Furthermore, ΦΔ values for both dimers are higher in toluene than in more polar benzonitrile. We rationalize this trend by considering two aspects. On one hand, the lower viscosity of toluene relative to benzonitrile allows for better diffusion and, therefore, more efficient sensitization of and). This analysis was aided by 45 the fact that the GSB and triplet ESA related extinction coefficients remain constant throughout the dissociation process. Therefore, the dissociation yield can be calculated using the ratio between the ΔOD values of the EAS of (T1T1) and (T1 + T1). The dissociation yield (ΦDiss) for mAdTc2 in benzonitrile (46%) is 10-times greater than that for mPhTc2 (4.5%). It is noted that high values of ΦDiss were found in pentacene dimers with a 1,3-diethynyladamantyl spacer, while dimers with a 1,3-diethynylphenylene spacer fail to produce significant amounts of (T1 + T1). In line with quantum chemical calculations, weak electronic coupling in mAdTc2 favors 1 (T1T1)-5 (T1T1) spin-mixing and allows for dissociation of (T1T1) to form (T1 + T1). Stronger inter-tetracene coupling in mPhTc2 lifts the degeneracy of 1 (T1T1) and 5 (T1T1) and, therefore, inhibits 1 (T1T1)-5 (T1T1) mixing. Consequently, (T1T1) dissociation is very unlikely in mPhTc2. a ΦΔ is determined using C60 in toluene as reference. An error margin of ±10% is implicit in the determination of ΦΔ.