Green Phosphorescent Zn(II) Halide Complexes with N,N,N′,N′‐tetramethyl‐P‐indol‐1‐ylphosphonic Diamide as Ligand

Abstract

Tetrahedral Zn(II) complexes having general formula [ZnX 2 {O=P-(NMe 2 ) 2 Ind} 2 ] (X = Cl, Br, I, NCS) were isolated from the reaction between the indol-1-yl substituted phosphoramide N,N,N',N'tetramethyl-P-indol-1-ylphosphonic diamide O=P(NMe 2 ) 2 Ind and anhydrous Zn(II) precursors under mild conditions. The structures of the three halide derivatives were ascertained by single-crystal X-ray diffraction. The bromo-and iodo-derivatives revealed to be appreciably luminescent in the green region upon excitation with light below 300 nm, with emission bands centred between 520 and 530 nm. The large Stokes shifts and the excited state lifetimes in the milliseconds range indicated that triplet excited states are involved in the emission. TD-DFT calculations indicated that the luminescence is related to a ligand-centred transition with the involvement of triplet states.

Synthesis, Structural Characterization, and Phosphorescence Properties of Trigonal Zn(II) Carbene Complexes

“…The nonradiative deactivation of the 1 LLCT­(CN) state might be related to somewhat weaker π-electron density-accepting properties in the excited states of N -heterocyclic carbenes compared to cAAC, which results in higher LLCT excitation energies for 8 and makes the 3 LC­(bdt) state accessible. Although a couple of recently published articles reported the population of triplet excited states in the case of Zn II molecules, such a photophysical behavior remains uncommon for the complexes based on light and earth-abundant zinc metal. ,,− …”

Luminescent Behavior of Zn(II) and Mn(II) Halide Derivatives of 4-Phenyldinaphtho[2,1-d:1′,2′-f][1,3,2]dioxaphosphepine 4-Oxide and Single-Crystal X-ray Structure Determination of the Ligand

“…Another interesting metal center to be combined with [O=P]-donor ligands for optics is zinc. For instance, non-linear optical properties were observed for [ZnCl 2 (O=PPh 3 ) 2 ] [ 32 ], and Zn(II) halide complexes with N , N , N ′, N ′-tetramethyl- P -indol-1-ylphosphonic diamide showed intense green phosphorescence [ 33 ]. Given our interest in the preparation of luminescent metal complexes with phosphonates and cyclic organophosphorus compounds [ 34 , 35 , 36 , 37 ], we synthesized the two enantiomers of O=PPh(BINOL), and we started investigating the luminescent properties of the related Zn(II) and Mn(II) halide complexes.…”

Luminescence of ESIPT-capable zinc(ii) complexes with a 1-hydroxy-1H-imidazole-based ligand: exploring the impact of substitution in the proton-donating moiety

“…Recently, we demonstrated that 1-hydroxy-1H-imidazoles decorated with proton-accepting groups at position 2 of the imidazole ring and a pyridin-2-yl group at position 4 to assist the N 3 imidazolic atom in binding metal ions can act as ESIPT-capable ligands and coordinate Zn 2+ ions without deprotonation (HL p and HL q , see Scheme 2). Since Zn 2+ ions are known to be able to enhance the emission originating from the ligand-centered excited states due to so-called chela-tion-enhanced fluorescence (CHEF) effect, [125][126][127][128][129][130] their coordination by ESIPT-capable 1-hydroxy-1H-imidazoles led to a noticeable increase in the photoluminescence quantum yield (PLQY). 131,132 Moreover, the emission of the free ligands and complexes appeared to be tunable through the extension of the π-conjugation in the proton-accepting part of the molecule.…”