Syntheses, characterization and structures of 2-(2-pyridyl)-4-methylcarboxyquinoline ligand and bis(2,2′-bipyridine)-2-(2-pyridyl)-4-methylcarboxyquinoline ruthenium (II) hexafluorophosphate

Crystal structure of bis(2-(3-(carboxylatomethyl-κO,O')-4-(phenylthio)- phenyl)propanoate-κO,O')bis(2,2'-dipyridyl-κN,N')dizinc(II), C54H44N4O8S2Zn2

C54H44N4O8S2Zn2, monoclinic, P21/c (no. 14), a = 13.299(4) Å, b = 12.019(3) Å, c = 15.320(4) Å, β = 93.256(4)°, V = 2444.8 Å3, Z = 2, Rgt(F) = 0.0502, wRref(F2) = 0.1430, T = 296 K.

catena-Poly[[[diaqua-sodium]-di-μ-aqua] 2-(2-pyrid-yl)quinoline-4-carboxyl-ate]

In the title compound, [Na(H₂O)₄](C₁₅H₉N₂O₂), the Na⁺ ion is coordinated by six water mol­ecules in an octa­hedral geometry. The NaO₆ octa­hedra are connected by sharing edges, forming a cationic chain along the b-axis direction. O—H⋯O and O—H⋯N hydrogen bonds link the chains and the 2-(2-pyrid­yl)quinoline-4-carboxyl­ate anions into a two-dimensional network parallel to (100).

DNA binding and cytotoxicity of ruthenium(II) and rhenium(I) complexes of 2-amino-4-phenylamino-6-(2-pyridyl)-1,3,5-triazine

[Ru(tBu2bpy)2(2-appt)](PF6)2 [1.(PF6)2, tBu2bpy = 4,4'-di-tert-butyl-2,2'-bipyridine, 2-appt = 2-amino-4-phenylamino-6-(2-pyridyl)-1,3,5-triazine] and [Re(CO)3(2-appt)Cl] (2) were prepared and characterized by X-ray crystal analysis. The binding of 1.(PF6)2 and 2 to calf thymus DNA (ct DNA) led to increases in the DNA melting temperature (Delta Tm = +12 degrees C), modest hypochromism (29% and 5% of the absorption bands at lambda max = 450 and 376 nm, respectively), and insignificant shifts in the absorption maxima. The binding constants of 1.(PF6)2 and 2 with ct DNA, as determined by absorption titration, are (8.9 +/- 0.5) x 104 and (3.6 +/- 0.1) x 104 dm3 mol-1, respectively. UV-vis absorption titration, DNA melting studies, and competition dialysis using synthetic oligonucleotides [poly(dA-dT)2 and poly(dG-dC)2] revealed that 1.(PF6)2 and 2 exhibit a binding preference for AT sequences. A modeling study on the interaction between 1 or 2 and B-DNA revealed that the minor groove is the most favored binding site and an extensive hydrogen-bonding network is formed. As determined by MTT assays, 1.(PF6)2 and 2 exhibited moderate cytotoxicities toward several human cancer cell lines (KB-3-1, HepG2, and HeLa), as well as a multi-drug-resistant cancer cell line (KB-V-1). According to confocal microscopic and flow cytometric studies, 1.(PF6)2 and 2 induced apoptosis (50-60%) in cancer cells with <5% necrosis detected.

Reversible Luminescence Switching in a Ruthenium(II) Bis(2,2‘:6‘,2‘ ‘-terpyridine)-Benzoquinone Dyad

An electroactive luminescent switch has been synthesized that comprises a hydroquinone-functionalized 2,2':6',2''-terpyridine ligand coordinated to a ruthenium(II) (4'-phenylethynyl-2,2':6',2''-terpyridine) fragment. The assembly is sufficiently rigid that the hydroquinone-chromophore distance is fixed. Excitation of the complex via the characteristic metal-to-ligand charge-transfer (MLCT) absorption band produces an excited triplet state in which the promoted electron is localized on the terpyridine ligand bearing the acetylenic group. The triplet lifetime in butyronitrile solution at room temperature is 46 +/- 3 ns but increases markedly at lower temperature. Oxidation of the hydroquinone to the corresponding benzoquinone switches on an electron-transfer process whereby the MLCT triplet donates an electron to the quinone. This reaction reduces the triplet lifetime to 190 +/- 12 ps and essentially extinguishes emission. The rate of electron transfer depends on temperature in line with classical Marcus theory, allowing calculation of the electronic coupling matrix element and the reorganization energy as being 22 cm(-1) and 0.84 eV, respectively. The switching behavior can be monitored using luminescence spectroelectrochemistry. The on/off level is set by temperature and increases as the temperature is lowered.

Telechelic poly(ε-caprolactones) with tethered mixed ligand ruthenium(II) chromophores

Well-characterized templates of polymer-forming ligands and their ruthenium tris(α,α′-diimine) initiators were utilized to divergently ring open an ε-caprolactone monomer. The same polymers were also obtained through the synthesis of quinoline and bipyridine diimine ligands incorporating poly(ε-caprolactone) (PCL) chains. These polymers contain vacant molecular recognition sites, enabling subsequent chelation of these macroligands to metal precursors. Both methods provided telechelic (ε-caprolactone) ruthenium(II)-centered polyesters of various hierarchy. Solution properties and thermal behaviour of such polyesters are described.Key words: redox polymers, poly(ε-caprolactone), telechelics, metal–polymer complexes, macroligands, ring-opening polymerization (ROP).