An efficient preparation and characteristic properties of tetramethyl 3,3 ',3 '',3 '' (p-quinodimethane-7,7,8,8-tetrayl) tetraazulene-1,1 ',1 '',1 ''-tetracarboxylate

Reaction of methyl 1-azulenecarboxylate (1) with a 0.25 molar amount of ter ephthalaldehyde in acetic acid in the presence of hydrochloric acid at room temperature (25 degrees C) for 2 h under acrobic conditions gives tetramet hyl 3,3',3 ",3''' -[1,4-phenylenebis (methylidyne)] tetraazulene-1,1', 1 ", 1'''-tetracarboxylate (2) in a good yield (92%), which upon oxidation with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) in chloroform quantitatively affords the title compound 3 as the first example of 7,7,8,8-tetra (1-azule nyl)-p-quinodimethane derivatives. Structures of these products were establ ished on the basis of their spectroscopic data (UV/VIS, IRI MS,H-1- and C-1 3-NMR). A plausible reaction pathway for the formation of those compounds i s discussed. The characteristic properties (i.e., TGA/DTA and CV/DPV) are a lso described for compound 3, which upon reaction with electron accepters [ i.e., tetracyanoethylene (TCNE), 7,7,8,8-tetra (1-azulenyl)-p-quinodimethan e (TCNQ), and DDQ] in dichloromethane rapidly gives the corresponding charg e transfer (CT) complexes. Along with these data, a result of the semiempir ical molecular orbital calculation (WinMOPAC V2.0, the semiempirical Hamilt onian: AM1) for compound 3 is shown.