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趙奕姼 Ito Chao. Charge-Controlled Hydrogen Bonds in Conjugated Molecules. Rosette Nanotubes as Conduits. H. Fenniri et al , J. Am. Chem. Soc . 2002 , 124 , 11064. Time. Covalent bond + Non-covalent bond synthesis. Covalent bond synthesis. How about control hydrogen bonding via
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趙奕姼Ito Chao Charge-Controlled Hydrogen Bonds in Conjugated Molecules
Rosette Nanotubes as Conduits H. Fenniri et al, J. Am. Chem. Soc. 2002, 124, 11064 Time Covalent bond + Non-covalent bond synthesis Covalent bond synthesis
How about control hydrogen bonding via a remote center? Hydrogen bonding changes properties of bound molecules – e.g. sensors • UV-visible absorption and luminescence spectra changed upon H-bonding Watanabe, S. et al. J. Am. Chem. Soc. 1998, 120, 229.
Beer, P. D. Polarized amide groups enhance binding strength in hydrogen-bonded metallocene complexes * KFe2+ = 4600 M-1 K Fe3+ = 158000 M-1 KCo2+ = 2800 M-1 KCo3+ = 98000 M-1 * * * * * * * More acidic amide proton based on X-ray and IR results Tucker, J. H. R. et al. Angew. Chem. Int. Ed. 2000, 39, 3296.
Implication of charge control in supramolecular chemistry
n C=C(N) C=C(P) N=N(N) N=N(P)1 -6.84 -13.17 -7.39 -15.50 2 -6.73 -12.04 -7.66 -16.45 3 -6.64 -11.18 -7.84 -17.99 4 -6.57 -10.47 -7.95 -19.07 4-i H+ H3N Table 1. Ammonia binding energies (kcal/mol) with three-component and two-component systems (4i) calculated at the HF/6-31G* level 4-i -6.22 -7.27 Signal does not die out! Chao, I.; Hwang, T.-S. Angew. Chem. Int. Ed. 2001, 40, 2703.
(C=C)n 1.5 n=3 n=4 n=1 n=2 1.4 r 1.3 N P 1.2 r s t u v 1.5 (N=N)n 1.4 r 1.3 1.2 r s t u v Bond length variation in pyrrole-(X=X)n-imine systems
n C=C(N) C=C(P) N=N(N) N=N(P)1 -6.84 -13.17 -7.39 -15.50 2 -6.73 -12.04 -7.66 -16.45 3 -6.64 -11.18 -7.84 -17.99 4 -6.57 -10.47 -7.95 -19.07 4-i Q(pyr)a Q(pyr)a (0.27) (0.42) (0.22) (0.47) (0.18) (0.59) (0.15) (0.66) a Difference in Mulliken group charge of pyrrole between protonated and neutral three-component systems. H+ H3N Table 1. Ammonia binding energies (kcal/mol) with three-component and two-component systems (4i) calculated at the HF/6-31G* level 4-i -6.22 -7.27 Signal does not die out! Chao, I.; Hwang, T.-S. Angew. Chem. Int. Ed. 2001, 40, 2703.
Table 2. Ammonia binding energy (kcal/mol) of protonated three-component systems with (N=N)n bridges calculated with ab initio and DFT methods. n = 1 n=2 n=3 n=4 HF/6-31G* -15.50 -16.45 -17.99 -19.07 HF/6-31+G** -13.41 -14.29 -15.77 -16.78 HF/6-31+G(2d,2p) -12.94 -13.90 -15.36 -16.33 B3LYP/6-31G* -19.19 -19.37 -19.57 -19.79 B3LYP/6-31+G** -16.06 -16.26 PW91PW91/6-31G* -21.77 -21.88 PW91P86/6-31G* -22.76 -22.87 MP2/6-31G* -18.72 -19.27 -20.08 -21.43 MP2/6-31G*// -18.73 -19.30 -20.07 -21.10 B3LYP/6-31G* MP4(SDQ)/6-31G* -17.75 -19.04 MP4(SDQ)/6-31G*// B3LYP/6-31G* -17.42 -18.30 CCSD(T)/6-31G*// MP4(SDQ)/6-31G* -20.30a -21.04a a Not corrected for BSSE.
