New Fluorenyl-Substituted Dioxotetraamine Ligands and Their Copper(II) Complexes − Crystal Structure and Fluorescent Sensing Properties in Aqueous Solution

Abstract

Two new ligands consisting of a fluorenyl and dioxotetraaza unit, namely, 2,10-diamino-6-(9H-fluoren-9-yl)-4,8-diazaundecane-5,7-dione (L 1 ) and 1-(9H-fluoren-9-yl)-1,4,7,10-tetraazadecane-5,6-dione (L 2 ) along with their copper(II) complexes have been synthesized. Their properties were examined by ES-MS and CV in aqueous solution and the crystal structure of the copper(II) complex of L 1 has also been deter- [a] mined. The recognition of the transition metal ions (Cu 2+ , Ni 2+ , etc.) by receptors has been studied in aqueous solutions using pH-potentiometric and fluorimetric titrations. The results show that the binding of Cu 2+ or Ni 2+ ion with L 1 leads to quenching of the fluorescence of the fluorenyl group, but on the contrary the fluorescence of L 2 is enhanced. The mechanisms are discussed.Scheme 1. Syntheses of ligands and complexes

Synthesis andin vitroactivity of platinum(II) complexes of two fluorenylspirohydantoins against a human tumour cell line

“…Moreover, there are data for potential application of such compounds as fluorescent sensors for metal ions, such as Cu(II) and Ni(II). [ 22,23 ] We have recently described synthetic procedures for formation of thioanalogues of (9′-fluorene)-spiro-5-hydantoin. [ 24 ] Moreover, the synthesis and structure of Cu(II) and Ni(II) complexes of (9′-fluorene)-spiro-5-(2,4-dithiohydantoin) have also been studied.…”

A Medium‐Controlled Fluorescence Dual‐Responsive Probe for Cu2+ and Hg2+ in Aqueous Solutions

“…In addition, the fluorene group is often used as a monomer in the synthesis of luminescent materials due to its special photophysical properties (13–15). The high quantum yield and long fluorescent lifetime make it an excellent fluorescent chromophore (16,17). In this report, we display a new fluorescence probe based on histidine, whose NH groups in the imidazole ring and the amino group have been modified by trityl group and Fmoc group, respectively.…”

“…The characteristic absorption bands of fluorenyl group increased gradually with the addition of Cu 2+ , indicating that the interaction of the fluorenyl group with Cu 2+ enhanced the UV–vis absorption ability of fluorenyl group. This result displays a hyperchromic effect from the complex of 1 with Cu 2+ which is due to the electron‐transfer from the bound Cu(II) to the photoexcited state of fluorenyl group (17,23). The electron‐transfer is favorable to obtain more excited states of the fluorenyl group, but the electron of the excited states can be captured by the metal ions, so the fluorescence intensity is quenched.…”

“…5. The coordination of Cu 2+ with 1 affected the electron density distribution of 1 , particularly for the fluorenyl group, according to the fluorescence and UV–vis experiments (16, 17, 26). However, the NMR experiment results of 1 ‐Hg 2+ exhibited different changes in contrast to 1 ‐Cu 2+ (Figures S6 and S7; Tables S1 and S2).…”

“…3 and 8 can explain the distinct fluorescence responses of 1 to Cu 2+ and Hg 2+ in different solvents. The coordination of Cu 2+ with the amino nitrogen could cause fluorescent quenching of fluorenyl group by the electron transfer from Cu 2+ in 3:1 CH 3 OH/H 2 O (17). But in 1:1 CH 3 OH/H 2 O, the interaction mode of 1 ‐Cu 2+ was very different from that one in 3:1 CH 3 OH/H 2 O, and the electron transfer process did not occur.…”