Synthesis and structural characterization of the Z-isomer of 1,2-bis(tetrazol-5-yl)ethylene (H2bte) via photoinduced isomerization

Abstract

This study demonstrates the photoinduced E→Z isomerization of 1,2-bis(tetrazol-5-yl)ethylene (H₂bte), leading to the first successful growth and structural characterization of its Z-isomer single crystal. Through optimized 365 nm UV irradiation and subsequent recrystallization, phase-pure Z-1,2-bis(tetrazol-5-yl)ethylene (Z-H₂bte) (91.9%) was obtained. Single-crystal X-ray diffraction analysis uncovered a non-planar molecular structure for Z-H₂bte, which fosters a distinct hydrogen-bonding network and crystal packing architecture compared to the planar E-isomer. The two isomers were further applied to the construction of sodium and cesium-based metal complexes, with the findings indicating that both isomers present a similar packing and connection mode. This work establishes an experimental foundation for understanding the E/Z photoisomerization and concomitant structural evolution in the H₂bte system, while providing a potential pathway for modulating energetic molecular properties through photoinduced cis–trans isomerization.