Recent developments in bottom-up nanocarbon synthesis methods have enabled the preparation of well-defined nanocarbons with tunable size, shape, and functional groups. These methods often start with the synthesis of soluble polyphenylene precursors using Diels-Alder addition/decarbonylation, Suzuki-Miyaura , or Yamamoto coupling reactions. The aromatization of these soluble poly-phenylenes is achieved using oxidative cyclodehydrogenation to form insoluble nanographene products. More recently, one-shot annotative π-extension has been developed as a useful 'growth from template' method to selectively modify K, L and bay-regions of nanographenes using Diels-Alder or C-H activation chemistry. These synthetic tools have enabled numerous studies on the effect of nanographene size, shape and heteroatoms on the electronic and optical properties of welldefined carbon materials. Only a limited number of studies report the optical properties of GNRs. Using wet chemistry synthetic methods discussed above, several GNRs with 0.5-2 nm ribbon widths (where width is defined as the shortest edge-to-edge distance in the ribbon) were prepared and their optical bandgaps were reported to fall off with the increased ribbon width and to exhibit 1-2 eV range. Such width-dependent optical properties are consistent with theoretically predicted quantum confinement effects in GNRs. Theoretical calculations also indicate that the width dependence on GNR bandgap depends on C, the number of carbon atoms across the ribbon width. In GNRs with C=3p+1 (p is an integer), the fall-off of the optical bandgap with the ribbon width is more pronounced than that for GNRs with C=3p and 3p+2. The optical gap was also found to be affected by the solubilizing alkyl chains owing to their steric effects induce the nanoribbon non-planarity and the reduction in the bandgap. The optical excitation of GNRs was found to be dominated by excitonic features, which is consistent with their quantum confinement and low dielectric screening, both of which prevent the exciton dissociation into free charge carriers. Free charge carriers were observed, using time-resolved THz spectroscopy, when the excess energy from the excitation pulse after excitation exceeded the exciton binding energy in GNRs (~ 700 meV). These free carriers were found to exhibit excellent mobilities (in the 150-15,000 cm 2 /Vs range), but short lifetimes (few picoseconds). Excitons were also found to be highly mobile, as demonstrated by the presence of biexcitonic features in the pumpfluence dependent experiments. However, the exciton lifetimes were found to be relatively short-lived due to the excimer formation and the presence of dark states. As part of our ongoing interest in light-harvesting properties of nanographenes , we investigate here the photophysical properties of hydrogenated and chlorinated GQDs and GNRs that contain bipyrimidine moieties in their edges (Scheme 1). Here, H-GQD and Cl-GQD can be thought of as the basic building blocks of H-GNR and Cl-GNR, respectively. In a previous electrochemical (non-photophysical) study, we showed that bipyrimidine units behave as redoxactive electron accepting moieties, undergoing efficient proton-coupled electron transfer processes. In this study, we show that GQD and GNR exhibit excited states with chargetransfer character, where bipyrimidine units serve as electron acceptors, an important property for efficient photoinduced charge separation required in photocatalytic applications. Furthermore, we find that the edge chlorination has a beneficial effect on the excited-state lifetimes of GNRs, due to the significant reduction in the non-radiative decay pathways associated with -stacking between aromatic cores. These prolonged lifetimes also enable efficient intersystem crossing to produce long-lived (106 μs) triplet states, a behavior that has never been observed previously in the graphene nanoribbon literature. These excellent photophysical properties, combined with the fact that GNRs absorb a broad range of visible frequencies and that the bipyrimidine sites can serve as coordinating sites for transition metalbased catalysts, makes these nanographenes excellent building blocks for future photocatalytic applications.