Conformational Locking of the Geometry in Photoluminescent Cyclometalated N^C^N Ni(II) Complexes

In our research aimed at replacing precious transition metals like platinum with abundant base metals such as nickel for efficient triplet emitters, we synthesized and studied Ni(II) complexes [Ni(LNHR)Cl]. These complexes containing the N^C^N cyclometalating dipyridyl-phenide ligand, equipped with...

Full description

Saved in:
Bibliographic Details
Published in:Molecules (Basel, Switzerland) Vol. 30; no. 9; p. 1901
Main Authors: Niazi, Maryam, Maisuls, Iván, Mai, Lukas A., Schäfer, Sascha A., Oster, Alex, Diaz, Lukas Santiago, Guldi, Dirk M., Doltsinis, Nikos L., Strassert, Cristian A., Klein, Axel
Format: Journal Article
Language:English
Published: Switzerland MDPI AG 24.04.2025
Subjects:
cyclometalation
DFT calculations
electrochemistry
Geometry
Hydrogen bonds
Ligands
nickel(II)
NMR
Nuclear magnetic resonance
Optimization
photoluminescence
cyclometalation
photoluminescence
electrochemistry
nickel(II)
DFT calculations
ISSN:1420-3049, 1420-3049
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:In our research aimed at replacing precious transition metals like platinum with abundant base metals such as nickel for efficient triplet emitters, we synthesized and studied Ni(II) complexes [Ni(LNHR)Cl]. These complexes containing the N^C^N cyclometalating dipyridyl-phenide ligand, equipped with pending H-bonding amine groups (NH(C₆H₅) (LNHPh) and NH(C₆H₅CH₂), ClLNHBn). Molecular structures determined from experimental X-ray diffractometry and density functional theory (DFT) calculations in the ground state showed marked deviation of the Cl− coligand (ancillary ligand) from the ideal planar coordination, with τ4 values of 0.35 and 0.33, respectively, along with hydrogen bonding interactions of the ligand NH function with the Cl− coligand. The complexes exhibit long-wavelength absorption bands at approximately 425 nm in solution, with the experimental spectra being accurately reproduced through time-dependent density functional theory (TD-DFT) calculations. Vibrationally structured emission profiles and steady-state photoluminescence quantum yields of 30% for [Ni(LNHPh)Cl] and 40% for [Ni(LNHBn)Cl] (along with dual excited state lifetimes in the ns and in the ms range) were found in frozen 2-methyl-tetrahydrofuran (2MeTHF) glassy matrices at 77 K. Furthermore, within a poly(methyl methacrylate) matrix, the complexes showed emission bands centered at around 550 nm within a temperature range from 6 K to 300 K with lifetimes similar to 77 K. Based on TD-DFT potential scans along the metal–ligand (Ni–N) coordinate, we found that in a rigid environment that restricts the geometry to the Franck-Condon region, either the triplet T5 or the singlet S4 state could contribute to the photoluminescence.
Bibliography:ObjectType-Article-1
SourceType-Scholarly Journals-1
ObjectType-Feature-2
content type line 14
content type line 23
ISSN:1420-3049
1420-3049
DOI:10.3390/molecules30091901