Four members of mixed ligand cyclometalated iridium(III) complexes, fac-[Ir(ppy)(n)L(3-n)] (ppy = 2-phenylpyridine; L = 2-(3-octadecyloxyphenyl)pyridine; n = 0-3), were prepared in a one-pot reaction between [Ir(ppy)(2)(O(boolean AND)O)] (O(boolean AND)O = acetylacetonato) and LH in glycerol at 170 degrees C. Each compound was purified and optically resolved to Delta- and Lambda-enantiomers chromatographically on a chiral column. A film of fac-[Ir(ppy)(n)L(3-n)] floating at an air-water interface was transferred horizontally onto a hydrophobic glass plate as a Langmuir-Blodgett (LB) film. The emission from a single layered LB film was monitored under the atmosphere of various kinds of gases. As a result, molecules with functional groups such as -OH, (sic)C=O and -CN were found to quench efficiently excited fac-[Ir(ppy)(n)L(3-n)] in a film. The effects of isotope and molecular chirality on energy transfer were also investigated, comparing the quenching ability between H(2)O and D(2)O or between R-2-butanol and S-2-butanol on a racemic or chiral film of fac-[Ir(ppy)(2)L], respectively.