Synthesis and Photophysical Studies of aNHC Supported Coinage Metal Complexes

Abstract

For 160 years, carbene as a ligand has played a powerful role in organometallic chemistry, but carbene is first considered a fugitive species. Arduengo and co workers synthesize the first stable carbene known as NHCs (N-Heterocyclic carbenes). This indication that carbene is no longer a fugitive species helps provide a diaspora in this field. NHCs show strong σ-donating and π-accepting properties that are utilized to make a strong bond with the metal center. cAAC (cyclic (alkyl)(amino)carbenes), aNHC (abnormal N-heterocyclic carbene, MAC (Monoamido-amino carbene), and DAC (Diamidocarbene) are other well-explored carbenes. The energy gap of NHCs is 4.8 eV, aNHC is 4.6 eV and cAAC is 3.3 eV. NHCs and cAAC with coinage metal are well explored from the photophysical aspects. Still, aNHC for the same is not documented despite having better σ donating properties than NHCs. A detailed study on the structural, electrochemical, and photophysical behavior of previously reported two-coordinated coinage metal (copper and silver) complexes with aNHC and two new compounds by inserting carbazolide as an anionic ligand in the place of halide were scrutinized. Previously reported Cu and Ag complexes show emissions in the range of 380-420nm (blue emissive) and provide excitation-dependent emission. The electrochemical study reveals the redox-active behavior of ligand and metal complexes