Thermodynamics and photochemical properties of α, β, and γ-hexabromocyclododecanes: A theoretical study

The thermodynamics and photochemical properties of −α, +β, and −γ-hexabromocyclododecanes (HBCDs) have been investigated by density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations. The optimized geometries of HBCDs are in agreement with recently published X-ray crystallographic data. The thermodynamic properties of three HBCDs indicate that α-HBCD is the most stable one. The TD-DFT calculations obtain the UV absorption spectra of the three HBCDs and provide a detailed assignment of the UV spectral features. Inspections of the frontier molecular orbitals reveal the n → σ∗ nature of the lowest-lying transition and predict the photodegradation and photostereoisomerization trends of HBCDs under the UV illumination with wavelengths shorter than 240 nm.