為了有效的調控氫鍵，我們設計一個三元件系統:包含反應中心(imine)、連結器及氫鍵結合中心 (pyrrole) 三部分;當反應中心被質子化時，三元件系統之氫鍵結合能力會因反應中心電荷之變化而受到改變。本篇研究是以理論計算的方式，研究以碳鏈為骨架之連結器，其上取代基及骨架之結構如何影響質子化前後氫鍵結合能力的變化，同時也尋求如何避免因反應中心與結合中心距離的加大，而使得結合能力之變化大幅縮小。
首先，我們在pyrrole-(X=X)n-imine, n = 1 ~ 2的系統中使用 (CH=CH)n，(CF=CF)n，(C(CN)=C(CN))n 等拉電子性不同的的連結器，觀察其質子化前後氫鍵強度的變化，並與 (N=N)n連結器之結果比較。結果顯示，連結器隨著反應中心和鍵結中心之間的距離加長，其質子化前後氫鍵強度的變化最能達到維持效果之連結器依次為(C(CN)=C(CN))n > (CF=CF)n > (CH=CH)n ;其中(C(CN)=C(CN))n 僅略遜於(N=N)n。即碳鏈上有強取代基，可增進三元件系統之效能。對於這樣的結果，我們也用其他不同的計算層次及取基底函數來驗證，獲得了相近的趨勢。
另外，我們也研究連結器上取代位置之影響，而考慮以下系統: pyrrole–(CR1=CR2)n–imine (n = 1 ~ 4, R1 = -CN, -F, R2 = H; R1 = H, R2 = -CN, -F) 及 pyrrole–(CR1=CR1-CR2=CR2)n–imine (n = 1~2; R1 = -CN, -F, R2= H; R1 = H, R2 = -CN, -F)。我們發現，當使用(CH=CR)n 或(CH=CH-CR=CR)n 形式的連結器(即取代基在靠近反應中心的位置)，其質子化前後氫鍵強度的變化量相對於使用 (CR=CH)n 或(CR=CR-CH=CH)n形式的連結器要來得大。
基於cyano取代基之強拉電子性有助於增進三元件系統之效能，我們使用cyano取代基，在一系列不同結構碳鏈 (transoid-、cisoid-linear conjugated bridges 及 quinoidal ring bridges，包含十個不同取代的位置) 的系統中找出質子化前後氫鍵強度的變化量較大的位置。結果顯示，取代位置離反應中心越近，其質子化前後氫鍵強度的變化量較高。而當我們在系統中增加取代數目並使它們的取代位置靠近反應中心時，則氫鍵的結合能力又比單取代增強一些。對於這一系列不同結構碳鏈的系統中，我們發現，不同構形的連結器(即transoid- vs. cisoid-linear conjugated bridges)，這兩者質子化前後氫鍵強度的變化量差別不大;但使用quinoidal 形式的環類連結器，其質子化前後氫鍵強度的變化量相較於linear conjugated bridges 有顯著的提升;而quinoidal 形式的環類連結器中，六圓環又比五圓環的效果來的好，因其電荷轉移時獲得較多aromaticity。

The importance of hydrogen bonding has prompted us to investigate systems in which the strengths of hydrogen bonds can be modulated at will by external stimuli. Three-component systems consisting of a hydrogen-bonding site (electron donor), a bridge, and a reaction center (electron acceptor) have been designed to achieve this goal of hydrogen-bonding modulation. When the reaction center was protonated, a signal was sent out to the other end of the three-component molecule via intramolecular charge transfer (ICT) and thus affected the binding ability of the binding site. It has been found that the constituents of the bridge greatly influence the efficiency of remote signal communication between the reaction and binding centers. In the current theoretical study, we focused on the carbon-based conjugated bridges and studied the effects of bridge structure and substituents on signal transduction. It was found that the quinoidal bridges or bridges with cyano substitutions near the reaction center were more effective than the parent unsubstituted transoid (CH=CH)3 bridge. For bridges such as (CR1=CR2)n or (CR1=CR1-CR2=CR2)n, signal reduction due to longer bridge lengths could be minimized if R2 are substituted with electron-withdrawing substituents such as F and CN. Finally, the (C(CN)=C(CN))n bridges are signal amplifying, i.e., longer bridge lengths cause stronger binding change at the binding site.

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17. The inductive and mesomeric constant, σI and σR for cyano group is 0.48 and 0.22, respectively; for fluoro group is 0.52 and -0.32, respectively. Values are taken from reference 6a.
18. The orbitals are derived from fully geometry optimized closed-shell molecules as labeled in Figure 3.
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20. See appendix C. Figure C-1, the correlation coefficient (R2) of QH(N) and ΔEcp(N) for A is 0.9904; for QH(P) and ΔEcp(P), the R2 is 0.9385.
21. Appendix C. Table C-6.
22. Appendix C. Table C-15.
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