by xenografting MPM487, a patient-derived malignant pleural mesothelioma. MPM487 confirms the well-known resistance of malignant pleural mesothelioma to cisplatin treatment while an interesting 50% reduction of tumor growth is observed when mice are treated with the PtIV , entrapped in the nanocages, at an equivalent dose of the platinum complex.
Project description:Two bis-tridentate Os(II) compounds based on a heteroditopic terpyridine-bipyridine-type ligand were synthesized, and their photophysical properties were thoroughly studied. The compounds exhibit strong spin-allowed 1MLCT bands in the visible domain (489-521 nm) as well as weak 1GS to 3MLCT bands within the 668-815 nm domain. The compounds display strong luminescence from the 3MLCT state in the near-infrared domain (728-780 nm) at room temperature having lifetimes in the range of 20.0-171.0 ns. After coordination of [Os(tpy-PhCH3/H2pbbzim)2]2+ unit to the terpyridine site of tpy-Hbzim-dipy, the complexes offer vacant pyridine-imidazole motifs for interacting with cationic and anionic guests. Consequently, photophysical properties of the compounds were tuned to a great extent upon interaction with selected cations, anions, pH, as well as protons. Anion-induced alteration of the ground- and excited-state properties of the compound lead to recognition of specific anions in solution. Significant change in the optical spectral behaviors as well as switching of emission spectral properties of the compounds was done in the NIR region upon treating with anions, cations, protons, and solvents (dichloromethane, acetonitrile, methanol, dimethylsulfoxide, and water). Moreover, the optical outputs in response to external stimuli were used to demonstrate binary functions of two-input IMPLICATION, NOR, and XNOR logic gates.
Project description:The need for smart materials in the area of biotechnology has fueled the development of numerous stimuli-responsive polymers. Many of these polymers are responsive to pH, light, temperature, or oxidative stress, and yet very few are responsive toward multiple stimuli. Here we report on the synthesis of a novel dual-stimuli-responsive poly(ethylene glycol)-based polymer capable of changing its hydrophilic properties upon treatment with UV light (exogenous stimulus) and markers of oxidative stress (endogenous stimulus). From this polymer, smart microparticles and fibers were fabricated and their responses to either stimulus separately and in conjunction were examined. Comparison of the degradation kinetics demonstrated that the polymer became water-soluble only after both oxidation and irradiation with UV light, which resulted in selective degradation of the corresponding particles. Furthermore, in vitro experiments demonstrated successful uptake of these particles by Raw 264.7 cells. Such dual-stimuli-responsive particles could have potential applications in drug delivery, imaging, and tissue engineering.
Project description:Organometallic ruthenium(II) complexes [(η⁶-arene)Ru(en)Cl][PF₆] (arene = benzene (1), p-cymene (2), indane (3), and biphenyl (4); en = ethylenediamine) are promising anticancer drug candidates both in vitro and in vivo. In this paper, the interactions between ruthenium(II) complexes and 15-mer single- and double-stranded oligodeoxynucleotides (ODNs) were thermodynamically investigated using high performance liquid chromatography (HPLC) and electrospray ionization mass spectroscopy (ESI-MS). All of the complexes bind preferentially to G₈ on the single strand 5'-CTCTCTT₇G₈T₉CTTCTC-3' (I), with complex 4 containing the most hydrophobic ligand as the most reactive one. To the analogs of I (changing T₇ and/or T₉ to A and/or C), complex 4 shows a decreasing affinity to the G₈ site in the following order: -AG₈T- (K: 5.74 × 10⁴ M-1) > -CG₈C- > -TG₈A- > -AG₈A- > -AG₈C- > -TG₈T- (I) ≈ -CG₈A- (K: 2.81 × 10⁴ M-1). In the complementary strand of I, the G bases in the middle region are favored for ruthenation over guanine (G) bases in the end of oligodeoxynucleotides (ODNs). These results indicate that both the flanking bases (or base sequences) and the arene ligands play important roles in determining the binding preference, and the base- and sequence-selectivity, of ruthenium complex in binding to the ODNs.
Project description:This study presents the development of a β-hairpin (tryptophan zipper, Trpzip)-based molecular tweezer (MT) that can control the folding and binding of α-helical peptides. When an α-helix isolated from the p53 protein was conjugated with Trpzip in an optimized macrocyclic structure, the folded β-hairpin stabilized the helix conformation through the side chain-to-side chain stapling strategy, which notably enhanced target (hDM2) affinity of the peptide. On the other hand, the helicity and binding affinity were significantly reduced when the hairpin was unfolded by a redox stimulus. This stimulus-responsive property was translated into the effective capture and release of model multivalent biomaterials, hDM2-gold nanoparticle conjugates. Since numerous protein interactions are mediated by α-helical peptides, these results suggest that the β-hairpin-based MT holds great potential to be utilized in various biomedical applications, such as protein interaction inhibition and cancer biomarker (e.g., circulating tumor cells and exosomes) detection.
Project description:In this work, we report a series of dinuclear Zn(ii) complexes and their corresponding catalytic properties for a transesterification reaction. We show that the structures and catalytic activity of the complexes are strongly dependent on their molecular structures surrounding the metal centres. The use of halides yields a series of [Zn2X4L] (X = Cl, Br, and I) complexes with low catalytic activity because of the fully saturated coordination environment, whereas Zn(ClO4)2 results in two isomeric [ZnL] n 1D coordination polymers with efficient catalytic properties, despite being susceptible to structural rearrangement and consequent changes in catalytic activity over time. The response to chemical stimuli to trigger anion exchange allows for switching on/off the systems' catalytic activity, simultaneously recovering the catalytic effect upon degradation and thus reconstructing the coordination environment of the 1D polymer.
Project description:We report an approach to rotaxanes in which the metal ion of a cyclometallated PtII luminophore is embedded in the space created by the mechanical bond. Our results show that the interlocked ligand environment stabilises a normally labile PtII-triazole bond against displacement by competing ligands and that the crowded environment of the mechanical bond retards oxidation of the PtII centre, without perturbing the photophysical properties of the complex. When an additional pyridyl binding site is included in the axle, the luminescence of the PtII centre is quenched, an effect that can be selectively reversed by the binding of AgI. Our results suggest that readily available interlocked metal-based phosphors can be designed to be stimuli responsive and have advantages as stabilised triplet harvesting dopants for device applications.
Project description:Rotaxanes and molecular knots exhibit particular properties resulting from the presence of a mechanical bond within their structure that maintains the molecular components interlocked in a permanent manner. On the other hand, the disassembly of the interlocked architecture through the breakdown of the mechanical bond can activate properties which are masked in the parent compound. Herein, we present the development of stimuli-responsive CuI -complexed [2]catenanes as OFF/ON catalysts for the copper-catalyzed alkyne-azide cycloaddition (CuAAC) reaction. The encapsulation of the CuI ion inside the [2]catenanes inhibits its ability to catalyze the formation of triazoles. In contrast, the controlled opening of the two macrocycles induces the breaking of the mechanical bond, thereby restoring the catalytic activity of the CuI ion for the CuAAC reaction. Such OFF/ON catalysts can be involved in signal amplification processes with various potential applications.