Highly photoluminescent copper carbene complexes based on prompt rather than delayed fluorescence

Simple carbene complexes of copper halides give photoluminescence quantum yields of up to 96%, with sub-nanosecond emission lifetimes.


Supporting Information
Synthesis and Characterization of Complexes  Table S2. Structural parameters of the optimized ground and excited state geometries of copper and gold halides Figure S6: Photoluminescence spectra of 1a at 4 K to 300 K for 420-700 nm.   Table S3. Photophysical properties of ( Ad L)MX complexes in aerated CH 2 Cl 2 solution Table S4. Binding energies and M-O distances of the S 0 and T 1 states of the THF-coordinated halide complexes Figure S9. Optimized calculated geometries of the S 0 and T 1 states of THF-coordinated halide complexes. Table S5. Electrochemical data Cryogenic and time-resolved PL measurements.
X-ray Crystallography Figure S10. Crystal structure of independent molecules A for ( Ad L)CuX (X = Cl, Br, I).

Synthesis of Complexes
General Considerations. Unless stated otherwise all reactions were carried out in air. Solvents were distilled and dried as required. Sodium tert-butoxide and carbazole were purchased and used as received.
All electrochemical experiments were performed using an Autolab PGSTAT 302N computer-controlled potentiostat. Cyclic voltammetry (CV) was performed using a three-electrode configuration consisting of either a glassy carbon macrodisk working electrode (GCE) (diameter of 3 mm; BASi, Indiana, USA) combined with a Pt wire counter electrode (99.99 %; GoodFellow, Cambridge, UK) and an Ag wire pseudoreference electrode (99.99 %; GoodFellow, Cambridge, UK). The GCE was polished between experiments using alumina slurry (0.3 μm), rinsed in distilled water and subjected to brief ultrasonication to remove any adhered alumina microparticles. The metal electrodes were then dried in an oven at 100 °C to remove any residual traces of water, the GCE was left to air dry and residual traces of water were removed under vacuum. The Ag wire pseudoreference electrodes were calibrated to the ferrocene/ferrocenium couple in MeCN at the end of each run to allow for any drift in potential, following IUPAC recommendations. S3 All electrochemical measurements were performed at ambient temperatures under an inert Ar atmosphere in MeCN containing the complex under study (0.14 mM) and [n-Bu 4 N][PF 6 ] as supporting electrolyte (0.13 mM). Data were recorded with Autolab NOVA software (v. 1.11). Elemental analyses were performed by the London Metropolitan University. Thermogravimetric analysis (TGA) was performed using a METTLER-TOLEDO TGA-1. The solid sample (approx. 7 mg) was placed in a 70 µL platinum pan and measurements were taken while heating of the sample from 50 °C to 600 °C under nitrogen atmosphere. The background measurement was performed during heating the empty pan over the same temperature range.

3
Synthesis of ( Ad L)CuCl. An oven-dried 100-mL Schlenk flask was equipped with a stirring bar and charged with Ad L (1.58 g, 4.2 mmol) and CuCl (0.42 g, 4.2 mmol) under an argon atmosphere.

Cryogenic and time-resolved PL measurements.
For PL measurements, the samples (spin-cast films on quartz substrates) were photoexcited using a 407 nm pulsed laser with pulse width <200 ps. The time-integrated PL spectra were measured with a spectrograph (SpectraPro 2500i, Princeton Instruments) coupled with a thermo-electronically cooled CCD camera (PIXIS 100-F, Princeton Instruments). A time-correlated single photon counting (TCSPC) setup (Lifespec-ps, Edinburgh Instruments) was used to measure the PL kinetics. The cooling of the sample was provided by a liquid helium cryostat.

X-Ray Crystallography.
Crystals suitable for X-ray study for copper complexes were obtained by layering of CH 2 Cl 2 solutions with hexanes, while gold complexes were crystallized by slow evaporation of benzene solutions. Crystals were mounted in oil on glass fibers and fixed on the diffractometer in a cold nitrogen stream. Data were collected on an Oxford Diffraction Xcalibur-3/Sapphire3-CCD diffractometer, using graphite monochromated Mo K α radiation (λ = 0.71073 Å) at 140 K. Data were processed using the CrystAlisPro-CCD and -RED software. S4 The principal crystallographic data and refinement parameters are listed in Table S1. The complexes ( Ad L)CuX (X = Cl, Br, and I) crystallized with two independent molecules in the unit cell. The structures were solved by direct methods and refined by the full-matrix least-squares against F 2 in an anisotropic (for non-hydrogen atoms) approximation. All hydrogen atom positions were refined in isotropic approximation in "riding" model with the U iso (H) parameters equal to 1.2 U eq (C i ), for methyl groups equal to 1.5 U eq (C ii ), where U(C i ) and U(C ii ) are respectively the equivalent thermal parameters of the carbon atoms to which the corresponding H atoms are bonded. All calculations were performed using the SHELXTL software. S5

Computational details
The ground states were fully optimized by the hybrid density functional PBE0 S6 method in combination with def2-TZVP basis set of Ahlrichs and coworkers. S7 Relativistic effective core potentials of 28 and 60 electrons were used to describe the core electrons of I and Au, respectively. S8 The excited states were studied similarly by time-dependent DFT. S9 The methods and basis sets have been previously employed with success in studies of luminescent Cu-and Au-complexes. S10 All calculations were carried out by Gaussian 09. S11