Heteroleptic copper(I) complexes with coumarin-substituted aminodiphosphine and diimine ligands: Synthesis and photophysical studies

The synthesis of heteroleptic Cu(I) complexes with coumarin-functionalized aminodiphosphine and diimine ligands is described. The complexes show yellow to deep-red phosphorescence in the solid state at ambient temperature with quantum yields up to 21%. The emission color of the complexes can be tuned by systematic modifications in the ligand system.

Elemental analyses were carried out with an Elementar vario MICRO cube.
NMR spectra were recorded on Bruker spectrometers (Avance III 300 MHz, Avance Neo 400 MHz or Avance III 400 MHz).Chemical shifts are referenced internally using signals of the residual protio solvent ( 1 H) or the solvent ( 13 C{ 1 H}) and are reported relative to tetramethylsilane ( 1 H, 13  Infrared (IR) spectra were recorded in the region 3500-400 cm -1 on a Bruker Tensor 37 FTIR spectrometer equipped with a room temperature DLaTGS detector, a diamond attenuated total reflection (ATR) unit and a nitrogen-flushed chamber.In terms of their intensity, the signals were classified into different categories (s = strong, m = medium, w = weak, and sh = shoulder).

Synthesis of di-substituted coumarin aminophosphines (L 2 ):
7-Amino-4-methylcoumarin (5.6 mmol, 1.0 g) was suspended in THF and triethylamine was added in excess.It was followed by drop-wise addition of bis(4-(tert-butyl)phenyl)chlorophosphine (11.9 mmol, 3.7 g) dissolved in 20 mL of THF at 0 °C.The reaction mixture was sonicated for 10 min and left for stirring for 3 days at room temperature.The volatiles were evaporated under vacuum and the remaining solid was dissolved in THF.The resulting colorless precipitate of HNEt3Cl was filtered off.The volume of the reaction mixture was reduced to one-third and an equal volume of pentane was added.On storing the mixture at -30 °C, white colored solid was formed.The solid was washed with pentane thrice, dried under reduced pressure.

Synthesis of Cu complex 2:
To a flask containing L .

Synthesis of copper complex 4:
To a flask containing L 2 (181.8mg, 0.24 mmol, 1.0 eq) and [Cu(CH3CN)4]BF4 (75.5 mg, 0.24 mmol, 1.0 eq), 10 mL of DCM was added.After stirring for 3 h, 2-(2′-pyridine)benzthiazol (50.9 mg, 0.24 mmol, 1.0 eq) dissolved in 5 mL of DCM was added to the flask and left for stirring overnight at room temperature.Orange colored single crystals were grown from a mixture of DCM solution of complex 5 and n-pentane.The same experiment with L 1 instead of L 2 led to the isolation of orange colored insoluble solid during the crystallization process.

Analytical data for 4:
Yield

Synthesis of copper complex 5:
To a flask containing L 1  1 H NMR (400 MHz, 298 K, CD2Cl2): Homoleptic complex is the major compound formed on dissolving the crystals due to which all the peaks could not be assigned unambigiuosly.
13 C{ 1 H} NMR (100 MHz, 298 K, CD2Cl2): Homoleptic complex is the major compound formed on dissolving the crystals due to which peaks could not be assigned unambigiuosly.Suitable crystals for the X-ray analysis of all compounds were obtained as described above.A suitable crystal was covered in mineral oil (Aldrich) and mounted on a glass fibre.The crystal was transferred directly to the cold stream of a STOE StadiVari (100 K or 150 K)

III. IR spectra
diffractometer.All structures were solved by using the program SHELXS/T 4,5 and Olex2. 6The remaining non-hydrogen atoms were located from successive difference Fourier map calculations.The refinements were carried out by using full-matrix least-squares techniques on F 2 by using the program SHELXL. 5,6The H-atoms were introduced into the geometrically calculated positions (SHELXL procedures) unless otherwise stated and refined riding on the corresponding parent atoms.In each case, the locations of the largest peaks in the final difference Fourier map calculations, as well as the magnitude of the residual electron densities, were of no chemical significance.Summary of the crystal data, data collection and refinement for compounds are given in Table S1.
Crystallographic data for the structures reported in this paper have been deposited with the

VI. Photoluminescence data
Photoluminescence measurements were carried out on a PTI QuantaMaster™ 8075-22 fluorometer with double excitation and emission monochromators (HORIBA Jobin Yvon).The samples (polycrystalline solids) were sealed under inert atmosphere in a Young-type NMR tube (material: Suprasil® quartz).The tube was placed in a glass dewar vessel (equipped with a quartz finger on the bottom where spectroscopy takes place) which was filled with liquid nitrogen for measurements at 77 K.For emission detection a R928 photomultiplier (250-800 nm) or a liquid nitrogen cooled DSS IGA020L/CUS detector (800-1550 nm) was used.The PL spectra at temperatures down to 3.2 K were measured on a Fluorolog-322 spectrometer (HORIBA Jobin Yvon) equipped with an optical cryostat based on a PT403 pulse tube cryocooler (Cryomech).All spectra were corrected for the wavelength dependent response of the detector and the spectrometer (in relative photon flux units).For detection of the emission decay traces, the samples were excited with either a Delta Diode™ (HORIBA Jobin Yvon, Model DD-370, λexc = 371 nm, pulse < 2 ns, 2 µW) for fluorescence lifetimes or a PTI XenonFLash™ pulsed lamp (set before the excitation monochromator) for phosphorescence decay times.In case of using the Delta Diode, signal was recorded until a satisfying signal-to-noise ratio was obtained.When using the Xenon Flash lamp, 10000 traces were recorded and averaged.For determination of the lifetimes the obtained traces were fit with an exponential decay curve (one or two exponentials) using Origin(Pro), Version 2019 (OriginLab Corp.).The absolute PL efficiency of polycrystalline samples at ambient temperature was determined using an integrating sphere made of optical PTFE, which was installed into the sample chamber of the spectrometer.The uncertainty of these measurements was estimated to be ±10 %.

