engleski

Phenanthridine-pyrene conjugates as fluorescent probes with peculiar kinetic behaviour

Phenanthridine derivatives are promising fluorescent probes whose properties can be modified by different substituents attached to the aromatic core. On the other hand, pyrene derivatives are one of the earliest known fluorescent probes for biomolecules. Also, it is known that two or more pyrenes form an excimer [1], where fluorescence band of single pyrene molecule is significantly shifted to longer wavelengths upon inter- or intramolecular stacking of pyrene moieties. Some of the compounds from both described classes show intriguing biological activity. It has been reported recently that some pyrene- guanidiniocarbonyl pyrrole derivatives exhibit strong pH-dependent affinity towards ds-DNA which can be modified by the flexibility of the linker connecting those two units [2]. Also, one of them binds to human dipeptidyl peptidase III enzyme with a micromolar affinity which can be monitored by significant changes in fluorescence spectra of the compound [3]. Moreover, previous studies have shown that two phenanthridine units can also form an excimer, characterized by specific fluorescence band [4]. Two phenanthridine-pyrene conjugates, differing only in linker connecting them, have been prepared. New conjugates exhibit excimer formation: 1 and 2 show new fluorescence emission bands at 475 nm and 485 nm, respectively, which are significantly red- shifted compared to fluorescence of single phenanthridine or pyrene molecule. To the best of our knowledge, it is the first reported phenanthridine-pyrene excimer. Further on, excimer band is not kinetically stabile and shows strong fluorescence decrease upon consecutive excitations.

pyrene ; phenanthridine ; excimer ; fluorescent probes

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