Diphenylether based derivatives as Fe(iii) chemosensors: spectrofluorimetry, electrochemical and theoretical studies

By Sharma, Rashmi; Chhibber, Manmohan & Mittal, Susheel K.
Published in RSC Adv. The Royal Society of Chemistry 2015

Abstract

4-(2,4-Dinitrophenoxy)-3-methoxybenzaldehyde (DPE-I) and (4-(2,4-dinitrophenoxy)-3-methoxyphenyl)methanol (DPE-II) were synthesized with high yield and characterized by spectroscopic techniques. The complexation behaviours of DPE-I and DPE-II for various cationic species (Na+, K+, Mg2+, Cu2+, Ba?+, Cr3+, Fe?+, Co?+, Ni2+, Zn2+, Cd2+, and Pb2+) in HEPES buffered CH3CN : H?O system were investigated and compared by spectroscopic and voltammetric techniques. Both receptors showed high degree of selectivity for Fe?+ over other cations. Receptors showed 1 : 1 complexation with Fe?+. DPE-I showed fluorescence quenching on complexation with Fe?+ ion at 350 nm due to PET (photon induced transfer) mechanism between Fe?+ and the large [small pi] electron conjugate system of ligand, while DPE-II displayed emission band at 314 nm which underwent fluorescence quenching selectively on gradual addition of Fe?+ at 314 nm and simultaneously a new band at 424 nm emerged with isosbestic point at 355 nm which increases with increase in Fe?+ conc. Electrochemically, DPE-I due to presence of electron withdrawing (aldehydic group) facilitates reduction of nitro group on benzene ring of the molecule so, peak potentials of the two curves obtained for DPE-I appear at -1.16 V (Epc1) and -1.39 V (Epc2) respectively, while in DPE-II (methanolic group) due to its electron donating character makes the reduction of nitro group a little difficult due to which peak potentials occur at higher potential as compared to DPE-I i.e. at -1.30 V (Epc1) and -1.43 V (Epc2) respectively.

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