# A responsive Co(ii) 19F PARAShift probe: activation of Fermi contact interactions triggered by pH-dependent coordination changes **Authors:** Kathleen M. Scott, Rahul T. Kadakia, Christopher D. Hastings, Georgia E. F. Barone, Jackson A. Reyna, Jin Xiong, Yisong Guo, Emily L. Que PMC · DOI: 10.1039/d6cc00957c · Chemical Communications (Cambridge, England) · 2026-03-09 ## TL;DR A new 19F MRI probe shows a large chemical shift change in response to pH changes, useful for imaging. ## Contribution A novel 19F MR probe with a large pH-dependent chemical shift change is introduced. ## Key findings - The probe CoNO2ASF5 shows over 30 ppm 19F chemical shift change with pH. - Fermi contact interactions are identified as the mechanism behind the shift. ## Abstract We report a novel 19F MR imaging probe CoNO2ASF5 exhibiting a large 19F chemical shift change of over 30 ppm in response to physiological pH changes. Calculations identify Fermi contact interactions drastic as the mechanism of enhanced 19F MR shift. We report a novel 19F MR imaging probe CoNO2ASF5 exhibiting a large 19F chemical shift change of over 30 ppm in response to physiologically relevant pH changes. ## Full-text entities - **Diseases:** cancer (MESH:D009369), metabolic and respiratory acidosis (MESH:D000142), pneumonia (MESH:D011014), chronic obstructive pulmonary disease (MESH:D029424), alkalosis (MESH:D000471) - **Chemicals:** acetonitrile (MESH:C032159), F (MESH:D005461), methanol (MESH:D000432), CHES (MESH:C050927), HCl (MESH:D006851), S (MESH:D013455), metal (MESH:D008670), water (MESH:D014867), Co-F (MESH:C043212), N (MESH:D009584), MES (MESH:C004550), 1,4,7-triazacyclononane (MESH:C075712), hydrogen (MESH:D006859), carboxylic acid (MESH:D002264), 1H (-), chloroacetyl chloride (MESH:C045557), anilide (MESH:D000813), carbon (MESH:D002244), lactic acid (MESH:D019344), O (MESH:D010100), amide (MESH:D000577), sulfonic acid (MESH:D013451), HEPES (MESH:D006531), Co (MESH:D003035), NaOH (MESH:D012972) ## Full text _Full body text omitted from this summary view._ Fetch the complete paper as Markdown: https://tomesphere.com/paper/PMC12991042/full.md ## Figures 6 figures with captions in the complete paper: https://tomesphere.com/paper/PMC12991042/full.md ## References 31 references — full list in the complete paper: https://tomesphere.com/paper/PMC12991042/full.md --- Source: https://tomesphere.com/paper/PMC12991042