Synthesis, X-ray structure, and electrochemical oxidative coupling reactions of 1,5-and 2,6-bis(1,4-dithiafulven-6-yl)naphthalenes

Novel pi-extended tetrathiafulvalene (TTF) derivatives (12a-c, 13a-c, 15a-c ) in which the two 1,3-dithiole units are connected through a naphthalene s pacer have been prepared in high yields by Wittig-Horner olefination reacti on from dialkoxy-subsitituted diformylnaphthalenes (11a,b, 14) and differen tly substituted phosphonate esters (10a-c). The electrochemical study revea led a similar behavior for the novel electron donor molecules (12a-c, 13a-c , 15a-c) regardless of the position of the 1,3-dithiole rings on the naphth alene core. The extended donors undergo an efficient electrooxidation proce ss affording new oligomeric extended TTF species which exhibit lower oxidat ion potential values than their precursor donors. EPR experiments confirm t he presence of the cation radical derived from the oligomeric TTF vinylogue s and support an ECE process. The structural study has been carried out by X-ray analysis of 12a and semiempirical PM3 calculations and reveals a dist orted geometry from the planarity with the naphthalene moiety forming an an gle of similar to 35 degrees with the thiafulvalene rings. A good agreement was found between the experimental and calculated values, thus validating the PM3 method. The chemical oxidation of the synthesized donors (12a-c, 13 a-c, 15a-c) with strong electron accepters give rise to charge transfer com plexes (CTC) which were characterized by UV-vis, FTIR, and EPR spectroscopy .