Electron-, Proton-, and Photon-Induced Spectroscopic Changes in Chromophore-Quencher Tricarbonyl(2,2′-Bipyridine)rhenium(I) Complexes with 4,4′-Azobis(pyridine)

Photo-/Electroinduced Irreversible Isomerization of 2,2'-Azobispyridine Ligands in Arene Ruthenium(II) Complexes

Novel arene Ru^II complexes containing 2,2'-azobispyridine ligands were synthesized and characterized by using ¹ H and ¹³ C NMR spectroscopy, UV/vis spectroscopy, electrochemistry, DFT calculations and single-crystal X-ray diffraction. Z-configured complexes featuring unprecedented seven-membered chelate rings involving the nitrogen atom of both pyridines were isolated and were shown to undergo irreversible isomerization to the corresponding E-configured five-membered chelate complexes in response to light or electrochemical stimulus.

Dinuclear Rhenium Complexes with a Bridging Helicene-bis-bipyridine Ligand: Synthesis, Structure, and Photophysical and Chiroptical Properties

By attaching pyridine groups to a diaza[6]helicene, a helical, bis-ditopic, bis-N N-coordinating ligand can be accessed. Dinuclear rhenium complexes featuring this bridging ligand, of the form [{Re(CO)₃ Cl}₂ (N N-N N)], have been prepared and resolved to give enantiopure complexes. These complexes are phosphorescent in solution at room temperature under one- and two-photon excitation. Their experimental chiroptical properties (optical rotation, electronic circular dichroism and circularly polarized emission) have been measured. They show, for instance, emission dissymmetry factors of c.a. ±3x10^-3 . Quantum-chemical calculations indicate the importance of stereochemistry on the optical activity, pointing towards further design improvements in such types of complexes.

Synthesis, structure and biological evaluation of mixed ligand oxidovanadium(iv) complexes incorporating 2-(arylazo)phenolates

Synthesis and characterization of mixed ligand oxidovanadium(iv) complexes [V^IVO(L^1–4)(L^NN)] incorporating arylazo ligands: evaluation of DNA/BSA interaction and cytotoxicity activity.

Photoswitchable and pH responsive organoplatinum(ii) complexes with azopyridine ligands

Several platinum(ii) complexes with ligands containing azo groups have been prepared and structurally characterised, and their photoswitching between trans and cis azo group isomers has been studied. The azo groups in the cationic complexes [PtMe(bipy)(4-NC₅H₄-N[double bond, length as m-dash]N-4-C₆H₄X)][PF₆], X = H, OH or NMe₂, and in the dicationic complex [Pt(bipy)(4-H₂NC₆H₄-N[double bond, length as m-dash]N-C₆H₅)₂][OTf]₂ undergo trans to cis photoswitching on irradiation at 365 nm. The complex [PtMe(bipy)(4-NC₅H₄-N[double bond, length as m-dash]N-4-C₆H₄NMe)₂][PF₆] also exhibits a reversible halochromic effect on protonation to give the dicationic complex [PtMe(bipy)(4-NC₅H₄-NH[double bond, length as m-dash]N-4-C₆H₄NMe₂]²⁺. The nature of the frontier orbitals in the platinum(ii) complexes depends on the charge on the complex and on the degree of metal-ligand π-bonding.

Azobenzene-functionalized iridium(iii) triscyclometalated complexes

Photochromic triscyclometalated iridium(iii) organometallic complexes based on azobenzene-containing phenylpyridyl-type ligands.

pH luminescence switching, dihydrogen phosphate sensing, and cellular uptake of a heterobimetallic ruthenium(II)-rhenium(I) complex

A new heterobimetallic ruthenium(II)-rhenium(I) complex of [Ru(bpy)2(HL)Re(CO)3Cl](ClO4)2·6H2O (RuHLRe) {bpy = 2,2'-bipyridine and HL = 2-(4-(2,6-di(pyridin-2-yl)pyridin-4-yl)phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline} was synthesised and characterised by elemental analysis, proton nuclear magnetic resonance spectroscopy, and mass spectrometry. The ground- and excited-state acid-base properties of RuHLRe were studied using UV-Vis absorption spectrophotometric and spectrofluorimetric titrations in a 100 : 1 (v/v) Britton-Robinson buffer-CH3CN solution combined with luminescence lifetime measurements. The complex exhibited two-step separate protonation-deprotonation processes in both the ground and excited states. The complex acted as pH-induced "off-on-off" luminescence switches (I(on)/I(off) = 31.0 and 14.6), with one of the switching actions being driven by pH variations over the physiological pH range (5.3-8.0). Importantly, cellular imaging and cytotoxicity experiments demonstrated that RuHLRe rapidly and selectively illuminated the membrane of HeLa cells over fixed cells and exhibited reduced cytotoxicity at the imaging concentration compared to the Re(I)-free parent Ru(II) complex. In addition, RuHLRe acted as an efficient "turn on" emission sensor for H2PO4(-) and "turn off" emission sensor for F(-) and OAc(-).