N-Heterocyclic Carbene Coinage Metal Complexes Containing Naphthalimide Chromophore: Design, Structure, and Photophysical Properties

Pierre-Henri Lanoë,Hani Amouri,Btissam Najjari,Florine Hallez,Geoffrey Gontard

doi:10.3390/inorganics5030058

Pierre-Henri Lanoë, Hani Amouri + Show 3 more

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https://doi.org/10.3390/inorganics5030058

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Abstract

A series of novel N-heterocyclic carbene coinage metal complexes containing a naphthalimide (NI) chromophore has been prepared and fully characterized. Two types of molecules are described those where the NI unit is directly attached to the carbene unit with the general formulae [(L1)–M–X], M = Cu, X = Cl (1a); M = Ag, X = I (1b) and M = Au, X = Cl, (1c). While in the second family, a π-extended carbene ligand precursor L2–H+I− (3) was prepared where the NI unit is distant from the imidazole unit via a phenyl-alkyne bridge. Only two N-heterocyclic carbene metal complexes were prepared [(L2)–M–Cl], M = Cu (2a) and M = Au (2c). The related silver carbene compound could not be isolated. The molecular structure of the carbene complex 1c was determined and confirmed the formation of the target compound. Interestingly, the structure shows the presence of an aurophilic interaction Au···Au at 3.407 Å between two individual molecules. The photophysical properties of the compounds were investigated in solution at room temperature. Preliminary results suggested that all compounds are luminescent and act as blue emitters (420–451 nm). These transition emissions can be attributed to the intraligand origin of the NI chromphore. Moreover, the carbene complexes featuring L2 ligand with π-extended system were found to be more luminescent.

Highlights

N-heterocyclic carbene (NHC) ligands have received much attention since the isolation of the free imidazole-2-ylidene ligand by Arduengo et al in 1991 [1]
Paper, we we describe describe the the synthesis synthesis and and photophysical photophysical properties properties of of aa novel novel class class of of N-heterocyclic
We found that the complexes with L2 -type ligand displayed higher quantum yields (Table 1)

Summary

Introduction

N-heterocyclic carbene (NHC) ligands have received much attention since the isolation of the free imidazole-2-ylidene ligand by Arduengo et al in 1991 [1]. The first metal complexes were reported back in 1965 by Ofele and Wanzlick et al [2,3] They allow the formation of stable compounds that have important applications in various fields of chemistry [4,5] such as organometallics [6], homogeneous catalysis [7], metallosupramolecular chemistry, metallodrugs [8], and more recently as luminescent materials [9,10,11]. We recently reported the synthesis and characterization of a family of cyclometalated iridium carbene complexes containing a naphthalimide chromophore [17] The latter behaved as deep red phosphorescent compounds with good quantum yields and long lifetimes.

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