VI. Quantum chemical calculations
The geometry optimizations were initiated from the crystal structure coordinates.Counter anions were removed and not included in the calculations.All calculations were performed with the Gaussian 16, revision C.01, package. 7The molecular geometries in the ground state calculations, respectively.Vibrational frequencies were obtained for all optimized geometries to ensure that the latter did not lead to any imaginary frequencies.Geometry optimizations were carried out using CAM-B3LYP functional, 8 which is considered suitable for long-range electronic interactions.The basis set was LANL2DZ for the copper and 6-31G** for C, N, O, P, S and H atoms. Figure S53 and S54 display the frontier molecular orbitals (visualized employing the Chemcraft software) 9 of the homoleptic copper complex Cu(L 1 )2 (A) and heteroleptic complexes 1-5.
C{ 1 H}), H3PO4 ( 31 P).All NMR spectra were measured at 298 K, unless otherwise specified.The multiplicity of the signals is indicated as s = singlet, d = doublet, dd = doublet of doublets, t = triplet, m = multiplet and br = broad.Assignments were determined based on unambiguous chemical shifts, coupling patterns and 13 C-DEPT experiments.
mmol, 1.0 eq) dissolved in 5 mL of DCM was added to the flask and left for stirring overnight at room temperature.Yellow-colored single crystals were isolated from a mixture of DCM, acetonitrile and diethylether solution at room temperature.

Figure S2. 31
Figure S2.31P{ 1 H} NMR spectrum of L 2 in CDCl3.#-unidentified minor products, which were not observed for the metal complexes.

Figure S4. 1 H
Figure S4. 1 H NMR spectrum of 1 in CDCl3.*, residual protio solvent signal.Integration was performed for all compounds in the solution.

Figure S15. 1 H
Figure S15. 1 H NMR spectrum of 4 in CD2Cl2.*, residual protio solvent signal.Integration was performed for all compounds in the solution.

Figure S22 .
Figure S22.Changes in 31 P{ 1 H} NMR spectra of 1-5 in CD2Cl2 after nearly 3 months ( 80-85 days) storage (at ambient temperature, in sealed NMR tubes, in dark).Practically no decomposition of the sample solutions is observed for 3 and 4, moderate decomposition for 5, and a more significant decrease of the NMR signals for 1 and 2. Green crystalline precipitate is observed in the NMR tube of complex 1.

Figure S23 .
Figure S23.Changes in the 31 P{ 1 H} NMR spectra of 1-5 in CDCl3 after heating the freshly prepared samples at 50 °C for 5 h.Rapid decomposition into ligand was observed for complexes 1 and 2 followed by complexes 3 and 4. Practically no decomposition was observed for complex 5.

Figure S31 .Figure S32 .
Figure S31.MS-ESI spectra of complex 1. Indicated are the molecular ion peak [M-PF6 ] + of 1 and the peak of the related homoleptic complex.

Figure S33 .Figure S34 .
Figure S33.MS-ESI spectra of complex 2. Indicated are the molecular ion peak [M-BF4 ] + of 2 and molecular ion peaks of two related homoleptic complexes.

Figure S35 .Figure S36 .
Figure S35.MS-ESI spectra of complex 3. Indicated are the molecular ion peak [M-PF6 ] + of 3 and the peaks of two related homoleptic complexes.

Figure S39 .
Figure S39.MS-ESI spectra of complex 5. Indicated are the molecular ion peak [M-PF6 ] + of 5 and the peaks of two related homoleptic complexes.

Figure S45 :
Figure S45: PL and PLE spectra of complex 1 recorded at 77 K at the given emission (PLE spectra λem) and excitation wavelengths (PL spectra λexc).

Figure S46 :
Figure S46: PL and PLE spectra of complex 2 recorded at 77 K and room temperature at the given emission (PLE spectra: λem) and excitation wavelengths (PL spectra: λexc).

Figure S47 :
Figure S47: PL and PLE spectra of complex 3 recorded at 77 K and room temperature at the given emission (PLE spectra: λem) and excitation wavelengths (PL spectra: λexc).

Figure S48 :S37Figure S49 :
Figure S48: PL and PLE spectra of complex 4 recorded at 77 K and room temperature at the given emission (PLE spectra: λem) and excitation wavelengths (PL spectra: λexc).

Figure S51 :
Figure S51: PL and PLE spectra of solid complex 5 recorded at 3.5 K at the given excitation (λexc) and emission ( λem) wavelengths, respectively.The weak, vibronically structured emission within 460-590 nm is attributed to the coumarin groups (see the main text).It is only observed at temperatures below ~50 K.

Figure S52 .
Figure S52.Photogaphs of DCM solutions of the copper complexes 1-5.left: under day light; right: under UV illumination.
and the lowest singlet and triplet excited states (S1 and T1) were optimized via density functional theory (DFT), time-dependent DFT (TD-DFT) and spin-unrestricted DFT (UDFT)

Table S1 .
Summary of crystal data Cambridge Crystallographic Data Centre as a supplementary publication no.2266992-2266996.Copies of the data can be obtained free of charge on application to CCDC, 12 V.2.

Table S4 .
Correlation between the heteroatom in the diimine ligand and other parameters.