Anomalous cage effect in the excited state dynamics of catechol in the 18C6-catecol host-guest complex

Morishima Fumiya

Kusaka Ryoji

Inokuchi Yoshiya

Haino Takeharu

Ebata Takayuki

Journal of Physical Chemistry B

We present the structure of 18C6-catechol host-guest complex and the effect of the complexation on the S1 dynamics of catechol studied under a supersonically cooled gas phase condition and in cyclohexane solution. In the gas phase bare catechol, two adjacent OH groups have an intramolecular hydrogen-bonded structure. On the other hand, in the 18C6-catechol (1:1) complex both of the catechol OH groups are hydrogen-bonded to the oxygen atoms of 18C6. This complex formation greatly changes the character of the S1 state of catechol. That is, the S1 lifetime of bare catechol is reported to be 7 ps, while the 18C6-catechol complex was obtained to be 10.3 ns. This anomalous S1 lifetime elongation of catechol upon the complexation is attributed to a large energy gap between the S1 (ππ*) and S2 states by the switching from the intramolecular hydrogen-bond to the intermolecular hydrogen-bond in the host-guest complex. The formation of the18C6-catechol complex formation was also confirmed in cyclohexane solution, and an anomalous increase of fluorescence quantum yield of catechol was also observed. From the concentration dependence of the fluorescence intensity, it was confirmed that 18C6 and catechol also form (1:1) host-guest complex in bulk system. An equilibrium constant for the18C6 + catechol ⇄ 18C6・・・catechol reaction was obtained. It is suggested that that 18C6 can act as a sensor of detecting catechol.

Chemistry [ 430 ]

eng

American Chemical Society

Copyright (c) 2014 American Chemical Society

[ISSN] 1520-6106

[DOI] 10.1021/jp508619f

[DOI] http://dx.doi.org/10.1021/jp508619f isVersionOf

[PMID] 25350575