189008-31-9Relevant academic research and scientific papers
How the terminal methyl group affects the S0, S1 and T1 electronic structures of a conjugated aldehyde chain: A comparison between all-trans-β-apo-12′-carotenal and its analogue by NMR and Raman spectroscopy
Hu, Ying,Zhang, Jian-Ping,Mizoguchi, Tadashi,Koyama, Yasushi,Yamano, Yumiko,Ito, Masayoshi
, p. 277 - 286 (1997)
An analogue of all-trans-β-apo-12′-carotenal, with a methyl group being shifted from the 13′ to the 14′ position, has been synthesized. The electronic absorption, the 1H and 13C NMR, and the S0-, S1- and T1-state Raman spectra of β-apo-12′-carotenal (C25 aldehyde) and the analogue (C25′ aldehyde) were recorded for comparison. No clear differences were found for the Ag → Bu absorption, but systematic differences were found in the 13C and 1H chemical shifts in the vicinity of the methyl group; the differences were explained in terms of the inductive effect and van der Waals interactions. The frequency of the in-phase C=C stretching Raman line (a measure of the overall carbon-carbon bond order of the conjugated chain) was almost the same in the S0 state, but the C=C stretching frequency of C25′ aldehyde was lower than that of C25 aldehyde in both the S1 and T1 states. Thus, the methyl position affects only the local electronic structure in the S0 state, but it can affect the electronic structure of the entire conjugated backbone in the excited states.
