Luminescent methods in the chemistry of lanthanides

Abstract

One of the strongest Ln{sup 3+} ion quenchers via the mechanism of induction-resonance interaction is a water molecule, which forms a coordination bond together with Ln{sup 3+} ions via an oxygen atom. The same atom is bonded with two protons that vibrate relative to the oxygen atom with a frequency of about 3750 cm{sup -1}. It is also known that this stretching vibration possesses anharmonicity and its overtones are rather intense. An almost equal contribution to the deactivation of Ln{sup 3+} ions is made by the N-H group that is nitrogen-bonded with the ion. The alcohol group -CH{sub 3} (methyl alcohol) makes an approximately one order smaller contribution to the deactivation of Ln{sup 3+} ions: R(Ln-CH{sub 3}) = 3.6-3.9 {Angstrom}. A further 2-4-fold smaller contribution to the deactivation is made by the -CH{sub 3} group located of 5.0-5.3 {Angstrom} from the ion (acetone, dimethyl sulfoxide). Knowing the above facts, in many cases one may evaluate the number of strongly deactivation molecules (e.g., water molecules) in the first coordination sphere of the ion from the measured luminescence decay time ({tau}{sub l}). Thus, luminescent methods make it possible to obtain information about the structure of the internal coordination sphere on Ln{sup 3+}more » ions.« less