Coordination-driven molecular switch on the base of an ESIPT-capable pyrimidine ligand: Synthesis, fine-tuning of emission by the halide anion and theoretical studies
Nikita A. Shekhovtsov , Elena B. Nikolaenkova , Sofia Vorobyeva , Alexey A. Ryadun , Mark B. Bushuev
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引用次数: 0
Abstract
ESIPT-based materials (ESIPT = Excited State Intramolecular Proton Transfer) find diverse applications in optoelectronics and biomedicine owing to the peculiarities of their luminescence properties. Here, an ESIPT-capable compound 2-(3,5-dimethyl-1H-pyrazol-1-yl)-4-(2-hydroxyphenyl)pyrimidine (HL4,2,Me) featuring a short O–H⋅⋅⋅N intramolecular hydrogen bond and two N,N-sites for metal binding has been synthesized. HL4,2,Me is the first reported molecule which can act as an ESIPT molecular switch triggered by metal ion coordination without its deprotonation. Drastic changes in the HL4,2,Me conformation in the [Zn(HL4,2,Me)X2] (X = Cl, Br, I) complexes significantly alter the photoluminescence response compared to the free ligand. In the solid state, HL4,2,Me exhibits barrierless ESIPT and large Stokes-shifted yellow-orange emission due to the interplay of anti-Kasha S2 → S0 fluorescence and Kasha-like T1 → S0 phosphorescence radiative channels. The violation of Kasha’s rule for HL4,2,Me is justified by an extraordinarily large S2 – S1 energy gap (ca. 0.9 eV), slowing down the rate of S2 → S1 internal conversion. The photoluminescence behavior of the ESIPT–incapable zinc(II) coordination compounds strongly depends on the halide anion: the chlorido complex exhibits only fluorescence, the bromido complex displays a minor phosphorescence channel in addition to a major fluorescence channel, while the iodido complex exhibits predominantly phosphorescence. As a result, the emission color of the [Zn(HL4,2,Me)X2] complexes changes gradually from blue for X = Cl to orange for X = I, providing a platform for the fine-tuning of emission by the halide anion.
期刊介绍:
JPPA publishes the results of fundamental studies on all aspects of chemical phenomena induced by interactions between light and molecules/matter of all kinds.
All systems capable of being described at the molecular or integrated multimolecular level are appropriate for the journal. This includes all molecular chemical species as well as biomolecular, supramolecular, polymer and other macromolecular systems, as well as solid state photochemistry. In addition, the journal publishes studies of semiconductor and other photoactive organic and inorganic materials, photocatalysis (organic, inorganic, supramolecular and superconductor).
The scope includes condensed and gas phase photochemistry, as well as synchrotron radiation chemistry. A broad range of processes and techniques in photochemistry are covered such as light induced energy, electron and proton transfer; nonlinear photochemical behavior; mechanistic investigation of photochemical reactions and identification of the products of photochemical reactions; quantum yield determinations and measurements of rate constants for primary and secondary photochemical processes; steady-state and time-resolved emission, ultrafast spectroscopic methods, single molecule spectroscopy, time resolved X-ray diffraction, luminescence microscopy, and scattering spectroscopy applied to photochemistry. Papers in emerging and applied areas such as luminescent sensors, electroluminescence, solar energy conversion, atmospheric photochemistry, environmental remediation, and related photocatalytic chemistry are also welcome.