The New Tetrafunctional π 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 equivalent α-diimine chelate sites. Spectroelectrochemistry of intensely blue {(μ-bmtz)[Ru(bpy) 2 ] 2 } n+ , n = 4, reveals a very facile reduction (n = 3) at -0.40 V vs. FeCp 2 +/o and a metal oxidation (n = 5) at + 1.18 V to a diruthenium(II/III) mixed-valent form which exhibits an intervalence transfer absorption at 1490 nm. The corresponding complex {(μ-H 2 bmtz)[Ru(bpy) 2 ] 2 } 4+ with the 1,4-dihydro form H 2 bmtz of the tetrafunctional ligand is oxidized in two steps at 0.58 and 1.07 V vs. FeCp 2 +/o .