The use of a quinone functionality in the linkage unit of laterally bridged oligoporphyrins as aswitch for controlling electronic coupling between the termini is examined. The quinone-bridged bisporphyrinP
2TA-O
2 was synthesized by condensation of 2 equiv of the dione 2,3-dioxo-5,10,15,20-tetrakis(3,5-di-
tert-butylphenyl)chlorin with 2,3,5,6-tetraamino-1,4-benzoquinone. The electronic absorption spectra of P
2TA-O
2 and its conjugated benzenoid analogue P
2TA are measured and assigned, in conjunction with thespectra of the fragment monomers and porphyrin-bridge compounds. Band homologies and CASPT2calculations are used to make the assignments. Chemically, the dimer in one case is bridged by a through-conjugated,
-delocalized 1,4,5,8-tetraazaanthracene molecule. This is shown to display significant inter-porphyrin coupling, with an observed
difference in the exciton couplings of the B
x and B
y bands being ca.0.18 eV. However, the other dimer is bridged using a derivative in which the central ring is converted to across-conjugated,
-localized quinonoid form; this molecule displays no observable inter-porphyrin coupling.This scenario provides a paradigm for the use of molecular electronic devices in sensing, control, andhigh-capacity relatively low-speed data storage applications.