Interplay of the Cu⋯Cu distance and coordination geometry as a factor affecting the quantum efficiency in dimeric copper(I) halide complexes with derivatives of 4-pyrazolylpyrimidine-2-thiol

Interplay of the Cu⋯Cu distance and coordination geometry as a factor affecting the quantum efficiency in dimeric copper(I) halide complexes with derivatives of 4-pyrazolylpyrimidine-2-thiol Full article

Journal

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

Output data

Year: 2025, Volume: 54, Number: 22, Pages: 9000-9015 Pages count : 16 DOI: 10.1039/D5DT00498E

Authors

Skvortsova Sofia V. ^1,2 , Verkhov Fyodor K. ^2,3 , Nikolaenkova Elena B. ³ , Rakhmanova Marianna I. ¹ , Kokina Tatiana E. ¹ , Sukhikh Taisiya S. ¹ , Shekhovtsov Nikita A. ¹ , Bushuev Mark B. ¹

Affiliations

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

Bicyclic pyrazolylpyrimidine compounds, 2-benzylthio-4-(3,5-dimethyl-1H-pyrazol-1-yl)pyrimidine (LH) and 2-benzylthio-4-(3,5-dimethyl-1H-pyrazol-1-yl)-6-methylpyrimidine (LMe) were synthesized and studied as ligands for the preparation of copper(I) halido complexes. In the solid state, LH and LMe demonstrate dual excitation-wavelength dependent emission, i.e. fluorescence at higher excitation energies and phosphorescence at lower excitation energies due to the presence of a heavy sulphur atom. The reactions of LH and LMe with CuBr and CuI afforded a series of centrosymmetric binuclear complexes of the [Cu2L2Hal2] type (L = LH, Hal = Br, I; L = LMe, Hal = I). The possibility of rotation of the benzylthio group relative to the pyrazolylpyrimidine core leads to the isolation of two polymorphic modifications of the copper(I) iodido complex with LH, which differ by the Cu···Cu distance by more than 0.2 Å (2.86 Å for [Cu2(LH)2I2] (form I) vs. 2.65 Å for [Cu2(LH)2I2] (form II)). The isolation of the [Cu2(LH)2I2] complex in two different crystalline forms made it possible to reveal the influence of a rarely explored factor, namely the change in the Cu···Cu distance in a single molecule, on the photoluminescence quantum efficiency. Two structural indices, τdim, which showcases the degree of merging of CuLHal monomers into the centrosymmetric [Cu2L2Hal2] dimers, and τplan, which characterises the degree of planarization of the N2CuHal2CuN2 unit, were introduced and used for combined experimental and theoretical analysis of the relation between the structure of the complexes and their luminescence. All complexes exhibit phosphorescence of the ligand-to-halide charge transfer (LXCT) character in the orange region. According to TDDFT calculations, an increase in the Cu···Cu distance facilitates structural rearrangement in the T1 state followed by a rapid decrease in the T1-S0 energy gap and subsequent non-radiative decay via electron-phonon coupling, which substantiates the higher photoluminescence quantum yield (PLQY) of [Cu2(LH)2I2] (form II) (Cu···Cu 2.65 Å) compared to [Cu2(LH)2I2] (form I) (Cu···Cu 2.86 Å).

Skvortsova S.V. , Verkhov F.K. , Nikolaenkova E.B. , Rakhmanova M.I. , Kokina T.E. , Sukhikh T.S. , Shekhovtsov N.A. , Bushuev M.B.
Interplay of the Cu⋯Cu distance and coordination geometry as a factor affecting the quantum efficiency in dimeric copper(I) halide complexes with derivatives of 4-pyrazolylpyrimidine-2-thiol
Dalton Transactions. 2025. V.54. N22. P.9000-9015. DOI: 10.1039/D5DT00498E WOS OpenAlex

Submitted:	Feb 28, 2025
Accepted:	Apr 22, 2025
Published online:	Apr 24, 2025
Published print:	Jun 14, 2025

Web of science:	WOS:001487332800001
OpenAlex:	W4409764698

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