Pt^II Phosphors with Click-Derived 1,2,3-Triazole-Containing Tridentate Chelates

Abstract

A series of Pt II complexes featuring 1,2,3triazole-derived N ∧ N ∧ N-, N ∧ C ∧ N-and C ∧ N ∧ C-coordinating ligands were studied both experimentally and computationally aiming at the design of new Pt II phosphors. By virtue of click chemistry, the new complexes were readily functionalized, e.g., with bulky groups in order to suppress aggregation of the complexes. For a N ∧ C ∧ N-type cyclometalated Pt II complex, the high energy of the π* orbitals of the 1,2,3-triazole units gave rise to deep-blue phosphorescence; the poor luminescence quantum yield was attributed to an inadequate energy separation between the emissive state and the d−d states. However, when the 1,2,3-triazole donor moiety acted as a spectator/ancillary ligand only, an intense green emission could be achieved (Φ PL = 0.57, τ = 4.6 μs).

Photoluminescence of Ni(II), Pd(II), and Pt(II) Complexes [M(Me2dpb)Cl] Obtained from C‒H Activation of 1,5-Di(2-pyridyl)-2,4-dimethylbenzene (Me2dpbH)

“…Furthermore, our study allowed us to trace the influence of the two methyl groups of the dpb ligand system. Starting from the parent [Pt(dpb)Cl] systems, various substituents on both ligand parts have been introduced previously and the effects on UV-vis absorption, photoluminescence, and electrochemical potentials were studied [ 5 , 16 , 38 , 52 , 54 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 ]. Within this series, [Pt(Me 2 dpb)Cl] was very recently synthesised from the protoligand Me 2 dpbH and K 2 [PtCl 4 ] in a 50% yield using the “classical” procedure of heating in glacial acetic acid [ 60 ].…”

Direct Base-Assisted C‒H Cyclonickelation of 6-Phenyl-2,2′-bipyridine

“…Later, Constable et al introduced cycloruthenation, cycloplatination, and cyclopalladation through C-H activation (direct cyclometalation) of aryl/N-donor moieties [5,6]. This straightforward synthetic approach coupled with the potential diversity of π-conjugated derivatives of CˆN ligands to tailor photophysical properties led to intensive development in the field with more than 1000 congeners published today [7][8][9][10][11][12][13][14][15][16][17][18][19]. For Pd(II) salts (e.g., chloride or acetate) the direct cyclometalation of 2-phenylpyridine proceeds already at room temperature [6,14,20].…”

Bright luminescent lithium and magnesium carbene complexes

“…[41][42][43][44] Similar ligands, which had been studied mainly as NNN pincers (Fig. 1 II), [45][46][47][48][49][50][51][52][53][54][55][56][57] have been pioneered by Bezuidenhout [58][59][60][61][62] (CNC pincer, C: mesoionic carbene MIC; III and IV) and Kunz [63][64][65][66][67][68] (CNC pincer, C: N-heterocyclic carbene NHC; V). Mesoionic carbenes, [69][70][71][72][73][74][75] in general, and 1,2,3-triazolinylidenes, in particular, excel through their donating properties 76,77 and, as such, are expected to stabilize high-valent transition metals.…”

“…Despite the fact that they are much less popular than conventional NHCs 42 and less explored in photochemistry, they increasingly attract attention. 52,[78][79][80][81][82][83][84][85][86][87][88][89] During our initial coordination experiments with the 1,2,3-triazolinylidene decorated car-bazolide obtained by deprotonation of 3, we noticed strong luminescence upon deprotonation (vide infra). Intriguingly, Kunz had already noticed luminescence for lithium carbazolyl bridged dicarbenes, however, these systems have not been studied spectroscopically yet (Fig.…”