We are entering a golden age for astrochemistry, with the simultaneous increase in detector sensitivity, band pass and telescope collecting area. The analysis of astronomical spectra, and the detection of new interstellar species is nevertheless hampered by the lack of knowledge molecular spectroscopy, both for stable species and for ions and radicals. Despite the hostile environment conditions, the interstellar and circumstellar chemistry is remarkably rich, with many species, their isomers and isotopologues (notably those where a D atom is substituted for an H). Another issue is the lack of understanding of the chemical formation pathways to interstellar molecules, leading to a low efficiency in the search for new species. This interdisciplinary project aims at improving both points by developing jointly : i) new techniques for more sensitive molecular spectroscopy based on instrumental developments in the THz domain, ii) new production techniques for possible interstellar molecules, iii) new observation and modeling programs. The team gathers well known experts in astrophysics, microwave instrumentation, molecular spectroscopy and organic synthesis who will share their knowledge.