title: Synthesis and Characterization of Tetrachlorodiarylethyne-Linked Porphyrin Dimers. Effects of Linker Architecture on Intradimer Electronic Communication.
abstract: The effects of incorporating chloro groups at all ortho positions of a diphenylethyne linker that bridges the zinc and free base (Fb) components of a porphyrin dimer (ZnFbB(Cl(4))) have been investigated in detail via various static and time-resolved spectroscopic methods. The excited-state energy-transfer rate in ZnFbB(Cl(4)) ((134 ps)(-)(1)) is 5-fold slower than that in the corresponding dimer having an unsubstituted linker (ZnFbU, (24 ps)(-)(1)) but is only modestly slower than that in the dimer having o-methyl groups on the linker (ZnFbB(CH(3))(4), (115 ps)(-)(1)). The ground-state hole/electron-hopping rates in the oxidized bis-Zn analogues of all three dimers are much slower than the excited-state energy-transfer rates. There is no discernible difference between the hole/electron-hopping rates in the o-chloro- and o-methyl-substituted arrays. The similar ground- and excited-state dynamics observed for the o-chloro- and o-methyl-substituted arrays is attributed to the dominance of torsional constraints in mediating the extent of through-bond electronic communication. These constraints attenuate intradimer communication by restricting the rotation toward coplanarity of the phenyl rings of the linker and the porphyrin rings. Thus, the o-chloro groups on the linker decrease electronic communication via a steric, rather than purely electronic, mechanism.
authors.affiliation: Departments of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, Washington University, St. Louis, Missouri 63130-4899, and University of California, Riverside, California 92521-0403.
authors.forename: Jon-Paul
authors.initials: JP
authors.lastname: Strachan
authors.forename: Steve
authors.initials: S
authors.lastname: Gentemann
authors.forename: Jyoti
authors.initials: J
authors.lastname: Seth
authors.forename: William A.
authors.initials: WA
authors.lastname: Kalsbeck
authors.forename: Jonathan S.
authors.initials: JS
authors.lastname: Lindsey
authors.forename: Dewey
authors.initials: D
authors.lastname: Holten
authors.forename: David F.
authors.initials: DF
authors.lastname: Bocian