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Issue 10, 2018
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A chiral lactate reporter based on total and circularly polarized Tb(III) luminescence

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Abstract

The coordination features and signaling of a L-lactate ion by a [Tb(bpcd)]+ (bpcd = N,N′-bis(2-pyridylmethyl)-trans-1,2-diaminocyclohexane-N,N′-diacetate) complex have been investigated by means of a combination of techniques, including total luminescence, calorimetry and circularly polarized luminescence. The L-lactate/[Tb(bpcd)]+ association constant, determined by both luminescence titration and isothermal titration calorimetry, indicates a weak interaction (log K = 1.3–1.45) between the analyte and both enantiomers of the complex. The theoretical DFT calculations suggest that the most likely coordination of L-lactate to the possible stereoisomers of the [Tb(S,S-bpcd)]+ complex (trans-O,O or trans-Npy,Npy) is one involving a hydroxyl group. The results of [Tb(rac-bpcd)]+ as a chiroptical luminescent probe of L-lactate underline the peculiar role of the chiral 1,2-diaminocyclohexane (DACH) backbone. Indeed, the target anion is capable of inducing CPL activity in the racemic mixture of Tb complexes containing DACH-based ligands. The same is not observed for the achiral analogue [Tb(bped)]+ (bped = N,N′-bis(2-pyridylmethyl)ethylenediamine-N,N′-diacetate) complex, likely because of the flexibility of the ethylenic group which allows an interconversion between different isomers which produces a null net CPL activity. Thanks to the differential quantum yield of the two diastereomeric species (R,R)-L and (S,S)-L, one can use the racemic complex to reveal L-lactate by measuring the induced CPL spectrum. Interestingly, this has been demonstrated in a commercial complex solution for medical use, containing several electrolytes, namely Ringer's lactate.

Graphical abstract: A chiral lactate reporter based on total and circularly polarized Tb(iii) luminescence

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Publication details

The article was received on 27 Nov 2017, accepted on 16 Jan 2018 and first published on 16 Jan 2018


Article type: Paper
DOI: 10.1039/C7NJ04640E
Citation: New J. Chem., 2018,42, 7931-7939
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    A chiral lactate reporter based on total and circularly polarized Tb(III) luminescence

    M. Leonzio, A. Melchior, G. Faura, M. Tolazzi, M. Bettinelli, F. Zinna, L. Arrico, L. Di Bari and F. Piccinelli, New J. Chem., 2018, 42, 7931
    DOI: 10.1039/C7NJ04640E

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