1029002-25-2Relevant academic research and scientific papers
Aromatic and aliphatic CH hydrogen bonds fight for chloride while competing alongside ion pairing within triazolophanes
Hua, Yuran,Ramabhadran, Raghunath O.,Uduehi, Esther O.,Karty, Jonathan A.,Raghavachari, Krishnan,Flood, Amar H.
, p. 312 - 321 (2011)
Triazolophanes are used as the venue to compete an aliphatic propylene CH hydrogen-bond donor against an aromatic phenylene one. Longer aliphatic C-H...Cl- hydrogen bonds were calculated from the location of the chloride within the propylene-ba
Pure C-H hydrogen bonding to chloride ions: A preorganized and rigid macrocyclic receptor
Li, Yongjun,Flood, Amar H.
, p. 2649 - 2652 (2008/12/23)
Strength in numbers: When traditionally weak C-H hydrogenbonds are preorganized in a shape-persistent macrocycle, a strong affinity for chloride ions emerges. This discovery arises from the dual use of click chemistry for efficient macrocyclizationan d the favorable steric properties of the resulting 1,2,3-triazoles. (Figure Presented)
Strong, size-selective, and electronically tunable C-H...halide binding with steric control over aggregation from synthetically modular, shape-persistent [34]triazolophanes
Li, Yongjun,Flood, Amar H.
scheme or table, p. 12111 - 12122 (2009/02/05)
A series of shape-persistent [34]triazolophanes bearing t-butyl or triethylene glycol (OTg) substituents on the phenylene linkers have been prepared in a modular manner from simple building blocks. Triazolophane-halide binding affinities were determined using UV titrations in order to help in understanding the driving forces behind the large receptor-anion binding strengths supported solely by CH hydrogen-bond donors. The fixed size of the central cavity provides a means for selective recognition of Cl- and Br- anions with large binding strengths (Ka > 1 000 000 M-1; ΔG > -8.5 kcal mol-1). The smaller F - and larger I- anions are bound less tightly by ～1 and ～3 orders of magnitude, respectively. The four triazole-based H-bond donors are believed to be of primary importance, while the four phenylene CH H-bond donors take on a secondary role. Consistent with this idea, the binding affinity can be tuned by as much as 1 kcal mol-1 by changing the character of the four phenylene-based substituents from more (OTg) to less (t-butyl) electron-donating. Preorganization was also found to play a central role, on the basis of comparisons with a foldamer analogue that shows much-reduced binding. Aggregation was facilitated as the substituents were changed from t-butyl to OTg, increasing the degree of self-association from KE ≈ 0 to 230 M-1 in CD2Cl2. Diffusion NMR experiments established aggregation as opposed to dimerization. These findings indicate the importance of the cavity size for selective anion recognition as well as the role of the phenylene linkers in tuning the binding strengths and modulating the aggregation of the [34]triazolophanes.
