Charge Transfer and Addition Products between Alkylated Phenazine Donors and Ethanetetracarbonitrile (TCNE): Crystal and Molecular Structure of the Dye 2,2'-(2,3,5,10-Tetrahydro-5,10-dimethylphenazine-2,3-ylidene)bis(propanedinitrile) (TMPP)

Article abstract of DOI:10.1021/ja00390a032

Mixing solution of 5,10-dimethyl-5,10-dihydrophenazine (M2P) and TCNE yields different solid reaction products with nearly 1:1 donor:acceptor stoichiometry.Without excluding air the reaction leads to an oxygen-containing intermediate of stoichiometry C19H15N5O (1).The dark green to black crystals are twinned having cell dimensions a = 14.34 Angstroem, b = 30.10 Angstroem, c = 4.17 Angstroem, β = 90.1 deg and crystallizing in the monoclinic space group P2₁/n.Violet needles of the 1:1 salt, M2P⁺TCNE^- (2), are obtained only by excluding moisture and oxygen.They crystallize in always twinned specimens in a tetragonal space group, the unit cell along the needle axis being 7.46(3) Angstroem.Lustrous (brass-like) crystals of TMPP (3) (formula C20H12N6), M_r = 336.358, d_c = 1.35 Mg*m^-3) are obtained under air and in most solvents.They crystallize in the monoclinic space group C2/c with a = 9.674(3) Angstroem, b = 19.411(8) Angstroem, c =9.603(3) Angstroem, V = 1657.4(9) Angstroem³, β = 113.20(2) deg, and Z = 4.The structure determination yielded in the final refinement an R_w index of 0.076. 3 is a condensation product of M2P and TCNE under loss of 1 mol of H2.Two rings of the former M2P molecule are planar.The ring with two "condenced" >C=(CN)2 groups is twisted.The >C=(CN)2 groups are also twisted with respect to each other and out of the "molecular" plane because of sterical hindrance.The molecules form regular stacks along the z axis with interplanar distances of 4.75(2) Angstroem.The linearly polarized strong optical reflection which causes the metallic luster is polarized perpendicular to the molecular planes, indicating appreciable intermolecular CT interactions.Corresponding products are obtained with the donors 5,10-dihydro-5,10-dimethylphenazine (E2P) and 5-methylphenazinium hexafluorophosphate (MP⁺PF6^-), thus representing a new class of thermally and chemically highly stable dyes with strong electron-donating and -withdrawing centers on one molecule.