Universität zu Köln

Niazi, Maryam ORCID: 0009-0006-3486-3690, Maisuls, Iván ORCID: 0000-0002-6494-1446, Strassert, Cristian A. ORCID: 0000-0002-1964-0169, González-Herrero, Pablo ORCID: 0000-0002-7307-8349 and Klein, Axel ORCID: 0000-0003-0093-9619 (2025). A tight binding pocket in photoluminescent N^C^N cyclometalated Pt( ii ), Pd( ii ), and Ni( ii ) complexes. Dalton Transactions, 54 (37). pp. 14025-14039. Royal Society of Chemistry. ISSN 1477-9226

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Abstract

In the frame of our research aiming to develop efficient triplet-emitting materials, we are exploring the role of the second coordination sphere in enhancing the rigidity of structures and its controlling aspect over the extents of excited state distortions. We thus synthesised three N^C^N cyclometalated complexes [M(L Bn )Cl] (M = Pt, Pd, and Ni), where the two ortho -positions of the pyridyl moieties in 1,3-di(2-pyridyl)-benzene are benzyl substituted (Bn) forming a tight binding pocket for the metal and the Cl − ancillary ligand. The molecular structures from single-crystal X-ray diffraction show a markedly distorted square planar M( ii ) coordination with τ 4 values of around 0.4. UV-vis absorption spectra show long-wavelength bands in the range 350 to 5400 nm with the energies increasing along the series Ni < Pt < Pd. The Pt( ii ) complex emits in solution at 298 K ( λ max = 544 nm) and displays aggregated emission within poly(methyl methacrylate) (PMMA) films at various concentrations at 298 K. The Pd( ii ) derivative exhibits a broad emission band at 77 K in a frozen glassy 2-MeTHF matrix, peaking at 530 nm. Very different from the Pt( ii ) and Pd( ii ) spectra, the Ni( ii ) sample showed a broad emission with λ max = 699 nm at 77 K, with a quantum yield of 20% and ms lifetime. TD-DFT calculated decomposition of the assumed emissive T 1 state showed similar 3 MLCT character of about 30% for all three complexes, but marked differences in LC character of about 38% for Pd and Pt and only 5% for Ni. In turn, for Ni the by far the highest MC character (42%) was calculated which strongly speaks against triplet photoluminescence from the Ni( ii ) complex.

Item Type:	Article
Creators:	Creators Email ORCID ORCID Put Code Niazi, Maryam UNSPECIFIED https://orcid.org/0009-0006-3486-3690 UNSPECIFIED Maisuls, Iván UNSPECIFIED https://orcid.org/0000-0002-6494-1446 UNSPECIFIED Strassert, Cristian A. UNSPECIFIED https://orcid.org/0000-0002-1964-0169 UNSPECIFIED González-Herrero, Pablo UNSPECIFIED https://orcid.org/0000-0002-7307-8349 UNSPECIFIED Klein, Axel UNSPECIFIED https://orcid.org/0000-0003-0093-9619 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-811548
Identification Number:	10.1039/D5DT01385B
Journal or Publication Title:	Dalton Transactions
Volume:	54
Number:	37
Page Range:	pp. 14025-14039
Number of Pages:	15
Date:	7 October 2025
Publisher:	Royal Society of Chemistry
ISSN:	1477-9226
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Chemistry > Institute of Inorganic Chemistry
Subjects:	Chemistry and allied sciences Life sciences
['eprint_fieldname_oa_funders' not defined]:	Publikationsfonds UzK
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/81154