jp0269423_si_001.pdf (561.27 kB)
Synthesis and Excited-State Photodynamics of Perylene-Bis(Imide)-Oxochlorin Dyads. A Charge-Separation Motif
journal contribution
posted on 2003-03-20, 00:00 authored by Christine Kirmaier, Eve Hindin, Jennifer K. Schwartz, Igor V. Sazanovich, James R. Diers, Kannan Muthukumaran, Masahiko Taniguchi, David F. Bocian, Jonathan S. Lindsey, Dewey HoltenThree perylene-oxochlorin dyads have been prepared and characterized with the goal of identifying charge-injection or molecular-switching motifs for use in molecular photonics. Each dyad consists of a perylene-bis(imide) dye (PDI) joined at the 10-position of a magnesium, zinc, or free base (Fb) oxochlorin via a
diphenylethyne linker. Each dyad has been studied in both polar and nonpolar media using static and time-resolved optical spectroscopy and electrochemical techniques. Dyad PDI−MgO is an excellent charge-separation
unit in which the excited perylene (∼3.5 ps lifetime) or the excited oxochlorin (lifetimes of 0.5 ns in benzonitrile
and 1.0 ns in toluene) give rise to state PDI- MgO+ in high overall yield (>90%); the charge-separated state
has a lifetime of ≥1 ns in both toluene and benzonitrile. The pathway for generating PDI- MgO+ from the
excited perylene (PDI*) involves both hole transfer and energy transfer to the oxochlorin followed by electron
transfer from the resulting MgO* to PDI. Similar decay of PDI* by energy transfer and hole transfer is found
for dyads PDI−ZnO and PDI−FbO. However, electron-transfer quenching of the excited oxochlorin in these
two dyads either does not occur or occurs to a much lesser degree than for PDI−MgO in both polar and
nonpolar solvents. For PDI−FbO the decay of the charge-separated state occurs significantly by charge
recombination to give the excited oxochlorin, making this a good light-harvesting system even though the
early stages of the dynamics include charge separation/recombination. The observed differences in the extent
of the possible excited-state processes (energy, hole, and electron transfer) among the dyads and in polar
versus nonpolar media are consistent with the estimated energy ordering of the excited- and charge-separated
states. This study has provided a new class of arrays containing perylene accessory pigments and oxochlorin
chromophores that can be utilized for applications in light harvesting and molecular optoelectronics.