Complexations of 2-Aminofluorene and 2-N,N'-Dimethylaminofluorene to b-Cyclodextrin in Presence of Sodium Perchlorate in Aqueous Solution
The complexations of 2-aminofluorene (2-AF) and 2-N,N'-dimethylaminofluorene (DMAF) to b-cyclodextrin (b-CD) have been studied in phosphate buffer (pH = 7.4) in presence of varying concentrations of sodium perchlorate (NaClO4) in aqueous solution using absorption and fluorescence spectroscopy. In case of DMAF, association constant is about four times higher than that of 2-AF in absence of NaClO4. The association constant of 2-AF passes through a maximum at around 0.01 M NaClO4 with increasing concentration of NaClO4. However, in case of DMAF there is a continuous decrease of association constant with an increase in the concentration of NaClO4. The variation of association constants with the change in concentration of NaClO4 for both the molecules is consistent with the variation of fluorescence quantum yields with the change in concentration of NaClO4. Structures of 2-AF-b-CD and DMAF-b-CD inclusion complexes have been proposed. Aromatic ring without -NH2 group in case of 2-AF and the same without -N(CH3)2 group in case of DMAF enter first into the b-CD cavity from the side of larger rim. The stability of ternary complex formed in the low concentration range of NaClO4 depends on the hydrogen bond donor ability of the functional group(s) of the substrate explained with the help of the values of total atomic charges on the hydrogen atoms of -NH2 group of 2-AF molecule obtained from ab initio quantum mechanical calculations by Restricted Hartree-Fock (RHF) method using 6-31G** basis set.
2-Aminofluorene, 2-N,N'-Dimethylaminofluorene, B-Cyclodextrin, Inclusion Complex, Sodium Perchlorate, Fluorescence.
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