Photogenerated organic triplet–doublet systems hold great promise for a range of technological applications in the emerging field of molecular spintronics, including quantum sensing and optoelectronic devices. Typically, they consist of an organic chromophore covalently attached to a stable radical. Upon photoexcitation, the chromophore triplet state is rapidly generated by a process referred to as radical-enhanced intersystem crossing. If the exchange coupling between the chromophore triplet state and the radical spin centres is strong, compared to other magnetic interactions active in the system, quartet states may be formed by spin mixing. For any applications of such photogenerated high-spin systems in molecular spintronic devices, their optical and magnetic properties are of major interest. In this contribution, we present our recent work focussed at exploring how to control the properties of photogenerated quartet states by rational design.