Thorough investigation of key intermediates, such as long-lived singlet diradicals, is essential to understand the homolytic bond cleavage reactions. In this study, we evaluate the effect of bulky substituents at the meta-position of the phenyl ring on the bond formation process in singlet 2,2-diethoxy-1,3-diarylcyclopentane-1,3-diyls. The bulky groups have significant influence on the diradical lifetime, as such, when the triisopropylphenyl group was used, the lifetime was 45 times longer than that of the parent diradical in benzene at 293 K.