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

摘要

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(2)3]~(2+),[Fe(3)3]~(2+),[Ru(l)(phen)2]~(2+),[Ru(2)3]~(2+),[Ru(3)3]~(2+),[Re(2)(py)(CO)3]~+,and[Re(3)(py)(CO)3]~+.For the ligands,the optical properties as observed in dichloromethane are in line with expectations based on the predominant 1 pi pi* nature of the involved excited states,with contributions at lower energies from 1 n pi* and 1ILCT(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 mu s range)is of mixed 3MLCT/3LC character(and similarly at 77 K);and(iii)the room-temperature emission of the Re(I)complexes(phi_(em)~3X10~(-3),tau<1 ns)is of 3MLCT character and becomes of 3LC(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.