Investigations on the manipulation of excited state properties in luminescent copper(I)-carbene complexes

Abstract

In the first part of this work, various copper(I) carbene complexes are investigated for their suitability as (near) infrared emitters. First, the synthesis and photophysical characterisation of a series of copper(I) halide complexes containing N-substituted phthalazinylidene ligands as chromophores is reported. In accompanying TD-DFT studies for other doctoral projects, the influence of coordination geometry and donor strength on the emission mechanism and the origin of the observed bathochromic shift is being investigated. The investigation of copper(I) complexes for mechanoresponsive and circularly polarised luminescence is discussed in the second part of this work. Building on mechanoluminochromic complexes of the type [Cu(NHC)(Rpy)]BF4, the exchange of the BF4 anion for chiral anions was investigated. The aim was to realise CPL through mechanically stimulated Cu-anion interaction. In the course of this work, some anions could be excluded due to chemical incompatibility, but the synthesis of stable complexes by metathesis was not successful. However, qualitative experiments provided evidence that Cu-F interactions are important for mechanoresponsivity. In [Cu(CAAC)(NR2)] complexes, however, mechanoluminescence is not based on the association of an anion in the inner coordination sphere, but on the dissolution of dipole-dipole interactions. However, our theoretical investigations showed that for NR2 = pnz (phenoxazinate), a local minimum structure with increased rotational strength is thermally accessible. This bent geometry, stabilised in a PMMA matrix by hydrogen bonds, provides an explanation as to why, despite a small absorption dissymmetry of about -1∙10^4, a high glum of -3.4∙10^3 could be measured for transition metal complexes.