Excimer emission in norepinephrine and epinephrine drugs with α- and β-cyclodextrins: spectral and molecular modeling studies.

The inclusion complexation behavior of norepinephrine (NORE) and epinephrine (EPIN) with native cyclodextrins (α-CD and β-CD) were investigated by UV-visible, fluorimetry, time-resolved fluorescence, SEM, TEM, FT-IR, (1)H NMR, DSC, powder XRD and PM3 methods. Single emission was observed in aqueous solution where as dual emission (excimer) noticed in the CD solutions. Both drugs form 1:1 drug-CD complexes in lower CD concentrations and 1:2 CD-drug2 complexes in the higher CD concentrations. Time-resolved fluorescence studies indicated that both drugs showed single exponential decay in water and biexponential decay in CD. Nano-sized self-aggregated particles of drug-CD were found by TEM studies. Molecular modeling studies indicated that aliphatic chain part of the drug was entrapped in the CD cavity. Thermodynamic parameters and binding affinity of complex formation of the CD were determined according to PM3 method. The PM3 results were in good agreement with the experimental results.