The photochemical and thermal synthesis of a series of [Ru(tpy)(phen)L] 2ϩ complexes where terpy = 2,2Ј:6Ј,2Љterpyridine (terpy) or 4-(3,5-di-tert-butyl)phenyl-2,2Ј;6Ј,2Љ-terpyridine (terpy*), phen = 1,10-phenanthroline and L monodentate ligands such as Cl Ϫ , NC Ϫ , CH 3 CN, pyridine, isoquinoline (iq), 4-dimethylaminopyridine (dmap), 4-(4Ј-methylpyridinium)pyridine (mqt), phenothiazine (ptz), 3,5-lutidine(lut) and H 2 O are described. The complexes have been characterized by 1 H (COSY and ROESY) NMR spectroscopy, mass spectrometry (FAB and ES-MS), cyclic voltammetry, UV-vis absorption and emission spectroscopy and single-crystal X-ray diffraction. Photochemical experiments have shown that the ligands L can be photochemically expelled and replaced by CH 3 CN molecules used as solvent. This type of ligand interchange occurs efficiently and very selectively. The reaction has the potential to be applied to a wide range of entering ligands (thioethers, ethers, pyridines, sulfoxides, nitriles, amides) and indicates the high stability of the Ru(terpy)(phen) core under the irradiation conditions.

A ruthenium(II) complex containing a 1,10-phenanthroline unit and a terpyridine fragment covalently linked to a benzonitrile group has been synthesised; coordination and decoordination of the benzonitrile group can be induced thermally and photochemically respectively, in an acetone-water mixture.

The present work completes and extends our previous reports on the determination of the magnetic ground state and on the strength of the through bond exchange coupling within series of biradicals. This knowledge was subsequently exploited for the analysis of the magnetic interactions in their crystals. We report here the studies of series of triradicals incorporating alpha-nitronyl nitroxides (NN) or alpha-imino nitroxides (IN) as terminal radical fragments connected through a m-phenylene coupling unit in one case and a phenyl acetylene unit in other case. Tetraradical derivatives have also been studied. The studies of isolated molecules (EPR in solution and DFT calculations) allow the assessment of the magnetic interactions through the magnetic coupling unit. All triradical derivatives are found to exhibit a quartet ground state, whereas a singlet ground state is determined for the tetraradical. This last result reinforces previous findings that the singlet ground state is favoured in related biradicals involving similar m-phenylene couplers. Moreover, the through bond magnetic exchange coupling for the ortho-meta connectivity could be demonstrated as being ferromagnetic, thus ascertaining our previous hypotheses. The magnetic properties of the triradicals and tetraradicals in their solid state have been rationalized by using a previously proposed methodology, allowing to identify the most relevant magnetic pathways.

The preparation of several covalently linked [6]-helicene-porphyrins is reported. A fused [6]-helicene-porphyrin π-extended aromatic system was isolated, the enantiomers separated and the chiroptical properties determined. The oxidative cyclodehydrogenation proved to...