The photophysical properties of linear triazenes have not been fully investigated. Their usefulness arises from the delocalized π-electrons present in their triazo (N=N-N) linker. Triazene systems based on 4-[(E)-2-phenyldiazenyl]-morpholine show changes in their photophysical properties that are attributed to delocalization and hybridization character of the morpholine N and the location and type of EWG on the phenyl ring. Acetyl and bromo substituents were used to probe the inductive and resonance effects on the photophysical properties of the triazenes of interest. TD-DFT methods were used to rationalize observed photophysical properties. Optimized geometries were compared with crystal structure data of related triazenes and gave a MAPD of 0.88% for nitrogen bond lengths on the triazo moiety. The calculated absorption spectrum of (4-[(E)-2-phenyldiazenyl]-morpholine) resulted in a MAPD of 3.46% when compared to the experimental spectrum. The absorption bands of (4-[(E)-2-phenyldiazenyl]-morpholine) were characterized by TD-DFT as a HOMO-1 and HOMO to LUMO transition, with associated energy changes of 5.291 and 4.448 eV, respectively. The total vertical excitation energy for this peak was calculated to be 3.831 eV, compared to an experimental energy of 3.875 eV. Acetyl groups were found to shift the most intense absorption maximum to longer wavelength by a mean of 13 nm, compared to an average shift of 9.5 nm for bromo groups. Increased electron delocalization also was found to shift theoretical spectra by 10 nm, caused by increased sp2 character on the morpholine nitrogen. This shift in spectra was observed experimentally as two convoluted peaks, and we associate this with increased electron delocalization. Emission maxima for (4-[(E)-2-phenyldiazenyl]-morpholine) was found at 364 nm, compared to a shift to 471 nm for p-acetyl substitution and 368 nm for p-bromo substitution. The complete presentation of our experimental and theoretical investigations will be given on our poster. Our work demonstrates the effectiveness of our theoretical methods to characterize an unstudied triazene family and give insight into how their structures give rise to their photophysical properties.

Synthesis, photophysical and computational studies of a series of linear triazenes

253rd National Meeting (2017)

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