Structural, Photophysical, and Electrophosphorescent Properties of Platinum(II) Complexes Supported by Tetradentate N₂O₂ Chelates

Abstract

We present an examination of the structural and photophysical characteristics of [Pt(N(2)O(2))] complexes bearing bis(phenoxy)diimine auxiliaries (diimine=4,7-Ph(2)phen (1) and 4,4'-tBu(2)bpy (2)) that are tetradentate relatives of the quinolinolato (q) ligand. These neutral derivatives display high thermal stability (>400 degrees C in N(2)). While the crystal lattice in 1 consists of (head-to-tail)-interacting dimers, molecules of 2 are arranged into infinitely stacked planar sheets with possible pi-pi interactions but no close Pt.Pt contacts. Complexes 1 and 2 exhibit moderately intense low-energy UV/Vis absorptions around lambda=400-500 nm that undergo negative solvatochromic shifts. Both derivatives are highly luminescent in solution at 298 K with emission lifetimes in the micros range, and mixed (3)[l-->pi*(diimine)] (l=lone pair/phenoxide) and (3)[Pt(d)-->pi*(diimine)] charge-transfer states are tentatively assigned. The excited-state properties of 2 are also investigated by time-resolved absorption spectroscopy and by quenching experiments with pyridinium acceptors to estimate the excited-state redox potential. These emitters have been employed as electrophosphorescent dopants in multilayer OLEDs. Differences between the brightness, color, and overall performance of devices incorporating 1 and 2 are attributed to the influence of the diimine substituents.

Synthesis and Properties of Salen–Aluminum Complexes as a Novel Class of Color‐Tunable Luminophores

“…Such negative solvato- www.chemeurj.org chromism is consistent with the polar character of the electron-rich phenoxide ring in the ground state. This finding may suggest an involvement of partial charge transfer from a phenoxide ring to an imine in the salen-centered transition, similar to that found in the salen-Pt derivatives [17,19] and the 8-hydroxyquinoline-related metal complexes [20,37] (vide infra).…”

“…Furthermore, the salen ligands have often been employed in the phosphorescent emitters based on platinum. [17][18][19][20] All these reports have prompted us to consider whether the salen-Al complexes could be utilized as versatile materials for OLEDs; our group has recently demonstrated that the pentacoordinated salen-Al complexes with an aryloxy ancillary ligand can serve not only as efficient hole-blocking materials [21] for phosphorescent OLEDs, but also as hosts in the dopant assembly OLEDs based on a heterodinuclear Al/Ir complex. [22] They found that the salen-Al complexes possess suitable HOMO and LUMO energy levels, high thermal stability, and high PL efficiency, all of which may render them promising as emitting materials in OLEDs.…”

Binding Studies of Metal–Salphen and Metal–Bipyridine Complexes towards G‐Quadruplex DNA

“…Several complexes with 6,6'-diphenyl-2,2'bipyridine ligand derivatives have been reported. [28,29] We therefore adapted some of the previous protocols to prepare our new ligand (7)a nd corresponding metal complexes (4 and 5). AS uzuki cross-couplingr eactionu sing 6,6'-dibromo-2,2'-bipyridine and 2,4-dimethoxyphenyl boronic acid was carried out, followed by demethylation with boron tribromide to yield compound 7.T he phenolic scaffold was metalated by using Ni 2 + or VO 2 + salts to yield the corresponding metal-bipyridine precursor complexes 8 and 9,w hichw ere then reacted with chloroethyl piperidine to yield the new complexes 4 and 5.I t should be pointed out that no vanadyl complexes with 6,6'-diphenyl-2,2'-bipyridine ligandsh ave been previously reported.…”

Recent Advances in Transition Metal Complexes and Light‐Management Engineering in Organic Optoelectronic Devices

“…One approach to further rigidify the platinum complex framework is to adopt tetradentate ligands composed of C, N, or O donors. The use of Schiff base or hydroxyphenyl substituted phenanthroline platinum complexes for OLED applications was reported in early 2000s . A series of O 2 N 2 type Schiff base platinum complexes was synthesized and their photophysical and OLED properties were investigated.…”