Uncorrelated Dynamical Processes in Tetranuclear Carboxylate Clusters Studied by Variable-Temperature 1H NMR Spectroscopy.

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• 作者：Femke F. B. J. Janssen ; Laurens C. J. M. Peters ; Paul P. J. Schlebos ; Jan M. M. Smits ; Ren茅 de Gelder ; Alan E. Rowan
• 刊名：Inorganic Chemistry
• 出版年：2013
• 出版时间：November 18, 2013
• 年：2013
• 卷：52
• 期：22
• 页码：13004-13013
• 全文大小：491K
• 年卷期：v.52,no.22(November 18, 2013)
• ISSN：1520-510X

文摘

Tetranuclear carboxylate clusters with the general structural formula [M₄(L)₂(O₂CR)₄] (M = Cd, Zn; LH₂ = 2,6-bis(1-(2-hydroxyphenyl)-iminoethyl)pyridine; R = CH₃, C₆H₅) were studied by variable-temperature (VT) ¹H NMR spectroscopy. The dynamics of these clusters in solution can be described by two uncorrelated dynamical processes. The first dynamical process is the interconversion, both inter- as well as intramolecular, between syn鈥?i>syn bridging and chelating carboxylate ligands. It is shown that this carboxylate interconversion mechanism is predominantly intramolecular for [Cd₄(L)₂(O₂CCH₃)₄] (1a), whereas for [Zn₄(L)₂(O₂CCH₃)₄] (2a) it is predominantly intermolecular. Two models for the second dynamic process, which involves the diiminepyridine ligand, are described. The first model comprises a nondissociative rotation around an internal axis, which changes the chirality of the cluster. The second model is based on the dissociation of the tetranuclear cluster into two dimeric species, which recombine again. This last model is supported by scrambling experiments between [Zn₄(L)₂(O₂CCH₃)₄] (2a) and [Zn₄(L3)₂(O₂CCH₃)₄] (5) (L3H₂ = 2,6-bis(1-(2-hydroxyphenyl)-iminoethyl)4-chloropyridine).