Synthesis of a xanthene-based macrocyclic imine ligand and two-step planarization by metalation with Ni2+ and Na+Electronic supplementary information (ESI) available. CCDC 2448855–2448857. For ESI and crystallographic data in CIF or other electronic format see DOI: https://doi.org/10.1039/d5dt01183c

Abstract

A xanthene-based macrocyclic π-containing imine ligand, H₄L², was newly designed and synthesized in order to obtain a series of metal-containing planar structures. Due to the xanthene framework with the methylene bridge, the macrocyclic molecule, H₄L², had a more planar structure than the corresponding diaryl-ether-type analogue, H₄L¹. This macrocyclic molecule, H₄L², was converted into the dinuclear nickel(II) complex, L²Ni₂, which was characterized by spectroscopic techniques as well as crystallography. The planarity of the macrocyclic ligand, H₄L², was greatly improved by the introduction of two Ni²⁺ ions. Furthermore, the L²Ni₂ molecule became more planar by incorporation of a Na⁺ ion in the central O₆ binding cavity. Thus, the xanthene-based macrocycle, H₄L², allowed complexation with two different metal ions, Ni²⁺ and Na⁺, to demonstrate a two-step improvement in the planarity.