Issue 7, 2016

Synthesis of new phosphorescent imidoyl-indazol and phosphine mixed ligand Cu(i) complexes – structural characterization and photophysical properties

Abstract

Four mononuclear Cu(I) complexes were prepared, described as [Cu(N,N)2]PF6 (1) and [Cu(N,N)(P,P)]PF6 (2–4), where N,N is N-(1-(2H-indazol-2-yl)ethylidene)-2,6-diisopropylaniline and P,P are phosphine derived ancillary ligands (bis[2-(diphenylphosphino)phenyl]ether (POP), bis(diphenylphosphino)ethane (dppe) or 2 PPh3). These new species were characterized by NMR, FT-IR, elemental analyses, cyclic voltammetry, UV-Vis – emission spectroscopy, transient absorption spectroscopy and DFT calculations. In addition, complexes 1 and 2 were characterized by X-ray diffraction. The four complexes showed an MLCT absorption band between 400 and 450 nm, in addition to a weakly structured phosphorescence in a 4 : 1 ethanol : methanol glassy matrix at 77 K. Complexes 2–4 have emission profiles that resemble the phosphorescence of the protonated N,N ligand, suggesting a triplet LC character of the lowest lying excited state at 77 K. By contrast, a mixed MLCT/LC triplet emission is most likely responsible for the phosphorescence in complex 1. Weak ligand-centered emission is also detected in the solid state at room temperature but only in the case of complexes 2 and 4, suggesting thermally activated deactivation processes in the case of 1 and 3. Notably, the transient absorption spectroscopy of complexes 2–4 in CH2Cl2 solution confirms a strong contribution from a ligand-centered (LC) triplet excited state, pointing towards a mixed 3MLCT/3LC character of the transient species in solution at room temperature, undergoing a non-radiative deactivation in the μs time-scale. This behavior markedly differs from that observed for complex 1, whose short-lived 3MLCT excited state is followed by ultrafast transient absorption spectroscopy.

Graphical abstract: Synthesis of new phosphorescent imidoyl-indazol and phosphine mixed ligand Cu(i) complexes – structural characterization and photophysical properties

Supplementary files

Article information

Article type
Paper
Submitted
02 okt 2015
Accepted
23 dec 2015
First published
05 jan 2016

RSC Adv., 2016,6, 5141-5153

Author version available

Synthesis of new phosphorescent imidoyl-indazol and phosphine mixed ligand Cu(I) complexes – structural characterization and photophysical properties

A. R. Cabrera, I. A. Gonzalez, D. Cortés-Arriagada, M. Natali, H. Berke, C. G. Daniliuc, M. B. Camarada, A. Toro-Labbé, R. S. Rojas and C. O. Salas, RSC Adv., 2016, 6, 5141 DOI: 10.1039/C5RA20450J

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