Crystal structure of solvated zinc complexes based on salicylic acid derivatives

A zinc complex based on salicylic acid derivatives (E-84 from Orient Chem.) is a powerful charge-control agent for toners used in electrophotography. However, its charge-control ability is known to greatly depend on the process of toner preparations. It is therefore probable that the structure of E-84 can be modified during the process, or the molecules might rearrange themselves in a different way, leading to different characteristics. For this reason, structure analysis of E-84 has been carried out on single crystals recrystallized from solution in dimethylacetoamide (DMA), or dimethylsufoxide (DMSO) in the presence or absence of water. As a result, a variety of complexes have been isolated. 3,5-di-tert-butyl-salicylic acid (TBS) is found to coordinate to the Zn atom as a monodentate ligand in all complexes: four-coordinate E-84/(DMSO)(2), five-coordinate E-84/(H(2)O)(3) and. four-coordinate E-84/(H(2)O)(2). The present results lead us to conclude that various Zn complexes form easily in the process of toner preparations, depending on solvents, polymers etc. This may result in scattered characteristics of the charge-control ability.