Use of a Dihydrogen Osmium Complex as a Versatile 1 H NMR Recognition Probe

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Abstract
A new recognition probe for biomolecules, [en 2 Os(η 2 -H 2 )] 2+ (1; en, ethylenediamine), is reported. In aqueous solution, 1 binds readily to a variety of biomolecules, including nucleotides, RNA, amino acids, peptides, and phospholipids. In each case, binding leads to a characteristic proton nuclear magnetic resonance ( 1 H NMR) for the dihydrogen that appears in a spectral window in the range δ = 0 to -20 parts per million, and as well to characteristic values of the coupling J HD and of the relaxation time T 1 . Small structural differences in molecules such as DGMP (2′-deoxyguanosine 5′-monophosphate) and IMP (inosine 5′-monophosphate) or Asp and Glu can readily be distinguished, such as when 1 binds to the N-7 position of the nucleobase of DGMP or IMP and when 1 binds to the carboxylate of Asp or Glu. Upon one-electron oxidation of the metal center, diamagnetic 1 is converted to a paramagnetic probe.