Structure of Metiram, a Crystalline Zinc Coordination Complex with Amorphous Side Phase
METADATA ONLY
Loading...
Author / Producer
Date
2024-10-16
Publication Type
Journal Article
ETH Bibliography
yes
Citations
Altmetric
METADATA ONLY
Data
Rights / License
Abstract
Ethylenebis(dithiocarbamates) (EBDTCs) have been extensively used as fungicides in agriculture for nearly 80 years. Modern fungicides based on EBDTCs contain metal ions, such as zinc in Zineb and Metiram, manganese in Maneb, or combinations of both, such as in Mancozeb. Despite being commercially available since the 1940s, the molecular structure of the metal complexes of EBDTCs was not described in detail until the crystal structure of Zineb was published in 2020. Zineb (C₄H₆N₂S₄Zn) is a single-phase crystalline material. In this study, we present a comprehensive multimethod structural characterization of Metiram (C₁₂H₂₇N₉S₁₂Zn₃), which is the active ingredient of Polyram WG, a highly effective and plant-compatible organic contact fungicide. Our findings reveal that Metiram comprises two distinct phases. The primary phase, phase I, of Metiram is ethylenebis(dithiocarbamate) zinc(II) ammine, which constitutes 81 wt % of the material, or three-quarters of EBDTC. It is a zinc-coordinating crystalline phase. The crystal structure of this phase was determined by powder X-ray diffraction, revealing 1D S-shaped chains of EBDTC connected by strongly distorted Zn[NH₃][S₄] tetragonal pyramids. These pyramids share their sulfur atoms, and ammonia molecules occupy the apex of the pyramids, pointing alternately up and down. The secondary phase, phase II, constitutes 19 wt % of the material or one-quarter of EBDTC, and is amorphous. Using a combination of different techniques, including microscopy, diffraction, and spectroscopy, we have concluded that phase II consists of Zn-free EBDTC. We infer that the primary structure of this secondary constituent aligns with previous assumptions, notably the absence of a significant amount of Zn and the presence of disulfide bonds.
Permanent link
Publication status
published
External links
Editor
Book title
Journal / series
Volume
24 (20)
Pages / Article No.
8185 - 8202
Publisher
American Chemical Society
Event
Edition / version
Methods
Software
Geographic location
Date collected
Date created
Subject
Ammonia; Crystal Structure; Molecular Structure; Nuclear Magnetic Resonance Spectroscopy; Zinc
Organisational unit
03872 - Copéret, Christophe / Copéret, Christophe