Synthesis and luminescence studies of lanthanide complexes (Gd, Tb, Dy) with phenyl- and 2-pyridylthiolates supported by a bulky β-diketiminate ligand. Impact of the ligand environment on terbium() emission

• Published in: New journal of chemistry Vol. 44; no. 45; pp. 19769 - 19779
• Main Authors: Mironova, Olga A, Ryadun, Aleksey A, Sukhikh, Taisiya S, Konchenko, Sergey N, Pushkarevsky, Nikolay A
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 07.12.2020
• Subjects: Chelation; Coordination; Crystal structure; Crystallography; Dysprosium; Emission; Environmental impact; Gadolinium; Ligands; Luminescence; Metathesis; Photoluminescence; Recrystallization; Terbium; Tetrahydrofuran; Toluene
• ISSN: 1144-0546; 1369-9261
• DOI: 10.1039/d0nj04201c

The range of lanthanide complexes with bulky N , N ′-bis(Dipp)-substituted β-diketiminate ligand Nacnac − = CH(CMe(NDipp)) 2 − (Dipp = 2,6-diisopropylphenyl) has been expanded to the complexes [Ln(Nacnac)I 2 (thf) n ] ( 1 Ln , Ln = Gd , Tb , n = 2; Dy , n = 1; thf = tetrahydrofuran). They were further used in salt metathesis reactions with KSPh and KS(2-Py) (2-Py = 2-pyridyl), resulting in thiolato complexes [Ln(Nacnac)(SPh) 2 (thf)] ( 2 Ln ) and [Ln(Nacnac)(SPy) 2 ] ( 3 Ln ). As an analogue of 2 Tb without coordinated thf molecules, binuclear complex [{Tb(Nacnac)(SPh)} 2 (μ-SPh) 2 ] ( 4 Tb ) was obtained by reaction of dry TbI 3 with K(Nacnac) and KSPh in Et 2 O followed by recrystallization from toluene. The diiodo complexes possess different numbers of coordinated thf molecules and different coordination polyhedra owing to the lanthanide contraction. On the contrary, all 2 Ln and 3 Ln have the same molecular and crystal structures for a given thiolate, owing to the coordination rigidity provided by edge coordination of a Ph cycle or by chelating binding of a S(2-Py) − ligand. UV-vis and photoluminescence spectra were registered for all compounds. A triplet level of the Nacnac − ligand of 2.22 × 10 4 cm −1 was determined from the solid-state emission of Gd complex 1 Gd at 77 K; the triplet level in 2 Gd and 3 Gd was found at 2.16 × 10 4 cm −1 . Emission lifetimes and quantum yields were measured for all Tb compounds with the highest values for thiolato complexes 2 Tb and 3 Tb , while 1 Tb showed only weak emission. The relationship of the emission properties with the molecular and crystal structures is discussed, and better antenna properties are proposed for thiolato rather than for Nacnac − ligands. Structure-dependent photoluminescence was studied for lanthanide complexes with widespread Nacnac ligands, supplemented by thiolates; notable antenna properties of the latter are revealed.