Triplet Photosensitized para-Hydrogen Induced Polarization.
ACS Cent Sci
; 8(11): 1548-1556, 2022 Nov 23.
Article
em En
| MEDLINE
| ID: mdl-36439314
ABSTRACT
Despite its enormous utility in structural characterization, nuclear magnetic resonance (NMR) spectroscopy is inherently limited by low spin polarization. One method to address the low polarization is para-hydrogen (p-H2) induced polarization (PHIP) which uses the singlet spin isomer of H2 to generate disparate nuclear spin populations to amplify the associated NMR signals. PHIP often relies on thermal catalysis or, more infrequently, UV-activated catalytic hydrogenation. Light-activated hydrogenation enables direct and timed control over the hyperpolarization of target substrates, critical for identifying short-lived intermediates. Here, we use an established Ir(III) triplet photosensitizer (PS) to visible light sensitize the triplet ligand-field states in the d6-transition metal dihydride Ru(CO)(PPh3)3(H)2 (1). Excitation inside a 9.4 T NMR spectrometer with the PS and a 420 nm blue LED, under 3 atm of p-H2, successfully photosensitized hyperpolarization in 1 and in a range of unsaturated substrates at and below room temperature, up to 1630-fold. In otherwise identical experimental conditions without light activation, no polarization was realized in 1 or the substrates evaluated. We believe triplet-sensitized PHIP (Trip-PHIP) represents a facile experimental means for probing triplet sensitized light activation in transition metal catalysts possessing low-lying triplet ligand-field states, providing mechanistic insight of potentially tremendous value in chemical catalysis.
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Base de dados:
MEDLINE
Idioma:
En
Revista:
ACS Cent Sci
Ano de publicação:
2022
Tipo de documento:
Article
País de afiliação:
Estados Unidos