Detailed memory studies have been carried out based on In2O3 nanowires coated with self-assembled monolayers of porphyrins. Devices with redox-active Co-chelated porphyrin coatings exhibited prominent memory effects, where the bit was represented by the charge stored in the molecules and the nanowire conductance was used as the readout. These devices exhibited reliable operation with on/off ratios of similar to10(4) and were electronically programmable and erasable. Temperature-dependent retention measurements revealed a thermal activation behavior with a barrier of 264 meV. While devices with Co-porphyrin coatings showed efficient memory operation, analogous protio porphyrin coated nanowire devices exhibited no memory effects. A largely metal-centered oxidation (e.g., Co2+/3+) appears to be important for achieving a memory effect in these devices. Our results have convincingly established a direct correlation between the molecular structure and the observed memory effect, and further in-depth studies may eventually lead to systems useful for practical applications.