Superconductivity with Tc=33 K has been reported in alkali-doped polyaromatic hydrocarbons (PAHs). The compositions and structures are unknown owing to the multiphase nature and low crystallinity of the samples. We have recently developed synthetic methods to afford phase-pure highly-crystalline binary alkali PAH salts. In particular, Cs(C14H10) is Mott insulating and comprises spin-½ antiferromagnetic chains of phenanthride radical monoanions. The absence of long-range magnetic order above 2 K renders it a model system of p-electron one-dimensional molecular quantum antiferromagnetism. With this proposal, we want to address the nature of the magnetic state down to mK temperatures using the ZF/LF muSR technique and search for the emergence or not of long-range antiferromagnetic order. Complementary measurements will be performed on the isoelectronic AFM analogue Rb(C14H10)(THF).