SIMULTANEOUS DOUBLE PROBING OF THE MICROENVIRONMENT IN COLLOIDAL SYSTEMS AND MOLECULAR ASSEMBLIES BY DPH DERIVATIVES

The spectroscopic properties of two derivatives of DPH, viz. DPH-N(CH3 )(2) and DPH-NO2 (Chart 1), were examined as prospective fluorescence probes. It was found that, contrary to the parent molecule DPH, these two derivatives exhibit fluorescence spectra strongly dependent on the polarity of their immediate environment. It was also found that their fluorescence anisotropy r is as high as that of DPH (r = 0.38). Conse quently, DPH-N(CH3)(2) and DPH-NO2 can be used for the simultaneous me asurement of micropolarity and microviscosity (or any other property r elated to r, e.g. phase transition), at the site of their solubilizati on, in molecular assemblies and microheterogeneous media. Since probin g by either one of these two DPH derivatives involves the use of the s ame probe for the determination of two different microproperties, it i s assured that the two microproperties measured correspond to exactly the same microsite, viz. that of the solubilization of the one and onl y probe. Ordinarily, one uses different probes to determine different microproperties, in which case it is almost certain that these micropr operties reflect different sites of the microenvironment. The suitabil ity of these probes for the simultaneous determination of microviscosi ty and micropolarity has been demonstrated for a number of typical mic roheterogeneous systems. In all cases the microparameters obtained sim ultaneously by means of DPH-N(CH3)(2) or DPH-NO2 were at least as good as the ones determined separately by means of well established probes such as pyrene or DPH.