biostudies-literatureCampanella AJNIBIB NIH HHSU.S. Environmental Protection AgencyNational Institutes of HealthNIH HHSNational Institute of Biomedical Imaging and BioengineeringColorado State UniversityNational Science Foundation3341-3348https://www.ebi.ac.uk/biostudies/studies/S-EPMC8992015biostudies-literatureUnknown51(8)Complexes of encapsulated metal ions are promising potential metal-based electron paramagnetic resonance imaging (EPRI) agents due to zero-field splitting. Herein, we synthesize and magnetically characterize a series of five new Ni(II) complexes based on a clathrochelate ligand to provide a new design strategy for zero-field splitting in an encaged environment. UV-Vis and X-ray single-crystal diffraction experiments demonstrate slight physical and electronic structure changes as a function of the differing substituents. The consequence of these changes at the remote apical and sidearm positions of the encaging ligands is a zero-field splitting parameter (<i>D</i>) that varies over a large range of 11 cm^-1. These results demonstrate a remarkable flexibility of the zero-field splitting and electronic structure in nickelous cages and give a clear toolkit for modifying zero-field splitting in highly stable ligand shells.Dalton transactions (Cambridge, England : 2003)Ligand design of zero-field splitting in trigonal prismatic Ni(II) cage complexes.PMC8992015CHE-13396741S10OD021814-01R21-EB027293S10 OD021814R21 EB027293Campanella AJOzvat TMZadrozny JMfalseLigand design of zero-field splitting in trigonal prismatic Ni(II) cage complexes.Complexes of encapsulated metal ions are promising potential metal-based electron paramagnetic resonance imaging (EPRI) agents due to zero-field splitting. Herein, we synthesize and magnetically characterize a series of five new Ni(II) complexes based on a clathrochelate ligand to provide a new design strategy for zero-field splitting in an encaged environment. UV-Vis and X-ray single-crystal diffraction experiments demonstrate slight physical and electronic structure changes as a function of the differing substituents. The consequence of these changes at the remote apical and sidearm positions of the encaging ligands is a zero-field splitting parameter (<i>D</i>) that varies over a large range of 11 cm^-1. These results demonstrate a remarkable flexibility of the zero-field splitting and electronic structure in nickelous cages and give a clear toolkit for modifying zero-field splitting in highly stable ligand shells.2022-01-01T00:00:00Z2022 Feb2026-05-09T19:46:54.73Z2025-02-19T02:23:58.228ZS-EPMC89920153513773210.1039/d1dt02156g