We present Spitzer 10-34 μm spectroscopic observations of the diffuse gas in the inner region of the star-forming region IC 348 of the Perseus Molecular Cloud. We find evidence for the strongest mid-IR bands of common molecules as H2, OH, H2O, CO2 and NH3 and of several carbonaceous molecules which may play an important role in the production of more complex hydrocarbons: HCN, C2H2, C4H2, HC3N, HC5N, C2H6, C6H2, C6H6. The excitation diagram of H2 reveals the presence of warm gas (270 +- 30 K) at the observed locations. Assuming this temperature, the derived abundances of CO2 and NH3 relative to H2 are 10-8 and 10-7, respectively. From the water lines we obtain an abundance of order 10-6 and higher gas temperatures. The abundances derived for HCN and C2H2, key molecules in the development of prebiotic building blocks, are of order 10-7 and 10-9, respectively. More complex molecules such as PAHs and the fullerenes C60 and C70 are also present. IC 348 appears to be very rich and diverse in molecular content. The JWST spectroscopic capabilities may provide details on the spatial distribution of all these molecules and extend the present search to more complex hydrocarbons.