Supramolecular dyad derived from a buckybowl series of O2N2-donor naphthodiaza-crowns coordinated to C-60: photophysical, NMR and theoretical studies

摘要

Supramolecular complexation of C-60 with L-1-L-5 were studied in toluene, chloroform and 1,2-dichlorobenzene solvents using UV-vis, fluorescence, H-1, C-13 NMR spectroscopy as well as density functional theory (DFT) calculations. The Job's plot of continuous variation method established 1:1 stoichiometry for L-1-L-5/C-60. Binding constants (K) calculated for L-1-L-5/C-60 were also determined employing UV-vis and fluorescence spectroscopy. Both steady-state and time-resolved fluorescence spectroscopic surveys showed remarkable fluorescence quenching phenomenon for L-1-L-5 in the presence of C-60 which was primarily attributed to involvement of a static process. The observed fluorescence quenching in L-1-L-5 was described in terms of both - and n- interactions of the naphthalene moieties and the nitrogen donor groups on the aza-crown macrocyclic ligands with C-60, respectively. Moreover, DFT calculations using B3LYP/6-31G* basis set confirmed on the aforesaid - interaction of naphthalene groups on the aza-crowns with C-60. The DFT calculations also established significant distributions of charge between C-60 and L-1-L-5 in according to the electronic structure and geometry of L-1-L-5/C-60, very similar to phthalocycnine/C-60 systems.