Signal maintenance still possible with more feasible bridges Table 3. Ammonia binding energy (kcal/mol) of the protonated three-component system with different -((CH=CH)n-N=N)x- bridges at the HF/6-31G* level. x = 1 x = 2 -(CH=CH-N=N)x- -14.63 -15.62 -((CH=CH)2-N=N)x- -13.90 -14.49 -((CH=CH)3-N=N)x- -13.19 -13.64 -((CH=CH)4-N=N)x- -12.61 -12.98
H+ Protonated (P) Neutral (N)
Ammonia binding energy of protonated pyrrole-(X=X)n-imine -20 (N=N) n -18 -16 Binding Energy (kcal/mol) -14 (C=N) n -12 (C=C) n -10 (C C) ≡ n (N=C) n -8 1 2 3 4 n
Ammonia binding energy of protonated pyrrole-(X=X-X=X)n-imine -20 (N=C-N=N) n -18 -16 (C=C-N=N) n (N=N-C=N) n (C=N-N=N) n Binding Energy (kcal/mol) (N=N-C=C) -14 n (C=C-N=C) -12 n (C=C-C=N) n (C=N-C=C) n -10 (N=N-N=C) n (N=C-C=C) n -8 1 2 n
Model construction DE d+ QH QH (whole mol.)
QH QH Correlation of QH and energy gap between pyrrole HOMO and two-component LUMO QH(a.u.) • Through-bond intramolecular charge transfer (ICT)
+ C H = N H 2 Correlation of binding energy and molecular electrostatic potential (MEP) of the two-component system MEP Q = +1 • Through-space electrostatic effect important when ICT is absent
Model construction (C=C)n-iminium 2 1 Signal reduction 1 2 (N=N)n-iminium Signal maintaining
Bridge effect on two-component LUMO Better bridge: Low-lying p-HOMO and p-LUMO • Confirmed by three-component systems containing CF=CF units
Table 1. Ammonia binding energies (kcal/mol) with three-component systems at the HF/6-31G* level n C=C(N) C=C(P) CF=CF(N) CF=CF(P) 1 -6.84 -13.17 -7.07 -14.002 -6.73 -12.04 -7.27 -13.31 3 -6.64 -11.18 -7.38 -12.82 4 -6.57 -10.47 -7.54 -12.51 • CF=CF superior in terms of signal maintenance and signal sensitivity. Hwang, T.-S. et al. Chem. Eur. J., accepted.
Ammonia binding energy of protonated pyrrole-(X=X)n-imine -20 (N=N) n -18 -16 Binding Energy (kcal/mol) -14 (C=N) n -12 (C=C) n -10 (C C) ≡ n (N=C) n -8 1 2 3 4 n • Introduction of N lowers p/p* orbital energies, but orientation important.
Ammonia binding energy of protonated pyrrole-(X=X-X=X)n-imine -20 (N=C-N=N) n -18 -16 (C=C-N=N) n (N=N-C=N) n (C=N-N=N) n Binding Energy (kcal/mol) (N=N-C=C) -14 n (C=C-N=C) -12 n (C=C-C=N) n (C=N-C=C) n -10 (N=N-N=C) n (N=C-C=C) n -8 1 2 n • Introduction of N lowers p/p* orbital energies, but orientation important.
Recent success in employing a remote charge center to affect hydrogen bonding Ka(F-; DMSO) = 440 M-1 Ka(F-; DMSO) = 12000 M-1 Ka(F-; DMSO) = 54000 M-1 Sessler, J. L. et al. J. Am. Chem. Soc. 2002, 124, 1134.
Conclusion • Coupled with experimental evidences, remote control of hydrogen bonds by charge alteration is feasible. • A model is established to understand the signal reduction/maintaining phenomenon. A bridge with low-lying -HOMO and -LUMO is expected to facilitate the signal amplifying behavior. • Orientation of the bridge is important. • Limited structure units can be used to construct bridges of very different properties.
Acknowledgement $$$國科會、中央研究院 黃聰松 阮寧 陳信允 陳政仲 駱思融