In case of a non-polar solvent like benzene, the dissociation of chlorine is hindered and 2 is formed preferentially. After eliminating Cl -from solution (via exchange with the weakly coordinating PF6 -ion) 1 becomes the main form again. Accordingly, two samples were prepared in such a way that the chemical equilibrium was shifted strongly to either 1 or 2 (see ESI for details). Figure compares the singlet life-times of the two samples with and without spin-lock pulse. With the spin locking pulse a lifetime of the pH2 spin order in solution is 2.23±0.03 s for 2 and of 27.2±1.2 s for 1, respectively (Figure ). Without the spin-lock pulse (Figure ) the lifetimes for 2 and 1 are 1.35±0.03 s and 5.4±0.1 s, respectively. These results clearly corroborate our hypothesis, that it is possible to substantially suppress the singlettriplet leakage pathway by chemically selecting the proper reaction intermediates.