title: Conformation and electronic population transfer in membrane-supported self-assembled porphyrin dimers by 2D fluorescence spectroscopy.
abstract: Two-dimensional fluorescence spectroscopy (2D FS) is applied to determine the conformation and femtosecond electronic population transfer in a dimer of magnesium meso tetraphenylporphyrin. The dimers are prepared by self-assembly of the monomer within the amphiphilic regions of 1,2-distearoyl-sn-glycero-3-phosphocholine liposomes. A theoretical framework to describe 2D FS experiments is presented, and a direct comparison is made between the observables of this measurement and those of 2D electronic spectroscopy (2D ES). The sensitivity of the method to varying dimer conformation is explored. A global multivariable fitting analysis of linear and 2D FS data indicates that the dimer adopts a "bent T-shaped" conformation. Moreover, the manifold of singly excited excitons undergoes rapid electronic dephasing and downhill population transfer on the time scale of ∼95 fs. The open conformation of the dimer suggests that its self-assembly is favored by an increase in entropy of the local membrane environment.
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, United States.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Perdomo-Ortiz
authors.forename: Julia R
authors.initials: JR
authors.lastname: Widom
authors.forename: Geoffrey A
authors.initials: GA
authors.lastname: Lott
authors.forename: Alán
authors.initials: A
authors.lastname: Aspuru-Guzik
authors.forename: Andrew H
authors.initials: AH
authors.lastname: Marcus
mesh_terms: D019281:Dimerization; D004579:Electron Transport; D008051:Lipid Bilayers / Q000737:chemistry*; D008274:Magnesium / Q000737:chemistry; D008958:Models, Molecular; D010713:Phosphatidylcholines / Q000737:chemistry; D011166:Porphyrins / Q000737:chemistry*; D013050:Spectrometry, Fluorescence
chemical_list: D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D011166:Porphyrins; C409084:tetraphenylporphyrin; C010942:1,2-distearoyllecithin; D008274:Magnesium