Structural and Photophysical Studies of Phosphorescent Three-Coordinate Copper(I) Complexes Supported by an N-Heterocyclic Carbene Ligand

Abstract

A series of four neutral luminescent three-coordinate Cu(I) complexes (IPr)Cu(N ∧ N), where IPr is a monodentate N-heterocyclic carbene (NHC) ligand (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) and N ∧ N denotes monoanionic pyridyl-azolate ligands, have been synthesized and characterized. A monomeric, three-coordinate geometry, best described as distorted trigonal planar, has been established by single-crystal X-ray analyses for three of the derivatives. In contrast to the previously reported (IPr)Cu(N ∧ N) complexes, the compounds described here display a perpendicular orientation between the chelating N ∧ N ligands and the imidazolylidene ring of the carbene ligand. The geometrical preferences revealed by X-ray crystallography correlate well with the NMR data. The conformational behavior of the complexes, investigated by variable-temperature 1 H NMR spectroscopy, indicate free rotation about the C NHC −Cu bond in solution. The complexes display broad, featureless luminescence at both room temperature and 77 K, with emission maxima that vary between 555 and 632 nm depending on sample conditions. Luminescence quantum efficiencies of the complexes in solution (Φ ≤ 17%) increase markedly in the solid state (Φ ≤ 62%). On the basis of time-dependent density functional theory (TD-DFT) calculations and the experimental data, luminescence is assigned to phosphorescence from a metal-to-ligand charge-transfer (MLCT) triplet state admixed with ligand-centered (LC) character.

A Bis(Diphosphanyl N‐Heterocyclic Carbene) Gold Complex: A Synthon for Luminescent Rigid AuAg2 Arrays and Au5 and Cu6 Double Arrays

“…Such an assignment is also in agreement with the observed long excited‐state lifetimes (see Table S1) . Lastly, Cu6 displayed a moderate emission (photoluminescence quantum yield, PLQY=6 %) centered at λ =710 nm, and is tentatively attributed to an excited state with 3 CC character on the basis of similarities with the [CuIpy] 4 cubane‐like complexes ,…”

“…The former is attributable to the spin and optically allowed singlet manifold metal‐metal‐to‐ligand charge transfer, 1 MMLCT, and the latter to a 1 [5dσ*→6pσ] transition with strong metal centered ( 1 MC) character, respectively . In CH 2 Cl 2 , Cu6 displayed a featureless absorption spectrum which can be attributed to a convolution of singlet‐manifold cluster centered ( 1 CC) and metal‐to‐ligand charge‐transfer transitions ( 1 MLCT; see Table S2 and Figure S4) …”

Photoluminescence of Seven‐Coordinate Zirconium and Hafnium Complexes with 2,2′‐Pyridylpyrrolide Ligands

“…Inspired by theser esults, we sought to furtheri nvestigate the luminescentp roperties of group 4c oordination compounds containing electron-rich N-heterocycle ligands.D ue to their close relationship to the pyridine dipyrrolide (PDP) ligand system,s ubstituted 2,2'-pyridylpyrrolide ligands (PMP = pyridine monopyrrolide) were identifieda s promisingc andidatest os upport photoluminescence via LMCT. While various favorable aspects of the coordination chemistry of PMP compounds including rich redox chemistry, [63][64][65] stabilization of high oxidations tates, [66,67] and photoluminescent properties [68][69][70] have been reported for late transition metals, few reportsa re available for early metals. [71] Here we describe the synthesis and characterization of seven-coordinate zirconium and hafnium species carrying three Me PMP Me ligands( Me PMP Me = 3,5-dimethyl-2-(2-pyridyl)pyrrolide).T hese complexesa re rare examples of group 4c ompounds exhibiting photoluminescence in solution at room temperature.…”

Mechanochemical preparation of copper iodide clusters of interest for luminescent devices

“…[1][2][3][4][5][6][7][8] The interest stems from the increasing demand of more-affordable complexes in preference to luminescent metal complexes based on precious (i.e. the platinum group) and rare-earth metals, which are oen quite expensive and environmentally problematic.…”