Synthesis and Optical Properties of Phenanthroline‐Derived Schiff Base‐Like Dinuclear Ru^II–Ni^II Complexes

Abstract

Two phenanthroline-derived Schiff base-like ligands with a covalently linked ruthenium(II) phosphorescent unit were synthesised and converted into bimetallic Ru -Ni complexes. The optical properties were studied to examine a possible photoluminescence quenching through a nonradiative energy-transfer upon a coordination-induced spin-state switch (CISSS) at the nickel(II) centre. Therefore, the metalloligands and the nickel(II) complexes were studied using UV/Vis absorbance, steady-state, and time-resolved emission spectroscopy in solutions of MeCN and pyridine. It is demonstrated that the nature of the bridging ligand between the ruthenium(II) donor and the nickel(II) acceptor strongly influences the photophysical behaviour upon CISSS. For the complex with a phenazine bridge, photoluminescence quenching is observed in the presence of a paramagnetic nickel(II) centre.

Spin-Crossover Iron(II) Coordination Polymer with Fluorescent Properties: Correlation between Emission Properties and Spin State

“…It also increases the robustness with respect to possible photobleaching, as the latter tends to quench the entire emission of the molecule, thus leaving the intensity ratio of the peaks of the overall sample largely unaffected. In order to verify the proposed hypothesis regarding the origin of the luminescence features, further, more detailed measurements as well as quantum chemical calculations and the synthesis of further slightly modified examples are required.…”

Iron(II) Spin Crossover Polymers of Planar N2O2 Schiff Base Templates and 4,4’-bis(pyridyl)urea Bridges

“…Please note, the carbon value obtained in the CHN analysis is too low due to incomplete combustion. The same difficulties were encountered for similar complexes of this ligand type with extended aromatic units [35,51,57,70].…”

Molecular Sensors Operating by a Spin‐State Change in Solution: Application to Magnetic Resonance Imaging

“…In 2018, the fluorophore portion of the ligand was equipped with a Ruthenium(II)-binding phenancine unit. [57] Treatment of this dinuclear, phosphorescent Ru(II)-Ni(II) complex in acetonitrile with roughly 10 5 equivalents of pyridine switches it entirely to the hexa-coordinate paramagnetic system (S = 1, μ eff = 2.57 μ B ), also quenching the chelate's emission (of its phosphorescence). The possibility for bimodal detection is new; and will be appreciated by Life Sciences professionals in any future design performing in physiological media.…”

“…Interestingly, passage to the paramagnetic species quenched the fluorescence. In 2018, the fluorophore portion of the ligand was equipped with a Ruthenium(II)‐binding phenancine unit [57] . Treatment of this dinuclear, phosphorescent Ru(II)‐Ni(II) complex in acetonitrile with roughly 10 5 equivalents of pyridine switches it entirely to the hexa‐coordinate paramagnetic system (S=1, μ eff =2.57 μ B ), also quenching the chelate‘s emission (of its phosphorescence).…”