Laser Spectroscopic Study of β-Estradiol and Its Monohydrated Clusters in a Supersonic Jet

The structure of 17β-estradiol (estradiol) and its monohydrated clusters is studied in a supersonic jet. The laser induced fluorescence (LIF) spectrum of estradiol shows several sharp bands in the 35050－35200 cm-1 region. Ultraviolet-ultraviolet hole-burning (UV-UV HB) and infrared-ultraviolet double-resonance (IR-UV DR) spectra of these bands indicate that they are due to four different conformers of estradiol originating from the orientation of two OH groups in the A- and D-rings. Attachment of one H2O molecule to estradiol shifts the monomer origin bands to red by ~350 cm-1 with keeping the interval between the four bands, suggesting that estradiol-H2O 1:1 complexes have conformations similar to those of the four bare estradiol conformers, and that the H2O molecule is bonded to the OH group of the A-ring (phenyl ring). In addition, very weak bands are also found near the origin bands of bare estradiol. These bands are attributed to isomers of estradiol-H2O 1:1 having a hydrogen-bond at the D-ring OH. We determine the conformation of bare estradiol and the structures of its monohydrated complexes with the aid of density functional theory, and discuss the relation between the stability of hydrated clusters and the conformation of estradiol.This is a preprint of an article published by American Chemical Society in Journal of Physical Chemistry A, 2012, available online: http://pubs.acs.org/doi/abs/10.1021/jp302209z.This work is supported from the Japan Society for the Promotion of Science (JSPS) through a Grant-in-Aid project (Nos. 18205003 and 21350016) and from MEXT through a Grant-in-Aid for the Scientific Research on Priority Area “Molecular Science for Supra Functional Systems” (No. 477)