| Autor: |
Choi H; Department of Chemistry and Biochemistry, San Diego State University, San Diego, California 92182-1030, United States., Baek K; Department of Chemistry and Biochemistry, San Diego State University, San Diego, California 92182-1030, United States., Toenjes ST; Department of Chemistry and Biochemistry, San Diego State University, San Diego, California 92182-1030, United States., Gustafson JL; Department of Chemistry and Biochemistry, San Diego State University, San Diego, California 92182-1030, United States., Smith DK; Department of Chemistry and Biochemistry, San Diego State University, San Diego, California 92182-1030, United States. |
| Abstrakt: |
A new strategy to create highly redox-responsive H-bond dimers based on proton-coupled electron transfer is proposed that capitalizes on the importance of secondary H-bonds in determining overall binding strength in H-bond dimers. Electron transfer induced proton transfer across a H-bond can be used to significantly strengthen the overall binding by both creating strong ionic H-bonds and changing the secondary H-bonds from unfavorable to favorable. The viability and potency of this approach are demonstrated with an electroactive DAD (A = H-acceptor, D = H-donor) array, H(MQ + )H, paired with an electroinactive ADA array, O(NH)O. NMR titration of H(MQ + )H with O(NH)O in 0.1 M NBu 4 PF 6 /CD 2 Cl 2 gives a K assoc of 500 M -1 , typical of DAD-ADA dimers. However, upon two-electron reduction in 0.1 M NBu 4 PF 6 /CH 2 Cl 2 , cyclic voltammetry studies indicate a 1.8 × 10 5 increase in binding strength, corresponding to a very large K assoc of 9 × 10 7 M -1 . The latter value is typical of DDD-AAA H-bond dimers, consistent with proton transfer across the central H-bond upon reduction. |
