Photoinduced charge transport over branched conjugation pathways: donor-acceptor substituted 1,1-diphenylethene and 2,3-diphenylbutadiene.

Photoinduced charge transport in 1,1-diphenylethene and 2,3-diphenylbutadiene functionalized with an electron donating dimethylamino group and an electron accepting cyano group is reported. UV-spectroscopy reveals that in these compounds, which incorporate a cross-conjugated spacer, a direct charge transfer transition is possible. It is shown by application of the generalized Mulliken-Hush approach that introduction of an additional branching point in the π-electron spacer (i.e., when going from the 1,1-diphenylethene to the 2,3-diphenylbutadiene) leads to only a moderate reduction (68-92%) of the electronic coupling between the ground and the charge separated state. The σ-electron system is however likely to be dominant in the photoinduced charge separation process.

Pseudomerohedrally twinned crystal structure of 2,3-diphenylbuta-1,3-diene.

The title compound, C16H14, is twinned by reticular pseudomerohedry of twin index 2. The primitive monoclinic cell of the single crystal can be transformed into a B-centred pseudo-orthorhombic supercell with a fourfold volume. The twofold twin operation about the reciprocal a* axis of the primitive monoclinic cell is co-directional with the approximate C2 axis of the molecule and a symmetry element of the orthorhombic supercell. A tentative twin domain model is proposed.

Photoinduced charge separation in a donor-acceptor functionalized 2,3-diphenylbutadiene: charge transport over a doubly bifurcated pi-spacer.

By studying photoinduced charge transfer processes in 2-(4-cyanophenyl)-3-(4-N,N-dimethylaminophenyl)-1,3-butadiene it is shown that insertion of branching points in a pi-conjugated pathway has a relatively small effect on the donor-acceptor interaction.