Photoinduced intramolecular electron transfer in Schiff-base bridged Ruthenium(II)-quencher molecules

A series of Schiff-base bridged polypyridine ruthenium(II)-quencher [here a fter abbreviated as Ru-Q] molecules have been prepared and characterized, w here the functional groups Q were dimethylamino(-N(CH3)(2), methyloxyl(-OCH 3), hydroxyl(-OH) and nitro group(NO2). Steady state and time resolved lumi nescence measurements of these ruthenium complexes show that the luminescen ce properties of the Ru(II) MLCT excited state of Ru-OCH3 is only slightly modified from that of Ru(bpy)(3)(2+), whereas the quenchers group Q in the Ru-N(CH3)(2), Ru-OH and Ru-NO2 complexes can quench the yield and lifetime of the Ru MLCT emission. Electrochemistry measurement suggests that the que nching processes were the long-range intramolecular electron transfer reduc tive quenching for the Ru-OH and Ru-N(CH3)(2) and oxidative quenching for t he Ru-NO2, respectively. Single crystal structure analysis of the Ru-N(CH3) (2) complex revealed that the coordination geometry of the ruthenium is a s lightly distorted octahedron with four nitrogen atoms of the two bipyridine molecule and two nitrogen atoms from the L-N(CH3)(2) ligands, p-dimethylam ionbenzaldehyde 4, 5-diazafluorene-9-hydrazone. The Ru-N distances are in a greement with those in the other polybipyridine ruthenium complexes. (C) 19 98 Elsevier Science Ltd. All rights reserved.