Chen, P, Ge, W, Lu, Y, Wu, Z, Xu, J, Woodfine, SE, Darton, RJ and Hawes, CS ORCID: https://orcid.org/0000-0001-6902-7939 (2019) Substituent effects in the zinc(II) coordination chemistry of isomeric pyridylpyrazole ligands. Journal of Coordination Chemistry.

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Abstract

Pyrazoles with unsymmetric substitution are useful ligands in coordination chemistry, but are under-developed due to synthetic challenges in accessing the pure isomers. We have prepared four new structurally related N-(2-pyridyl)-3,5-dialkylpyrazole ligands, L1-L4, and probed their coordination chemistry in the crystalline phase and in solution to elucidate a relationship between steric influence of the alkyl substituents, the stability of the subsequent metal complexes, and their crystal packing influences. We find that L1 and L2, bearing linear or branched alkyl substituents, show similar stabilities and crystal packing motifs featuring pi center dot center dot center dot pi and C-H center dot center dot center dot Cl interactions in the crystalline complexes 1 and 2, respectively. The cyclohexyl-fused species L3 and L4 vary both in the solution stability of complexes 3 and 4, respectively, and in their crystal packing. Complex [ZnCl2(L3)] (3) is a mononuclear complex similar to 1 and 2, albeit with pi center dot center dot center dot pi interactions disallowed by the bulk of the cyclohexyl ring. Reaction of isomeric L4 with ZnCl2 gives two polymorphic complexes, 4 alpha and 4 beta, of the form [Zn2Cl2(mu(2)-Cl)(2)(L4)(2)], varying only in their long-range packing modes. These results show the importance of understanding the steric influences in substituted pyridylpyrazoles, which determine both stability in solution and speciation in the crystalline phase.

Item Type: Article
Additional Information: This is the accepted author manuscript (AAM). The final published version (version of record) is available online via Taylor & Francis at https://www.tandfonline.com/doi/full/10.1080/00958972.2019.1587613 - Please refer to any applicable terms of use of the publisher.
Uncontrolled Keywords: Coordination chemistry, Pyrazole, Zinc, Crystallography, Fluorescence
Subjects: Q Science > QD Chemistry
Divisions: Faculty of Natural Sciences > School of Chemical and Physical Sciences
Depositing User: Symplectic
Date Deposited: 05 Mar 2019 08:34
Last Modified: 29 Apr 2019 08:45
URI: http://eprints.keele.ac.uk/id/eprint/5998

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