Design of Luminescent, Heteroleptic, Cyclometalated Pt II and Pt IV Complexes: Photophysics and Effects of the Cyclometalated Ligands

Autor: Nora Giménez, Elena Lalinde, Rebeca Lara, M. Teresa Moreno
Rok vydání: 2019
Předmět:
Zdroj: Chemistry – A European Journal. 25:5514-5526
ISSN: 1521-3765
0947-6539
Popis: Neutral pentafluorophenyl benzoquinolinyl Pt II [Pt(bzq)(HC^N−κN)(C 6 F 5 )] (1 a–g) complexes, bearing nonmetalated N-heterocyclic HC^N ligands [HC^N=2,5-diphenyl-1,3,4-oxadiazole (Hoxd) a, 2-(2,4-difluorophenyl)pyridine (dfppy) b, 2-phenylbenzo[d]thiazole (pbt) c, 2-(4-bromophenyl)benzo[d]thiazole (Br-pbt) d, 2-phenylquinoline (pq) e, 2-thienylpyridine (thpy) f, 1-(2-pyridyl)pyrene (pypy) g], and heteroleptic bis(cyclometalated) Pt IV fac-[Pt(bzq)(C^N)(C 6 F 5 )Cl] (2 b–g, bzq: benzo[h]quinolinyl) derivatives, generated by oxidation of 1 b–g with PhICl 2 , are reported. The oxidation reaction of 1 a evolved with formation of the bimetallic Pt IV complex syn-[Pt(bzq)(C 6 F 5 )Cl(μ-OH)] 2 3. The crystal structures of 1 a,d,f, 2 b,d,e and 3 were corroborated by X-ray crystallography. A comparative study of the absorption and photoluminescence properties of the two series of complexes Pt II (1) and Pt IV (2), supported by time-dependent DFT calculations (TD-DFT), is presented. The low-lying transitions (absorption and emission) of Pt II complexes 1 a–e [solution and polystyrene (PS) films] were assigned to the IL/MLCT mixture located on the cyclometalated Pt(bzq) unit, with minor IL′/ML′CT/LL′CT contributions involving the non-metalated ligand. Complex 1 g, bearing the more delocalized pyridyl pyrene (Hpypy) as an ancillary ligand, shows dual 1 ππ* and 3 ππ* (Hpypy) emission in fluid CH 2 Cl 2 and dual 3 IL/ 3 MLCT [Pt(bzq)] and [ 3 ππ*, Hpypy] phosphorescence at 77 K. Upon oxidation, Pt IV complexes 2 b–f display (solution, PS) ligand-based phosphorescence that arises from the bzq in 2 b ( 3 LC) or from the second C^N ligand in 2 c–f ( 3 L′C) with some 3 LL′CT in 2 f. Despite metalation of the pyrenyl group, 2 g exhibits dual emission 1 ππ*/ 3 ππ* located on the pypy chromophore.
Databáze: OpenAIRE
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