Thiacalixarene-Supported MoNa Clusters: Crystal Transition and Mo-S Coordination on Visible-Light Absorption
Xinxin Hang, Yanan Yu, Zhao Wang, Yanfeng Bi
Abstract
Here, we report four molybdenum-sodium-based molecular architectures featuring the dinuclear molybdenum units built from p-tert-butylthiacalix[4]arene through solvent-induced assembly. The Mo8Na6 cluster crystallized from a methanol and N,N-dimethylformamide mixed solution, whereas not only an infinite coordination polymer Mo4Na4 but also a cluster Mo8Na8α were formed simultaneously in sole methanol solvent. Digestion of Mo8Na8α in dichloromethane, followed by addition of methanol, recrystallized into the Mo8Na8β cluster, exhibiting conformation transformation of the thiacalix[4]arene. Two unprecedented Mo-S coordination modes displayed in a Mo2 unit for the four complexes. The clusters Mo8Na6, Mo8Na8α, and Mo8Na8β showed UV–vis absorption up to 700 nm with a band gap at 1.98 eV (Mo8Na6), 1.82 eV (Mo8Na8α), and 1.75 eV (Mo8Na8β). Density functional theory calculations indicated that the solid-state visible-light absorption differences of clusters Mo8Na6 and Mo8Na8β were attributed to the different Mo-S coordination geometry.