Alternating and statistical copolymers of 9-vinylcarbazole with diethyl fumarate (1), diethyl maleate (2), methacrylic acid (3), maleic anhydride (4), or maleic acid (5) were synthesized and characterized. These copolymers were tested as polymer ligands, that might be able to suppress the environmental vibronic quenching of a lanthanide ion and, simultaneously, to function as energy donors in the ligand-to-metal energy transfer processes. Time-resolved luminescence of a series of [Tb(III)-ligand] complexes in common and deuterated solvents revealed that the complexing properties of copolymers 3 or 5 are stronger than those of 1 or 2. Consequently, the strong binding affinity decreases the ligand-metal (donor-acceptor) distance and gives rise to an efficient ligand-to-metal energy transfer. Thus, the intensities of the long-lived emission (5D4→7F6, 5D4→7F5, 5D4→7F4, 5D4→7F3) of the [Tb(III)-3], [Tb(III)-5], and [Tb(III)-1] or [Tb(III)-2] complexes were found to be eight times, five times, and less than twice that of uncomplexed Tb3+, respectively.
Polymer ligands containing a covalently bonded quinolinone fluorophore and COOH (L1) or COONa (L2) binding sites were synthesized by the reaction of high-molecular-weight poly[styrene-alt-(maleic anhydride)] with 7-amino-4-methylquinolin-2(1H)-one and methanol and subsequent neutralization. The ligand-to-metal energy transfer and ligand binding properties in a series of [Tb(III)-ligand] complexes were investigated by steady-state and time-resolved luminescence spectroscopy in methanol or deuterated methanol. The intensity of the long-lived terbium(III) ion emission at 490, 545, 585 and 620 nm was greatly enhanced upon addition of L1 or L2. Based on the differences in luminescence data obtained for [Tb(III)-L1] and [Tb(III)-L2] complexes, a qualitative model for the interaction of terbium(III) ion with L1 and L2 is put forward. The experimental luminescence decay curves were double-exponential (τ1, τ2) with predominating longer component (rel B1 > 85%) for both [Tb(III)-L1] and [Tb(III)-L2] complexes. About 2.5 or 2 methanol molecules were coordinated to Tb3+ in [Tb(III)-L1] or [Tb(III)-L2] complexes, respectively, whereas ca. 6.5 methanol molecules were coordinated to Tb3+ in methanol.
Summary: Polymer ligand containing a quinolinone fluorophore and carboxyl binding sites (III) was synthesized by the reaction of parent poly[styrene‐alt‐(maleic anhydride)] with 7‐amino‐4‐methylquinolin‐2(1H)‐one (I) and methanol. The ligand‐to‐metal resonance energy transfer and ligand binding properties of Tb(III)‐III complexes were investigated by steady‐state and time‐resolved luminescence spectroscopy in methanol or deuterated methanol and compared with those of the low‐molecular‐weight model compound, N‐[4‐methyl‐2‐oxo‐1,2‐dihydroquinolin‐7‐yl]succinamic acid (II). The long‐lived emission intensity of Tb3+ at 490, 545, 585, and 620 nm corresponding to the 5D4 → 7F6, 5D4 → 7F5, 5D4 → 7F4, and 5D4 → 7F3 transitions, respectively, was strongly increased by the addition of III (as much as 10 000 times) and decreased in the order of Tb(III)‐III ≫ Tb(III)‐II > Tb(III)‐I > Tb(III). The efficiency of energy transfer (E) was evaluated from emission intensity of the donor (III) in the presence or absence of the acceptor (Tb3+) as E = 0.71–0.94, depending on the acceptor concentration and ligand neutralization. The experimental luminescence‐decay curves were double‐exponential (τ1, τ2) with a predominating longer component (rel B1 = 85%) for Tb(III)‐III and single‐exponential (τ) for Tb(III)‐II. One or three methanol molecules were coordinated to Tb3+ in Tb(III)‐III with or without neutralization of III, respectively, whereas approximately 6.5 methanol molecules were coordinated to Tb3+ in Tb(III)‐II. Terbium ion coordinates with 7–8 molecules of methanol in methanolic solution.Schematic energy‐level diagram for fluorescence resonance energy transfer in a Tb(III)‐ligand complex.magnified imageSchematic energy‐level diagram for fluorescence resonance energy transfer in a Tb(III)‐ligand complex.
Summary: New conjugated copolymers containing 9,9-dioctylfluorene and terephthalate units (as dimethyl ester or free acid) were synthesized by the Suzuki coupling and characterized by GPC and NMR, FT-IR and UV-VIS spectroscopies. These copolymers proved to be good luminescent materials showing emissions in the blue region of the visible spectrum both in solution (l em ¼ 450 nm) and in thin layers. Differences in the luminescence properties were attributed to various extents of aggregation. It was shown that interchain interaction can be avoided by the formation of the copolymer sodium salt. The copolymers were tested as active layers in light-emitting devices and the formation of their Eu(III) complexes was studied.
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