Example of Lifetime Measurements on a Supramolecular System

A very nice example of how lifetime measurements can be used to study supramolecular systems is shown in the following paper where time-resolved luminescence measurements were employed to investigate the photophysical behavior 

The almost coincident Ru-based emission lifetime (9 ns) and Os-based emission rise-time (8 ns) is a clear evidenee of the connection between these two processes indeed, they are the two different sides of the same, efficient photoin-dueed energy-transfer process occurring between the Ru (the donor) and Os (the aeeeptor) units in 1. Moreover, from the lifetimes determined at 610 nm in the model eompound (ti) and in 1 (T2) it is possible to calculate (ke = I/T2 —  

Air-equilibrated solution. See individual references. Very dilute solution is recommended ( 10 mol ) to avoid excimer formation. For other polar solvents, see Ref. [15]. Recommended by Eaton in Ref. [22]. EPA = ethanol/isopentane/diethyl ether 2 5 5 

The significant decrease in the efficiency of Ru Os photoinduced energy-transfer can be ascribed to an increase in the Ru-Os separation in l(Ba) with respect to 1, most likely due to electrostatic reasons. 

In fact some calculations based on the very plausible assumption of a Forster type energy-transfer mechanism (see Sect. 2.5.1) [6] and on the energy-transfer rate values measured in the two cases leads to an estimated increase of the Ru-Os separation from 13.5 A in 1 to 15.5 A in l(Ba). 

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