Table 1:

Hyperpolarization of diazirines 2–4 with Ir-chloride precatalyst B via the SABRE-SHEATH method.^[a]

Entry	Diazirine	Additive	Ɛ[e]	T1 [s] [f]
1		none	_[g]	n/a
2[b]		pyridine	3500	168 ± 18
3[c]		MeCN	3400	179 ± 16
4[d]		D2O	11200	176 ± 3
5		none	_[g]	n/a
6[b]		pyridine	6000	215 ± 22
7[c]		MeCN	3200	172 ± 17
8[d]		D2O	1900	234 ± 28
9		none	_[g]	n/a
10[b]		pyridine	16 000	141 ± 4
11 [c]		MeCN	1000	263 ± 83[h]
12[d]		D2O	2500	164 ± 25

^[a]Conditions for all experiments: diazirines 2–4 (12.5 mm) and Ir precatalyst B (125 μm) in [D₄]MeOH. See the Supporting Information for more details on the hyperpolarization method.

^[b]Pyridine (1.00 mm, 8 equiv with respect to B).

^[c]Acetonitrile (1.00 mm).

^[d]D₂O (925 mm).

^[e]Signal enhancement measured at 8.45 T and calculated by comparison to a reference of neat ¹⁵N-acetonitrile.

^[f]T₁ measured at 1 T. See the Supporting Information for measurements at other fields.

^[g]No hyperpolarized signal observed.

^[h]The low signal enhancement and volatility of acetonitrile contribute to the larger T₁ error. n/a=not applicable.