Probing of the local environment and calculation of J.O. parameters for Eu3+ CMPO functionalized pillararene complexes by time resolved fluorescence spectroscopy

Abstract

An attempt was made to understand the complexation of Eu3+ with structurally modified CMPO-functionalized pillararenes by luminescence spectroscopy. Formation of single species with different numbers of inner sphere water molecules was found to be present for all the complexes. On increasing spacer length between ligating moieties and supramolecular pillararenes, the stereo-chemical crowding around ligating oxygen decreased. Therefore, strong covalent metal–oxygen bond was formed which was reflected in the increasing trend of the computed Ω2 values (Judd–Offelt parameter): LI (4.66×10−20)<LII (6.82×10−20)<LIII (7.85×10−20). Deconvolution of each 5D0→7F1, 5D0→7F2 and 5D0→7F4 transitions into two peaks revealed that the most probable local symmetry around Eu3+ was C6/C6v. The radiative lifetime for the Eu complexes followed LI (4.09ms)>LII (3.19ms)>LIII (2.94ms) while the branching ratio values for all three complexes followed the same trend as β2>β4>β1. The other photo-physical constants like asymmetric factor, quantum efficiency, magnetic and electric dipole transition probabilities were also computed.