Related Experiment Video
Updated: Feb 5, 2026

Hollow Microneedle-based Sensor for Multiplexed Transdermal Electrochemical Sensing
Published on: June 1, 2012
Towards Ni(II) complexes with spin switches for 19F MR-based pH sensing
Da Xie1, Lauren E Ohman1, Emily L Que2
1Department of Chemistry, The University of Texas at Austin, 105 E. 24th St Stop A5300, Austin, TX, 78712, USA.
Objectives:
Our aim was to demonstrate the potential of exploiting simultaneous changes in coordination geometry and spin state in fluorinated Ni(II) complexes as an avenue for 19F magnetic-resonance (MR)-based pH sensing.
Materials And Methods:
Crystal structures were studied using an Agilent Technologies SuperNova Dual Source diffractometer. Solution magnetic moment was determined using Evan's method. MR images were collected on a 7.0-T MR scanner equipped with a quadrature 19F volume coil.
Results:
NiL1 and NiL2 were synthesized; crystallographic and spectroscopic data supported NiL1 as being diamagnetic and NiL2 as being paramagnetic. In aqueous solution, ligand dissociation from Ni(II) center was observed for both complexes at around pH 6, precluding their use as reversible pH sensors. The two complexes have distinct 19F nuclear magnetic resonance (NMR) signals in terms of both chemical shift and relaxation times, and selective imaging of the two complexes was achieved with no signal interference using two 19F MRI pulse sequences.
Conclusion:
The significant difference in the chemical shift and relaxation times between NiL1 and NiL2 allowed selective imaging of these species using 19F MRI. While NiL1 and NiL2 were not stable to acidic environments, this report lays the framework for development of improved ligand scaffolds that stably coordinate Ni(II) in acidic aqueous solution and act as agents for ratiometric pH mapping by 19F MRI.
More Related Videos
Related Concept Videos
Switching of BJT
Cut-off Mode ("Off" State): In this state, both the emitter-base and collector-base junctions are...
The Sense of Self: Reflected Self-Appraisal and Social Comparison
NMR Spectroscopy: Spin–Spin Coupling
Spin–Spin Coupling: One-Bond Coupling
Spin–Spin Coupling Constant: Overview
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must...
Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...

