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

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 Full article

Journal

Journal of Photochemistry and Photobiology A-chemistry
ISSN: 1010-6030 , E-ISSN: 1873-2666

Output data

Year: 2025, Volume: 459, Article number : 116091, Pages count : DOI: 10.1016/j.jphotochem.2024.116091

Authors

Shekhovtsov N.A. ¹ , Nikolaenkova E.B. ² , Vorobyeva S. ¹ , Ryadun A.A. ¹ , Bushuev M.B. ¹

Affiliations

1	Nikolaev Institute of Inorganic Chemistry, Siberian Branch of Russian Academy of Sciences, 3, Acad. Lavrentiev Ave., Novosibirsk 630090, Russia
2	N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Branch of Russian Academy of Sciences, 9, Acad. Lavrentiev Ave., Novosibirsk 630090, Russia

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.

Shekhovtsov N.A. , Nikolaenkova E.B. , Vorobyeva S. , Ryadun A.A. , Bushuev M.B.
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
Journal of Photochemistry and Photobiology A-chemistry. 2025. V.459. 116091 . DOI: 10.1016/j.jphotochem.2024.116091 WOS Scopus OpenAlex

Submitted:	Aug 24, 2024
Accepted:	Oct 10, 2024
Published online:	Oct 19, 2024
Published print:	Feb 1, 2025

Web of science:	WOS:001342434400001
Scopus:	2-s2.0-85206884674
OpenAlex:	W4403557019

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