Synthesis, Air Stability, Photobleaching, and DFT Modeling of Blue Light Emitting Platinum CCC-N-Heterocyclic Carbene Pincer Complexes

Abstract

The recently reported metalation/transmetalation route for the synthesis of CCC-bis­(NHC) pincer ligand supported transition-metal complexes was extended to Pt. 2-(1,3-Bis­(N-butylimidazol-2-ylidene)­phenylene)­(chloro)­platinum­(II) (1) and its bromo analogue 2 were synthesized and characterized. X-ray crystal structure determinations revealed complexes 1 and 2 to have distorted-square-planar configurations around the metal. Photophysical and thermal properties of these complexes are reported, and their extended photostability in air is discussed and contrasted. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) computations of the ground state and various low-lying excited states have revealed admixing of Pt 5d orbitals and the ligand π* orbitals for both the ground state and the low-lying excited states of complex 1, indicating the low-lying states to be a mixture of metal-to-ligand charge-transfer and ligand-centered transition (MLCT-LC). Somewhat surprisingly, the computed gas-phase geometry of the excited state of complex 1 had a significant distortion, mostly about the Caryl–Pt–Cl angle. These complexes were congeners of materials for organic light emitting diodes (OLEDs).

Synthesis, characterization, photophysical properties, and catalytic activity of an SCS bis(N-heterocyclic thione) (SCS-NHT) Pd pincer complex

“…2 contains two 6,6-fused palladacycles in a twisted rac-conformation. [52][53][54] Furthermore, the rac-conformation of 3 has a chiral twist similar to the 5,6-fused-ring systems reported by Odinets 29 and to the 5,5-fused-ring complexes synthesized by Kruithof and coworkers. 43 While it is similar to the racconformation of the S-N-S ligand reported in 5-coordinate Cu complexes.…”

Correlating the Structural and Photo­physical Features of Pincer Luminophores and Monodentate Ancillary Ligands in PtII Phosphors

“…The Pt–P bond lengths are almost invariable and within the expected range (2.242–2.253 Å). The shorter Pt–C bond length of 1.977 Å is comparable to those of related platinum–NHC complexes 18,19. The location of the phenyl groups of the PPh 3 ligand above and below the coordination plane efficiently excludes the possibility of π–π stacking and Pt–Pt interactions between individual molecules.…”

HOMO–LUMO energy gap control in platinum(ii) biphenyl complexes containing 2,2′-bipyridine ligands

“…1,2,4,7,11 According to Kasha's rule, fast decay occurs in the triplet manifold to the lowest-lying triplet state (LLTS), which is the emissive state. 22 Density functional theory (DFT) 23 calculations have been extensively employed to study the geometry and electronic structure of square planar transition metal complexes of Pt(II), 17,24,25,26,27 Ni(II), 28,29 and Pd(II) 30,31 as well as those embedded in doped carbon nanocones, nanotubes and fullerenes. 22 Density functional theory (DFT) 23 calculations have been extensively employed to study the geometry and electronic structure of square planar transition metal complexes of Pt(II), 17,24,25,26,27 Ni(II), 28,29 and Pd(II) 30,31 as well as those embedded in doped carbon nanocones, nanotubes and fullerenes.…”