[Study on the effect of pressure on the molecular structure and pi-electron delocalization of beta-carotene by raman spectroscopy].

In the present paper, studies on in-situ Raman spectra at high pressure up to 12.85 Gpa were performed on beta-carotene using a diamond anvil cell (DAC), and the effects of pressure on the characteristic peaks and pi-electron delocalization of beta-carotene were discussed. The results showed that Raman frequencies of the main characteristic peaks of beta-carotene shifted to high wavenumber with the increase in pressure. The relation between pressure and the three main characteristic peaks of beta-carotene was given as follows: nu1, (C==C) = 4. 74P + 1511.4, w (C-C) = 2.55P + 157.6 and nu3 (CH3) = 2.25P + 1011.3. Under the pressure of 5.38 GPa, Raman spectrum of nu1 + nu2 sum frequency of beta-carotene was subjected to cleavage. Fuethermore, the degree of relectron decolization was reduced with the increase in pressure, leading to C==C double bond more compressible than C-C bond on the main chain of beta-carotene.