A new tridentate ligand based on acridine has been synthetized. The central acridine heterocycle bears two pyridine coordinating units at positions 4 and 5. The terdentate 2,7-di-tert-butyl-4,5-di(pyridin-2-yl)acridine (dtdpa) was then coordinated to a ruthenium(II) cation. The corresponding homoleptic complex could only be obtained where both ligands coordinate to the ruthenium in a fac fashion. Thus, a heteroleptic compound (2) was constructed in combination with a terpyridine ligand in order to constrain the ligand to adopt a mer geometry. Such a coordination imposes a dramatic twist on the acridine heterocycle, resulting in an unexpected photophysical behavior. The electrochemical and photophysical properties of both complexes were studied, and the molecular structure of 2 was determined by X-ray diffraction. The two compounds absorb at low energy wavelengths, and a very weak luminescence is detected only for complex 2 in the near-infrared region.
A new heteroleptic ruthenium complex based on a 2,2′;6′,2′′‐terpyridine (tpy) and a thioether‐based tridentate ligand, btap (btap: 2,6‐bis(2‐thioanisyl)pyridine) was synthesized. Under visible light irradiation, this complex in solution in acetonitrile undergoes a photochemical ejection of the thioether ligand leading to [Ru(tpy)CH3CN)3]2+ and the free ligand. The reaction was monitored using NMR and UV‐Vis spectroscopies. This is very probably the first example of a tridentate ligand being expelled by the action of light.
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