New C^∧N^∧C Bis-Cyclometalated Platinum(II) Complexes: Synthesis, Structures, and Photophysical Properties

Abstract

The reaction of a new ligand, ethyl 2,6-diphenylisonicotinate (EtO 2 C-C^N^C-H 2), with K 2 PtCl 4 in acetic acid affords the mono-cyclometalated complex, [{(EtO 2 C-C^N^C-H)Pt(-Cl)} 2 ] (1), which transforms to the bis-cyclometalated derivative, [Pt(EtO 2 C-C^N^C)(DMSO)] (2), when heated in hot DMSO. Complex 2 is the precursor for preparing a new series of neutral mononuclear bis-cyclometalated complexes [Pt(EtO 2 C-C^N^C)(L)] [L= tht (3), PPh 3 (4), CN-t Bu (5), py (6), py-t Bu (7), py-NH 2 (8), py-CN (9) and py-CONH 2 (10)]. These new complexes have been characterised spectroscopically and structures of 2-10 have been determined crystallographically. Within each crystal structure the individual molecules pack in a head to tail arrangement. Non-covalent interactions including •••, C-H•••O, C-H•••N, N-H•••Pt, N-H•••, C-H••• and N-H…O contribute significantly to the supramolecular structures displayed by these complexes in the solid state. All complexes display UV-Vis absorptions in dichloromethane solution. Excitation and emission studies as well as lifetime measurements are described and can be correlated to the solid state structures of 2 the complexes. DFT and TDDFT computational studies have been performed on 5 and 8 which support the conclusions drawn from the photophysical studies.

Neutral benzoquinolate cyclometalated platinum(II) complexes as precursors in the preparation of luminescent Pt–Ag complexes

“…The pentafluorophenyl ligand is in a trans position with respect to the nitrogen atom of the bzq ligand. As previously observed in other platinum(II) complexes containing the bzq ligand [13,17,27,30,47,59] or other cyclometalated planar ligands [28,29,60]. The complexes establish a supramolecular arrangement through pÁ Á Áp interactions of the bzq aromatic ring system of different moieties that stack in a parallel fashion, forming an infinite array with interplanar distances of ca.…”

Unusual Metal–Metal Bonding in a Dinuclear Pt–Au Complex: Snapshot of a Transmetalation Process

“…[34] Nevertheless, ar emarkable feature of complex 2 is the persistence of the Pt À Au bond in solution. In agreement with the existence of aPt À Au bond, the room-temperature 31 PNMR spectrum of 2 shows two signals corresponding to the two phosphorus atoms of the PPh 3 ligands,b oth of which show 195 Pt- 31 Pc oupling (Figure 4a). Thes ignal corresponding to the Patom bonded to Pt appears as asinglet at 22.5 ppm with Pt satellites ( 1 J P-Pt = 3680 Hz), whereas that corresponding to the Patom bonded to Au appears as as inglet at 34.6 ppm, also with Pt satellites ( 2 J P-Pt = 254 Hz).…”

“…Concomitantly,t he Pt-C7 distance becomes significantly longer than the Pt-C13 distance, which is in the typical range found for Pt II complexes containing this or quite similar CNC ligands. [15,16,31,32] The C7 phenylene ring remains perfectly planar. However, whereas the rest of the CNC ligand remains coplanar with the square-planar environment of the Pt center,t he C7 ring deviates remarkably from this plane (23.1 (1)8 8).…”

Luminescent PtII Complexes of Tridentate Cyclometalating 2,5‐Bis(aryl)‐pyridine Ligands

“…Consequently, the idea arose of using tridentate dicarbanionic cyclometalating ligands of the 2,6-di(phen-2-yl)pyridine ( -PhPyPh -, see Scheme 1) type with Pt II . [21][22][23][24][25][26][27][28][29][30][31][32] Recently, Che et al employed several derivatives of this ligand type, with the aim of providing suitable excited states through variation of the 2,5-aryl groups at the central pyridine unit, and they achieved very efficient triplet emitters, which show phosphorescence, even at room temperature. One crucial move in their ligand design was the use of thiophene as one of their pending metalated aryl groups, with complex 4 in Scheme 2 being the most efficient triplet emitter.…”