Copper(I) complexes attract considerable attention as a replacement for precious metals in photoluminescent materials based on its rich structural, photophysical properties and its low price. For practical application, photoluminescent properties of transition metal-based materials should be tuned in a desirable and predictable way. In this work, we report copper(I) mononuclear complexes supported by modular N-donor macrocyclic ligands that show photoluminescent properties controlled by the steric properties of the flexible amine arm of the ligand. We have synthesized a series of cationic and neutral CuI complexes with N,N’-dialkyl-2,11-diaza[3.3](2,6)-pyridinophane ligands RN4 (R = H, Me, iBu, iPr, tBu). The sterics of the axial amine substituent in these ligands affect the conformational preference and dynamics in solutions of the derived (RN4)CuI complexes, with more sterically hindered complexes showing slower dynamics of conformational exchange. Moreover, detailed EXSY studies revealed two types of exchange processes in solution involving flexible amine arms of pyridinophanes. Electrochemical studies showed that steric hindrance at the amine also affects the redox properties of the cationic complexes. The comparison of photoluminescent properties of the neutral (RN4)CuI complexes (R = Me, iBu, iPr, tBu) revealed a clear correlation between the steric hindrance and the absolute photoluminescence quantum yield (PLQY) both in the solid state and in solution at 298 K. Thus, complexes with more sterically hindered substituents showed PLQY up to 78% in the solid state and up to 29% in solution.

Influence of tetradentate macrocyclic ligand sterics on the conformational flexibility and photoluminescent properties of copper(I) complexes

255th National Meeting (2018)

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