Chimera Diimine Ligands in Emissive [Cu(P^P)(N^N)][PF6] Complexes

Abstract

The syntheses and characterizations of the chelating ligand 6-chloro-6′-methyl-2,2′-bipyridine (6-Cl-6′-Mebpy) and of the copper(I) compounds [Cu(POP)(6-Cl-6′-Mebpy)][PF6] and [Cu(xantphos)(6-Cl-6′-Mebpy)][PF6] (POP = bis(2-(diphenylphosphanyl)phenyl)ether and xantphos = 4,5-bis(diphenylphosphanyl)-9,9-dimethyl-9H-xanthene) are described. The single crystal structures of both complexes were determined; the copper(I) ion is in a distorted tetrahedral environment and in [Cu(xantphos)(6-Cl-6′-Mebpy)][PF6], the disorder of the 6-Cl-6′-Mebpy ligand indicates there is no preference of the ‘bowl’-like cavity of the xanthene unit to host either the methyl or chloro-substituent, consistent with comparable steric effects of the two groups. The electrochemical and photophysical properties of [Cu(POP)(6-Cl-6′-Mebpy)][PF6] and [Cu(xantphos)(6-Cl-6′-Mebpy)][PF6] were investigated and are compared with those of the related compounds containing 6,6′-dichloro-2,2′-bipyridine or 6,6′-dimethyl-2,2′-bipyridine ligands. Trends in properties of the [Cu(P^P)(N^N)]+ complexes were consistent with 6-Cl-6′-Mebpy behaving as a combination of the two parent ligands.

The Tail Wags the Dog: The Far Periphery of the Coordination Environment Manipulates the Photophysical Properties of Heteroleptic Cu(I) Complexes

“…This phenomenon appears due to electronic communication between the chromophoric center and the heavy metal atom through the C≡C bond, and is typical of alkynyl-phosphine Au(I) complexes [ 50 , 51 ]. The extinction coefficients are of the order of 10 4 M −1 cm −1 and 10 3 M −1 cm −1 for the high energy and low energy absorption bands, respectively, which is in accordance with the data reported for other complexes [Cu(Xantphos)(N^N)] + [ 23 , 24 , 25 , 26 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 37 , 38 , 39 , 48 ]. The empirical assignment of the bands in absorption spectra of 1–6 was confirmed by TDDFT calculations, vide infra .…”

“…Molecular structures of 1 , 2 and 6 are presented in Figure 1 and Figure S1 ( Figure S2 shows DFT-optimized structures of 1 – 6 ); crystallographic data are given in Table S1 , and selected structural parameters are listed in Table S2 . Solid state structures of 1 , 2 and 6 are similar to those of the related heteroleptic [Cu(Xantphos)(N^N)] + complexes bearing substituted 2,2′-bipyridines [ 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 ]. The structures demonstrate the expected chelating mode of both Xantphos and N^N ligands as well as the moderately distorted tetrahedral coordination geometry of the Cu(I) centre ( Table S3 ) [ 40 , 41 ].…”

“…The reduction processes for compounds 1 − 5 were poorly resolved, while 6 demonstrates reversible reduction at a potential of −1.7 V. Due to the irreversibility of the oxidation processes, differential pulse voltammetry (DPV) ( Figure S19 ) was used to determine the precise values of the oxidation potentials, and further DPV data will be analyzed. The first oxidation potentials, (1) ( Table 1 ), for compounds 1 − 4 and 6 are close to 0.8 V vs. Fc/Fc + , while the voltammogram of the oxidation of compound 5 contains a less pronounced peak at 0.72 V. It indicates that the metal-centred oxidation processes of complexes 1 − 6 are similar to each other and the Cu + /Cu 2+ transition potential is close to that observed in similar complexes (0.8 V vs. Fc/Fc + ) [ 23 , 24 , 25 , 26 , 27 , 29 , 30 , 35 , 37 , 45 , 46 , 47 ]. The low intensity of the first oxidation peak in the complex 5 indicates that metal oxidation is suppressed, possibly, due to sterical reasons.…”

“…The UV–vis absorption spectra of 1 – 6 ( Figure 3 , Table 2 ) are typical for heteroleptic Cu(I) complexes with diimine and phosphine ligands in a coordination sphere, and exhibit strong bands in the range from 250 to 350 nm due to spin-allowed ππ* intraligand ( 1 IL) transitions located at the aromatic system of both the N^N and P^P ligands [ 23 , 24 , 25 , 26 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 37 , 38 , 39 , 48 , 49 ]. The intense bands in the 320–350 nm region observed for 1 – 6 can be tentatively assigned to the transitions localized within the {diimine + C 6 H 4 X} motif coordinated to the Cu(I) atom.…”

The Role of Percent Volume Buried in the Characterization of Copper(I) Complexes for Lighting Purposes

“…Similarly, PLQY values obtained under air were chosen over values obtained under an Ar atmosphere where such differentiations were made [31]. A total of 100 compounds were found and their %V bur was calculated for the (NN), (PP) and (NN)(PP) units which are referred to as %V bur (NN), %V bur (PP) and %V bur (NN + PP) (Table S1, supporting information) [17][18][19][20][21][23][24][25][26][27][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48]. All compounds contain bidentate diimine and bisphosphane ligands with one exception containing a bidentate diimine and two monodentate triphenylphosphano ligands (CCDC: 1558486) [45].…”