N-Hydroxy–N-oxide photoinduced tautomerization and excitation wavelength dependent luminescence of ESIPT-capable zinc(II) complexes with a rationally designed 1-hydroxy-2,4-di(pyridin-2-yl)-1H-imidazole ESIPT-ligand

N-Hydroxy–N-oxide photoinduced tautomerization and excitation wavelength dependent luminescence of ESIPT-capable zinc(II) complexes with a rationally designed 1-hydroxy-2,4-di(pyridin-2-yl)-1H-imidazole ESIPT-ligand Full article

Journal

Dalton Transactions
ISSN: 1477-9226 , E-ISSN: 1477-9234

Output data

Year: 2022, Volume: 51, Number: 25, Pages: 9818-9835 Pages count : 18 DOI: 10.1039/d2dt01232d

Authors

Shekhovtsov Nikita A. ¹ , Vinogradova Katerina A. ¹ , Vorobyova Sofia N. ¹ , Berezin Alexey S. ¹ , Plyusnin Victor F. ² , Naumov Dmitry Yu. ¹ , Pervukhina Natalia V. ¹ , Nikolaenkova Elena B. ³ , Tikhonov Alexsei Ya. ³ , Bushuev Mark B. ¹

Affiliations

1	Nikolaev Institute of Inorganic Chemistry, Siberian Branch of Russian Academy of Sciences
2	Institute of Chemical Kinetics and Combustion, Siberian Branch of Russian Academy of Sciences
3	N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Branch of Russian Academy of Sciences

The ability of 1-hydroxy-1H-imidazoles to undergo proton transfer processes and to exist in N-hydroxy and N-oxide tautomeric forms can be used in coordination chemistry for the design of ESIPT-capable complexes. A series of ESIPT-capable zinc(II) complexes [Zn(HL)Hal2] (Hal = Cl, Br, I) with a rationally designed ESIPT-ligand 1-hydroxy-5-methyl-2,4-di(pyridin-2-yl)-1H-imidazole (HL) featuring spatially separated metal binding and ESIPT sites have been synthesized and characterized. Crystals of these compounds consist of a mixture of two isomers of [Zn(HL)Hal2]. Only a major isomer has a short intramolecular hydrogen bond O–H⋯N as a pre-requisite for ESIPT. In the solid state, the complexes [Zn(HL)Hal2] demonstrate temperature- and excitation wavelength dependent fluorescence in the cyan region due to the interplay of two intraligand fluorescence channels with excited state lifetimes spanning from 0.2 to 4.3 ns. The coordination of HL by Zn2+ ions results in an increase in the photoluminescence efficiency, and the photoluminescence quantum yields (PLQYs) of the complexes reach 12% at λex = 300 nm and 27% at λex = 400 nm in comparison with the PLQY of free HL of ca. 2%. Quantum chemical calculations indicate that N-hydroxy–N-oxide phototautomerization is both thermodynamically and kinetically favourable in the S1 state for [Zn(HL)Hal2]. The proton transfer induces considerable geometrical reorganizations and therefore results in large Stokes shifts of ca. 230 nm. In contrast, auxiliary ESIPT-incapable complexes [ZnL2][Zn(OAc)2]2·2H2O and [ZnL2][ZnCl2]2·4H2O with the deprotonated ligand exhibit excitation wavelength independent emission in the violet region with the Stokes shift reduced to ca. 130 nm.

Shekhovtsov N.A. , Vinogradova K.A. , Vorobyova S.N. , Berezin A.S. , Plyusnin V.F. , Naumov D.Y. , Pervukhina N.V. , Nikolaenkova E.B. , Tikhonov A.Y. , Bushuev M.B.
N-Hydroxy–N-oxide photoinduced tautomerization and excitation wavelength dependent luminescence of ESIPT-capable zinc(II) complexes with a rationally designed 1-hydroxy-2,4-di(pyridin-2-yl)-1H-imidazole ESIPT-ligand
Dalton Transactions. 2022. V.51. N25. P.9818-9835. DOI: 10.1039/d2dt01232d WOS РИНЦ OpenAlex

Submitted:	Apr 20, 2022
Accepted:	Jun 1, 2022
Published online:	Jun 1, 2022

Web of science:	WOS:000811619200001
Elibrary:	48721945
OpenAlex:	W4283020503

DB	Citing
OpenAlex	17
Web of science	17
Elibrary	6