The focus of our project is on interactions between NH3 and Lewis acids of the form MX3CH3 where: X=F, Cl. Lewis acid-base complexes similar to these are apt to structural change in the condensed phase (e.g. gas to solid) and as such, we suspect these complexes may also be susceptible to medium effects. Broader interest in compounds of this general form stems from possible applications in nanotechnology or for the development of piezoelectric materials. We have investigated these systems with quantum-chemical calculations (M06/aug-cc-pVTZ) for both (H3N)n–GeCl3CH3 where n=1,2 and H3N–GeF3CH3. In addition, we have collected low-temperature IR spectra of H3N–GeCl3CH3 in inert matrices as well as H3N/GeF3CH3 thin-films. At this point, we have determined equilibrium geometries for each 1:1 compound among four geometric isomers, calculated the binding energies. For example, the lowest energy structure H3N(ax)–GeCl3CH3(eq) has binding energy -5.2 kcal/mol and N–Ge distance 3.522 Å. We also mapped the N–Ge potential energy curves in the gas phase and simulated bulk dielectric media for H3N–GeCl3CH3. From these data, we predict large condensed phase structural changes for the chlorinated systems because they exhibit flat potentials across a range of N-Ge distances with a relatively long equilibrium N–Ge distance (3.522 Å, gas phase), but the minimum shifts towards shorter N-Ge distances in bulk, dielectric media (2.221 Å, e =10.0). Deposition of NH3/GeCl3CH3 in inert matrices (Ne, Ar) at cryogenic temperatures (10-30 K) produced a set of product bands consistent with predicted frequencies for the 1:1 complex. However, we observe a stable product when NH3/GeCl3CH3 are mixed directly. We are attempting to identify and characterize the stable product via DFT calculations on the analogous 2:1 system ((H3N)2–GeCl3CH3) and through spectroscopic and crystallographic analysis.

Exploring the structural and energetic properties of H3N–GeX3CH3 complexes via IR spectroscopic and computational methods

2019 Spring National Meeting

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