Flipping the light switch 'ON' - the design of sensor molecules that show cation-induced fluorescence enhancement with heavy and transition metal ions

Real-time and real-space analysis of heavy and transition metal ions employ ing fluorescent sensor molecules has received much attention over the past few years. Since many of these cations possess intrinsic properties that us ually quench the fluorescence of organic dye molecules, a lot of research h as lately been devoted to designing fluorescent probes that show complexati on-induced fluorescence enhancement. Such an analytical reaction would be h ighly desirable in terms of increased sensitivity and selectivity. However, in this particular field of sensor research, the photophysical and photoch emical mechanisms involved as well as the chemical constitutions of the sen sor molecules employed are rather diverse and up to now, very few attempts have been made to establish some general concepts for rational probe design . By analyzing various systems published by other researchers as well as ow n work, this contribution aims at an elucidation of some of the underlying principles of heavy and transition metal ion-enhanced emission. (C) 2001 El sevier Science B.V. All rights reserved.