As 2 can be considered a trimer of the monomer unit 1, the maximum ICT absorption extinction coefficient for 2 is expected to be three times that of 1 in the absence of any electronic communication between fins. However, our experimental values, obtained from triplicate measurements on rigorously dried samples, yield a ratio of 3.4 (Table ) (for 1 ε = 3.5 × 10 3 M -1 cm -1 at 398 nm; for 2 ε = 12 × 10 3 M -1 cm -1 at 420 nm). An expansion of the ICT region of the UV-Vis spectra for 1 and 2 is provided in Figure .2. TD-DFT results indicate that the singlet ICT states of 2 have significant localisation over the homoconjugated iptycene core, while electrochemical measurements also indicate electronic communication between fins. Therefore, the larger than factor of three increase in ICT extinction coefficient for 2 compared to 1 is ascribed to a cooperative effect between the fins of 2 through homoconjugation. Concomitant with this increase, the solution values for ΦPL and kr S , are considerably enhanced for 2 compared with 1 (1 -ΦPL = 50%, kr S = 1.8 × 10 7 s -1 ; 2 -ΦPL = 63%, kr S = 2.4 × 10 7 s -1 ). Notably, for 2 the value of kr S is increased by a third compared with 1. Therefore, there is a clear enhancement in the probability of a radiative transition both to and from the ICT state in 2, crucially observed despite the narrower ΔEST of 2 compared with 1 (1 -ΔEST = 0.26 eV; 2 -ΔEST = 0.21 eV), as measured in a zeonex host (Table , Figures S9.1-S9.9 and S10.1). The acceleration of radiative transitions in 2 is very likely linked to homoconjugation, in-line with the computational predictions and electrochemical experiments above.