A series of copper(I) complexes with electron donor/acceptor embedded ligands: Synthesis, photophysical and electroluminescent properties

►Electron donor moieties and limited conjugation system may self-restrict the geometry relaxation in excited states, leading to narrowed and blue-shifted emission bands. ►Electron acceptor moieties and large coplanar conjugation system are ineffective in restricting geometry relaxation, leading to broadened and red-shifted emission bands. ►The introduction of electron donors compromises thermal stability of Cu(I) complexes.