Fe(II), Ru(II) and Re(I) complexes of endotopic, sterically non-hindering, U-shaped 8,8'-disubstituted-3,3'-biisoquinoline ligands: syntheses and spectroscopic properties.
The redox behaviour, optical-absorption spectra and emission properties of U-shaped and elongated disubstituted biisoquinoline ligands and of derived octahedral Fe(ii), Ru(ii), and Re(i) complexes are reported. The ligands are 8,8'-dichloro-3,3'-biisoquinoline (1), 8,8'-dianisyl-3,3'-biisoquinoline (2), and 8,8'-di(phenylanisyl)-3,3'-biisoquinoline (3), and the complexes are [Fe(3)(3)](2+), [Fe(2)(3)](2+), [Ru(1)(phen)(2)](2+), [Ru(2)(3)](2+), [Ru(3)(3)](2+), [Re(2)(py)(CO)(3)](+), and [Re()(py)(CO)(3)](+). For the ligands, the optical properties as observed in dichloromethane are in line with expectations based on the predominant (1)pipi* nature of the involved excited states, with contributions at lower energies from (1)npi* and (1)ILCT (intraligand charge transfer) transitions. For all of the Fe(ii), Ru(ii), and Re(i) complexes, studied in acetonitrile, the transitions associated with the lowest-energy absorption band are of (1)MLCT (metal-to-ligand charge transfer) nature. The emission properties, as observed at room temperature and at 77 K, can be described as follows: (i) the Fe(ii) complexes do not emit, either at room temperature or at 77 K; (ii) the room-temperature emission of the Ru(ii) complexes (phi(em) > 10(-3), tau in the micros range) is of mixed (3)MLCT/(3)LC character (and similarly at 77 K); and (iii) the room-temperature emission of the Re(i) complexes (phi(em) approximately 3 x 10(-3), tau < 1 ns) is of (3)MLCT character and becomes of (3)LC (ligand-centered) character (tau in the ms time scale) at 77 K. The interplay of the involved excited states in determining the luminescence output is examined.
Ventura
Barbara
B
Istituto per la Sintesi Organica e la Fotoreattività, Consiglio Nazionale delle Ricerche, Via P. Gobetti 101, 40129, Bologna, Italy. bventura@isof.cnr.it
Barigelletti
Francesco
F
Durola
Fabien
F
Flamigni
Lucia
L
Sauvage
Jean-Pierre
JP
Wenger
Oliver S
OS