title: Intramolecular Energy and Electron Transfer within a Diazaperopyrenium-Based Cyclophane.
abstract: Molecules capable of performing highly efficient energy transfer and ultrafast photoinduced electron transfer in well-defined multichromophoric structures are indispensable to the development of artificial photofunctional systems. Herein, we report on the synthesis, characterization, and photophysical properties of a rationally designed multichromophoric tetracationic cyclophane, DAPPBox4+, containing a diazaperopyrenium (DAPP2+) unit and an extended viologen (ExBIPY2+) unit, which are linked together by two p-xylylene bridges. Both1H NMR spectroscopy and single-crystal X-ray diffraction analysis confirm the formation of an asymmetric, rigid, box-like cyclophane, DAPPBox4+. The solid-state superstructure of this cyclophane reveals a herringbone-type packing motif, leading to two types of π···π interactions: (i) between the ExBIPY2+unit and the DAPP2+unit (π···π distance of 3.7 Å) in the adjacent parallel cyclophane, as well as (ii) between the ExBIPY2+unit (π···π distance of 3.2 Å) and phenylene ring in the closest orthogonal cyclophane. Moreover, the solution-phase photophysical properties of this cyclophane have been investigated by both steady-state and time-resolved absorption and emission spectroscopies. Upon photoexcitation of DAPPBox4+at 330 nm, rapid and quantitative intramolecular energy transfer occurs from the1*ExBIPY2+unit to the DAPP2+unit in 0.5 ps to yield1*DAPP2+. The same excitation wavelength simultaneously populates a higher excited state of1*DAPP2+which then undergoes ultrafast intramolecular electron transfer from1*DAPP2+to ExBIPY2+to yield the DAPP3+•-ExBIPY+•radical ion pair in τ = 1.5 ps. Selective excitation of DAPP2+at 505 nm populates a lower excited state where electron transfer is kinetically unfavorable.
authors.forename: Xirui
authors.initials: X
authors.lastname: Gong
authors.forename: Ryan M
authors.identifier: 0000-0002-5108-0261
authors.initials: RM
authors.lastname: Young
authors.forename: Karel J
authors.initials: KJ
authors.lastname: Hartlieb
authors.forename: Claire
authors.initials: C
authors.lastname: Miller
authors.forename: Yilei
authors.initials: Y
authors.lastname: Wu
authors.affiliation: Materials and Process Simulation Center, California Institute of Technology , Pasadena, California 91125, United States.
authors.forename: Hai
authors.identifier: 0000-0001-9399-1584
authors.initials: H
authors.lastname: Xiao
authors.forename: Peng
authors.identifier: 0000-0002-4273-4577
authors.initials: P
authors.lastname: Li
authors.forename: Nema
authors.initials: N
authors.lastname: Hafezi
authors.forename: Jiawang
authors.identifier: 0000-0002-2399-0030
authors.initials: J
authors.lastname: Zhou
authors.forename: Lin
authors.initials: L
authors.lastname: Ma
authors.affiliation: Materials and Process Simulation Center, California Institute of Technology , Pasadena, California 91125, United States.
authors.forename: Tao
authors.identifier: 0000-0003-4830-177X
authors.initials: T
authors.lastname: Cheng
authors.affiliation: Materials and Process Simulation Center, California Institute of Technology , Pasadena, California 91125, United States.
authors.forename: William A
authors.identifier: 0000-0003-0097-5716
authors.initials: WA
authors.lastname: Goddard
authors.affiliation: Department of Chemistry, Faculty of Science, King Abdulaziz University , Jeddah 22254, Saudi Arabia.
authors.forename: Omar K
authors.identifier: 0000-0002-9904-9845
authors.initials: OK
authors.lastname: Farha
authors.forename: Joseph T
authors.identifier: 0000-0003-3982-9812
authors.initials: JT
authors.lastname: Hupp
authors.forename: Michael R
authors.identifier: 0000-0003-2920-5440
authors.initials: MR
authors.lastname: Wasielewski
authors.forename: J Fraser
authors.identifier: 0000-0003-3161-3697
authors.initials: JF
authors.lastname: Stoddart