In our investigations of ligand systems that simultaneously incorporate three types of molecular affinity, (1) coordination of metal cations; (2) intermolecular interactions with anions; and (3) additional function modalities, we have recently focused on two classes of unsymmetric molecules based on (a) (thio-)urea and (b) aminopyrazole cores (Fig. 1a, b, c).1,2 Structural studies of these organic systems have revealed a previously unreported molecular allotwin3 in the case of one methoxyphenyl-substituted thiourea, while our suite of aminopyrazoles have all exhibited supercooling of between 34 and 100 oC. Upon coordination of ZnCl2 and ZnBr2 to aminopyrazoles with R = phenyl or pyridinyl groups, we have observed bright, solid state fluorescence, while reactions with MnCl2 or Mn(ClO4)2 have yielded mixed oxidation state Mn(III)6Mn(II)1 clusters with concomitant conversion of the amino group to an imine (Fig. 1d). The magnetic properties of these Mn7 clusters have been characterized via SQUID magnetometry. All reported ligands and coordination complexes have been characterized by single crystal X-ray diffraction. Herein, these results will be discussed, with a focus on structure-function relationships, future directions, and reflections on the guidance and direction provided by Prof. Marilyn Olmstead.

Functionalized thioureas and aminopyrazoles: Structural explorations in polymorphism, supercooled organic liquids, and coordination chemistry

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ACS Fall 2022

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