Issue 29, 2019

Iron(ii) complexes with diazinyl-NHC ligands: impact of π-deficiency of the azine core on photophysical properties

Abstract

Ligand field enhancing N-heterocyclic carbene (NHC) ligands were recently shown to prevent photo-induced spin crossover in Fe(II) complexes due to their intricate effects on the electronic excited state structure. Due to their pico- to nanosecond lifetimes, these complexes are now good candidates for photo-sensitizing applications. Herein we report the synthesis and photophysical characterization of a new family of homoleptic Fe(II) complexes with C^N^C ligands involving diazines as the central N-heteroaromatic ligand. For these four carbene bond complexes, ultrafast transient absorption spectroscopy revealed a significant improvement of the excited-state lifetime. A record 32 ps lifetime was measured for a complex bearing a ligand combining a π-deficient pyrazine nucleus and a benzimidazolylidene as NHC. When compared to other azine-based ligands investigated, we argue that the lifetimes are modulated by a small excited state barrier expressing the ability of the ligand to reach the Fe–N distance needed for internal conversion to the ground state.

Graphical abstract: Iron(ii) complexes with diazinyl-NHC ligands: impact of π-deficiency of the azine core on photophysical properties

Supplementary files

Article information

Article type
Paper
Submitted
25 tra 2019
Accepted
24 svi 2019
First published
27 svi 2019

Dalton Trans., 2019,48, 10915-10926

Iron(II) complexes with diazinyl-NHC ligands: impact of π-deficiency of the azine core on photophysical properties

M. Darari, E. Domenichini, A. Francés-Monerris, C. Cebrián, K. Magra, M. Beley, M. Pastore, A. Monari, X. Assfeld, S. Haacke and P. C. Gros, Dalton Trans., 2019, 48, 10915 DOI: 10.1039/C9DT01731C

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