A different iridium compound doesn't work well for hyperpolarization at room temperature because it holds onto pyridine too tightly, but it shows a little activity when warmed up.
Scientific Claim
The iridium complex [Ir(H)2(COE)(py)3]PF6 is SABRE-inactive at 298 K due to slow pyridine dissociation (0.007 s⁻¹), though limited SABRE activity is observed at 313 K.
Evidence Quality Assessment
Claim Status
appropriately stated
Study Design Support
Design supports claim
Appropriate Language Strength
association
Can only show association/correlation
Assessment Explanation
The study reports observed SABRE activity and pyridine dissociation rates, which is appropriate for describing an association between the complex and its catalytic properties.
More Accurate Statement
“The iridium complex [Ir(H)2(COE)(py)3]PF6 is associated with SABRE inactivity at 298 K due to slow pyridine dissociation (0.007 s⁻¹), though limited SABRE activity is observed at 313 K.”
Source Excerpt
“6 was also prepared independently from [Ir(COE)2(py)2]PF6 (5; Supporting Information). It proved to be SABRE-inactive at 298 K, in agreement with the py loss rate of 0.007 s–1; warming to 313 K produces limited SABRE, but the bound py signals are stronger than those of free py.”
Evidence from Studies
Supporting Evidence (1)
The study describes the SABRE inactivity of [Ir(H)2(COE)(py)3]PF6 at room temperature and its limited activity at higher temperatures, correlating with slow pyridine dissociation rates. The source excerpt directly states these observations.