An Agilent 7890A GC and 5975 MSD system was used for monitoring the photoreactions, using split-injection (1μL injection volume; split ratio: 100:1; 250 ºC inlet temperature; Flow Rate: 120 mL/min) and capillary column (19091S-433: 325 ºC: 30 m x 250 μm × 0.25 μm (front SS-inlet: He; out: vacuum)). The initial temperature of the column oven was 70 ºC (0.5 min equilibration time) and the final temperature of the sample run was 320 ºC. The rate of temperature was set to 20 ºC/min resulting in a 12.5 min total run time. Helium gas was used as a carrier gas at a flow rate of 1.2 mL/min. The source and Quad temperatures of the Mass spectrometer are, respectively, 230 and 150 ºC. The total yield of dimers was determined gravimetrically. The 1 H NMR spectra were recorded on a JEOL (400YH magnet) Resonance 400 MHz spectrometer. Chemical shifts δ are reported in ppm and coupling constants J in Hz. 1 H NMR chemical shifts are referenced to the residual solvent signal (CDCl3, 1 H 7.26 ppm).