Volatile halogenated hydrocarbons and ethers reveal strong analgesic and anesthetic effects. Among these
compounds, enflurane and isoflurane belong to isomers which often used for purposes of invasive surgery. These
halogenated compounds possess two CH groups which can act as weak CH donor in interactions with targets of
acceptor property [1-3]. One of the simplest acceptors including O atom with lone electron pair is dimethyl ether
(DME). The attention focuses on the features of noncovalent interactions between these isomers (particularly
isoflurane) and DME. As an experimental tool effective in detection of weak complex formation, the FTIR
spectroscopy of cryosolutions has been chosen.
Cryospectroscopic measurements, performed with isoflurane dissolved in liquefied Kr and Xe, have shown
that the basic features of the temperature changes in the region of CH stretching bands are defined by two largely
populated rotamers [4]. However, at T~118 – 130 K only one the most stable conformer lettered by a, with two CH
groups contrarily oriented, possess c.a. 90 % of the whole population. Thus, it contributes predominantly to the IR
spectrum registered in liquefied Kr.
In the case of enflurane, the FClCH and CHF2 groups act as CH donors of somewhat different strength when
interacting with dimethyl ether ((CD3)2O). It is worth noting that the complexes formed are stabilized by so called
blue-shifting H-bonds predominantly. In the case of isoflurane one can expect that both CH groups will interact
with molecular acceptors in a similar way. Somewhat stronger complexes are expected to be formed when H atom
of CHFCl-group is engaged in H-bonding type interactions. In this report, the results on the cryospectroscopic
temperature studies of isoflurane + dimethyl ether (DME) mixtures dissolved in liquefied Kr are presented at a
wide range of concentrations. Ab initio calculations were made to obtain geometric and spectroscopic parameters
of stable forms of dimers and trimer, and to interpret temperature and concentration changes revealed in the IR
spectrum of the system studied. To avoid the overlapping effect in the region of CH stretching vibrations the
wholly deuterium substituted form of DME was used.