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The effects of increasing protonation upon two [ 14]annulene dianions prepared by reaction of LiCH 3  with 5,14-dihydro-6,8,15,17-tetramethyldibenzo[b,i][l,4,8,l l]tetraazacyclotetradecine (IIIb) and 5,14-dihydro-6,17-dimethyl-8,15-diphenyldibenzo[b,i][l,4,8,l 1 ]tetraazacyclotetradecine (IIIc) have been studied by  1 H,  13 C NMR and UV-VIS spectroscopy in solution. The crystal structures of the diprotonated macrocycle IIIb x 2 HPF 6  (lIb) and of the neutral macrocycle IIIc have been determined by X-ray diffraction. For lIb, the crystal system is monoclinic with a space group of P2 1 /n: a = 12.019(3), b = 13.864(6), c = 33.547(9) Å, β = 99.82(2)°, Z = 8 . The final R factor is 0.083 for 5520 observed reflections (745 variables). For IIIc, the crystal system is triclinic with a space group of P1̄: a = 9.923(8), b = 11.633(9), c = 14.318(12) Å, ct = 110.50(6)°, β = 98.86(7)°, 7 = 103.12(6)°, Z = 2. The final R factor is 0.081 for 2174 observed reflections and 191 variables. Comparison of these structural data together with those obtained from the literature for the deprotonated macrocycle IVb and a wide variety of substituted [ 14]annule derivatives allows for the first time a discussion of protonation effects upon the highly π-conjugated pentadiimidato moiety. Additional information is derived from NMR and UV-VIS data.

zeitschrift für naturforschung b

Spektroskopische und strukturelle Aspekte der Protonierung von Tetraaza[14]annulen-Dianionen / Spectroscopic and Structural Aspects of the Protonation of Tetraaza[14]annulene Dianions