Inducing molecular isomerization assisted by water

Wen Sun,Lei Zhao,Xiaodong Liu,Mao-sheng Miao,Jiazun Wu,Manfred Wagner,Dongsheng Wang,Haiquan Zhao,Yonghao Zheng

doi:10.1038/s42004-019-0221-5

Abstract

Light is not the only stimulus that can induce linear-to-cyclic isomerization of donor-acceptor Stenhouse adducts (DASAs). Here we demonstrate the water-induced linear-to-cyclic isomerization of DASAs. The mechanism of the water-induced linear-to-cyclic isomerization of DASAs is investigated by density functional theory (DFT) calculations. Water molecules coordinate with DASAs and stabilize the intermediates and cyclic isomers, which favors cyclization thermodynamically. Moreover, the linear-to-cyclic isomerization is reversible. Heating removes the coordinated H2O molecules, which further triggers cyclic-to-linear isomerization. DASAs have been applied in information hiding/displaying and color switching under water vapor and heating control.

Highlights

Light is not the only stimulus that can induce linear-to-cyclic isomerization of donor-acceptor Stenhouse adducts (DASAs)
We demonstrate the water-induced linear-to-cyclic isomerization of DASAs, which is reversible under heating
Linear-to-cyclic isomerizations triggered by green light (530 nm) were observed for all DASAs (Fig. 2a and Supplementary Figs. 2–5)

Summary

Results

In addition to DASA-N, water-induced linear-to-cyclic isomerizations were observed for DASA-O, DASA-M and DASA-I All the DASA molecules show similar isomerization rates, indicating the universality of the water-induced linear-to-cyclic isomerization in both of the DASA molecules with zwitterionic and nonzwitterionic cyclic isomers (Supplementary Fig. 21). Similar results were concluded by calculating the energy difference (ΔE) between the linear and cyclic isomers (Ecyclic − Elinear), which shows a decreased ΔE as the number of surrounding H2O molecules increases (Fig. 3b and Supplementary Table 3). By further increasing the number of coordinated H2O molecules (DASAN·4H2O and DASA-N·5H2O), the ΔE does not further decrease (Fig. 3b and Supplementary Table 3) These results are in good accordance with MD simulations. The ΔE is negative when applying water as the solvent, which is thermodynamically favorable for the linear-to-cyclic isomerization of DASA-N

H N–R1 R2

Discussion

Methods