Knowledge Bank

Hydrogen bonded complexes of s-tetrazine with $H2O$ and s-tetrazine with HCl have been formed in a supersonic free jet expansion. The laser induced fluorescence excitation spectrum of an $s-tetrazine/H2O$ expansion shows three features near the origin region of s-tetrazine which have been assigned to $s-tetrazine(H2O)n$ where $n=1,2$, or 3. In an expansion containing s-tetrazine and HCl, three peaks are also observed in the spectrum; however, these have been identified as $s-tetrazine(HCl)1,s-tetrazine(HCl)2$, and a van der Waals vibration of $s-tetrazine(HCl)1$. Each of these features has been rotationally resolved. The geometries for the clusters have been determined with a rotational contour generating program combined with a nonlinear least squares program. Analysis of the high resolution spectra of $s-tetrazine(HCl)1$ and $s-tetrazine(H2O)1$ reveals that the hydrogen of the solvent molecule forms a hydrogem bond with the nitrogen lone pair of s-tetrazine and the resulting dimer is planar. In clusters involving more than one solvent molecule the solvent molecules bond to each other rather than the s-tetrazine ring. The rotational structure of the $s-tetrazine(HCl)1$ van der Waals vibration band shows that this is an out-of-plane bending motion with the HCl having an average displacement of $32\circ G$ from the plane of the ring.