S1 Supporting Information for Excimer Formation and Symmetry-Breaking Charge Transfer in Cofacial Perylene Dimers Rita E. Cook, Brian T. Phelan, Rebecca J. Kamire, Marek B. Majewski, Ryan M. Young,* and Michael R. Wasielewski* Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center Northwestern University, Evanston, IL 60208-3113 Contents 1. Materials and Methods ................................................................................................... S1 1.1 Materials .................................................................................................................... S1 1.2 Steady-state spectroscopy ........................................................................................... S2 1.3 Transient absorption spectroscopy.............................................................................. S3 1.4 Computational methods .............................................................................................. S5 2. Synthesis........................................................................................................................... S5 3. Isomer Characterization ................................................................................................ S9 4. Excitation Spectra of Dimers 1 and 2 .......................................................................... S11 5. Gaussian Fitting of Steady-State Emission Spectra and Excimer Emission Estimation ...................................................................................................................... S12 6. Transient Absorption Spectroscopy of Per-xy ........................................................... S14 6.1 fsTA spectra of Per-xy .............................................................................................. S14 6.2 nsTA spectra and global fits of Per-xy ..................................................................... S15 7. Transient Absorption Spectroscopy of Dimers 1 and 2............................................. S17 7.1 Kinetic and fit traces from global fits of fsTA data of Dimers 1 and 2 .................... S17 7.2 nsTA spectra and global fits of Dimers 1 and 2........................................................ S18 8. Gaussian Fitting of DAS Showing Decay of Shoulder in fsTA Spectra of 2 in MeCN.................................................................................................................. S22 9. References ...................................................................................................................... S22 1. Materials and Methods 1.1 Materials All chemicals were obtained from commercial suppliers and used as received unless otherwise noted. HPLC-grade THF was dried on a commercial system (GlassContour, Laguna Beach, CA), and 1,4-dioxane (99%) was purchased from Alfa Aesar and used as received. All other solvents for synthesis were ACS reagent grade. Column chromatography was performed