Reactivity and Spectroscopic Characterization of Interstellar Relevant Imine Species

• Applicant: Dr. André K. Eckhardt
• Subject Area: Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry ; Astrophysics and Astronomy ; Organic Molecular Chemistry - Synthesis and Characterisation
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 530220027

Simple imines are frequently used as building blocks in the synthesis of more complex molecules. In solution imines are typically prepared from carbonyl compounds and ammonia or primary amines. The simplest aldimine, formaldimine (H2CNH), has been discovered in space but cannot be isolated on Earth due to polymerization or oligomerization when concentrated. Aldimine building blocks play a key role in the formation of biorelevant molecules like amino acids or nucleobases in prebiotic chemistry. However, spectroscopic data of the compound class are rare or missing at all due to their high reactivity and the absence of molecular precursors for an on-demand mild generation. The overall goal of this project is to learn more about interstellar and prebiotic imine chemistry and characterize often proposed but yet elusive imine species. We will focus on the generation of simple substituted imines and α-imino acids under matrix isolation and interstellar conditions at cryogenic temperatures in solid argon matrices and in interstellar ice analogs. Suitable molecular precursors for a photochemical and thermal imine generation will be developed and synthesized. All prepared imines will be experimentally characterized by infrared and UV/Vis spectroscopy and all spectral data will be compared to highly accurate ab initio calculated theoretical properties including rotational constants. The formation of imines under interstellar conditions will be modeled in interstellar ice analogs. Highly energetic galactic cosmic rays will be simulated with free electrons in electron irradiation experiments, which will cause radical formation and complex non-equilibrium chemistry. Imine formation via simple radicals in electron processed interstellar ice analogs will be followed by a novel EPR experiment. This will allow us to monitor reactive open-shell species directly in the processed ice for the first time. The solvation and hydrolysis of imines in water ices and aqueous solutions will be followed by IR and NMR spectroscopy. The project will contribute to a better understanding of interstellar and prebiotic imine formation and (hydrolysis) chemistry.

• DFG Programme: Independent Junior Research Groups
• Major Instrumentation: IR Spektrometer ; Optical Kryostat
• Instrumentation Group: 1830 Fourier-Transform-IR-Spektrometer ; 8550 Spezielle Kryostaten (für tiefste Temperaturen)