Design of Luminescent, Heteroleptic, Cyclometalated PtII and PtIV Complexes: Photophysics and Effects of the Cyclometalated Ligands. Issue 21 (20th March 2019)

• Record Type: Journal Article
• Authors: Giménez, Nora; Lalinde, Elena; Lara, Rebeca; Moreno, M. Teresa
• Is Part Of: Chemistry. Volume 25:Issue 21(2019)
• Page Start: 5514
• Page End: 5526
• Publication Date: 2019-03-20
• Subjects: cyclometalated ligands -- density functional calculations -- luminescence -- photochemistry -- platinum; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201806240
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: Neutral pentafluorophenyl benzoquinolinyl Pt II [Pt(bzq)(HC^N−κN)(C6 F5 )] (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)(C6 F5 )Cl] (2 b –g, bzq: benzo[h]quinolinyl) derivatives, generated by oxidation of 1 b –g with PhICl2, are reported. The oxidation reaction of 1 a evolved with formation of the bimetallic Pt IV complex syn ‐[Pt(bzq)(C6 F5 )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 CH2 Cl2 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. Abstract : Luminescent platinum complexes : The influence of the electronic nature of a second heterocycle on the photophysical behavior of pentafluorophenyl benzoquinolinyl Pt II (as HC^N ligand) and Pt IV (as C^N) complexes has been investigated. These heteroleptic systems display strong single or multiple emissions depending on the heterocycle and the oxidation state of the Pt, which are useful for the design of multiple metal‐based chromophores with potential application in different fields.