THE NEW TETRAFUNCTIONAL PI-ACCEPTOR LIGAND 3,6-BIS(2'-PYRIMIDYL)-1,2,4,5-TETRAZINE (BMTZ) - DIRUTHENIUM COMPLEXES OF BMTZ AND OF ITS 1,4-DIHYDRO FORM

Synthesis, physical properties and the coordination with two [Ru(bpy)( 2)](2+) complex fragments are described for 3,6-bis(2'-pyrimidyl)-1,2, 4,5-tetrazine (bmtz), the first compact ligand which offers four equiv alent a-diimine chelate sites. Spectroelectrochemistry of intensely bl ue [(mu-bmtz)[Ru(bpy)(2)](2)](n+), n = 4, reveals a very facile reduct ion (n = 3) at -0.40 V vs. FeCp(2)(+/0) and a metal oxidation (n = 5) at +1.18 V to a diruthenium(II/III) mixed-valent form which exhibits a n intervalence transfer absorption at 1490 nm. The corresponding compl ex [(mu-H(2)bmtz)[RU(bpy)(2)](2)](4+) with the 1,4-dihydro form H(2)bm tz of the tetrafunctional ligand is oxidized in two steps at 0.58 and 1.07 V vs. FeCp(2)(+/0).