Thermal and Mechanochemical Syntheses of Luminescent Mononuclear Copper(I) Complexes

Abstract

Mononuclear CuI iodide complexes, [CuI(PPh3)2L] {PPh3 = triphenylphosphine; L = 4-aminoisoquinoline (4-aiq) (2), 5-aminoisoquinoline (5-aiq) (3), and 5-nitroisoquinoline (niq) (4)}, were prepared by three different methods: normally used reactions in the solution state, mechanochemical synthesis, and newly developed solvent-free thermal synthesis. Although no solvent was required for the mechanochemical synthesis of the parent complex [CuI(PPh3)2(iq)] (1; iq = isoquinoline), a minimal amount of assisting solvent (PhCN) was required for the mechanochemical syntheses of the three functionalized isoquinoline complexes. The amino-functionalized isoquinoline complexes were successfully synthesized by heating the ground mixture of three types of starting materials at ca. 100 °C, where the PPh3 ligand melted to promote complex formation by acting as the ligand and the solvent. The emission properties strongly depend on the L ligand: Complexes 2 and 3 showed vibronic emission spectra originating from the 3ππ* excited state localized on the L ligand, whereas complex 4 did not show any emission in the visible region.