Permittivity Threshold and Thermodynamics of Integer Charge-Transfer Complexation for an Organic Donor-Acceptor Pair.

Molecular charge doping involves the formation of donor-acceptor charge-transfer complexes (CTCs) through integer or partial electron transfer; understanding how local chemical environment impacts complexation is important for controlling the properties of organic materials. We present steady-state and temperature-dependent spectroscopic investigations of the p-dopant 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (FTCNQ) complexed with the electron donor and hole transport material ,'-diphenyl-,'-di--tolylbenzene-1,4-diamine (MPDA). Equilibrium formation constants () were determined for donor-acceptor pairs dissolved in a series of solvents covering a range of values of permittivity.

Multiphoton Control of 6π Photocyclization via State-Dependent Reactant-Product Correlations.

Multiphoton excitation promises opportunities for opening new photochemical reaction pathways and controlling photoproduct distributions. We demonstrate photonic control of the 6π photocyclization of -terphenyl to make 4,4-dihydrotriphenylene (DHT). Using pump-repump-probe spectroscopy we show that 1 + 1' excitation to a high-lying reactant electronic state generates a metastable species characterized by a red absorption feature that accompanies a repump-induced depletion in the one-photon -dihydro product (-DHT); signatures of the new photoproduct are clearer for a structural analogue of the reactant that is sterically inhibited against one-photon cyclization.

Intramolecular Photoinduced Charge Transfer and Recombination Dynamics in Vinylarene Terminated Organosilanes.

We report on charge-transfer dynamics of newly designed acceptor-donor-acceptor organosilanes, with a specific focus on how donor-acceptor combination and local chemical environment can be used to control the lifetime for intramolecular charge-separation between silane electron donors and organic acceptors. In this work linear oligosilanes were capped with arene-vinyl end groups of variable electron-accepting strength: weak (diester vinyl), intermediate (ester,cyano vinyl), and strong (dicyanovinyl). Ultrafast transient absorption spectroscopy was used to characterize their structure-dependent charge-transfer and recombination behaviors.