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

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.