Synthesis, spectral and excited state energy transfer studies on new supramolecular ruthenium polypyridyl triads with octakis(methylthio)tetraazaporphyrinzinc(II)

New bichromophoric di- and trinuclear complexes were synthesized through coordinate strapping of one or two (bpy)2RuII/(phen)2RuII/Cp(PPh3)RuII moieties to [Zn{(MeS)8TAP}] 1, core. Thus five new complexes of the type [Zn{(MeS)8TAP}{Ru(bpy)2}][PF6]22, bent and linear [Zn{(MeS)8TAP}{Ru(bpy)2}{Ru(phen)2}][PF6]43 and 4, bent and linear [Zn{(MeS)8TAP}{Ru(bpy)2}{RuCp(PPh3)}][PF6]35 and 6, were synthesized and characterized using IR, 1H NMR, UV-visible, and mass spectral data. The trinuclear complexes 3-6 possessed bent (κ4-S2,S3,S7,S8)[RuII]2 and linear (κ4-S2,S3,S12,S13)[RuII]2 arrangements of the peripheral metallo-chromophore units. Unlike the two reversible reduction waves in complex 1 observed at E1/2 −0.34 and −0.60 V, only one reversible reduction wave was observed, between E1/2 −0.56 to −0.58 V vs. Ag/AgCl, in the di- and trinuclear complexes 2-6. Also in the anodic scans, the dinuclear complexes 2, as well as linear trinuclear complexes 4 and 6, exhibited two successive one electron oxidations, the first at E1/2 ∼ 0.62 V due to Ru(II)/Ru(III) process and second at E1/2 ∼ 1.16 V vs. Ag/AgCl due to {(MeS)8TAP}/{(MeS)8TAP}+ processes, while the bent trinuclear complexes 3 and 5 exhibited three successive one electron oxidations, i.e. one additional oxidation wave at E1/2 0.88 and 0.90 V vs. Ag/AgCl, respectively. In the fluorescence measurements, Soret excitation led to strong [Zn{(MeS)8TAP}] centered S2 emission together with a rapid intercomponent excitation energy transfer (k 107-108 s−1) to peripheral Ru(II) unit that showed emission maxima between 535 and 545 nm. Lifetime analysis showed that Ru(II)∗ emission predominated in the dinuclear complex 2, but its contribution dropped significantly upon formation of the trinuclear complexes, which has been explained in terms of relative variation of the LUMO energies of the linked chromophores in the excited states.